Ultegra 6800 drive arm. TORN!?!

I'm not sure it is weight or power related.  Both mine lasted around 4 years, I'll have a look at Strava and Veloviewer to see if I can get an approx mileage.

The parts are bonded together, I think the glue gets eaten away by crap weather.  My bike gets ridden year round, no mudguards and I'm not the best at maintenance and post-ride cleaning.

Weight Dura Ace Crankset (according to the first google search result) 615g (50/34)
Weight TA Pro 5 vis (according to velobase) 611g in 52/42. (Mine's a 44/26, but not going to take it off to weigh).

Watching the Hambini video posted above, I've thought more about modern road bikes in the last 15 minutes than in the last 15 years...
I'd always wondered how Shimano and now even Campa ended up designing such eyesores.
But now I see it's (albeit perversely) logical: huge ugly carbon frame -> huge ugly crank...
So function follows form instead of the other way round.
And thus you are in trouble...

Fignon's ghost wrote:

I never knew this and won't buy another one. It's never been hammered. Is the r8000 as bad? If so, FSA light as recd by shiny.

Go for Shimano 105 cheaper and does the job. I did and bought with shorter cranks 172.5 are too long. I bought 170mm but should have considered 165mm. Maybe next time. 

FSA SLK Light, solid carbon; light, strong and not too expensive (despite Keith Bontrager's assertions).

Fignon's ghost wrote:

Thanks. Oh well. Will have to chalk it up as a product failure and not Hulkamania.

I've never used anything other than Ultegra or 105. Any alternative suggestions ?

105 should be fine - it's only Ultegra and Dura-Ace that have the problem as they're hollow bonded.

Fignon's ghost wrote:

Thanks. I'm pretty sure 105 will do for me. However, I'm on a mission to test out your 105 conclusion.

Go for it - I haven't seen any reports of 105 cranks breaking

Fignon's ghost wrote:

Here we go...

  Looks very typical to me!  I've got through two in 8 years, usually around 4 years of use.  There's a website on Instagram called "thankshimano" which has loads.

I managed to get a warranty replacement the first time, but it took a lot of nasty threatening letters & emails.  I've now switched to 105 cranks in the hope they last longer.

Fignon's ghost wrote:

Davey. Thanks for deflating my balloon! FWIW. I did it on 172.5. My other is a 105. As Chris pointed out. There are two sections to the ultegra 6800 composition. Compared with the 105, which looks a solid, single cast unit. Presumably it's slightly heavier. 105 is good enough for me.

I'm not sure 5800 is actually any different in the 6800's general construction, maybe they used a different/thinner alloy or different adhesive for Ultegra? I've got two 5800 and one R8000. I'm hoping the latter is less prone to the earlier Ultegra crank death.

Fignon's ghost wrote:

Davey. Thanks for deflating my balloon! FWIW. I did it on 172.5. My other is a 105. As Chris pointed out. There are two sections to the ultegra 6800 composition. Compared with the 105, which looks a solid, single cast unit. Presumably it's slightly heavier. 105 is good enough for me.

Both mine were 6800.  I got the 105 off Ebay, lightly used for under 50 quid, so even if it DOES go the same way, I don't feel like it has cost me a huge amount. 

I was furious the first time as I hadn't heard about it before.  I was on my way to Rosedale Chimney in N Yorks, and if it had failed going up there it could have been nasty   I would think long and hard about a bike with Ultegra ever again, which is a shame, because it has been great apart from that.

For what it's worth, virtually all the weight difference between Ultegra and Shimano cranks is in the chainrings. The arms themselves have only a very minor weight difference, something like 20g when I weighed mine.

Here you go, look: Ultegra vs 105