Broken 3 crank arm power meters.... What next?

imafatman

There is also the problem that Shimano have the lions share of the market so obviously we will see more issues in the wild.

ugo.santalucia wrote:

it's not a matter of tensile strength either... ALL these fractures are down to metal fatigue, which in some way is related to tensile strength, but also not

Good point. I suppose the fatigue lowers the tensile strength but it's practically impossible to know without extensive testing how reliable/strong a crank is over time.

jgsi

Svetty wrote:

JGSI wrote:

I'd certainly be drifting away from Shimano HT cranksets. Glueing on a LH power meter module though is not the issue.
Maybe think of going shorter if possible to 170, even 165 cranks?
Someone's DA crank broke recently at the pinch bolts and posted on here.
I use a Zayante alloy M30 crankset with 4iiii, not much worry of me breaking that crank

Crank length should relate to his height and hip flexibility. Assuming he is a reasonable height I don't think 165mm cranks is a great idea....

You have sound data suggesting that Shimano HT cranks are inherently less reliable than other brands? :roll:

Dont be an idiot, I'm not suggesting anything other than after 3 times.............................................
troll off

daniel_b

imafatman wrote:

JGSI wrote:

I'd certainly be drifting away from Shimano HT cranksets. Glueing on a LH power meter module though is not the issue.
Maybe think of going shorter if possible to 170, even 165 cranks?
Someone's DA crank broke recently at the pinch bolts and posted on here.
I use a Zayante alloy M30 crankset with 4iiii, not much worry of me breaking that crank

Thanks that's an interesting suggestion I have not thought about smaller cranks or trying different ones. By the sounds of it the Zayante's are very stiff so that looks like it could be a good option but I wonder if being crank arm based I might just have the same problem.

The Quarq DZero which I thought would be an easy option has carbon cranks and I'm not sure that's a good idea. If carbon frames and wheels are not suitable for heavier riders then I don't think cranks are either.

cougie wrote:

160 rpm is faster than Hoy..

Well I"m certainly not Chris Hoy..... I'm just reading my cadence figures from my Garmin. Maybe it's not accurate? I'm not really sure what is an unreasonable number to achieve.

I've hit 150\160 on my turbo with comparative ease - you managing that out on the road?
Never tried it out in the wild I must admit, only as part of workout drills.

sloppyschleckonds

imafatman wrote:

The Quarq DZero which I thought would be an easy option has carbon cranks and I'm not sure that's a good idea.

Whut

frisbee

Dzero is available in aluminium.

imafatman

Yeah sorry I was mixing up models - the DFour which is designed for Shimano rings has carbon cranks.

So I could get the DZero and buy some replacement rings and just throw all the Shimano gear out and keep it all metal.

All this crank stuff is new to me :P

philbar72

I've been pointed towards the dzero for power by my clubs best racer. he churns out big numbers and breaks cranks, head sets and others. he can't say enough good stuff about this PM.

I'd just go for solid cranks that work with your pedalling gait/style. get a powertap in your main rear wheel. job jobbed.

joey54321

I really don't think you'll have a problem with SRAM's carbon cranks. You aren't putting out that much power. These things are designed to be ridden by the worlds best sprinters.

Also, you have mentioned you have broken the strain gauges of other powermeters, you haven't snapped the cranks off! IMO you are over thinking this.

imafatman

I probably am over thinking but thinking is free :P

You are right I haven't broken cranks, I've just seemingly deflected them enough that the strain gauges stopped working, each time with Ultegra cranks so it may just be a Shimano specific issue.

philbar72 wrote:

I've been pointed towards the dzero for power by my clubs best racer. he churns out big numbers and breaks cranks, head sets and others. he can't say enough good stuff about this PM.

I'd just go for solid cranks that work with your pedalling gait/style. get a powertap in your main rear wheel. job jobbed.

Thanks that's good to hear, seems a fair few recommendations for Quarq here.

I think I'm gonna go for the Quarq Dzero AL with some Praxis chainrings and give that a go. Reports are it's a solid PM and it's in stock at my supplier who have given me credit for the last broken crank. If I break that then I should probably offer my services as a tester to these companies as I obviously good at breaking stuff!

sloppyschleckonds

^
A good choice, IMO Rotor rings are the stiffest I've tried.

imafatman

Got the DZero + Praxis 50/34 setup : https://i.imgur.com/Rt3U1jD.jpg

I went for an hour ride on each setup today and I'm really happy with the results.

I didn't think I would notice the difference but I swear the cranks just feel a bit snappier. It may be all in my mind but this setup is definitely an improvement. Shifting is great, the cranks feel very solid and the feeling is less spongy.

Also these are 175mm cranks so in theory being slightly longer would see more torque. I am quite certain I notice the difference with the cranks too.

Lets see if it holds up to some decent power, I've got a couple of days rest now so will come back and give it some beans.

Thanks for everyones help and suggestions.

redvision

imafatman wrote:

Also these are 175mm cranks so in theory being slightly longer would see more torque. I am quite certain I notice the difference with the cranks too.
.

If you notice a difference it could be the longer cranks have actually put you in a better position (even just a couple of mm can make a big difference).

Anyway, glad you got it sorted.