Tern Link D8 frame shearing in two

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:40 am

February 12, 2014 - 12:03am
Keith C. Johns

Joined: 2011-08-05




thor wrote:

you are right Keith  in so many ways



By the way I like a classic steel bike with filet brazing and beautiful lug work.... there is something magical about it.

Your sampling is a little biased as of course they will receive many more alloy bikes than steel, cause there are so many more alloy bikes out there. Except if it is a "classic" retro trendy store who sells more steel bikes than usual, they sell 90 % alloy bikes. No wonder they get more alloy bikes back. Even if they get 80 % more broken alloy frames, than the % would still be below steel. Right ?

But your concerns about longevity are indeed warranted, no matter what material. Tern gets a lot of flack as even there top of theline products are just a tad heavier than most of the competition, guess where this tad more weight comes into play ... down the road 5 or 10 years from now. Thats the Tern Biz plan, they want to deliver a better longer lasting bike than all of the competition.

Best Thor

I will ask both bike mechanics what percentage of bikes sold were aluminum frames--that is a significant statistic to include here. Good point!

I am glad to hear that Tern is in fact commited to durabile bikes and willing to make their frames stronger to achieve this end even when it adds some weight. I am not surprised that the industry takes advantage of any detail like the total weight to try to hurt the sales of the competition. Weight has been the industry brainwashing mantra for decades when it comes to comparing bikes, but I think it is time the public gets re-educated on this issue and reminded that light weight comes only at a cost in durability. My own experiences of riding a 40 pound bike for 2.5 years surely taught me to question the rhetoric that light weight is the most important specification about a new bike to be considered; I learned that it makes almost no difference on the road--I only noticed it when lifting the bike up steps.

I think durability ought to be emphasized in selling Tern bikes, and even to state right out front something like, "Our bikes do weigh a couple of pounds more than our competition's bikes, but we guarantee ours to last the lifetime of the purchaser, and our competition only promises five years."

One more comment about aluminum frames vs. steel: the more I think about this, the more I realize that this really is all about the design of the bike, and the material is just one element which has to be factored into the design. If the design emphasizes light weight, it will lean away from durable elements, and its life will be compromised. I know this is a balance and thus a subtle dance to keep it both as light as possible as well as retain as durable a design as possible. And the extremes of this range point out the fact that it must always be a balance, not just one or the other; a 100 pound bike might never fail, but would fail to be riden at all for obvious reasons; a 5 pound bike would be a delight to ride for about an hour, before the ambulance comes to pick you up. A poorly designed frame will fail regardless of the frame material used.

Having said that, and assuming some basic competence in engineering design on the part of the manufacturer, and integrity to try to make a reasonably durable bicycle, all things being equal overall, the steel frame owing to its inherent strength and resilience, if protected from corrosion, will tend to outlast an aluminum frame of similar cost, I believe, because the aluminum frame is less forgiving a material and will suffer more from the defects in the design than the steel one will. But if the aluminum frame is augmented to compensate for its fatigue-prone nature, it should last as long as the steel frame. Now comes the challenge: since aluminum bikes are inherently more expensive to manufacture, owing to cost of materials as well as more expensive welding technology and skills required, it is assumed that the manufacturer will want a dividend to justify this extra cost. Increased sales thanks to the perception of buying a "better" bike, made out of better materials, and lighter weight (to satisfy the industry bias and promotion), will justify a higher cost of manufacture. And here is the rub, once this course is decided upon, it is inevitable that the decisions will lean toward satisfying the desire to make it lighter weight rather than more durable, because nobody would choose aluminum for more durabilty, but more for the weight issue alone. So I almost don't even need to ask the manufacturer whether they wanted a durable bike more than a light weight bike when they chose aluminum frames; the fact of choosing aluminum implies that weight alone was what motivated this move. And since any gains in light weight would more than be wiped out by engineering out the weakness in the design by beefing up the frame at vulnerable points, it is likely that this is not occuring. Whereas the steel bike is probably leaning toward durabilty from the start, simply because the manufacturer is not trying to justify the choice of a more expensive material like aluminum by cutting down on weight, and since steel is a lot cheaper than aluminum, they might as well use more of it to guard against any liability issues which might come from under-engineering the frame: since it is not being pushed to compete with the lighter weight bikes, it can tolerate being a bit heaver and it will naturally be stronger as a result. Add to this the natural strength and resilience of even the cheapest grades of steel. So without knowing the details of whether the specific bike was designed better to compensate for its inherent materials flaws, it seems reasonable for me to conclude that aluminum bikes will tend to be lighter and less durable than steel. The exceptions being the odd steel bike which is really poorly designed, or the odd aluminum bike which was built heavier to compensate for it's fatigue tendency--both of which would be possible but unusual.

