FAILURE Shimano Cranksets

[wheelsONfire]

Pros, enthusiasts, weight weenies are no longer riding the inferior technology of aluminum frames. So why is anyone accepting aluminum crank arms? Seems to me it has been proven time and time again that aluminum is not up to the stresses and fatigues much more rapidly than admitted.

I've not seen a problem with Rotor cranks!

[wheelsONfire]

I have never heard of somebody having crack on Shimano cranks and it is by far the most used crankset..is it connected to some specific humid climate or so?
Btw Dura Ace is still among the lightest cranks and using 24mm heavy axle..it doesn't sound as old technology they use for getting money..which 24mm cranks are on par with Dura Ace in terms of weight and stiffness? What other cranks would you buy for BB86 frame for 400 euros to combine with Shimano di2 system?

Rotor

[hannawald]

I have never heard of somebody having crack on Shimano cranks and it is by far the most used crankset..is it connected to some specific humid climate or so?
Btw Dura Ace is still among the lightest cranks and using 24mm heavy axle..it doesn't sound as old technology they use for getting money..which 24mm cranks are on par with Dura Ace in terms of weight and stiffness? What other cranks would you buy for BB86 frame for 400 euros to combine with Shimano di2 system?

Rotor

Rotor is unfortunatelly heavier, like Ultegra, not Dura.
170g DM rings, 150g axle, 360g cranks.

[Frankie - B]

You might want to follow @thanksshimano on instagram.

It is indeed by far the most produced crankset, because of that there will be more visible failures. 1% of 10.000 is less then 1% of 100.000.

[jasjas]

Pros, enthusiasts, weight weenies are no longer riding the inferior technology of aluminum frames. So why is anyone accepting aluminum crank arms? Seems to me it has been proven time and time again that aluminum is not up to the stresses and fatigues much more rapidly than admitted.

Plenty of people with cracked carbon frames might disagree?
Any issues with Shimano cranksets are a tiny % of those manufactured, certainly in 40 + years of racing and riding, i have never heard or seen any broken crankarms (in real life) other than in crashes.

[ghostinthemachine]

And this is why I buy Campagnolo. Never had any of these issues in over 40 years of riding with lots of different ranges of cranksets.

I personally have snapped "more than one" campag crank, i've also done Shimanos and some other brands. i've also bent them, it happens.
Though out of the years i've spent racing, by FAR the most time has been spent on shimano, probably 85% or more, since the mid 90s i can tell you that i've done one season (road) and one season (mtb) on something else.

Pros, enthusiasts, weight weenies are no longer riding the inferior technology of aluminum frames. So why is anyone accepting aluminum crank arms? Seems to me it has been proven time and time again that aluminum is not up to the stresses and fatigues much more rapidly than admitted.

Can you quantify how aluminium is "inferior". (Without using "feelings" and "opinions". Just data, and physics.)

You might want to follow @thanksshimano on instagram.

It is indeed by far the most produced crankset, because of that there will be more visible failures. 1% of 10.000 is less then 1% of 100.000.

I would guess that shimano is making nearer 10 times that of bonded cranks. And the failure rate is more like 1/100th of a percent, or less.

[js]

I can appreciate the argument on numbers in some regards, but lets think of this as though it were a fork steerer tube...

Given how well known this type of failure is for Shimano cranks, and how dangerous it can be to have your crank fail, I'm rather disappointed that Shimano hasn't released at least an advisory to caution against this type of failure, even if they aren't going to do a full recall. Again, if it were a fork, you don't wait for multiple crashes before you issue the recall.

I suspect many of the failures on @thanksshimano happened slowly, but I doubt they all did. Mine certainly had some unwanted consequences - beyond the 7k one-legged ride home!

[GeoffS]

There's no doubt you mostly only hear about the failures, and the number that don't fail go unnoticed. But I have three neighbours who I cycle with on a regular basis. Two of them have had crank failures in the past couple of years. Suffice to say, I regularly inspect my Hollowtech cranks...

As a data point, our climate is sub-tropical with high humidity during summer. Seems to support the idea that corrosion is a key factor.

