Abu Mahendra

You really think Bickerton is gonna chime in here? The modus operandi is to keep it all in the shadows. As with his previous posts, he'll wish to avoid the sunlight, and tell people to email him privately if they have any questions.

Earlier he said he knew nothing about the bogus suit against you. You think he's now informed himself, or he continues in willful ignorance. Bickerton, Shtickerton...

Technician

That's where the idea of adding a supporting truss came from...

downtube

No I don't. I don't appreciate his fake condolences after a failure occurs. There have been three recalls with many frame failures, and recently there is another....I was not surprised, I find it hard to believe anyone was surprised.

Additionally on their forum they argued that their bikes are the safest in spite of the failures.....do these people understand the word statistically significant? Words do not apply when something can be statistically proved.

Thanks,
Yan

Bonzo Banana

That's often the case with recalls. Many people don't hear about them. My mother had a dangerous Hotpoint dishwasher (made by Bosch) and despite buying it new and being at the same address she never received any letters regarding it. It was only when she wanted to sell it and I went online to see its value for her did the recall information come up. Many companies are forced to do a recall because of the large number of units that are failing but clearly it is hugely expensive for that company and they are resistant to being proactive when doing so costs them a large amount of money.

Mountain bikes are difficult to recall because manufacturers claim they may be damaged in use with excessive drops and abuse but still when Decathlon's Rockriders were failing often only weeks after purchase in large numbers they were forced to recall them.

It seems like Tern don't really manufacture the bike themselves. They buy in the frames and components. It's a bit like Walmart, they do an order to factory #A but when they want to order again factory #B is cheaper but maybe factory #B can't produce all the quantity they need, so they buy from factory #C but then it turns out factory #C is a bit crap and they go back to factory #A who have always made a decent frame but cost 30 cents extra per unit. Later factory #C tenders again with a lower price after making improvements in manufacturing. It's pretty much a lottery with regard quality when a brand isn't really a manufacturer themselves and buy from multiple factories. There are brands that don't manufacture themselves but have an exclusive single factory arrangement like Birdy. In fact many of the improvements in Birdy bikes seems to have been instigated by Pacific Cycles of Taiwan the manufacturer.

My last comment is simply that innovation is not a friend of product quality. When you have a car model that has reached the end of its life, at that point its probably at its best possible quality and reliability. When the new model comes in there is the long process of discovering design problems and correcting them.

There is a lot to be said for the slow evolution of a bike design rather than radically refreshing the model range regularly with all the quality problems that entails in my opinion.

Here's a Dahon with a simple fix for a broken frame.



This Tern broke with a child rider of only 43kg although admittedly its the hinge so rider weight may not be the main factor.



Another one here caught before breaking.

Technician

WoW...and I Thought that new 'It' film was scary!

ThorUSA

about that jetstream above
cool guy ... actually i have a pic of his bike on my website
he was doing heavy duty downhill stuff with his bike. He told me myself, despite that ,we did replace the frame for him and a few other parts... gonzo rider for sure. he did some epic tours.( i would not ride with a full size bike)
thor

Abu Mahendra

Their use of hi-tensile steel in the second decade of the 21st century is backwards, particularly when one takes the price, and the hype about the quality of manufacturing into account.

dahoneezz

I think the failure mode is fatigue. Repeated stress cycles. Crack propagation. So not a small load of 43 kg at one instance, but cyclical loads over time.

With regards to the new bike frame cracks, are there any further details? When did it occur? Date of manufacture of the bikes? Are those on the recall list?

Joe Remi

In comparison to a similarly priced aluminum Tern which snaps in two? Sorry, my hi-tensile steel M6L looks great, rides great with no squeaks, folds into a magic little square, and goes back to riding mode with simple, tight hinges. It even worked as a fire-road bike last weekend without complaint, much to the amusement of the local mountain bikers. Brompton makes an excellent folder.

Abu Mahendra

False choice. The comparison for the rational thinker--i know that hardly applies to you--is not a bike with an obvious design flaw and/or poor workmanship. Wake up and smell some logic. You like your boat anchor of a bike? Swell, knock yourself out.

Joe Remi

The person you responded to was clearly comparing Bromptons to Terns.

badmother

I know. Searching for 24" rims at the moment and find several in "wheel chair size". Also stripped several wheelchairs for quick release hubs and axels for trailers

Bonzo Banana

A lot of premium products use high tensile steel, cars, motorbikes etc. I don't believe the Brompton frame is all high tensile steel anyway. That's why they use the brazing technique so they can use a selection of steel types each giving different properties for each part of the frame. However I think the majority of the frame is high tensile but considering the extended life this gives the frame over aluminium and the fact Brompton's cost so much you don't want to be replacing the bike after 3-4 years. Steel is more compact, it may not make the lightest frame but it can make the most compact frame that still offers decent ride quality, compared to aluminium anyway.

Bonzo Banana

I just love the simplistic solution. Shouldn't really have put the same image in with the Tern images which are genuine product quality failures. You can see the level of abuse that Dahon was getting just looking at that image.

I got the images from this thread which was very interesting. Make sure the browser you use supports translation unless your russian of course.

******************** ********************? ??? ? ********** ********************

Technician

I think the scariest thing about those pictures especially the first few is just how thin the frame material is on those bikes. If it were steel no problem but aluminium ? I hope the frame alloy is thicker than that on my folder....to heck with the weight I just want it to stay together !

sweeks

This one is an example of a fracture of one of the pivot bolts. This problem was less widely reported than the weld failures, mainly because they were usually noticed before both bolts broke, so the bike (like this one) did not break completely into two parts.
I think the most likely reason these bolts broke is that the upper and lower bolts were not completely coaxial, and the transition from threaded to unthreaded portions acted as a stress riser. The revised joint has a single pivot rod with no diameter changes.