But as I said earlier, this is a balancing game more that an absolute "this or that" debate, and perhaps I have overlooked the benefits of anti-corrosion and aethetics in this assessment. Meanwhile, I'm waiting for Tern's titanium and exotic-grade stainless steel frames. A boy can dream...

Addendum 2014-02-11:

I went back to my LBS and asked a few followup questions: Barry has 10 years of full-time pro bike mechanic experience; Mike has 19 years--so between them 29 years of experience to draw upon. Barry said that while almost no steel frames were brought in for breaks, they comprised about 20 to 25 % of all current sales, so the stats did not mirror the proportion of sales. Mike said that at his other bike shop selling Treks, that only about 2% of the bikes sold were steel, and only aluminum frames came back--here Thor's point has validity, although I think the stats quoted also included all frame breaks brought in for repair, not just warranty replacements of bikes purchased there, so this would include bikes purchased at other shops over a longer time span, so there may be plenty of steel bikes in this set which didn't come back with breaks. Apparently aluminum frames have come to dominate the regular bike market, but older steel frames, from when steel held the majority of the market, have had more time to break and be brought in and yet have not been a large percentage of the frame breaks these guys have witnessed. Since more aluminum bikes are being made today across the spectrum, assuming that not all are perfectly engineered, it seems likely that fewer of these bikes will survive as long as the older steel bikes which benefit from a more forgiving material. As these guys have noted, many more broken aluminum bike frames are coming in for repair or replacement than steel.


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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:40 am

January 31, 2014 - 9:15am
Re-tern



Country: UK


Hi Steve,

I am not certain of the process Tern follow when they manufacture their frames, but from my experience it appears that there has been insufficient or no post weld heat treatment on the broken weld. The stresses on the frame are very high in this area and the alloy will need all the strength it can get. 6061 Aluminium alloy that the D8 is made from can lose up to 80% of it tensile strength after being welded and therefore would need to go through a two stage heat treatment process (solution heat treatment followed by artificial aging); I hope this isthepractice that has been followed by the manufacturer.



I agree with you that there would havebeen no sensation of the crack developing due to the elastic characteristics of the alloy over steel; yes the dirty part of the fracture was on the bottom of the joint where the stresses are greatest, so I would inspect this thoroughly from now on if I were you.

I would insert pictures; however every time I try the images don't attach?



I will keep you updated


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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:41 am

January 31, 2014 - 11:20am
thor
Country: USA






all alloy frames get hardened AFTER they are welded, otherwise the whole process would be worthless...

Keith... what makes you think that ALloy frames are higher cost than steel ?  .... the other point is, that I will bet, that there are many many many more peeps out there, who have ample experience with alloy  versus steel. Not only the design people, but maybe more importantly the welders and fabrication guys on the shop floor. I have welded ( actually brazed) a Columbus sl frame some 30 years ago. Under the watchful eyes of my former boss. I can assure you that in order to do a good steel frame, you need at least or maybe even more experience than a modern alloy frame.

But You are right again in many points. Squeezing the last pound out of the total weight of the bike because of marketing hype is silly.

Best Thor

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:53 am


February 2, 2014 - 9:57pm
Keith C. Johns



Country: USA



thor wrote:

Keith... what makes you think that ALloy frames are higher cost than steel ?  .... the other point is, that I will bet, that there are many many many more peeps out there, who have ample experience with alloy  versus steel. Not only the design people, but maybe more importantly the welders and fabrication guys on the shop floor. I have welded ( actually brazed) a Columbus sl frame some 30 years ago. Under the watchful eyes of my former boss. I can assure you that in order to do a good steel frame, you need at least or maybe even more experience than a modern alloy frame.

But You are right again in many points. Squeezing the last pound out of the total weight of the bike because of marketing hype is silly.

Best Thor

I note the cost of scrap aluminum per pound is usually six or more times the cost of steel. Steel can be welded with simple stick arc or oxy-acetylene but aluminum usually requires TIG or MIG to do it right, due to excessive oxidation, and these require more expertise to learn and more expensive welding equipment. Not that steel welders are not highly skilled in their own right, it is just that aluminum requires an extra level of skills to master, I believe.

Thinking more about this, about the aluminum components of my bikes which have not failed from fatigue stress: I don't think they were primarily chosen for light weight, although weight was part of their choice. I think they were chosen for another of aluminum's good features, anti-corrosion. And then designed to be strong enough to be very durable. So they hold up, and don't fatigue appreciably. Any flex will lead aluminum to fatigue, but if the metal is supplemented by ample reserve, it will propagate so slowly as to never be a factor during the lifetime of the bike. So aluminum is not the bad boy. The bad boy is trying to make a bike too light. But when this is done with aluminum, it is especially bad since aluminum is so unforgiving of poor design.

