sram force chainring compatability

andyjday

I have sram force compact 34/50 , 110bcd crank and chainrings on my bike. I am wanting to replace the 34t inner with a 39t . Sram do no do a 39t 110 bcd chainringring and so bought a specialites ta 39t 110bcd and fitted it. but i cannot seem to get the chain to shift properly from this new 39 onto the existing sram outer 50t ring. I have spent a day at least fiddling but with no sucess. Are the Sram force rings, (with all the ramps and groves to enable good chain shifts) designed only to work together, and not with any other rings?.Does someone know which rings or combination of rings will work. I mentioned replacing the 34 for a 39, but will also be happy with a 38t ring . Frustrated, Please help. I just find the 34 gives me too low gearing. and want to up it a bit, but at the same time, are happy with the 50t outer, not to change that to a 53t.

Thank you for any assistance in this regard.
Andyjday

Monty Dog

The SRAM chainrings will be optimised to work together with the alignment of the shift pins. There's no reason why the TA ring shouldn't work - just don't expect such a snappy shift. You may have to tweak the front mech too.

John.T

Monty Dog wrote:

The SRAM chainrings will be optimised to work together with the alignment of the shift pins. There's no reason why the TA ring shouldn't work - just don't expect such a snappy shift. You may have to tweak the front mech too.

+1. Most of the shifting ramps and pins are on the big ring anyway. You could try moving the inner ring round a hole to see if it works any better. It will go on in any of the 5 positions and one may be better than the others.
As Monty says most rings are optimised as pairs so a 50/36 will have a different big ring as well.

andyjday

I'll check back how the sram inner ring was aligned with the outer ( pin positions etc.) then as you say rotate the new ta ring around to see if that makes a difference.