Anyone successfully use a 48/36t chainring combo (Sram 10sp)?

luv2ride

I'm having a 'mare trying to set up my Rival 10sp front mech. Long story short; took a look at the winter bike and found chain was worn, went to replace and found the outer chainring also worn (46t/36t Rival cx chainset). Took cranks off, needed new GXP BB....assembled the necessary parts but couldn't track down a 46t chainring, so got a 48t SRAM Power Glide 10sp ring from SJS.
Fitted new parts, raised the front mech a touch to clear the new ring, put originial chain back on (to test length before breaking new chain). All working well. Put new 10sp chain on...can't ship the chain onto the big ring...

After spending a fair hours following the Sram set up instructions to the letter without success, I've now also played with FD height, angle, limit screw adjustments and cable tension. Best I could achieve was shifting ok in the stand (though with chain occasionally unshipping outward off the big ring), but once under load there's no way it will shift from the small to big ring. Also put new inner cable in, but no real improvement.

I note that Sram recommend 50/34, 48/34 or 46/36 combos, but surely a 2t difference between 46t and 48t shouldn't make that much difference?

Anything I'm missing?

Cheers
L2R

imposter2.0

16t jump between inner and outer is generally seen as the maximum shift (accepting that some have gone higher without issue).

There is no 'minimum' gap.

luv2ride

@imposter2.0 - thanks, thats useful to know...looks like I'm after Sram 10sp front mech set up tips in that case! Google searches suggests they can be "temperental" and need just the right amount of cable tension, so any forumite tips more than welcome...

imposter2.0

As you say, cable tension seems critical with Sram FDs (it probably is with most FDs to be fair), so if you have some kind of in-line adjuster that would help. Otherwise, it's going to be trial and error. They work well enough once set right though...

bobones

I've had this issue and fixed it before. There's a right way and wrong way to attach the cable to the clamp bolt on these FDs and it's easy to do it wrong. The cable needs to go outside the guide first to ensure there is enough leverage, otherwise shifts to the big ring need excessive cable tension and are very stiff. Make sure you're doing it the right way!

luv2ride

bobones said:

I've had this issue and fixed it before. There's a right way and wrong way to attach the cable to the clamp bolt on these FDs and it's easy to do it wrong. The cable needs to go outside the guide first to ensure there is enough leverage, otherwise shifts to the big ring need excessive cable tension and are very stiff. Make sure you're doing it the right way!

Thanks. Ive tried both ways, and whilst it seemed better routing the cable outside the guide before pulling taught and tightening the retainer bolt, it didn't solve it. Am out of ideas so it's now with the LBS!

trevor.hall12

Does it not lift up in any gear (on the small cogs on the rear)?
Would an extra link in the chain help as you've went up 2 teeth on the front. I'm assuming you broke the chain the same length as the old one

luv2ride

trevor.hall12 said:

Does it not lift up in any gear (on the small cogs on the rear)?
Would an extra link in the chain help as you've went up 2 teeth on the front. I'm assuming you broke the chain the same length as the old one

You might have something there...though after the LBS failed to solve it (andcharging me £55 for the pleasure...) I've done the following:
Stripped chainset back,
Reinstalled the (checked correct) GXP BB - LBS though the chainline looked off...
Reverted to old 46t chainring (with 36t inner ring)
Put old chain back on
...no improvement

Changed FD for an old Apex 10 speed one, no improvement..

LBS told me they also swapped the left hand shifter, resulting in them changing the day old cable - also no improvement.

This is "wits end" territory, and is turning out to be a costly bit of preventative maintenance!