I think anything made of aluminum should be made of solid chunks or thick tubes, and moves to hollow out aluminum parts to squeeze out a little more weight are asking for future fractures. Perhaps the manufacturer thinks they can have it both ways by simultaneously lightening the bike and saving money on buying aluminum, too. But this reminds me of food preparers who give you less food for your money, and then brag about how their meals are under a certain calorie count, and thus charge more for giving you less; my reaction is to point out that I can do even better by not buying anything and thus getting the perfect zero calories meal for FREE. Don't piss on my leg and tell me it is raining.

But even with Chromoly steel, which is so strong that thinner tubes can achieve the same strengths, and thus lighter bikes can be made with thinner tubes: my thought is, don't make it thinner! Use Chromoly and keep it the same thickness and make a really strong, durable bike. Not just lighter. Or just a little lighter but much stronger.

I realize that bikes are made for different purposes, and not all need to be as stong as, for instance, mountain bikes or BMX, but still, within their range, bikes ought to be made to last, not just made to sell fast. Of course, the buying public needs to look ahead too, and not just buy the cheapest bike, or be fooled into thinking that they can have a super light weight bike which will also last a long time. We need to educate our consumers and not feed into the industry hype that lighter is always better. Granted, as better alloys are developed, and better means of shaping tubes are employed, lighter weights are possible while maintaining durable strengths, but we must beware of lighter weights which actually come at the expense of strength and durability--unless you really want to sell throw-away bikes. I don't believe Tern is interested in making anything other than durable bikes, and so if they want to make aluminum bikes, they better be made for durability, not weight.

I came across a statistic that to get aluminum to be the same strength as steel, it has to be 3x thicker; at this amount of aluminum, it will still weigh less than the same strength of steel, but only by a small margin. Imagine how light the bike would be if it were made the same thickness as steel--but it would fail readily. Any business except a fly-by-nght con would avoid this tactic, even though it would initially draw a lot of sales--until the failures came to light. But how do we know if the bike is being made with 2.5x instead of 3x the aluminum, to fool the public into thinking they had a new super alloy. Failures would not come instantly but might take several years before this too would show its defective design through fractures. So we need to be time tested before we know for sure. And this 3x number is just for comparable initial strength, not taking into account stress fatigue over time. How much more must it be strengthened before it actually is as durable long-term as steels? 4x? 5x? I don't know this. But this will assuredly negate the weight savings initially achieved at 3x. I would say, if it must be (hypothetically) 4.5x to not only be as strong as steel initially, but resist long-term fatigue issues at every significant stress point, then the manufacturer needs to make that their choice if they are serious about durability. Or switch to a different metal which allows such durability with lower cost.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:54 am


February 2, 2014 - 9:29am
orbit

Country: UK


What was the out come of this situation? I.m asking because I was going to buy a a Tern, but after reading this I am now reluctant do do so.

It really worrys me the thought of a bike doing a "Prof Pat Pending" and turning into a uni cycle in traffic. Not saying it will happen but even the thought of such a

situation gives me goose bumps.

I imagine Tern sell a lot of bikes so two bikes falling in half does not seem that bad on the statistical side of things. However it.s the nature of the breakages and

the concequences of such an occurance which frightens me.

So it would be interesting to see what the out come of the investigation is.

Yours sinerely ORBIT. Hopfully a happy Tern owner in the future.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:54 am


February 2, 2014 - 3:48pm
Steveroot

Country: USA




I'm interested in the results of the investigation as well. One thing I wonder is whether the bikes' frames were made at the same time; the serial numbers should provide that information. There was a recall of some Verge frames last year around the time I bought mine. I am sure Tern will issue a recall if they think there's a systemic problem with the welds. It's also possible that these two cases were random failures.

Most bikes come with some sort of warning that bike riding is an inherently risky activity. Though the risk may be small, vigilance is still necessary at some level. It's not possible to have a manufacturing process on the scale of Tern or the other large bike manufacturers without having some defects. Quality assurance protocols may not be able to catch every defect.

I really didn't consider the possibility of a sudden frame failure seriously when I rode a borrowed Eclipse or when I bought my Verge. I think I'd buy another one today if I were in the market. But... I'd keep an eye on the welds and pretty much all the parts the same way I keep an eye on my old steel-framed 10-speed, my aluminum-framed mountain bike and my titanium-framed road bike.

Folding bikes have extra joints, though, and these deserve extra attention. At the moment I can't think of a frame failure that could result in the bike suddenly collapsing except a break at the head-tube/top-tube joint or at the frame hinge joint. I'd have a close look at those areas every time I folded the bike. As we've heard in at least one case, the joint seems to have started failing on the under-side... not in a readily visible place, so a bit of deliberate inspection would be required here.

