Back pedaling/reversing causes gear down shift

[TheoG]

Same here, I have a 1x11 (36 & 11-48) and 1x12 (38 & 10-51) and both no issue with back pedaling.

 

I did however make sure my chain-line is very close to the middle of my cassette and not as the recommendation to be slightly biased to the smaller (harder gears).

 

I can back pedal like crazy on both of them.

Edited January 26, 2021 by TheoG

[DR ◣◢]

Why are you pedaling backwards?

 

To reset the position of the cranks before pulling off.

To ratchet when navigating technical parts of the trail. 

[TheoG]

Why are you pedaling backwards?

 

To check if the chain drop ...   

[DieselnDust]

Uhm ....    I seem to recall ....

 

Giant - 36 front, 42 rear

 

Titan - 30 front, 46 rear

 

Mongoose - 32 front, 50 rear

 

PS - last two are 26" with shorter chain stays, so should have even worse chain angles.

 

 

so you're saying when the chain is in the largest sprocket at the rear, and you pedal backwards that the chain does not drop down to the next sprocket?

 

If this is the case then you're lucky. 

 

My 2 x 10 26er doesn't drop the chain. My daughters 3 x10 drops the chain. My 1x12 Eagle doesn't drop the chain, my old 1x11 Anthem dropped the chain, switched it to 1x12 Eagle and it didn't so chain line wasn't a factor. since the crankset and chainring remained unchanged.

 

for further interest

 

[ChrisF]

Just lucky 

 

No dropping .... touch wood !!

[ChrisF]

Why are you pedaling backwards?

 

With A-frames, tree stumps, etc I sometimes back-pedal a quater stroke .... to have level pedals when going over the high point.

 

Granted, very seldom this happens in the large ring on the back ...

[TheoG]

I still believe it's all about chain angle (hence chain line) and maybe to a lesser degree, brand.

 

I have Shimano on the 1x12 and Garbaruk on the 1x11, as mentioned, zero issues.

[Headshot]

I still believe it's all about chain angle (hence chain line) and maybe to a lesser degree, brand.

 

I have Shimano on the 1x12 and Garbaruk on the 1x11, as mentioned, zero issues.

 

I agree and also think chain tension is a factor. My Gx 1 x11 used to do it but when I swapped to a smaller front ring it stopped completely with the now slightly looser fit of the chain.

 

My HT with short rear stays and a 2x crank converted to 1x has a terrible chain line and derails badly if you backpedal in the 42 cog. You can see the chainline is the issue. I am sure if I space the chainring closer to the frame it will go away. 

[Jewbacca]

None of my 1x bikes slip gears when I pedal backwards. 1x11 and 1x10.

 

32/42

34/50

 Both 1x11

 

42/42 

 1x10

 

I remember this being discussed before but cannot remember the prescribed 'reason'.

 

I put it down to bad mechanics and setup. It is part of my gear tuning process, to check the back pedal accuracy.

 

I remember I couldn't fix it once and it turned out my hanger was slightly out of alignment.

[lechatnoir]

None of my 1x bikes slip gears when I pedal backwards. 1x11 and 1x10.

 

32/42

34/50

 Both 1x11

 

42/42 

 1x10

 

I remember this being discussed before but cannot remember the prescribed 'reason'.

 

I put it down to bad mechanics and setup. It is part of my gear tuning process, to check the back pedal accuracy.

 

I remember I couldn't fix it once and it turned out my hanger was slightly out of alignment.

 

Actually... the bent hanger is a good thing to check... back pedaling with a bent hanger could make the derailleur 'shift' when the chain's going the other way... and because the top pulley wheel isn't nicely aligned, the chain can just shift willy-nilly... i've not tried that and i'm not about the bend a hanger to check... just seems plausible to me.

[DieselnDust]

I agree and also think chain tension is a factor. My Gx 1 x11 used to do it but when I swapped to a smaller front ring it stopped completely with the now slightly looser fit of the chain.

 

My HT with short rear stays and a 2x crank converted to 1x has a terrible chain line and derails badly if you backpedal in the 42 cog. You can see the chainline is the issue. I am sure if I space the chainring closer to the frame it will go away. 

 

 

but then it will derail in the smaller sprockets. 

 

chain length could be a factor. A Shorter chain with more tension is less likely to hang up on the sprocket teeth when the tension comes off, especially if the freehub seal or clutch is a little sticky, which isn't uncommon as that area is seldom serviced unless it derails the chain while pedalling forward.

 

Its also worth checking the derailleur alignment under the sprockets.if its off by a fraction it will compound with other minor misalignments like a worn guide pulley bearing or bush, worn guide pulley wheels, misaligned derailleur hanger.

 

chain stay length and bb drop could also be contributory factors along with chain ring size to a lesser extent.

Edited January 26, 2021 by DieselnDust

[martinza]

Thanks for all the feedback so far.

 

It is the stock drivetrain, with 28T MegaTooth front cog.

 

I tested the chain tension by pushing the derailleur forward while back pedaling and this makes no difference.

 

The chain climbs off the rear cog at the top, so the chain is still properly wrapped around the cog up to the derailleur when this happen, which to me says the derailleur can't have any impact at this point. This would also eliminate the hanger, now that I think about it. After some further testing, I see it also starts climbing off from the 2nd largest cog. 

 

It must be alignment, but does that mean Trek made the bike with this problem? 

[DR ◣◢]

B tension? How much chain wraps around the cogs?

 

Same with the clutch on and off?

Edited January 27, 2021 by DR ◣◢

[Mojoman]

How many spacers do you have on your drive side BB? I originally had 2 when I first went to 1x route...That is what was there from the 3x days....

I wound up just using one and that helped for a marginally better chain line...

 

[martinza]

 

How many spacers do you have on your drive side BB? I originally had 2 when I first went to 1x route...That is what was there from the 3x days....

I wound up just using one and that helped for a marginally better chain line...

 

Would I see the spacers? Lol, I don't see anything...

 

 

B tension? How much chain wraps around the cogs?

Same with the clutch on and off?

[Mojoman]

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...