I'm sure i've heard something on this before, but my lads setup was XX1 mech on an 11 speed setup, if he's in gear 1 (42 i think) and pedals backwards, it goes nuts and drops 2-3 gears into say 3rd/4th.
We changed the mech today as we've been having some shifting issues and it still does the same thing in gear 1.
Is this a common thing ? it doesn't seem to do it on my Aether7 with what is now the same mech, 11sp GX
Usually down to chainline, you can sometimes move the issue to somewhere less troublesome on the cassette by using a different chainring spacing (chainstay, and tyre clearance permitting), but you're asking a lot of the chain by expecting it to swing across those angles trouble-free.
Yeah on the SRAM xx1 canon cranks I've got a spacer on the nds, but that takes up slack, but I cant move the chain line unless I'm missing something obvious.
I've gone with "don't bloody pedal backwards then child"
Is this a common thing ?
Yes
Just be glad it’s the cassette it’s dropping down and not big ring to little ring to jamming in the bottom bracket area on a 2x11 carbon road bike. Hypothetical choice of bike of course 🙁
Sticking freehub or even jockey wheels, allows the chain to bunch up.
Yeah on the SRAM xx1 canon cranks I’ve got a spacer on the nds
Just to clarify, is that a spacer between the BB cup and the frame or between the crank and the BB cup?
Which type of bottom bracket is it? If it's GXP or DUB with a 73mm BB shell there should be no spacers on either side between the frame and the BB cup, but for the latter there will be a spacer on the drive-side between the BB cup and the crank (i.e. on the axle).
DUB BB manual here.
It can be. Pretty sure the 11-46 Shimano 11 speed cassettes did / do it. I didn’t have it on my GX 11 speed at all. Both my XT 12 speed and GX 12 speed do it.
I find it really annoying but I can see what I can do about it. The chainline is fixed on both bikes, the free hubs are in good condition and it’s all fitted tightly. Chains both sizes according to the manufacturer guidelines for 12 speed. B screw done with the 51t line on the xt mech and using the plastic tool on Gx. 1 is full suss and one is hardtail. Guess it’s just a thing 🤷♂️
Edit - to add - I ran both these current bikes with gx 11 speed on their current hubs with the 10-42 cassette with no back pedalling issue.
The chainline is fixed on both bikes
Fixed in what way? Chainline can be changed by different chainrings (for SRAM cranks) or different cranks themselves (for Shimano cranks).
It's to do with chainline as others have said, and although there's no easy solution. Having said that, I quite like messing around riding fakie and I've generally been able to sort it (I still try and avoid the biggest sprocket for this). 11/12spd (SRAM) is way better for this than 9/10 speed ever was. Check the rear mech (hanger) is not mis-aligned and play with the B-tension. Sometimes a shorter (or longer) chain affects the angle between the front chainring and the mech. That's about all you can do.
My new bike did this but once it wore in a bit, was fine.
Fixed in what way? Chainline can be changed by different chainrings (for SRAM cranks) or different cranks themselves (for Shimano cranks).
Well it has boost chainrings on sram cranks on both bikes (one gxp / 1 dub). I don’t think I could get away with non boost chainrings and going to a 0 offset would probably entirely mess up the chainline. So there’s not much to be done about chainline.
What cassette is it?
The chinese Bolany ZTTO Sunshine etc big range cassettes are notorious for it. Check youtube reviews.
You need to pedal back sometimes on low speed tech
Just to clarify, is that a spacer between the BB cup and the frame or between the crank and the BB cup?
The latter, between arm and BB. I can take a pic, it has 3 grub screws you tighten one cranks are done up.
What cassette is it?
SRAM x1 I think. Will check but it's at the higher end for sure
It's a new chain and rear mech, but did it on old ones exactly the same.
I'm not overly worried, he was out on it today and it's smoother than ever on all changes. It's only rare times it ends up being an issue
Bent RD?
I think this is often to do with Shimano chains being directional.
Bent RD
Brand new. Same on old.
think this is often to do with Shimano chains being directional.
SRAM chain. Xx1 and pc1130 one new, one old.
Pretty sure the 11-46 Shimano 11 speed cassettes did / do it
Not of usefulness to op, but the 11-46 SLX 11spd setup on my Bird lets me pedal back fine... I say fine, it often didn't exactly sound happy about it IIRC. Fine = without dropping gears.
Just to clarify, is that a spacer between the BB cup and the frame or between the crank and the BB cup?
The latter, between arm and BB. I can take a pic, it has 3 grub screws you tighten one cranks are done up.
And which BB?
Basically, measure the chainline (distance between centre line of the frame and the chainring teeth).. on a Boost frame you are aiming for ~50mm as the ideal.
Wolftooth has a good article on the subject.
When I was changing to 1X I checked some videos on YT. Seem to recall a fella doing a fair bit of testing to cure this. I think he found SRAM chains were best and less prone to jumping during freewheel/back pedal. (It was a while ago, so it may not have been SRAM, but he definitely cured it by changing chain. )
Frame is non boost 2015 sworks enduro. BB is a pf30.
I've had this on two bikes (Boost and non-Boost) - but it only drops once from 42 - on an 11speed SRAM X1 and NX with all types of chain (KMC, SRAM, Shimano) and Shimano cranks (XT 104 bcd and XT 96 asym) and a variety of cassettes including XD and HG types.
Doesn't happen when i use a Shimano mech.
Well known thing with the wide range cassettes, best and cheapest cure is don't pedal backwards
I don’t think I could get away with non boost chainrings and going to a 0 offset would probably entirely mess up the chainline.
Boost chainrings make the chain line worse in the gears used most (biggest half of cassette). But they help clearance at the BB end of the chainstay. If you can run non-Boost cranks/chainrings without fouling the chainstay, it’s better IMHO.
I am suffering this on my hardtail (admittedly with shimano 11spd), I put it down to having a non-boost rear hub in the boost frame with adaptors.
I know you can buy washers and bolts to space your chainring inboard of the chainring tabs to try and adjust chainline.
Basically, measure the chainline (distance between centre line of the frame and the chainring teeth).. on a Boost frame you are aiming for ~50mm as the ideal.
49.90mm non boost.
Using that spacer shifts the cranks the wrong way, i assume i'd want the chainring closer to the frame, but even doing that has the same effect anyway.