So while I wouldn't say I have "blind" confidence in my Verge (or any of my other bikes), I don't fear riding it because I have looked it over regularly. There's still some risk, but like most risks, it can be managed so I choose to accept it..

I might add that many developing problems have warning signs: sounds or "feel" that if you're paying attention can be caught early. I'm not saying the two riders whose frames broke were negligent... this particular problem might well have no early warning "feel" as we've discussed previously. I speculate that a close look in the right place could, in principle, detect this problem before frame failure. If I'm right, we should see some reports here eventually. But I'm not holding my breath, or suspending my riding.

Steve



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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:55 am


February 2, 2014 - 6:28pm
vavavoom

Joined: 2014-02-02
Country: Greece



Hey everybody, new member here...

I am in the exact same position as orbit. I am just about to buy a Link D8, actually I am about to do it next week. I am probably going to go for it anyway. Judging from the company's feedback and the way that the team listens to everybody and takes action, I believe that if they find something wrong, they will not hesitate to issue a recall. So, if I see that my bike gets recalled, I'll just send it back and buy a different frame number.

This amazing company attitude is maybe the main reason that I am buying a Tern. This company's policy is a winner. It is one of a kind. Even if there are better bikes for the same money out there, I doubt that you would be able to make your comments and ask your questions to the team that builds them. Wow. Respect.

Steve, I agree with what you say about checking the welds, etc, but this is not how it is supposed to work, from a company's viewpoint. I mean, welds are not meant to be checked by the user. No vechicle manufacturer that I am aware of recommends that you check their welds (I could be wrong). If they are uncertain about the single most important thing on any vechicle, they'd better not manufacture it at all.

My main means of transportation is a motorbike *until I buy the tern*. Now, if Suzuki for example tells me to check the welds for cracks, as a standard user manual-procedure, I will never ever ride it again. Ok, it's not aluminum, but it is irrelevant to my point : If a motorbike frame cracks (which has happened), it would be lucky for your body to remain in one piece, even luckier for you to stay alive and you'd be the luckiest person alive if you would stay unharmed. If Suzuki was to trust me, the end user, to inspect the frame welds....that would seriously put me off. I would assume that they are relying on me, the non-mechanic, to put my life on the line by making judgements for a very technical issue. So, if I'm the one who is checking the frame, who is the one who's welding it? A toddler? I don't believe that any company would take such risks. I hope you understand my viewpoint, as English is not my native language.

Also, 2 broken frames is anecdotal. If you take into account that the d8 is cited in many websites as the company's best seller, you can imagine how many d8's are out there. I've checked in various forums, and I haven't found any other such cases. So, I believe that these things are -sadly- bound to happen sometimes.

I will keep on checking frequently, because it is very interesting...

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:55 am


February 2, 2014 - 8:29pm
orbit

Country: UK



Vavavoom has a very good point. I work in manufacturing(car parts not bikes). I would imagine that the area that broke is a safety critrcal area and as such would have many procedures in place to make sure it will not break under normal use.

However we should make some checks on our bikes, but as vavavoom says we are not all experts, defects can be missed. The big issue here is would the two riders have even seen the defect if they had looked?

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:56 am


February 2, 2014 - 8:45pm
Steveroot

Country: USA



vavavoom wrote:

... welds are not meant to be checked by the user. No vechicle manufacturer that I am aware of recommends that you check their welds (I could be wrong). If they are uncertain about the single most important thing on any vechicle, they'd better not manufacture it at all.

Inspection of the welds falls under "general inspection" of the bike. If you can find a manufacturer that offers a guarantee that no part of the product will have a problem, be sure to let us know.

Meanwhile, with due respect to the two riders who had the problem, I think we're possibly making a mountain out of a mole hill. Two frame failures reported out of many (thousands?) does not necessarily mean that this is a general problem. The problem is being looked into, and I think more speculation at this time is counter-productive. I hope the results of the investigation will be released, or at least summarized, once it's complete.

Meanwhile, now that there is general awareness of this as a possible problem, why not keep an eye on this joint? Add it to the list of things you'd check routinely: tire pressure, chain lubrication, brake shoe alignment... and so on.

Steve

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:57 am


February 2, 2014 - 11:40pm
Keith C. Johns




Country: USA


vavavoom wrote:

...Judging from the company's feedback and the way that the team listens to everybody and takes action, I believe that if they find something wrong, they will not hesitate to issue a recall. So, if I see that my bike gets recalled, I'll just send it back and buy a different frame number.

This amazing company attitude is maybe the main reason that I am buying a Tern. This company's policy is a winner. It is one of a kind. Even if there are better bikes for the same money out there, I doubt that you would be able to make your comments and ask your questions to the team that builds them. Wow. Respect.

