Help. How can I shorten my Q-Factor

Discuss light weight issues concerning mountain bikes & parts.

Moderator: Moderator Team

satanas
Posts: 370
Joined: Sat Jul 04, 2020 5:45 pm

by satanas

^ I think what Q factor might suit varies with individual biomechanics, so it's hard to generalise and predict what might work for someone else. In my case lower Q makes my knees happier and increases my ability to spin, plus I spend more time on other bikes with 140-150mm Q, so keeping things similar eases adjustment - as does keeping crank length the same IME. FWIW, one bike has those 174mm Q XT cranks in 175mm, and I'm intending to swap them for 163mm Q M985 XTR cranks in 172.5mm. Past experience suggests this will make a significant difference *for me*, but everyone is different.

boots2000
Posts: 1415
Joined: Mon Oct 15, 2007 9:28 pm

by boots2000

Upcountry- Has this worked out long term for you? And were you able to ride the Epic Evo succesfully without having the cranks rub the chainstays? I just got a Force wide crankset and checked it out on both the Epic and Epic Evo (like you did). Measurments seem to agree with yours. Just making sure rear end motion was not an issue before I order a 2nd set of crankarms.
Upcountry wrote:
Sat Dec 16, 2023 4:11 pm
satanas wrote:
Sat Dec 16, 2023 3:21 am
The chances of a SRAM Wide gravel crank clearing the chainstays on any post-2000 MTB frame are near zero; the Q factor is 150mm, versus 178mm for the original cranks. Not that many MTBs will clear the 162mm Q M9100 XTR cranks, or anything else less than ~168mm. There are few - if any - current MTB cranks with a Q less than 162mm. (Why MTB frame and crank designers don't care about this is a mystery to me - maybe just laziness?)
This isn't entirely true... Limited sample size, but I'd imagine they'd fit more than people think, but its an expensive experiment, and you then have to order separate chainrings and such, so its a barrier most people aren't willing to jump over. I'm running a Sram Force Wide w/ Quarq spindle crankset on both my 2023 Epic Hardtail, as well as my 2022 S-Works Epic Evo... The clearance is tighter on the Epic Evo(~2.5mm versus nearly 4mm on the Epic HT), as expected wth the bulk and movement of the rear swing arms, but I've put several hundred miles on it without issue. I have put some helicopter tape on the chainstay to protect it in case. You have to keep in mind that although the Q-factor as measured at the pedal washer interface is only 150mm, the arms are slimmer than many out there, so you gain a few mm's on the back side when comparing to an XTR or similar. Chainline is really easy to adjust with tons of offerings in 0mm, 3mm, and 6mm offsets. The factory Sram Wide chainrings are like 8.5mm offset and won't clear much, in addition to their limited sizes(38t smallest maybe?).

Image

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Upcountry
Posts: 186
Joined: Mon Aug 07, 2023 10:59 pm

by Upcountry

I still have the Force Wide on the Epic Hardtail, zero issues with either 3mm 36t chainring on there currently, and a 0mm 38t cleared with more than 5mm. I actually pulled the Force Wide Quarq off of the shown Epic Evo... Never had issues with rubbing, even with the rubber crank arm boots on there(although it was close, and I helicopter taped the chainstays to be safe), but wanted to ditch the power meter for the couple Ultra races upcoming, and also sized down to 165mm's.

boots2000
Posts: 1415
Joined: Mon Oct 15, 2007 9:28 pm

by boots2000

Got it- that is super helpful. I don't think I will run into chainring issues. I will not run a big ring on the Evo, though even an older style XX1 powermeter on the Force crank seems to have plenty of clearance on the Evo. More woriied about crankarms and stays.
I think I will end up running the Assioma MX pedals rather than a crank based powermeter. I obtained a set a few weeks ago, they seem to be a good choice.
Upcountry wrote:
Tue Jun 04, 2024 3:40 am
I still have the Force Wide on the Epic Hardtail, zero issues with either 3mm 36t chainring on there currently, and a 0mm 38t cleared with more than 5mm. I actually pulled the Force Wide Quarq off of the shown Epic Evo... Never had issues with rubbing, even with the rubber crank arm boots on there(although it was close, and I helicopter taped the chainstays to be safe), but wanted to ditch the power meter for the couple Ultra races upcoming, and also sized down to 165mm's.

Post Reply