Affordable power meters for SRAM MTB drivetrains?

You also have to be careful as chainline is different among some of those cranks too

Hmmm… that’s a new detail for me. We’ll see how my M9020 / M5100 series mix goes later this week.

Looks like the spindles get narrower every gen and the crank arm gets thinner. Again, this can be solved with BB spacers, especially if you’re on a threaded BSA. Looks like there’s a 3-5mm difference in arm thickness. New gen has narrower spindle and arms.

Edit: good news for me, my OEM Deore crank is the older spec. I think the difference is on the direct mount vs the spider cranks.

I ended up buying a Sigeyi AXO chainring power meter for my SRAM cranks. It only costs $350 and means I don’t need a new crank, plus I get dual sided power and a 50 hour rechargeable battery.

GPLama really rated it pretty good and I found other positive experiences. Only downside is it might need an offset applied to be accurate to other power meters. Since this is for my MTB, that’s not a concern. But since I have Assioma DUO for my road/gravel bike, I can correct for it anyways.

I ordered from the official website and picked up an extra charging cable just in case.

Well the M9020 fit my OEM Boost M6100 / M5100 series crank. The center preload nut is concave on the XTR unit, so I put a 2.5mm BB spacer on the NDS side to compensate. You might not need to do this with a normal crank.

FYI - the OEM MTB cranks are weird and may have a decent q-factor difference L/R. These are the 178mm Q-factor cranks (x030 spec). I think they make them this way so you can stock the same crank for QR141 / Boost / Super Boost chainlines. What they do is just move the spacers around at the BB and move the crank L to R. My Specialzied Chisel has a M511 crank, 52mm chainline, the crank had a 6mm difference in q-factor, where the NDS side was +3mm from the centerline and the DS was -3mm from an even split.

Now I’ve got a BB mount chain catcher on the DS side with the same crank acting as a 2.5mm spacer and a 2.5mm spacer on the NDS side. I also had to shim the NDS crank off the BB because I think it was rubber the BB shell a bit. Clearly I can pull the q-factor in 5mm, but I’d need to spend $100 on another crank for that.

I had to go with the Power2Max on my MTB. There was not enough clearance for the Stages SRAM crank arm to clear my frame with the battery that sticks out on the back of the crank arm. Also the power2max will measure both left and right power since power is measured at the chain ring.

So I got the Sigeyi AXO. I found it to be great and didn’t need any correction to be accurate.

I’m recently got the newer, slimmer 4iiii on my xx1 carbon crank. Works great. Had to send in the non-drive side arm. They mounted it and sent it back in 10-ish days.


I run a Power2Max NG (non-eco) on my Yeti SB130. Got the Garbaruk 30T boost chainring since that what my original Eagle ring was which I liked, but wasn’t compatible with the PM…

It’s mentioned above, but if you want to to 30T you need to use the Garbaruk chainring for clearance and offset reasons.

Just chiming in that I have been running a Power2Max NGeco with 30t Garbaruk for a year now. It’s been really good. Only issue I have had was in a crazy muddy race, the mud built up on the 104 bcd chainring interface and popped the chain off. I had to pull to scrape off the mud to get my chain on. That only happened once it that race (4 hour) race.

1 Like

I have been using xcadey spider powermeter on my mtb. Battery life is great, reading seems to be consistent without connection drops and such. I have offset the data flow by a factor of 0.9 and compared with Assioma Duos on a trainer. Looks sufficiently good to me.

I have been thinking about doing this and it has been some time since you posted this. How has the 4iiii powermeter held up?

It’s been great. It is right in sync with my H3 trainer as well so it seems to be pretty accurate.

1 Like

How do I know which spider I need? Can you tell from these pictures and info?

This must be the right one?

Do they work with the stock chainrings?

Drive Train Specs

No, you have a direct mount chainring. The power meter mounts to the crank instead, and then you mount a 104BCD chainring to the power meter.

1 Like

Thanks. I wasn’t sure how that worked.

It looks like the new Eagle Transmission cranksets work with the “old” Eagle Axs drive train. If this the case the XO crankset is $400 with a Powermeter.

That is a good deal, even if it’s left only and only 3% accuracy. The chainline is 55mm so not ideal for most older Eagle drivetrains (they were 52mm) but could still work alright. Although I’d rather move my chainline inboard than outboard.