I really want to applaud what you have just said here. I think this openness to communicate directly with the people who buy and use their products sets Tern apart from all the others. And while I will always respect Dr. David Hon for what his company Dahon has done for the folding bike industry, I must shout out kudos to his son Josh Hon, owner of Tern Bicycles, and his team for building on this great idea and working into it his own fantastically innovative business ethic, which includes this openness to direct communication with the customers. Thank you for noticing this important distinction about this company.

vavavoom wrote:

Steve, I agree with what you say about checking the welds, etc, but this is not how it is supposed to work, from a company's viewpoint. I mean, welds are not meant to be checked by the user. No vechicle manufacturer that I am aware of recommends that you check their welds (I could be wrong). If they are uncertain about the single most important thing on any vechicle, they'd better not manufacture it at all.

...

I will keep on checking frequently, because it is very interesting...



In your shoes, I would be sure to do the following while awaiting the report: (when riding your bike)

<> Always wear a protective helmet.

<> Always wear gloves.

<> Always wear safety goggles.

<> Consider wearing other protective gear like elbow and knee pads.

<> Choose roads with less traffic.

<> Choose travel times with less traffic.

<> Choose to travel during daylight hours.

<> Use a mirror.

<> Avoid riding in the rain/snow...

<> Avoid jarring motions such as jumping off curbs or pot holes.

<> Listen carefully for any new sounds while riding, and investigate them.

<> Be sensitive to any differences in feel of riding and investigate--it could be something giving way.

<> When investigating, use a magnifier to see clearly under strong light.

<> Stop riding and walk the bike if you notice anything which looks like a crack on a critical portion.

<> Keep the bike tuned properly--alignment, wheels trued, lubrication, tire pressure and wear, etc.



Note that all of these apply to riding any bike, but are advised for the bikes in question here especially. Since none of us ever can control every aspect of our bikes, it just makes sense to be aware of warning signs and realize that we are always ultimately personally responsible for the ridable condition of our bikes. No matter how it came from the factory, things age or get out of true and require maintenance.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:58 am


February 3, 2014 - 3:40am
vavavoom

Country: Greece


Steveroot wrote:

Inspection of the welds falls under "general inspection" of the bike. If you can find a manufacturer that offers a guarantee that no part of the product will have a problem, be sure to let us know.

Meanwhile, with due respect to the two riders who had the problem, I think we're possibly making a mountain out of a mole hill. Two frame failures reported out of many (thousands?) does not necessarily mean that this is a general problem. The problem is being looked into, and I think more speculation at this time is counter-productive. I hope the results of the investigation will be released, or at least summarized, once it's complete.

Meanwhile, now that there is general awareness of this as a possible problem, why not keep an eye on this joint? Add it to the list of things you'd check routinely: tire pressure, chain lubrication, brake shoe alignment... and so on.

Steve

Exactly. No manufacturer can give you such guarantee, that's why you have the scheduled service, where technicians check up your vechicle.

I completely agree with what you say about speculating and exaggerating, it is pointless. Absolutely pointless.

And, of course I would regularly check all joints even without reading this thread. After all, I like these things, I'm a DIY guy. But lets say that I wouldn't trust my girlfriend to do this, she is hopeless in such things and this is why I expect from the company to not expect this from her. On the other hand, I do not expect from any company to build an invincible bike. This is why I do agree with user manual phrases such as: "If you notice anything wrong, bring your bike to the LBS" or "bring your bike for an annual checkup" Do you get my point?

Lets not forget that tiny cracks which would compromize the integrity of the frame could be very difficult to spot, especially if you have a black frame.

Enough said, I think that it is a really not as important as we made it.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:59 am


February 4, 2014 - 8:19am
Re-tern



Country: UK

In Reply to Steveroot who stated that ".....many developing problems have warning signs: sounds or feel that if you are paying attention can be caught early".I would like to point out that I am aware of these things and having been an avid cyclist for 30 plus years I have experienced these warnings before, much as you do when you drive a car and notice noises others don't as you are the one that drives it every day. I have also experieced cracked frames in mountain bikes which normally start with an abnormal noise and then some minor movement can be felt in the frame etc. Additionally as a degree qualified Mechanical Engineer and an experienced Mechanical Inspector, I do know what I am looking for when I inspect my bike for defects/abnormalities, probably more so than most. I do inspect my bikes once every few weeks (not before every ride that would be crazy), usually when I was washing the bike and tightening everything up that reguarly came loose. I couldn't visably see any sign of cracking around the weld, and I did look as I was aware this was a higly stressed area, although the crack does appear to have propagated for a while before it finally failed as there was signs of dirt inside the crack. Th frames are warranted by Tern for 5 years; mine lasted 13 months and Lee's only 10 months; I am also aware there are lot of D8's out there and these are fairly isolated incidents, although if this had happened in my field (avaiation) the oucome could have been catstrophic. I am not saying that the quaility control should be the same for bicycles as in avaition, otherwise bikes would be incredibly expensive, but Tern should react quickly and publish the results of their findings

