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markka

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I bought my bike (Santa Cruz Chameleon) new in Feb. of this year. It's always had some issues when rolling the pedals back or when the bike rolls backward if its in the biggest gear it will start to skip down gears. It wasn't to bad at first it did it every now and then, but now its happening all the time. It's at the same spot on the gear every time the chain is rolled backwards, I've never had an issue with a cassette like this before. I really don't want to replace it with the same one since this one didn't last long and I don't want to pay a lot of money for an upgraded SRAM Cassette. Is there a good non-SRAM replacement. Thanks!
 
I bought my bike (Santa Cruz Chameleon) new in Feb. of this year. It's always had some issues when rolling the pedals back or when the bike rolls backward if its in the biggest gear it will start to skip down gears. It wasn't to bad at first it did it every now and then, but now its happening all the time. It's at the same spot on the gear every time the chain is rolled backwards, I've never had an issue with a cassette like this before. I really don't want to replace it with the same one since this one didn't last long and I don't want to pay a lot of money for an upgraded SRAM Cassette. Is there a good non-SRAM replacement. Thanks!

Extreme chainline + large rear cog is the problem. It's going to happen with any/every cassette on that bike eventually. Maybe not when brand new, but very soon thereafter.
 
I don't think the cassette is the issue. I just replaced my beat-up original 3 year 10-50t SRAM Eagle cassette with a bunch of missing teeth. Once I broke a third consecutive tooth on the 50t cog I bent my chain. I repaired the chain and it just bent again and broke. When it the chain broke it also damaged the upper pully on my GX derailleur. I replaced both pullies and bought a new GX 10-50t Cassette ($250.) New Sram Eagle chain too. It pedals like new and doesn't come off when back pedaling. The only time it shifted down while back pedaling was when I put a new smaller chainring on. It didn't have any offset so the chain-line angle was too extreme. I changed it to a 3mm offset chainring and it doesn't shift or come off while back pedaling at all. They even make 6mm offset chainrings that moves the chain-line so it's even more inline with the 50t cog. Might be a cheap fix??
 
I've got several of the E13 TRS+ cassettes and they haven't let me down, big ultra-races on them.
 
Extreme chainline + large rear cog is the problem. It's going to happen with any/every cassette on that bike eventually. Maybe not when brand new, but very soon thereafter.
It sure would be interesting to know what the max angles that the Sram/Shimano engineers suggest for chains. I mean if you are running a 28t oval on a 50t cassette with a 425mm chainstay length, that is a pretty crazy compound angle. You don't state the chainring you are using, but I would be curious if you stepped up to a bigger one if that would still happen.

Wouldn't super boost (157mm) be ideal for these situations as well, as it pushes the cassette out a little further, making for a better chainline for the short chainstay bikes?
 
Chain dropping down a gear or two when back pedaling is normal with 1-x drivetrains. It's a result of the chain ling being skewed when you're at the top of the cassette.
The cure is really cheap, don't pedal backwards.
 
As you say, I never have a problem with this, probably because I just don't have a habit of pedaling backwards. I will slowly move it backwards to position my pedal to start pedaling or a quick back pedal when I bail off on a steep uphill but that's about it. I'll have to try spinning mine backwards a bunch to see if it will actually come off. With an 'oval chainring I could see there being a problem because the chainline is constantly changing.
 
After reading this thread I went down and put each of my 3 bikes that have an Eagle drive train in the bike stand and pedaled backwards, slowly and fast. None came off the top gear...
All 3 are 10-50 XO1 or XX1 with 32t oval rings. Just super lucky with chain line or quality components...? IDK

That being said, if it is just coming off the top 50t gear I'm not sure that would be a problem. I can't see a situation where I would be in that gear and need to ratchet backwards but I don't have really super steep terrain in SWPa.
 
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