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Chain rubbing against chainring, not derailleur. Help?(12 posts)

Chain rubbing against chainring, not derailleur. Help?boy nigel
Jun 20, 2001 3:35 PM

I'm trying to figure out what to do about a noise. When I'm in my small chainring in front and in a middle-to-large gear in back, the chain (I have Shimano 105 53/39 double cranks with a 12-23 cluster) rubs against the inside of the big chainring, causing a scraping sound. I initially thought that my front derailleur needed further "trimming" or adjustment due to the sound, but realized that the chain was hitting the big chainring, not the derailleur. I'm using the proper Shimano chain, too.

I know all about cross-gears and why we shouldn't strain the chain like this, but this occurs when I'm only in the middle of my 9-speed cluster, not in a bad chain/gear combo.

Is this normal with 9-speed setups? My last bike was a 7-speed (wider spacing), by the way. Can I actually be wearing away the inside of my big chainring? It sure sounds like it.

Any suggestions/fixes would be much appreciated.

That sounds a little odd. I dont know how your chainline couldrailer
Jun 20, 2001 4:32 PM
be off by that much. You say it doesnt rub when your in your 12, but it does when your on say your 16?? Doesnt make sense.
Jun 20, 2001 4:36 PM
Did this just start out of the blue, or since you changed something, or did it always do it? Double cranks, not triple? Would help to know.

I've seen chains hit the large ring when in the small ring and small cog. I think we just accept that, particularly when the difference in size between the rings is large.

But, for it to rub in the middle cogs, something is wrong. Can figure that one. If your right crank was loosening on the bottom bracket spindle, it should do the opposite.

More info?

Tipsgrz mnky
Jun 20, 2001 4:56 PM
For the chain to rub either the spaceing between the CR's has to get smaller or the chain has to get wider.

First, verify that you in fact have the correct chain - pin length should be 6.8 mm, if it's 7.1 mm then you're running and 8 speed chain. The only way you can really measure is with a set of calipers or a micrometer - most goo LBS will have one.

For the CR's to get closer you could have enough wear that the chain can actually move laterally. It could also be that your CR bolts are a bit loose and allow the CR's to move while under load.

Finally something could be bent or you have a large burr that the chain hits or possibly the BB is a bit loose and allowing the CR's to rotate out of the plane.

All of this assumes something hasn't changed with the chainline. It's all physical so something has to be off.
re: Chain rubbing against chainring, not derailleur. Help?LC
Jun 20, 2001 10:49 PM
What model of chain are you using, hopefully a HG-92 or HG-72? Is you BB length 109.5 mm?
More info for the kind souls who've asked.boy nigel
Jun 21, 2001 8:30 AM
Thanks for the thoughts, mates.

I have an Ultegra cluster, HG-92 chain, and 105 chainrings and front and rear derailleurs. As I believe I mentioned in my original post, I've got a double, not a triple. 53/39 with 12-23 (12, 13, 14, 15, 16, 17, 19, 21, 23) on the back.

When I'm in my 15 in the back and in my 39 (small) up front, it starts making noise. It's more starting to touch, or rattling against, the 53 chainring, causing what sounds like a front-derailleur rub. Trimming the derailleur doesn't help, since the chain's not actually hitting it. Instead, it's hitting the 53 due to the angle, which doesn't seem particularly extreme to me.

I removed and cleaned my chainrings not too long ago. The sounds MAY have started at about the same time. I'll inspect the rings further to ensure they're on right and tight. I'll also check that they're not bent in any way. The chain's leaving little greasy imprints on the inside of my 53 chainring, so it's certainly touching. It doesn't sound like it's GRINDING away or anything, but the touching shouldn't be happening, right? Everything else is just fine, though, and the 105s are shifting perfectly otherwise.

Any other ideas? I'll write back when I've checked things out more.

Thanks again, all.
So it only rubs when its on the 15??railer
Jun 21, 2001 9:40 AM
Im not familiar with 105 but maybe you left out a washer or spacer making your two chainrings closer together. But this would have an affect on the 15 all the way to the 12. Not just the 15. Its normal to have marks on your big chainring from your chain. Whenever you shift from the 39 to the big it will rub breifly until it shifts.

Its also possible you reversed one of the chainrings I guess.

Take it to a shop if all else fails.
It rubs on the 15, 14, 13, and 12, actually.boy nigel
Jun 21, 2001 10:07 AM

There weren't any spacers of any sort with the chainrings, but I'll double-check that I didn't reverse the inner chainring (39) when reinstalling it. Valid guess. I'll check into it at once.

8sp chain? bent chainring?cyclopathic
Jun 21, 2001 5:35 AM
if not chainline is off but it shouldn't be by that much.
more info needed
8sp chain? bent chainring?peloton
Jun 21, 2001 10:12 AM
Did you recently switch bottom brackets? Going to a smaller spindle size might have thrown off your chain line.

Maybe when you took off your chainrings you accidently installed one backwards?

Good luck
Check the frame...Mike Prince
Jun 21, 2001 4:20 PM
I'm having the same problem but with a brand new bike. In fact, I built it up yesterday, a new Steelman (Ultegra 53/39 crank, Ultegra 109.5 mm BB, Dura Ace freehub/rear der, Ultegra 12-25 cass and SRAM PC-89 chain) I hear a little noise in the 17, then it just rubs in every cog down to the 12 when in the small ring. I have checked the front chainline (43.5 mm just like Shimano says it should be) and everything "looks" OK. As a last resort, I'm having a local shop check the rear triangle for mis-alignment tomorrow. I hope that's it as everything else checks out but the chain is rubbing badly.

Have you crashed lately or shipped the bike? It seems like it wouldn't take much to tweak the chain/seat stays out of alignment, especially w/o a wheel in the frame.

I'll see what my shop says tomorrow.
Mine's fixedMike Prince
Jun 27, 2001 2:49 AM

My chainrub problems are over but in a bizarre manner. My local shop ended up installing a new bb (XTR) to extend the chainline to 43.5mm (it was 40 mm) which is what Shimano recommends. This helped somewhat but I still had rubbing.

Anyway, USAirways managed to mangle my bike on the trip back to Europe this week and bent my big ring pretty bad. When I went to buy a replacement, all they had was the 53 that worked with the 42 (not 39) ring, so I bought the 53/42 set. Also, the power link in my SRAM chain went south and I had to remove it with a chain remover, making the chain too short. So I bought a new Dura Ace chain at the same time.

Got home and installed everything and guess what? No chainrub except in 42/12 which to me is normal and I don't use this combo on purpose. A total mystery to me. I guess the problem lied in the original (new) chainrings. I wish I still had the Ultegra double bb as I think it would work fine now. Maybe when the XTR wears out I'll go back to the Ultegra.