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Q-Factor and Hip Width

SJ10

Chimp
Dec 11, 2004
32
0
Q-factor doesn't seem to get mentioned much in dh bike sizing but as someone that is outside the norm of the average rider in size I think I could benefit from increased q-factor. My waist is ~40" and even though the reach and 810mm bar width on my Demo is great for upper body position I'm still riding on the the outside of the pedals more than I would like.

I noticed a big difference in comfort and foot placement when I went from my 135mm Demo 7 to a 150mm Demo 8 but still feel things are a bit narrow. I've tried wider pedals with some improvement as well but the best fitting pedals proved unreliable. Currently riding straitline de factos with descendant cranks. This setup gives me a solid platform but still not the width.

I'd like to try pedal extenders but am worried about the excess leverage given my weight (~240) and the nature of dh riding. Anyone try extenders or have any other recommendations?
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
Pedal extenders sound like a really bad idea on a DH bike.

I'm not finding a published Q-factor for the Descendant crank right now, but IIRC it's a bit narrower than a Saint. That would buy you a little more width.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,638
6,842
borcester rhymes
what about running fatbike cranks and spacers if you need more Q factor?

I personally can't stand the wider Q factor that wider BBs bring. Just part of the course, for the most part, though.
 

troy

Turbo Monkey
Dec 3, 2008
1,026
785
what about running fatbike cranks and spacers if you need more Q factor?
Wouldn't work - bb inner dia. - axle dia. interference fit is not constant along the axle, so You would end up having a giant play in there.

Actually, some dude in here has Specialized pedal axle extenders on his demo, and it works fine. He is much lighter tho...
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,638
6,842
borcester rhymes
You couldn't run a pair of (100mm-83mm= 17mm) spacers, one on each side, to spread the pedals, then space the chainring in 5mm, then drop the lowest couple of cogs? I'd think that would work...
 

Gary

my pronouns are hag/gis
Aug 27, 2002
8,420
6,306
UK
A 40" waistline alone has little relevance to optimum Q-factor. You don't mention your height or if you happen to have an especially wide pelvis?

Many older DH bikes (circa 2002-04ish) used 100mm BB shells and often fairly widely spaced cranks for swingarm clearance (back ends were sometimes 165/170mm). Although it initially did feel slightly more stable jumping aboard a bike with a wider pedal position it could quickly become a bit of a 'mare negotiating deep rutted turns IME... this will only get worse with a modern low BB bike. Just something else to bare in mind before making a decision.

If you were to go with a Profile 3 piece crankset and use their widest axle (suitable for 100mm shells), fit their MTB cups and using lots of spacers you should be able to mount an MTB spider inboard (MOAR spacers and a longer spider retaining bolt required) of the R/H crank arm. Then you can keep your chainline spot on and the cranks/BB will be nice and strong for the weight/extra leverage.


.
 

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
Wouldn't work - bb inner dia. - axle dia. interference fit is not constant along the axle, so You would end up having a giant play in there.
Depends on the crank. That's not true for RF Cinch, for example.

Actually, some dude in here has Specialized pedal axle extenders on his demo, and it works fine. He is much lighter tho...
You mean the ones that got recalled, because they break?

http://www.bicycleretailer.com/recalls/2015/07/15/specialized-recalling-body-geometry-pedal-extenders#.VckSh_lVhBc
 

marshalolson

Turbo Monkey
May 25, 2006
1,774
532
If you wanty your pedals wider, try some 3pc cromos like diety or profile.

Cheap to try and see if you like.

They will add ~10mm of width and hold up.