This looks like a weld defect, but probably not one that is leading to failure, for two reasons. First, most of the published images of the frames that broke showed evidence of corrosion at the lowest part of the joint. This suggests that the cracks started there, where the tensile stress is greatest, and propagated upward until the remaining weld could not support the load. There was one image on the Tern Forum of a small fracture line at the bottom of the joint, which is what would be expected; unfortunately, this was probably the last place anyone would look.
Secondly, there is paint *over* the defect, suggesting it was applied over an existing crack and also hasn't progressed since. I wonder why it wasn't picked up during inspection at the factory though.
Steve

Bonzo Banana

I would disagree about not leading to failure but see what you mean about existing paint. If the frame was supplied bare or primed to Tern who do the final paint finish I guess while processing the crack could have appeared and then the final paint coat hid the crack from view slightly. I'm amazed that this crack wasn't picked up at the Tern factory that did final assembly. I don't think it would have been repainted since leaving the factory. My opinion was that Dahon and Tern were about equal quality but the more I read the more I put Tern not just below Dahon but much worse than many of the smaller folding bike companies of China who churn out low numbers of bikes. Of course they may have improved dramatically more recently but I have that feeling that you get when you simply don't trust a manufacturer. My perceived quality of Tern bikes is now very low. If I see a Tern rider I think instead of being impressed by their stylish bike I'd more likely feel sorry for them wondering if they will end up under an articulated lorry if the frame breaks. I realise this may not be fair and statistically unlikely but by what I've seen is certainly more true of Tern than any other brand.

sweeks

Certainly any visible defect in a welded area is cause for concern. The history of that particular frame is not given, so it's hard to say whether its defect is structurally significant. If it's a brand new bike, then the crack is more worrisome. If it's got a few thousand miles on it, not so much, as the crack has not propagated since it was painted.

I certainly would not have accepted delivery of a frame like that. But I'm happy with my VS11i (no need to pity me! I'm pretty vigilant on frame inspection even with the new design) and am looking forward to Tern's reputation getting back up to where I think it should be. There is a fairly steep climb on that issue at present, I am afraid.

FWIW, I've had two Dahons break on my watch, so I'm well aware of the fine line between lightness and durability in aluminum frames.

Bonzo Banana

When I had a second look at that image I assumed that initially the whole crack was painted but with use and the fatigue of riding it started getting worse/larger from the bottom upwards. If you ride a bike and the frame fails it will likely want to bend or break upwards in a U or V shape. The crack on that frame is gradually increasing in size from the bottom upwards. To me that is crack working towards failure which was luckily caught before a possibly life threatening frame failure.

Thats the case I've always made that Tern and most of the Dahon's are performance folders with lightness and speed part of their appeal but with a shorter frame life just as you would expect from a performance full size road bike. It's clear there are strong Dahon's though with their original models and the new Curl but I don't actually know of any strong Tern models even if they were made to a consistent high quality. At best you are going to get a weaker than average frame only capable of the stated maximum rider weight and at worst pretty much destined to fail whatever the rider weight. It's the bike version of this.

sweeks

I'm a big fan of hyperbole.

Look at it again... it actually appears narrower closer to the top. Also, if it's propagating upwards, what's the explanation for the paint remaining intact over the crack? It's not "stretch" paint. Furthermore, the origin of the crack (if it is actually the origin) is not at the point of greatest tensile stress on the frame (the bottom of the frame tube).
It doesn't change the fact that it should have been caught and repaired or scrapped at the factory though.

Steve

Bonzo Banana

I just wanted to post that animated gif

Abu Mahendra

Again, false choice. Obviously--you folks are deliberately dense when it suits--is not between Hi-Ten and Al, but rather between Hi-Ten and Chrome Molybdenum Steel.

You know, I know, we know that if the shoe were on the other foot, that is, if the Dahons and other blue-collar folders were made of Hi-Ten, you'd view that add further evidente if they their low quality. Once again, evidente if the elitism and bias that afflicts this channel.

linberl

I prefer steel bikes, but I don't understand why brompton uses hi-ten when nearly all other steel bike manufacturers (except Walmart-type stuff) use base cromoly, butted cromo, or better. I would not expect it to be cost related, given what they charge for a bike.

bargainguy

In the world of bicycle messengers, using a hi-ten (or even MTB) frame is not unusual. Less likely to suffer damage from repeated abuse - potholes and the like. While it's a little heavier than cromoly, less likelihood of downtime from frame damage, which means less worry of not having a paycheck, a fair trade-off.

I wonder if Brommies fall into the same category. A folder has additional stress to deal with - frame stress around the folding bits as the bike is being ridden as well as the stress of being folded/unfolded. So in a sense, it's over-engineering the frame at the cost of a little more weight. You might have to push a little harder from the extra weight, but it's well worth having your Brommie frame intact at the end of the day.

linberl

Ok, I can see that. Bike Fridays don't have mid-tube frame hinges so they can use a lighter steel. Moultons are steel but their hinges aren't the usual Dahon/Brompton/Tern frame hinge. So maybe bikes with those kind of hinges benefit from the heavier material? And maybe the aluminum Tern uses contribute to their failure?

From what I've seen, low end MTB use hi-ten. Messenger bikes tend to be beaters as well. Just not something I expect on a high-end bike. Are there any other bikes out there $1000+ that use hi-ten? I'd be surprised. I would expect the "over-engineering" to be in triple butted framing at that price.