I’m trying to bodge a cheap power meter solution for my Orbea Occam for some longer events this summer. Normally it’s just a fun trail bike but power would be beneficial for these events.
Rather than spring for an entirely new power meter setup, is there any reason why upgrading the chainset from an Orbea OEM option to a Shimano Deore FC-M6100, then fitting my existing gravel bike Shimano GRX 810 power meter enabled left crank WON’T work?
I understand that a normal GRX chainset wouldn’t have a long enough axle, but the interface between the left crank and the axle look like it should be compatible. Sure, it won’t look the prettiest thing in the world but if it does the job and saves me £4-600 for something that will sit not being used for 80% of the time.
I can’t answer your compatibility question directly, but will caution that the splines may be the same but the thickness of the crank might be different.
I tried to mate a 4iiii m8000 crank with a m8100 crankset and it was a no-go.
Are the Q-factor between GRX and the Deore series the same?
(Which model occam/what is the standard crankset if you’re upgrading to Deore m6100?)
I think all the Shimano crank arms have the same zig. The difference is in the spindle length and arm thickness which varies a bit. I’d get an SLX one because you can find them used, they’re the same as the XT , and a good amount lighter than the Deore for about the same price.
You should be able to shim the arm/pedal to get the q-factor right. The spline thickness isn’t that big of a deal.
This might be another option (note the x000/x020/x030 arms are all the same)
It should be pretty easy to order a Shimano crank and see if the arm in the box matches your grx.
I had a root around in the shed this morning and with the bikes and spares to hand was able to establish:
The GRX crank would fit onto the end of a Shimano MTB crankset
The GRX crank is thinner than Shimano MTB cranks (but I don’t have enough spares sitting around to be able to establish if that’s a single difference or multiple differences per different tiers)
The GRX crank on it’s own looks like it would just work but there’s insufficient clearance for the power meter unit attached on the inside of the crank to pass through.
So overall, it looks like this idea is not a go-er and the easiest thing if I want power on the bike is as @jfranci3 suggests and looks for an SLX crankset and try to pair it with an XT power meter if there is clearance, or risk going for the Garmin Rally XC100 with associated risks of pedal strikes and issues that many users have been facing.
I cant say 100% about Deore/GRX but they look like they use they use the same left crank arm clamp. Ultegra and Dura Ace certainly do. Back in 2018 I had just bought a Avio powermeter for my left ultegra crank arm, when I got offered 2nd hand dura ace for a while I ran the ultegra left crank on the dura ace chainset.
Shimano MTB cranks and road cranks do use the same axle interface but the Q factor will be different and part of that is due to the profile/bend in the non-drive side crank arm. MTB cranks give a wider stance to clear the chainstays.
I tried to fit a 105 stages to an XT crank once and it worked in isolation but on a hardtail Cannondale MTB, the 105 non drive side arm wouldn’t clear the chainstay. It wasn’t even close.
So the question is, is GRX more similar to mountain bike cranks or is it more road based when it comes to the shape of the crank arms?