2017 Scott Scale and Spark RC crank q-factors?

Discuss light weight issues concerning mountain bikes & parts.

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hjb1000
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Joined: Wed Sep 16, 2009 10:25 am
Location: Australia

by hjb1000

I've noticed the 2017 Scale and Spark RC bike seem to come with the wider Q-factor SRAM cranks:

Sram XX1 Eagle GXP Boost PF Carbon crankarm
QF 168 / 700 Series: 34T / 900 Series: 32T

Anyone know whether it is possible to fit narrower QF 156 SRAM/ XTR Race M9000 QF 158 cranks to any of these bikes?
I would have thought Scott would have specified a narrow Q-factor given these are XC focused bikes...

Lastly all these bikes run Boost 148- does that preclude the use of narrower q-factor??

stoney
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Joined: Wed Jun 08, 2011 11:26 am

by stoney

I was wondering the same thing. I was looking to get either a 2017 Scale RC or a Canyon Exceed frameset to build up using my XTR Race M9000 cranks. But if they won't fit...

by Weenie


deltree
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by deltree

AFAIK Boost doesn't change the frame's BB width... however because the hub's flanges are spaced wider apart the chainline also needs to move outwards to match.

Edit: Actually thinking about it a bit more, some manufacturers might be using the extra 3mm the chainrings are out to make the chainstays thicker/shorter. Looking at the Spark RC it looks really close to the swingarm.

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hjb1000
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by hjb1000

Thanks for the thoughts guys.
After a quick search it would appear XX1 Eagle Boost is only available in QF 168mm?

Gullholm
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by Gullholm

hjb1000 wrote:Thanks for the thoughts guys.
After a quick search it would appear XX1 Eagle Boost is only available in QF 168mm?


As far as I know that's right.
Boost allows for shorter but wider/stiffer chainstays and it seems most manufacturers are going that way with their frame designs, so no more 156mm Q-factor then.
Maybe not very relevant since it's about another frame (haven't gotten my Scale/Spark frames yet so can't measure for you) but last spring I tried putting a 156mm XX1 crankset on a 2016 Trek Fuel EX with Boost and it didn't work out. Was just enough clearance for them to spin freely but when riding they rubbed the frame slightly under load due to flex.

stoney
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by stoney

Wow! Boost frames will make my loved 156Q XTR cranks obsolete. I wonder if Shimano knows about this Boost standard? They always seem slow to adopt the newest standards.

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hjb1000
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by hjb1000

stoney wrote:I wonder if Shimano knows about this Boost standard? They always seem slow to adopt the newest standards.


Shimano do indeed offer Boost cranks now- they are identified by the -B1 prefix I think.

Honestly though, if Boost means wider q-factor, they can count me out.

by Weenie


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