I’ve just swapped my SRAM 10-42 for an XT 11-40. Shifting is great, but back pedalling on the 40t drops up a few gears immediately.. Put the 10-42 back on and it stays put for at least 3-4 revolutions..

I’d have thought that with the smaller 40t it’d stay on for longer not less time.. Any ideas?

Cheers

Try a adjusting the b tension screw to account for the smaller diameter.

The top and bottom limits may also be out also.

Do you mean you’ve swapped the rear wheel for something with a Shimano 11spd cassette on it ?

I think Shimano 11spd cassettes sit slightly nearer the spokes.

I’ve heard this issue mentioned before, so it’s possible the Shimano tooth profile doesn’t quite hold the chain as well when back pedaling.

I don’t think chain tension or derailleur position has anything to do with it. Chainline would be more relevant, so too might the make/model of chain.

Although this won’t help, I have the 11-42 cassette and the chain never drops off when I back-pedal in 1st gear. That’s with a KMC 11-EL and X0 chainset with 30T Snaggletooth. Maybe I’m just lucky ?

I have a xt 11-46 on my bike and it doesn’t drop the chain when back pedalling. The b screw is normally the culprit it tends to be sensitive to adjustment.

if you have a spacer on the drive side of the bottom bracket try swapping it to the non-drive side, with bring the front chain ring inwards a bit.

I have found shimano to be more prone to this than a similarly sized sunrace or an even larger hope cassette although the above advice my improve things.

Why did you downgrade your cassette?

You dont say but I suspect you are on a 1X bike?

If you are your best bet is to upgrade it to a double front chainset

All 1X bike have to bend the chain so much in top and bottom gears that back pedalling will always do this.

if you really want a good bike upgrade to a triple chasinset and you will be able back pedal as much as you want and you will be faster than anyone on a 1X bike!

The rear mech does not and can not affect back pedalling. It’s not the mech. Mechs work by placing the chain somewhere BEFORE the cogs, when backpedaling they are AFTER the cogs.

Usually this is caused by stiff non Shimano chains, worn chains, or very dirty chains with no lube. Put a Shimano chain on and look after it and you’ll be fine assuming your cassette and chainset are in the right place. If your chainset is not on the proper line you’ll have issues, but that’s pretty forgiving generally.

FWIW I have one XT and two XTR setups all with 1×11 and XT 11-46t cassettes and none of them do this. All have XTR chains though.

Yep, 1x. Not interested in 2x as it’s unnecessary. I had 10-42 but 42 was unnecessary, hence the drop to 11-40, if I could get a 10-40 I’d go with that. Plus the 36-42 jump was really annoying!

It’s a brand new KMC X11 SL chain so is be surprised if it was that.

If the Shimano cassettes sit closer the spokes than the SRAM cassette that’s make sense.

The rear mech can cause issues with back pedalling on the largest cassette cog if the b screw isn’t adjusted properly as the jockey wheels can foul on the cassette teeth.

If the 42 didn’t get used why not just put a bigger front chainring on ?

11-46 xt 1×11 mine has a spacer on before cassette,no issue back pedaling.Worth a try?

@hambl90 read back what you just wrote and have a think about how the b-screw might make the chain drop a sprocket while pedalling BACKWARDS. The mech comes after the sprockets so while a poorly set up mech might be noisy it can’t and won’t change the gear because the chain has already gone all the way around the sprocket and fallen off the other side by that point.

@lustyd I don’t know why it does it but it did on mine until I fine tuned the b screw.

It’s possible I guess that you had it so badly set up that the mech was pushing on the cassette and making it sit at an angle, that would do it. Otherwise deffo not the mech, you can prove this by putting it in a middle sprocket then pedal backwards and change to a smaller one, all you get is noise and chain wear.