. I would like to point out that when I spoke to the guys in the bike shop that I bought this from, their first reaction was "oh... another issue with a Tern", so I wouldn't say their experience with selling the product has been great, although this was the first frame failure they had seen in the shop. Just be aware of thi if you arethinking of buying one; they ride great, better than my new Brompton, but they really need to improve their QC to be a class leader, and with other new companies selling similar product with better quality kit for the same price, Kansi for example, they need to react quickly to restore confidence in their product

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 1:59 am


February 4, 2014 - 9:48am
dshawkins

Country: UK




Hi all,

Sorry to hear about my fellow commuters in London having some pretty nasty incidents. I too commute daily from Waterloo to the East End and back on a Eclipse P9. My bike is 3 months old and is used on roads with some pretty big pot holes and cracks back home in Surrey, thery are not much better in London, I for one will be checking this joint before every ride from now on.

Meanwhile I have been riding MTB's with ally frames up hill and down dale for years and over all sorts of terrain, but these are made for such purpose. If Tern has a problem with the folding mechanism it is likely to be because of insufficient material to make the area strong enough to withstand repeated stress. There are many instances where parts have failed and have been beefed up to make them strong enough to do the job properly. Titanium and steel all have their problems and are not any less susceptible to stress fractures and sudden failure, titanium more than most!

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:00 am


February 4, 2014 - 1:35pm
Steveroot

Country: USA


Re-tern wrote:

In Reply to Steveroot who stated that ".....many developing problems have warning signs: sounds or feel that if you are paying attention can be caught early".

I was not questioning your observation skills, background, or any other qualifications. I did not say that *your* particular developing problem had any detectable warning signs. I said "many" of them do, which I would argue is true... but certainly not all of them. Sorry for the confusion.

Steve

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:00 am


February 4, 2014 - 5:48pm
dshawkins

Country: UK


Hi all,



The below link is interesting although it is for a different model in a different country.

http://www.bike-eu.com/Laws-Regulations/Recalls/2013/7/Tern-Bicycles-Recalled-1308087W/

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:03 am


February 4, 2014 - 11:01pm
edwinic



Country: Philippines



dshawkins wrote:

Hi all,



The below link is interesting although it is for a different model in a different country.

http://www.bike-eu.com/Laws-Regulations/Recalls/2013/7/Tern-Bicycles-Recalled-1308087W/

its a good move. Noticeably, there are numerous recall news!....its a good move.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:04 am


February 5, 2014 - 1:22am
Keith C. Johns
Keith C. Johns's picture



Country: USA



In this thread, I started out by saying that aluminum frames were inherently prone to stress fractures, but then amended my view to state that it mostly depends upon the design of the bike, i.e., the engineering of its materials, and that with properly engineered designs, aluminum might outlast steel which had been poorly designed. A too thin steel bike will fail before a beefy thick aluminum bike. It comes down to whether the bike was designed to be durable or whether its design had been compromised rather to chase the light weight prize. I hope Tern is focused on durability in every instance, and if this is true, I believe they can continue to make aluminum alloy bikes without worries about long term stress fractures in the frames. If their choice of aluminum was for other reasons than "keep it light!" then I have sincere faith that this current issue will turn out to be isolated and easily preventable in the future, too.

If, however, it is due to their falling under the industry mantra of "Light Weight is more important than anything else!" then there will be more and more of these instances until they reorganize their priorities toward making durable bikes out of aluminum, no matter what the resulting weight ends up being. And I am suspicious of the choice of aluminum as self-evident that light weight was the reason for the choice. But anti-corrosion and shiny metal looks may possibly be other reasons, and perhaps weight is not Tern's primary reason for using only aluminum.

Having stated that a poorly engineered steel bike will fail too, I want to react to your statement, " Titanium and steel all have their problems and are not any less susceptible to stress fractures and sudden failure, titanium more than most!" I disagree. All things being equal, and if equally well engineered as a durable aluminum bike, titanium and steel bikes should be far more resilient than aluminum, and capable of taking more punishment than aluminum owing to this flexibility. I will go even farther and say that a mediocre-engineered bike made out of steel or titanium will be able to hold up as long as a well engineered aluminum bike, owing to the forgiving nature of steel and titanium, especially titanium. Materials can be the deciding vote when design is not perfectly strong.

But to restate my view, ANY material will last a lifetime if it is designed to be durable from the start, and not compromised to impress the "Lighter is Better" crowd. We are waiting to learn which way Tern decided to go with this. And if they under-engineered their bikes to keep them light, will they change their minds and make them stronger albeit heavier? Or perhaps this particular Tern model is just an instance of the manufacturing process not matching the design specifications, and greater oversight is necessary during manufacturing.

