I noticed a very good deal on a Rotor Kapic (= aluminium) two-sided power meter crank, it is on sale for less than 400 €. I don’t have a power meter on my commuter (an MTB hardtail), and I dislike the 175 mm XTR cranks on it.Two points are holding me back:
Rotor 2InPower meters have not tested super well according to @dcrainmaker and GPLama.
This is a MTB crank and I plan to get a gravel frame next. Can I use “road” chain rings when I put them on a gravel frame? This is important as there are zero mountains (think Netherlands) and I put a 38-tooth chainring on my hardtail.
What do you say? Worth it?
Primarily, I’d use the power meter to keep myself in check and to log power numbers to get better prediction of fatigue in TR. Occasionally, I might also train on it.
I’ve had a Rotor single sided inPower crank on my spark then evo for like five years and have had zero issues with it. I honestly cannot remember the last time I had a dropout.
I use a 2inPower SL crankset on my gravel bike. Ray never reviewed this particular unit and whatever minor unremembered issues he had with the original 2in non-SL weren’t enough to put me off. Only fault is that it reads below my 2 other power sources which are Assioma duos and my Saris H3. It’s on average about 10 watts lower. Doesn’t bother me too much as otherwise it’s quite accurate to itself and the battery life is good. Never had anything I would call an issue. If I cared enough I could adjust the Faveros to meet it and leave the Saris the outlier. Mainly bought it as a 2 sided solution that allowed me to buy whatever pedals I wanted. Medium story short is good unit, no regrets.
Rotor is in financial trouble. So they may not honor the warranty or be available for customer support in the near future. Especially since the whole bike industry is not doing well, so they are unlikely to come out of this healthy. Maybe that’s why it’s on a big sale. Maybe there will be a bigger sale yet to come. Anyway, buyer beware.
I don’t know for sure about this particular power meter, but many crank spider based power meters claim to measure dual sided power, and technically they do, but they do it in a different way than you might want/expect.
I for some reason have a significant L/R power imbalance: 55% left, 45% right. Single-sided power meters measure only the left side power, then double it. So it will overestimate my power by 10% (2*55%=110%). That’s OK if you average 50/50 or 49/51. It’s also OK if have an imbalance and all your power measurements are left-only. It’s problematic if you have an imbalance and use dual power or true total elsewhere, such as on the trainer.
Many dual-sided crank spider power meters measure the true total power then simply divide by two to get “dual sided” power, which is always assumed to be 50/50. So if you pedal with just your right leg at 100W, it will tell you you’re doing 50W L and R. The total watts are correct but the L/R split is not. This is fine for almost every usage because the total power is accurate, even if you have an imbalance. Almost all trainers are just measuring total power. The only thing you really miss out on is knowing your L/R power balance, plus some advanced pedaling metrics, neither of which has an impact on your training.
If you want true dual sided power, you typically have to go with dual sided pedals or crank arm power meters.
Yah. I guess it depends on what they mean by “dual sided”, total L+R power or individual L and R power. My spider PM can only sense total torque, not which crank arm it’s coming from, so can’t do individual L and R power. It does estimate L/R power by doing something like assuming the torque is coming from the crank arm that’s in its forward 1/2 of rotation. I’ve recorded a few rides using both the spider and Assiomas and the spider’s avg L/R split is quite close to what the Assiomas report. It’s interesting to see, but not something I try to do anything about.
You’re right that it’s an old article. Actually they are presently in WORSE financial trouble than that, with the entire company in insolvency per this article from a few days ago.
The 2InPower has two strain gauges and measure left and right power separately. I definitely wanted at least correct total power measurement as my left/right balance can shift 5–7 percentage points within a ride (according to my Quarq DZero at least).