2nd crank failure (same place) - my fault?

[alvintc]

How long should cranks last? Just going through my post LEJOG clean up & my 2nd crank has failed in an almost identical way to the first... I think the mileage is about the same on both (around 5k miles at a guess).

My weight has varied (85-120 kg) but the new set has been lower (85-95 kg) should I really be treating these as consumable?

 

[iluvmybike]

My best bike crankset is 5 yrs old with about 12k miles on clock, my winter/touring bike is 15 yrs old with countless miles on clock and still has the same crankset. They should last a long time - the rings may wear but can be replaced of course. I'd not expect a crank to show that sort of fracture unless there has been an impact/crash or other trauma - even if you ride like a gorilla. Perhaps you should stop eating too many Weetabix for brekkie!

 

[Deleted member 1258]

Is that hollowtech 2? Some riders have had crank failures with those, I seem to remember there was a thread on here about them.

https://www.bikeradar.com/features/shimano-crank-failure/

 

[si_c]

It's a known failure mechanism for Ultegra cranks. I'd be contacting the Madison (Shimano's UK distributor).

 

[rogerzilla]

I've only seen one crank fail personally, and that was an old Dyna-Drive crank, which suffered from not having much meat around the oversize pedal hole.

I retired the Sugino cranks on which I commuted for a decade, as I reckoned 25,000 miles was probably enough for them.

 

[cougie uk]

5k is nothing. That is a defect and I'd use a different make in future.

 

[rogerzilla]

Hollowtech has certainly changed. The two halves of a crank used to be forged around a hard steel mandrel and then welded together. I've never been keen on bonding for bike parts. It may be just as strong but it has a limited lifespan. Old bonded carbon forks and frames tend to come apart as the alloy parts (lugs, crowns) corrode.

 

[alvintc]

I'll give Madison a shout & see if they can help... Will update with my findings!

 

[fossyant]

Seriously annoying on expensive parts.

 

[C R]

Seriously annoying on expensive parts.

And from the bikeradar article it seems to be a well known defect. You would have thought that the reputational damage would have got the product manager's attention by now.

 

[fossyant]

And from the bikeradar article it seems to be a well known defect. You would have thought that the reputational damage would have got the product manager's attention by now.

You've got to wonder how many are failing - probably not enough given the numbers they sell.

 

[davidphilips]

Have had the same fun myself, theres a video on Utube shows how to diy repair if not under warranty and have done it myself seems to work? but i have started to just fit the older shimano cranks bought of Ebay as even the chain rings are a lot cheaper, have bought used ultegra chainsets in good condition with chain rings for less than the cost of the new type chain rings.
Know the latest bonded shimano chainsets are said to be lighter stiffer and shift better than the older type but can not notice any difference myself when cycling, Maybe a stronger cyclist would be able to notice some more flex under high load?

View: https://www.youtube.com/watch?v=Vmp2G7zIby4

 

[rogerzilla]

I've never noticed crank flex. Frame and fork flex (to the extent of brakes rubbing and gears changing themselves), certainly.

 

[Deleted member 1258]

This article talks about how and why ultegra cranks fail:

https://www.bikeradar.com/features/shimano-crank-failure/

Thats duplicating my post.

 

[C R]

Thats duplicating my post.

Of course it is, shouldn't post when half asleep. Deleted now.