Hey all,
I’ve got an older FC-7900 Shimano crankset. Is there any reason (besides aesthetics) not to run one of the newer one-sided powermeters on that, a 4iiii or the like? I can just change the right-side crank and I’m good, right?
Someone asked this a while ago about a specific SRAM powermeter, but I thought maybe there’s some-brand specific considerations here?
Thanks!
Single or double sides pedals would be a lot easier than messing with replacing cranks.
Shimano cranks all have the same spindle profile so generally you can just swap the non-drive side crank arm.
I would advise checking the Q factor for the crankset. I gave myself a repetitive motion injury partially from running an older ultegra crank arm on a GRX crankset because they have different Q factors. I’d imagine mixing and matching different gens of road cranksets to be less of an issue.
I have been running single sided power meters for years and recently switched to double sided pedals. I will never go back.
My old power meter was reading at least 30 watts high (at FTP) and I’m reasonably sure this was due to a L/R imbalance. I’m actually pretty sure that the imbalance was caused over the years by the single sided power meter. I think that I unconsciously focused on my left leg because it resulted in more consistent power.
Long story short, spend the extra dough and get a double sided power meter if you want to use one.
Yep, all good to go.
And - I know you didn’t ask but others are giving you free advice too! - I have both single and double sided PMs, and I’d probably just go single sided again next time and save the $$. I know there’s a discrepancy between my L/R balance but for my very average punter racing I don’t think it’s enough to worry about.
That’s all helpful advice, thanks!
Re Q factors: Pretty well all 2x HT road cranks prior to 12 speeds have the same Q @ 146mm. 12 speed are 148mm, so 1mm difference each side, most likely unnoticeable. GRX are outliers though at 151mm; the difference is a bit larger, and some will care while others won’t. I’d be more likely to use a non-GRX LH crank to cut down the LH Q due to an old injury, but YMMV.