[pdlpsher1]

If the issue stems from galvanic corrosion (where the glue and aluminum exchange ions and weakens the bond), it takes an electrolyte between the two materials for corrosion to take place. Water alone won't cause corrosion. But water plus salt would accelerate corrosion to a great degree. So if your neighbors sweat a lot but don't clean their bikes often that could be the cause. Inspecting your bike is a good practice. But if I lived in a humid climate I would wipe down the crank with a wet towel. You want to remove any salt residue that may have found their way onto the crank.

A fix by Shimano could be a change in the formulation of their crank glue, one that doesn't react with aluminum in the presence of electrolyte. They could also resort to different bonding technologies such as friction and laser welding that don't use glue at all.

[youngs_modulus]

Seems to me it has been proven time and time again that aluminum is not up to the stresses

What stresses in particular is aluminum not "up to?" And how does one determine whether a material is "up to" (or not up to) those stresses?

and fatigues much more rapidly than admitted.

Huh? The fatigue life of aluminum is quantified in an s-n curve. The curve is the curve; there's nothing to admit or deny beyond that.

So who is it, specifically, that you think is fudging s-n curves?

[Andrew69]

If the issue stems from galvanic corrosion (where the glue and aluminum exchange ions and weakens the bond)

Does anyone actually have any evidence to show that the adhesive used by Shimano is actually conductive?
And even if it was, then the axle would be the first to corrode and that just isnt happening.

[pdlpsher1]

The adhesive itself isn't the electrolyte. It's the electrolyte like sweat getting in between the adhesive and aluminum through capillary action. The corrosion is beween the adhesive and the aluminum. In galvanic corrosion you need three ingredients for corrosion to happen. You need the anode, cathode, and the electrolyte. You remove any one of the three ingredients and the corrosion is stopped.

The 24mm steel axle isn't glued to the crankarm. It's pressed in via an interference fit (i.e. the spindle is made slightly larger than the crankarm).

[Andrew69]

The adhesive itself isn't the electrolyte. It's the electrolyte like sweat getting in between the adhesive and aluminum through capillary action. The corrosion is beween the adhesive and the aluminum. In galvanic corrosion you need three ingredients for corrosion to happen. You need the anode, cathode, and the electrolyte. You remove any one of the three ingredients and the corrosion is stopped.

The 24mm steel axle isn't glued to the crankarm. It's pressed in via an interference fit (i.e. the spindle is made slightly larger than the crankarm).

Sorry, misread you pressive post, the bolded part makes more sense.
I thought you meant that the adhesvie was conductive and lead to the galvanic corrosion

Found a possible mechanism for the failure mode.
https://www.pfonline.com/articles/fixin ... -and-steel
Anyone want to boil there durace cranks in de-ionized water and see what happens?

[pdlpsher1]

The only part of the crank made of steel is the 24mm axle spindle And I don't see any failures between the axle and the crank. All of the failures occur on the aluminum part of the crank. Steel pressed into aluminum is not the most ideal construction method. Ideally you want the same material pressed into the same material. But perhaps Shimano has done something like treating the steel with an anti-corrosion coating to make this a non-issue.

In addition to sweat, road salt can also be a source to make the electrolyte. Salt can get trapped in the crevices of the crank. When you ride your bike in the rain, water and trapped salt combine to make the electrolyte. Even sports drinks like Gatorade is an electrolyte.

Probably the most sensible solution to the problem is to make a crank with direct-mount chainrings, as Shimano has already done with their latest 12-speed MTB offerings. The current road crank design has too many small crevices that can trap salt and moisture.

[saldegracia]

I just read through this entire thread and am kind of shocked and fascinated at the same time. Based on my personal experience I always thought these cranks were bullet-proof. I used several since I got back into cycling seriously some 6 years ago:

- Ultegra 6800 must have done around 30,000km on a road bike before being converted to 1x and mounted on my CX bike where it's probably done another 7K or so in rough conditions. Has quite a few fairly big marks from rock strikes etc.
- Ultegra 6800 that probably done close to 20,000 on a road bike
- Ultegra 8000, 11,000km on the road

I weigh around 85kg and have never had any issues with any of those cranks (but will probably have a closer look at them before rides from now on!) I also have a fairly wide circle of cycling friends and have never heard of any similar issues, despite these Shimano cranks being by far the most popular around here. If the whole humidity/salt situation has something to do with it, that would make sense. Where I live it is bone-dry most of the time, corrosion is really not much of a problem in general.