This is a bit worrying

[Gunk]

I didn't buy a T-Line because unfortunately, somewhat obviously I don't have over four thousand pounds to spend on a bicycle

not many do, and if I did have a spare £4000 to spunk on a bike it wouldn’t be a Brompton.

 

[wafter]

I simply do not get why you are so upset.

Likewise.. you do understand that liking something and being critical of it don't have to be mutually exclusive?

get the popcorn in guys

No need; I've expended all the energy I'm prepared to on this drama..

 

[Illaveago]

I have the crankset I took off mine before fitting the hope one if anyone wants to make an offer

Has it only done 4999 miles ?

 

[Illaveago]

Well my first impression on seeing the break was that it was a poor design! As fossyant said I've not come across one before.
If it is Brompton who are recommending the cranks should be changed every 5,000 miles it would make me question why? If it is them then they must know of other failures and why haven't they changed to a different crank or manufacturer?
If it was caused by fatigue due to loading why don't they fit a smaller chainring or is that because of wheel size?
If I had a Brompton I would looking for an alternative make of crank .

 

[berlinonaut]

Well my first impression on seeing the break was that it was a poor design! As fossyant said I've not come across one before.

I am really wondering how this is possible and why everyone in this thread seems to blame Brompton for this. Even the article on wikipedia about material fatigue is illustrated with a broken bicycle crank:

https://en.wikipedia.org/wiki/Fatigue_(material)

So this can really considered to be common knowledge and clearly not a problem of Brompton.

If it is Brompton who are recommending the cranks should be changed every 5,000 miles it would make me question why? If it is them then they must know of other failures and why haven't they changed to a different crank or manufacturer?

As said before: It is not only Brompton that recommend exchange intervals for aluminium parts and not only cranks are affected but also bars and other aluminium parts. It is common thourhgout the bike industry and the cause is simply because of the properties of aluminium parts. Finger pointing on Brompton is thus simply a sure sign of ignorance and lack of knowledge on your side. It is obvious if you look once more at wikipedia, this time on the article about fatigue limits. Recognize the red line for Aluminium and the blue line for steel in the graph:

https://en.wikipedia.org/wiki/Fatigue_limit

There are tests for crank fatigue in ISO 4210 (on the norms that apply to bikes and are mandantory to pass to be allowed to sell them within the EU):

There has been lots of research about the topic, i.e. this:

• Fatigue failure analysis of bike crank arm using solidworks simulation (alternative version here and here)
• Comparative analysis between aluminium and steel based bicycle crank using numerical simulation
• Validation and Improvement of a Bicycle Crank Arm Based in Numerical Simulation and Uncertainty Quantification
• Influence of anodized depth on fatigue life for bicycle cranks

There are also articels about the topic like i.e. this:
https://velo.outsideonline.com/road/road-racing/technical-faq-aluminum-frame-crankarm-fatigue/ including this image:

Of course you are free to ignore all this real world evidence, mechanical basics and scientific research. Then (and probably only then) you may come to a conclusion like this:

If it was caused by fatigue due to loading why don't they fit a smaller chainring or is that because of wheel size?
If I had a Brompton I would looking for an alternative make of crank .

It lacks foundation, but of course you are free to claim whatever you want to claim.

 

[brommieinkorea]

I am really wondering how this is possible and why everyone in this thread seems to blame Brompton for this. Even the article on wikipedia about material fatigue is illustrated with a broken bicycle crank:
View attachment 706553
https://en.wikipedia.org/wiki/Fatigue_(material)

So this can really considered to be common knowledge and clearly not a problem of Brompton.

As said before: It is not only Brompton that recommend exchange intervals for aluminium parts and not only cranks are affected but also bars and other aluminium parts. It is common thourhgout the bike industry and the cause is simply because of the properties of aluminium parts. Finger pointing on Brompton is thus simply a sure sign of ignorance and lack of knowledge on your side. It is obvious if you look once more at wikipedia, this time on the article about fatigue limits. Recognize the red line for Aluminium and the blue line for steel in the graph:
View attachment 706554
https://en.wikipedia.org/wiki/Fatigue_limit

There are tests for crank fatigue in ISO 4210 (on the norms that apply to bikes and are mandantory to pass to be allowed to sell them within the EU):
View attachment 706556

View attachment 706557

There has been lots of research about the topic, i.e. this:

• Fatigue failure analysis of bike crank arm using solidworks simulation (alternative version here and here)
• Comparative analysis between aluminium and steel based bicycle crank using numerical simulation
• Validation and Improvement of a Bicycle Crank Arm Based in Numerical Simulation and Uncertainty Quantification
• Influence of anodized depth on fatigue life for bicycle cranks

There are also articels about the topic like i.e. this:
https://velo.outsideonline.com/road/road-racing/technical-faq-aluminum-frame-crankarm-fatigue/ including this image:
View attachment 706558

Of course you are free to ignore all this real world evidence, mechanical basics and scientific research. Then (and probably only then) you may come to a conclusion like this:


It lacks foundation, but of course you are free to claim whatever you want to claim.

