Custom dremel content Ultegra / Pioneer power meter

[floxy1]

Pioneer says their PM won’t work with ‘cyclocross’ gearing. I wanted to fit a single ring (absolute black 44t oval) on my gravel bike. When I started I though it would take just a little ‘trimming’ but the electronics on back side of the DS arm prevented the chainring from sitting flush. Little notch in the ring and viola it fits. Doesn’t appear to have compromised stiffness but time will tell. The AB rings have a clean look, the ring is threaded and bolts affix from the inside.

https://i.ibb.co/FYn7y7H/6-F9509-B5-D19-D-4196-9-FDD-89-FCA1816-B03.jpg (https://ibb.co/2M5KCKZ)
https://i.ibb.co/p1CbJwV/EA3-FFD23-EF8-A-4-FCE-894-D-8-CCF3-D62-EABE.jpg (https://ibb.co/51qGB4p)
https://i.ibb.co/jyTGb6K/58803201-1-C6-D-4-D7-B-9-DFD-C9236-FCB7-B25.jpg (https://ibb.co/8r02NK3)

[quickfeet]

That seems like more than a “notch” lol. Is that in the larger portion of the oval or the smaller side?

[floxy1]

It’s closer to the smaller side of the ring

[stien]

Belongs in the "is this ridable?" meta thread.

Too much material gone IMO.

[yinzerniner]

Belongs in the "is this ridable?" meta thread.

Too much material gone IMO.

It’s not the amount of material gone that’s concerning but rather where it was taken out from.

The inner circle of the chainring and diagonal trussing is what transfers the load from the crankarms to the teeth and chain. By eliminating a good portion of that grid the chainring bolt fixtures nearest the cutout will encounter much higher loads than what they’re designed for and will fail much sooner. Also the location of that failure can be catastrophic as it’s in the critical juncture of BB, crankarm, chain and foot.

This is a bodge of the highest order.

[floxy1]

Thanks for the input. I’ll search for plan B.

[quickfeet]

My main concern is that there really isn’t a dead spot on oval rings so there is (should?) be equal force all the way around. I’m no engineer so don’t quote me on that.

[wallymann]

you experiencing any inaccuracy issues with your pioneer? I have the dual-leg R8000 version pioneer and have read about any inherent/structural issue affecting the accuracy of these pioneers.

[weiwentg]

you experiencing any inaccuracy issues with your pioneer? I have the dual-leg R8000 version pioneer and have read about any inherent/structural issue affecting the accuracy of these pioneers.

For reference, that discussion is here (https://forums.thepaceline.net/showthread.php?t=239516&highlight=shimano+power+meter).

[chiasticon]

interesting that Pioneer says that. Lars Van Der Haar, Lars Boom, and Marianne Vos all rode (and occasionally raced) with Pioneer. that said, the two Lars likely rode with a 38 or 39 inner ring, 46 outer. not sure with Vos, but she does use elliptical rings. regardless...what about a 46/36 wouldn't work with the power meter? you can ride a 34 inner ring with it, right? or do the electronics on the inside of the arm interfere with that?

Van Der Haar's bike:

https://i.pinimg.com/originals/54/98/d8/5498d821c4633cb143ac8113dbf9a29a.jpg

[muz]

Why not mount the single chainring on the inside position and gain a little more clearance?

[weiwentg]

Actually, perhaps another question is: why do you need right side power in CX? Left side only power is probably a decent approximation to total power for most of us. You had to seriously compromise the chainring to get the right side unit to fit. Moreover, there's good reason to think that all power meters on the drive-side of Shimano cranks are going to measure low anyway (see the link I posted above).