Judging from the overall great attitude this company exhibits as evidenced by their willingness to listen to us on this forum, I suspect that it will make the best possible decision to remedy this once the cause is fully understood. I have faith in Tern.



dshawkins wrote:

...Meanwhile I have been riding MTB's with ally frames up hill and down dale for years and over all sorts of terrain, but these are made for such purpose. If Tern has a problem with the folding mechanism it is likely to be because of insufficient material to make the area strong enough to withstand repeated stress. There are many instances where parts have failed and have been beefed up to make them strong enough to do the job properly. Titanium and steel all have their problems and are not any less susceptible to stress fractures and sudden failure, titanium more than most!

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:05 am


February 5, 2014 - 8:03am
Lee Tibbetts

Country: UK


This thread makes for some interesting reading now!

dshawkins wrote:

Hi all,



The below link is interesting although it is for a different model in a different country.

http://www.bike-eu.com/Laws-Regulations/Recalls/2013/7/Tern-Bicycles-Recalled-1308087W/

yep... EXACT same place as my Link D8!!! The weld the held the top frame to the folding bracket.



I agree with James that checking the bike before every ride just isn't possible. I checked my bike often and found nothing untoward, however my bike was painted black so that may have disguised any fault.



I still have to post the images of my Link D8 (now 2 unicycles!). Also, just to let you all know, I spoke to Mark (UK Tern Rep) on the phone last week. A really nice nice and happy to help.

Evans however... I received an email (ONLY after pestering the staff at the store where I bought the bike from and sending them an email directly to their head office!!) a month after I dropped the bike in. Still not had any offer of a replacement OR a loaner bike. I have to be clear that the Evans staff at the West End branch in London ARE good and friendly but obviously they cant do anything without head office.



Interestingly though... Evans Cycles have removed the Tern link D8 from their website, however If you google search it you can get to the Evans Cycles Tern Link D8 page... it says the bike is now discontinued. Interesting.


[url= http://www.evanscycles.com/products/tern/link-d8-2014-folding-bike-ec045733] http://www.evanscycles.com/products/tern/link-d8-2014-folding-bike-ec045733[/url]

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:06 am


February 5, 2014 - 8:03am
Steveroot

Country: USA



dshawkins wrote:

Titanium and steel all have their problems and are not any less susceptible to stress fractures and sudden failure...

Titanium, steel and aluminum have different physical properties, which must be taken into consideration when designing a frame. If identical frames were constructed of each material, they most certainly would not have equal susceptibility to fatigue fracture or any other type of "sudden" failure.



dshawkins wrote:

...titanium more than most!

What is your evidence for this?

Steve
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Tern Verge S11i (2013), Dahon Mu XL (2006), Dahon Helios XL (2003), Strida 2 (2002), Airborne Carpe Diem (2002), Trek 6000 (2000)

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:06 am


February 5, 2014 - 4:48pm
dshawkins

Country: UK



Hi Steve,

My father was an aircraft engineer and the chief quality control inspector for a very large international manufacturer and titanium is widely used within that industry, I work within the scientific community and have been around all sorts of bikes for 40 plus years (never had a carbon frame though), between the two of us and not going in to specifics we have seen our fair share of titanium failures. But my point is that titanium is a difficult material to weld correctly and if not done to the very highest of standards it is easily compromised and then it is a failure waiting to happen. Ally and steel do not have that problem to the same extent, with titanium its all about the joint, otherwise the material is the ultimate if you can afford it.

Personally at the moment I would sooner have an ally bike with the tubes hydroformed and joints butted and swaged to a higher density and not have to worry about the vast additional cost of a titanium frame or the luxury of carbon (and there are some bad carbon components out there too, but thats another story).

No one material is perfect, they are all a compromise to some extent.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:07 am


February 5, 2014 - 5:26pm
Steveroot

Country: USA



dshawkins wrote:

No one material is perfect, they are all a compromise to some extent.

We can sure agree about that! The corollary probably would be that if the frame is designed well, any material works. Heck, there are high-end bikes made of bamboo!

My personal favorite, if I could afford it, would be lugged and brazed steel... Rivendell, for example. I've got an old Motobecane from the 1970s; it's a 10-speed, but I'm thinking of converting it into a hub-gear city bike because it's a pretty frame. I also have a 12-year-old titanium Airborne. Its frame was made by a Chinese aerospace company. It was affordable, and has been a good bike; the welds appear (to the eye, not necessarily to the X-ray) perfect. The front fork is steel, however. My "old reliable" mountain bike is a Trek that's over 13 years old... aluminum frame, no issues. The only bikes I've had frame crack issue with are my two old Dahons... both aluminum framed. My Tern seems much more solid than the Dahons, but as I am a bit over 200 pounds I keep an eye on the welded joints... so far, so good.

