Hi all,

Does anyone else with the above setup find that the chain drops off the 42t to the next cog when back-pedalling?
It only take about half a revolution of the cranks to get it to do it.

I’ve got SRAM X1 1×11 dérailleur and cassette.
Race Face Turbine Cinch 32t front.

It’s also quite a noisy drivetrain when pedalling – and I wonder how much of that is causing excessive wear.

I had this with a 40T Hope T Rex and new absolute black chainring. I wondered what caused it, checked adjsutment etc but couldn’t find anything wrong – i just rode the bike. Doesn’t do it anymore and the drivetrain is alot quieter now. It just seemed like the whole thing needed bedding in.

Sounds like chainline on noise and back peddling TBH.

Mine does too. No idea why. I rarely use the 42t anyway so isn’t a problem. Besides, if I do use it it’s normally on something very steep and back peddling doesn’t help in those situations!

There was a thread on this a while back. Think the culprit might be the B screw but might be worth doing a search for the thread.

have had the same problem from new,mine is on a fatbike with a hope 32t. chainline is not good when on the 42t but runs very quiet when in use just back peddling or pushing back will cause it to derail

It’s a common problem that settles down when the drivetrain wears in a bit. You also will never back peddle enough when actually riding for it to be an issue.

Forget about it, and ride 🙂

so the cog is too big/chainline waay off straight

what if we went with something with less cogs?

There was a similar thread about Shimano 11-speed last week

your derailleur hanger could be a bit skewed too.

Yeah, check alignment on everything – mech, hanger, chainring/crank. Does it do it in all gears, or just in the extremes of the cassette?

It happened to me a couple of days ago while pushing the bike up a steep hill (and probably rotating the cranks by hitting them on my leg as I usually do) – my cassette is well “worn in”, on its way to being “worn out”. I have a standard 3x crankset with a Hope 30t (offset) ring, but probably the chainline isn’t exactly up to SRAM spec.
Didn’t really gave much thought about it, though. The B screw shouldn’t have anything to do with it, as the derailment starts at the top of the cog.

It will be chainline.

I have just gone 1×11 shimano, and when looking at cranksets I noticed some of the sram xx1 setups mentioning a chainline of 48mm, whereas most cranksets/spiders are set for a chainline of 50mm.

As Ben Pinnick pointed out you can get a better chainline by putting the BB spacer from the drive side on the opposite side, so your chainline is then 47.5mm.

I have done this and the chainline is better, but I can still drop off the 42 after a few revolutions of backpedelling.