Back pedaling/reversing causes gear down shift

[TheoG]

Agree 100% with @martinza, hence it boils down to chain-angle which is influenced by:

 

  1.)  Size of rear cog (effective diameter/radius)

 

  2.)  Size of chain ring (effective diameter/radius)

 

  3.)  Chain stay length (fixed for a given bike and can do stuff-all about it)

 

  4.)  Location of the chain-ring in relation to the center of the cassette. (Chain line)

 

Other factors that might play a role

 

  A.)  Cassette brand, one might be better than the other to retain the chain

 

  B.)  Chain brand, one might be better than the other to stay on the cog

 

  c.)  Lubrication

 

 

And that is it, with 4. playing the dominant role imho.

Edited January 27, 2021 by TheoG

[TheoG]

Spacer is here...not saying this is the issue but I did have some problems at first and this helped get a few mm of better chain line...

 

 

If spacers add/remove is not helping enough, can consider a chain-ring that is "dished' inwards or outwards as required.

[DieselnDust]

if chainlnie is an issue why does it not occur on eagle when it does occur with an 11s system on the same bike.

playing with chainline is treating the symptom. The problem is the design of individual parts. Chain pick up and release angles on cassette teeth and chainring teeth coupled to chain inner plate design.

 

My very short chainstayed 29er has no issues with the chain dropping with Eagle.

With 11s it does so I never backpedalled when I had that system.

 

2x 10 on my old 26er with longer chain stays and its not a problem in either the 44T ring or the 29t chainring. The 44T is way outboard ut the release angle of the teeth is very shallow (much like Eagle).

 

All I can suggest to the OP is to try a XSYNC 2 chainring if your cranks accepts 104bcd or direct mount chainrings. 

[TheoG]

I can then only assume the eagle cassette & chain combination is doing a very good job in retaining the chain.  Since my experience is with Shimano only I can not dispute that at all.

[Lance Stephenson]

pretty much al bikes do this now due to shape of teeth for shifting Up smoothly and the chamfer on the chain to glide up (all in the direction you pedal) so obviously if you back pedal it will want to hop down. If you put the chain in a straight line (middle of your cassette) the problem won't occur.  It's the price you pay for much better up shift performance and 1x set ups.

 

Plus, I think if you are trying to back pedal on a steep climb then I think that is actually your bigger issue 

Edited January 27, 2021 by Lance Stephenson

[ChrisF]

....

 

My very short chainstayed 29er has no issues with the chain dropping with Eagle.

With 11s it does so I never backpedalled when I had that system.

 

.....

 

This thread has many of us scratching our heads .....

 

Yesterday afternoon I shifted to the large cogg at the back, track standing and back pedalling for about 30 seconds.  Chain stayed perfectly in place.

 

Full suspension

11 speed

Shimano gears, with KMC chain

 

 

 

Must have looked very strange in the work parking lot ....       

[TheoG]

I'm starting to think theres a very fine line between dropping or not.  If you lucky you are on the good side of that or unlucky if on the bad side ... 

 

I'm lucky twice on 1x11 and 1x12 all Shimano.

[DieselnDust]

Shimano 11 speed was designed to be run as a 2x system so the ramp angles on the teeth are not as aggressive as the SRAM 11 speed 1x systems.

[TheoG]

On my 1x11 I have a Garbaruk cassette with Shimano chain, that might be the difference between dropping or not and with a Shimano 11sp cassette I might see some dropping.  But that is all speculation.

 

To at least have a chance of not dropping, the chain line should be as good as possible.

[Headshot]

pretty much al bikes do this now due to shape of teeth for shifting Up smoothly and the chamfer on the chain to glide up (all in the direction you pedal) so obviously if you back pedal it will want to hop down. If you put the chain in a straight line (middle of your cassette) the problem won't occur.  It's the price you pay for much better up shift performance and 1x set ups.

 

Plus, I think if you are trying to back pedal on a steep climb then I think that is actually your bigger issue 

 

Except that of you are on a technical climb not a gravel road you might need to to ratchet back to get a pedal stroke in. 

[Headshot]

Shimano 11 speed was designed to be run as a 2x system so the ramp angles on the teeth are not as aggressive as the SRAM 11 speed 1x systems.

And yet my 1x11 GX backpedals fine with a 28th front cog...

[DR ◣◢]

<comic looking font>This thread has really gone backwards</comic looking font>

 

*I can't get myself so far as to use comic sans

Edited January 27, 2021 by DR ◣◢

[ChrisF]

This thread has really gone backwards

 

BUT, did it stay on cogg ... sorry, on course ...

[DR ◣◢]

I'm sure we can peddle the topic of proper chain line and tension a while longer.

[MrJacques]

Stop derailing the topic

[martinza]

Thanks for all the effort everyone.

 

If spacers add/remove is not helping enough, can consider a chain-ring that is "dished' inwards or outwards as required.

And thanks Theo. If it's not a tunable setup issue, then I will live with it, even though it is very frustrating. What I mean is, if this is just how the bike is brought out, then I probably need to adapt.

 

 

pretty much al bikes do this now due to shape of teeth for shifting Up smoothly and the chamfer on the chain to glide up (all in the direction you pedal) so obviously if you back pedal it will want to hop down. If you put the chain in a straight line (middle of your cassette) the problem won't occur.  It's the price you pay for much better up shift performance and 1x set ups.

 

Plus, I think if you are trying to back pedal on a steep climb then I think that is actually your bigger issue 

 

I think you only realize how much you back pedal until you have a problem like this. Ratcheting is the one case, but if you stop (for whatever reason) and you want to get going, you typically first align your pedal to get your foot on, and that is back pedaling. I can't imagine you would be able to get on your bike on a steep/rocky/loose section without aligning pedals. Then the other case is where you stop, you reverse a bit to get out of the way, again you've back pedaled. You don't have to actually pedal, reversing the bike has the same effect. Taking the bike out of a the house/garage, reversing it, you've back pedaled.