Shorter cranks, what are my options?

Thought the SRAM cranks were boosted / unboosted via the chainring 3mm or 6mm offset ?

I once read about some rigid bike that needed an external lower headset cup to run a suspension fork. This added some height to the frontend. No idea if such and angleset exists.

Only dub ones iirc

I had to fit a non-Boost XT crank to my Boost-rear Occam as I wanted 165mm and the shortest Boost versions were 170mm. It works just fine so I imagine it might work fine the opposite way too.

Where did you get a 165 non boost xt crank? Do you know the series number as I can only find them in 170

Just bought a 165 non boost slx from highonbikes. 52mm chain line, 172mm Q Factor. £105.

5 quid cheaper than most places. If you can fill a £175 basket at Bike discount, it's cheaper there.

M8000 could be had in 165, but doubt you would find one now unfortunately

Aye - M8000. It's absolutely crazy that there is such limited choice of crank length.

Another option would be to find longer cranks and have them drilled and tapped. We used to run a tandem with three taps in each crank arm so that it could accommodate a range of kids sizes on the rear.

Any crank that takes a 3 bolt direct mount (SRAM) chainring can be non boost, boost or super boost, as the offset is all in the chainring. Not just the DUB ones.

Hope do them too, all depends on what your budget is really.

isn’t the 52 mm chainline of non boost xt cranks the same as a boost chainline? for some reason boost shimano cranks have 55mm chainline.

raceface have recently updated the turbine. i believe that this has a 30mm spindle.

Id not want to spent more than 200 quid ideally, but as I can’t fit a shimano crank to my gxp bb then I’ll need to factor in 65 quid of that on a new bb

Given I barely use the bike I want to keep costs down, but it’ll be a false economy if I crack my £500 pedal in 2 on a rock the first time I go out

I should add that I’ll be riding fairly tame trails, xc trail centre stuff rather than smashing through rock gardens. What’s the lowest acceptable bb height for an xc bike? Could I get away with 170s, which would mean I’m effectively only losing 3mm in pedal clearance?

Only dub ones iirc

Same for GXP and 30mm

A 51/52mm chainline is boost (e.g. FC-M8100)

Shimano 55mm is also boost but with extra clearance (e.g. FC-M8120)

56.5mm is superboost (e.g. FC-M8130)

You need something with a sub 50mm chainline for a 135/142mm rear end.

bikerevivesheffield

Only dub ones iirc

Nope, GXP cranks also

I think I have some 165mm zee cranks in a cupboard if of interest

Hope EVO? Chainrings are what gives them boost/non-boost, available in various lengths and axle configurations - I don’t know about GOX though. Might be a tad over £200 but could be adapted for future bikes via different axle etc.

I’d try the angleset (go -2 deg) and leave the cranks for now. I’m a big fan of short cranks but with only 100mm of travel I don’t see that BB being too low for 175s.

I've been looking for some 165s too to replace my 175 XTRs which just smash off everything. My frame is a prototype so I'm unsure whether the BB is a touch lower than the production versions of the same frame...

So far been looking at:
- Middleburns (pushing £300 and their Uno rings aren't Shimano 12 speed compatible but I could keep my existing BB)
- Hope (over £350)
- Unite (again, over £300 once you've factored in a new 30mm BB as well)

Really fancy something a bit posh and UK made but at those prices, I might just hunt down a set of 165mm XTs for a fraction of the price...

I’ve found a set of 170 truvative descendent on eBay which will work with my current bb so may give that a shot. I’ll only be 3mm lower overall then, which I assume will be bugger all in the grand schemes of things on a 100mm bike

They look a bit on the heavy side but should suffice

I have some DMR Axe cranks in 165mm. Use SRAM direct mount rings and available in boost or non-boost. Unfortunately they have a specific Praxis BB so you wouldn’t be able to use your current BB.

Something else worth considering when I asked a similar question a few months back and something I didn't realise is that some companies actually use the same length arms but just move the pedal holes. Not sure who it is that does that or even whether it was a load of rubbish...

I once read about some rigid bike that needed an external lower headset cup to run a suspension fork. This added some height to the frontend. No idea if such and angleset exists.

Looking into this a big more:

"Since Slack-R effectively adds external upper and lower bearing cups, it raises the front end of your bike by the external height of the lower cup (about 10mm), and the upper cup adds about another 10mm to the stack measurement. Luckily, as you slacken the head tube angle, the front end of your bike drops as the fork kicks forward, and this effect balances out to a large degree the extra height due to the lower cup, which you can also see by the small change in bottom bracket height."

https://9point8.ca/blogs/9point8-technology/a-deeper-look-into-the-9point8%E2%84%A2-slack-r%E2%84%A2

RaceFace Atlas?

RF Atlas and Turbine can be had in shorter lengths and the offset for boost is in the chain ring not the crank. Avoid the Aeffect cranks as they use the same length crank arm for all lengths but just drill the hole in a different place for 165-175.

https://www.wiggle.co.uk/sram-nx-eagle-dub-chainset?

165mm SRAM NX on wiggle. £99.99. 49mm chainline.

What travel fork are you running? You could try adding 20-40mm of travel. I think 10mm more travel roughly equals 0.5 degrees off you head angle.

There was a shop selling 165mm M8100 XTs (52mm chainline) on eBay recently for £85, really should have got a set. Think they are now around £100.

As Jamz says, 52mm is Boost, 55mm is like MORE boost. Shimano have somehow made it more complicated than it had to be

55mm is like MORE boost.

Super Boost. Pivot and Knolly use it, among others.

Those nx Eagle look promising. I’m awaiting to hear back on a pair secondhand but if they don’t work out I’ll go with the ones in wiggle

Assuming I can get a dub bb for my old school frame

Shimano 12 speed single ring chainlines

https://bike.shimano.com/en-EU/product/component/deore-xt-m8100.html

FC-M8100-1 = 52 mm
FC-M8120-1 = 55 mm
FC-M8130-1 = 56.5 mm

I still have an unused XTR 12 speed 165mm crankset that I bought from the chap that bought it from the PSA many months ago.

If anyone wants it for £160 without ring, or £200 with then shout.

Where did you get a 165 non boost xt crank?

All mine are used off eBay... indeed all 2x 785's being run 1x.
If you don't mind the weight the Zee is more common in 165mm... 640 is the non boost (from memory).