SRAM MTB cranks with SRAM Road front derailleur

RichJS

Likes Dirt
Does anyone know whether a SRAM Rival derailleur (chainline 44.5mm?) is adjustable enough / has a wide enough range of movement / whatever to properly shift a SRAM X7 2x10 crankset (49.5mm?) underneath it.

Reason: I'm wondering how to get lower the gearing on a road bike and was thinking about the smaller front chainrings of a MTB crank. EG, swap out the factory FSA Gossamer crankset (with Megaexo external BB) with a SRAM X7 double crankset.

Alternatively, how about shifting the cranks a couple of mm to the left by swapping a space from the drive to non-drive side? Enough thread on the non-drive side cup to get away with it? Would my body care about cranks improperly spaced by a couple of mm?

I believe the BB should fit the same, but anyone confirm or have any other issues i've missed?
 

steve24

Likes Bikes and Dirt
I use a DA FD on my MTB to shift 22/34 chainrings and use an Ultegra on my cargo bike with 24/39 so shouldn't why you would have a problem....
 

Alo661

Likes Bikes and Dirt
No trim adjust. Thats the only hassle you'll have with using a road derailleur with a MTB shifter. Sram shifters have trim in the upper, but not lower ring.

So cross-chaining in big and big, it'll rub.
 

RichJS

Likes Dirt
No trim adjust. Thats the only hassle you'll have with using a road derailleur with a MTB shifter.
Not planning on using a MTB shifter. It will be road shifter and road derailleur - all SRAM Rival probably - on a road bike, but with MTB cranks as the best bang-per-buck way of lowering the gearing.

My biggest concern is the difference in chainline - perhaps the big ring on the MTB cranks' wider chainline is too far out for the Rival derailleur to reach?

I'm assuming the rings are the same distance apart on 10sp road vs mountain. Safe assumption?
 

redbruce

Eats Squid
Not planning on using a MTB shifter. It will be road shifter and road derailleur - all SRAM Rival probably - on a road bike, but with MTB cranks as the best bang-per-buck way of lowering the gearing.

My biggest concern is the difference in chainline - perhaps the big ring on the MTB cranks' wider chainline is too far out for the Rival derailleur to reach?

I'm assuming the rings are the same distance apart on 10sp road vs mountain. Safe assumption?
5mm out in chainline is likely not to be accommodated by the road derailleur. Shifting at least one spacer to the other side should get it close enough though.

MTB and road cranks have the same spacing between rings for a given "speed".

If you have the MTB cranks fine, otherwise a second hand set of compact road cranks (50/36 or 50/34) are cheap enough on ebay.
 
Last edited:

alchemist

Manly Warringah MTB Club
Does anyone know whether a SRAM Rival derailleur (chainline 44.5mm?) is adjustable enough / has a wide enough range of movement / whatever to properly shift a SRAM X7 2x10 crankset (49.5mm?) underneath it.
Yup, I run XX Cranks with a Force front derailleur on my cross bike.
 

RichJS

Likes Dirt
Yup, I run XX Cranks with a Force front derailleur on my cross bike.
Awesome, thanks! :tea:

... Except that you're giving me bad ideas: Can I convince the minister for finance I need to spend $200 extra on XX to save 200 grams?
 

alchemist

Manly Warringah MTB Club
Ha! I didn't have to convince anyone, the only reason I went that way is because at the time they were the only 2 ring mtb cranks available at that time and I got a ripper of a deal from City Bike Depot & Monza (because they all wanted to find out if it would work)
 
Top