Still waiting to hear something about the frame latch failures...

Steve

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:07 am


February 5, 2014 - 6:20pm
dshawkins

Country: UK



I too think Tern displays a great attitude and I dont think that they have underengineered the bike. The problem looks isolated to a batch and I would even go so far as to wonder what type of riding is being undertaken. The reason I say that is because here in Britain our roads are atrocious with large cracks, potholes, missing road surface (mettalling) and thats besides the dips and bumps from drain covers and manholes, my point being, do these conditions that predominate in this country expalin such a failure at this susceptible joint. I have limited knowledge of roads outside of Europe but I am sure ours are some of the worst. And on this basis I dont think this fault, if it is a fault is neccesarily that of either the rider or the company.

I have a P8 Eclipse and this is my first folding bike in over 40 years of riding as I have always shied away from them in the belief that they are fragile and prone to breakage. However that said I have had 2 titanium road bikes that were far too flexible for their own good and all failed at the steerer tube down tube weld, I also have a steel framed bike that failed on the chainstay bottom bracket weld and another steel framed bike from a big well known french car manufacturer that is now 30 years old and apart from some rust is perfect. Meanwhile my mountain bikes which are all ally from big names have yet to develop any faults. Is it that the mountain bikes really are over engineered and made to take the rough stuff whereas my road bikes are meant to be on smooth tarmac for their entire life but are subjected to dodgy road surfaces and then fail? I am positive that is the reason why mine failed and at times i wonder if I should wear a gum shield to stop my teeh from chattering through road vibrations. The material in each case is fine but the joints have failed and this is where the potential problems lay with any frame and in this case the folding joint.

I too have faith in Tern.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:08 am


February 6, 2014 - 12:43am
Keith C. Johns


Offline

Country: USA


dshawkins wrote:

Hi Steve,

My father was an aircraft engineer and the chief quality control inspector for a very large international manufacturer and titanium is widely used within that industry, I work within the scientific community and have been around all sorts of bikes for 40 plus years (never had a carbon frame though), between the two of us and not going in to specifics we have seen our fair share of titanium failures. But my point is that titanium is a difficult material to weld correctly and if not done to the very highest of standards it is easily compromised and then it is a failure waiting to happen. Ally and steel do not have that problem to the same extent, with titanium its all about the joint, otherwise the material is the ultimate if you can afford it.

I have heard that titanium is difficult to weld, and that adds to the cost of using this material. But if properly done, Ti bikes enjoy optimal resilience and corrosion resistance, too. And the resultant frame is MUCH less likely to experience stress fractures than an equally well designed, and skillfully welded aluminum frame. We are talking here about properly manufactured bicycles and just comparing the differences in frame materials--if you want to debate the skills of the workforce, that opens a whole new subject, but I will stipulate that I am confident that Tern would employ qualified welders for titanium, if we were ever so lucky as to convince them to go that route. That such a frame would cost considerably more is beyond the scope of our discussion: we were not debating the relative durability per dollar spent.

As for steel, while a rotten weld would weaken it too, a properly welded frame, equally well engineered as a comparison aluminum alloy frame, would outlast the alloy frame when both are equally subjected to a torture test. And if we were debating durability per dollar spent, hands down, the steel one would win every time over both Ti and Aluminum Alloy.

dshawkins wrote:

Personally at the moment I would sooner have an ally bike with the tubes hydroformed and joints butted and swaged to a higher density and not have to worry about the vast additional cost of a titanium frame or the luxury of carbon (and there are some bad carbon components out there too, but thats another story).

No one material is perfect, they are all a compromise to some extent.

I take it that you are willing to compromise to get your lighter bike. Just be aware that you will trade durability proportionally for lighter weight. And both qualities suffer when you insist on the lower cost, too, because to shave a few dollars, low cost will rush the welder and eliminate the quality assurance elements. You do get what you pay for, ultimately.

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:09 am

February 8, 2014 - 12:10pm
vavavoom

Country: Greece



Ok, maybe somebody is starting to panic, If you look at the first comment of this video. Two broken frames, and now you have people warning others on youtube to be careful when riding this bike. This may cause bad publicity if it gets viral and it is sad, because the importance of 2 broken frames out of thousands sold does not justify such things, unless an official warning is issued from Tern.

http://www.youtube.com/watch?v=hcyJYY8zbyw

 Crying or Very sad

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Re: Tern Link D8 frame shearing in two

Post by Admin on Fri Apr 04, 2014 2:17 am


February 8, 2014 - 9:29pm
orbit

Country: UK


That is why Tern must find the results fast. I still have not purchased a Tern although the bikes look great. I just would not feel comfortable with the thought of this sort of breakage. If a diamond frame fails it does not tend to fall in half completely it has a lot of reserve in the frame design.

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