Posting a photo of crash damage does not help your argument, but mostly I agree with the German this time. But , 5000 miles does seem a low limit, quite possibly since Brompton was incepted as a final mile solution no one thought the things might surpass this kind of distance in a couple of years. The cranks should be either solid aluminum or tubular steel, but that's just me because I prefer things a little overbuilt. And steel is NOT heavier than aluminum because aluminum must be 3 times as thick and just as heavy to be just as strong. Oh, the brakes are trash, any competent engineer who proposed a rubber block against an aluminum disc to stop a vehicle other than a bicycle, would be fired and laughed out of the industry, or prosecuted if the fecking thing got produced.

 

[berlinonaut]

I’ve never seen that before in all my sixty three years cycling.

I have heard of it on a very cheap bike. Still surprised me that it was possible.

Cheap cranks fitted on an expensive bike !

Have they gone as upmarket as hollowtech level cranksets yet?

I suspect the number of cranksets in use from Shimano is orders of magnitude higher than the million Bromptons you reference.

Ups! Today on road.cc

"Shimano finally recalls 11-speed road cranksets after more than 4,500 incidents​

Shimano announces a voluntary inspection and replacement recall notice for 760,000 Dura-Ace and Ultegra bonded 11-Speed road cranksets.
After receiving over 4,500 incident reports Shimano has announced a voluntary recall of Hollowtech II road cranksets produced between 2012 and 2019 for a possible bonding separation issue. That includes two generations of the popular Ultegra and Dura-Ace cranksets."

https://road.cc/content/tech-news/shimano-11-speed-hollowtech-road-crankset-recall-304003

 

[wafter]

Yes, this is a known problem and has already been discussed on this thread..

 

[Drago]

Ups! Today on road.cc

"Shimano finally recalls 11-speed road cranksets after more than 4,500 incidents​

Shimano announces a voluntary inspection and replacement recall notice for 760,000 Dura-Ace and Ultegra bonded 11-Speed road cranksets.
After receiving over 4,500 incident reports Shimano has announced a voluntary recall of Hollowtech II road cranksets produced between 2012 and 2019 for a possible bonding separation issue. That includes two generations of the popular Ultegra and Dura-Ace cranksets."
View attachment 707358
https://road.cc/content/tech-news/shimano-11-speed-hollowtech-road-crankset-recall-304003

So less failed cranksets than Brompton frames...

 

[berlinonaut]

So less failed cranksets than Brompton frames...

To be fair: A couple of years before Brompton made a voluntary recall for ~150.000 Bikes made between 2014 and 2017 to exchange the FAG made bottom bracket of these bikes. They had received a handful reports about breaks, extrapolatet a potential failure rate of 0,02% (1 in 5000 bikes), considered this unacceptable and decided to recall all bikes in question and to exchange the bottom bracket:

https://road.cc/content/tech-news/2...all-bottom-bracket-bikes-sold-over-last-three
https://www.condorcycles.com/blogs/journal/brompton-bottom-bracket-voluntary-recall

Worth noting that the bottom bracket in question was a 3rd party part used by many other manufacturers as well and as to my knowledge no other manufacturer has recalled bikes fitted with this bottom bracket.

 

[Drago]

So less failed cranksets than Brompton frames...

 

[berlinonaut]

Ups! Today on road.cc

"Shimano finally recalls 11-speed road cranksets after more than 4,500 incidents​

Shimano announces a voluntary inspection and replacement recall notice for 760,000 Dura-Ace and Ultegra bonded 11-Speed road cranksets.

The recall has widened. The initial number of failures and recalled cranksets was only the USA. Now it is worldwide and looks as this:

Shimano’s worldwide recall of 11-speed Ultegra and Dura-Ace cranksets now affects 2.8 million units globally.
The original recall was issued after a reported 4,519 incidents of cranksets delaminating in the US and Canada alone, resulting in six injuries.

BikeRadar have an article abut the topic that is totally worth reading. Absolutely embarrassing. The fact as such as well as how Shimano has behaved (the thing has been cooking since 2018) and how they do and plan to handle the issue.

Brompton have done and behaved way better with their bottom bracket recall. They extrapolated a potential failure rate of 0,05% and did not hesitate to recall out of own motivation and to exchange all bottom brackets potentially affected, no questions asked.
With Shimano's cranks the failure rate is way higher - "Shimano says the incidence rate of failures is “proportionally very low (less than 1 per cent)” -, they only went for an exchange program after getting pressure for a whole five years and the process they now initiate is as cumbersome as it is ridiculous and they only want to exchange units that are actually already broken as outlined by said article.

 

[tinywheels]

so glad I got the hope cranks

 

[Gunk]

Went for a very pleasant ride earlier, no broken cranks

 

[tinywheels]

must be a worry for shimano users,think I'd change em to be safe