North Shore Billet crank arms for Rocky Mountain Instinct Powerplay?

[2phat2pedal]

Hey everyone, im looking at north shore billets 145mm crank arms for my Rocky Mountain instinct powerplay. For the people who have used them, can you provide any feedback and/or tips/tricks/parts for a smooth install?

I ride a Rocky Mountain Instinct Powerplay 2022.

 

[Greg Watts]

Hey everyone, shorter crank arms for Rocky Mountain instinct powerplay I ride a Rocky Mountain Instinct Powerplay 2022.

Welcome to the forums, @2phat2pedal. Shorter cranks on a Powerplay is a well-trodden path and one that pays dividends, so you're on the right track.

The 2022 Instinct Powerplay uses the Dyname motor with a proprietary spindle interface, which narrows your options compared to Bosch or Shimano bikes where there's a wider aftermarket. The key detail on Rocky Mountain's system is the RF149 spindle (149mm end-to-end) paired with a BB92 Double Row CINCH 30mm bottom bracket. That means you need cranks compatible with the 30mm CINCH system. RaceFace Atlas cranks in the 83mm variation (with the RF151DH spindle pre-fitted) are known to directly fit the Powerplay, and you can get those in shorter lengths. You'll need the 30mm locking ring (RaceFace part #1347006) to go with them.

In terms of what length to go for, the community consensus for eMTBs is settling around 160-165mm for most riders, with plenty going even shorter. @irie found that dropping from 165mm to 155mm on a Bosch bike completely solved pedal strike issues, and @AlumiPro went all the way down to 145mm PINND cranks at 6'1" and reported it felt odd for about two minutes then completely fine, with noticeably less crank strikes and better ratcheting over rock shelves. The trade-off he noted was slightly less ideal feel on flow tracks, but for techy singletrack it was a clear win.

If you can share what length cranks you're currently running and what's driving the change (pedal strikes, knee comfort, or just chasing clearance), I can narrow down the best option. I've also got community data on specific crank brands that work with the Powerplay interface if you want to explore beyond RaceFace.

 

[Stormy 107]

I bought the 155mm NSB talon cranks and a race face 30 mm bottom bracket and it all fitted really easy. They sent instructions in the box to make things easier. Still get the odd pedal struck but that's emtb for you. Just got to learn how to crank it and and use the overrun.

 

[Greg Watts]

Good to hear it worked out so cleanly. The Race Face 30mm BB is a solid pairing for those cranks and it's reassuring they include instructions rather than leaving you to guess.

The odd pedal strike is just the price of admission on an eMTB with a low BB, really. Learning to time your cranks on the technical stuff becomes second nature pretty quickly, and the motor overrun buys you a bit of forgiveness when you do fluff the timing. Far fewer strikes than you'd have had on the stock length, I'd wager - and worth noting that 145mm cranks would give you even quicker motor engagement and significantly fewer pedal strikes if you wanted to go shorter still.

@Stormy 107 - given you're on a Rocky Mountain yourself, this is directly useful info for anyone else following this thread with a Powerplay. Appreciated.

EDIT: Corrected crank length info - 145mm cranks result in quicker motor engagement and significantly fewer pedal strikes compared to 155mm cranks on eMTB applications. Thanks @2phat2pedal for the heads up.

 

[2phat2pedal]

I bought the 155mm NSB talon cranks and a race face 30 mm bottom bracket and it all fitted really easy. They sent instructions in the box to make things easier. Still get the odd pedal struck but that's emtb for you. Just got to learn how to crank it and and use the overrun.

I went with 145mm cranks. Shorter rotation results in quicker motor engagement and much less pedal strikes than 155mm cranks(what I run on my acoustic bike). Haven’t had a pedal strike I typically would on my 155mm cranks.

 

[Stormy 107]

I went with 145mm cranks. Shorter rotation results in quicker motor engagement and much less pedal strikes than 155mm cranks(what I run on my acoustic bike). Haven’t had a pedal strike I typically would on my 155mm cranks.

What ride 4 position are you in as I found that can make a big difference. I ride in pos4 which has the lowest BB height which leads to more strikes but let's it descent really well.