skyhon

For some reason, when I am on the biggest chainring and cog, the chain doesn't wrap around the lower pully/jockey wheel. It's shifting fine on all chainring/cog combination except for big-big. I've tried:

1. Cleaned/lubed chain and cassette
2. Replaced the upper and lower pulley's on my derailleur
3. Aligned derailleur hanger
4. reverse the direction of the chain (I have 10 speed sram pc 1071)

It seemed like I don't have this problem when I pedaled backward. I made a short showing the problem: www.youtube.com/shorts/C2DgANS34nY
Thanks for helping.

smd4

Don't cross-chain your bike. There's simply no reason to be in the easiest gear in back, and the hardest gear in front.

Iride01 

How long has it been doing this and what happened or what did you change just before it started?

Maybe the cage holding the jockey and pully wheels is slightly bent in toward the wheel or twisted from some prior hit it took.

And does it do this while you are on the bike riding it? I've seen things happen with the chain while the bike is in the stand with no force on the wheel that I haven't seen when riding and it weight on the wheel.

Even if you don't x-chain, you still want it to work correctly. So thumb your nose at the anti-X chainers!

Nothing wrong with cross chaining for a moment or two when you need to get past the sudden but brief increase in grade.

smd4

Sure. Put the chain onto the big chainring to overcome that increase in grade. Makes perfect sense!

Iride01 

If I'm going up a hill in the large chain ring already and come to that sudden but brief rise in grade, then why should I have to shift the front to the small and the rear two or three times?

X-chaining isn't going to do anything but cause a few less miles on the chain.

prj71

There is also more friction on the system when X-chaining.

Iride01 

And?

Not everyone will benefit from saving those small fractions of a watt on a ride when they briefly go to the big cog on the rear for a brief time out of the 15 - 30 miles they probably ride regularly.

smd4

And...it's just a dumb thing to do.

Iride01 

Not as dumb as ignoring the issue the OP has and letting it grow into something potentially more costly.

smd4

Who's ignoring the issue? I gave him the solution.

Oh...and I forgot most of y'all can't just look at or feel your shifters and know what gear you're in. My bad.

Iride01 

Yes, you told the OP to treat the symptom and ignore the problem. Not always a permanent solution.

smd4

So..."Don't do the thing you're not supposed to be doing in the first place that's causing the problem" isn't a valid solution? Even the OP says it only happens in this particular gear combination. How can it not be a permanent solution, then?

deacon mark

I cross chain all the time no issues 34-50. It does not hurt the drive train and much easier than dropping to the small ring if you can manage to only need one more cog for a bit.

skyhon

I’ll try not to x-chain especially when this is happening. I don’t have this problem before with other bikes so I really want to know why.

I noticed the sound coming from the back the first time when I biked ~40 miles on mostly flat so don’t think I used biggest chainring and cog, at least not for a long period of time. I did dropped the chain once during the ride when shift from big to small chainring… not sure if it affected the rear derailleur. Don’t recall changing any parts prior to this problem.

Again thanks for helping… always learning from you guys.

Iride01 

Perhaps your low limit needs to be brought in and it's just the angle of the chain on the pulley wheel. But if it wasn't doing this before, then why would the low limit have changed. And certainly if moving the low limit in causes issues getting into the big rear cog then between poor shifting and the noise, I'd take the noise.

Might need to get a bike shop to look at it. Maybe the pulley wheel is worn out.

Nothing wrong with x-chaining for a short time. Shimano doesn't say to not x-chain. They do have a caution not to do so for long periods. And there were some groupsets long ago in the Shimano line that they advised strongly not to run in the small/small combo. If your stuff is SRAM, then I don't know what they say about it.

smd4

Shimano doesn't say that you shouldn't ride with your seat on backwards, either.

Eric F 

I'm not sure what issue you think is happening. Of course the chain won't wrap around the lower pulley the same way as it does in other gears because the derailleur cage is extended almost to it's maximum limit. The chain will run in straight lines from tangent point to tangent point between pulleys, cogs, and chainrings. That's exactly what's happening here.

The additional noise is because your chainline is at it's most extreme angle, and it's not happy about it. It also looks like the upper pulley may be a little too close to the cog, which will also add some noise. An adjustment of the B-tension might help a little.

KCT1986

Are the pulleys exactly the same as the original? Correct ones in upper/lower position? Rotation arrows correct, (if applicable)?

skyhon

I agree, but the chain is sitting between the gap touching the side of the cage and the lower pulley (not on the pulley) instead of running at an angle on the lower pulley. I will create another video when I have a chance.

Eric F 

I don't know. It's not my bike. I just watched the video posted by the OP.

skyhon

Supposed to be the right/genuine replacement to replace 10 speed SRAM Rival. Double check... upper/lower and rotation are correct.

Eric F 

The extreme lateral chainline angle of being big-big is the likely issue. The simple solution here is to try to avoid cross-chaining when you ride.

smd4

Someone once told me that's just treating the symptom.

Eric F 

Maybe. I see it as operating the system within the recommended range.

smd4

Same.