Chain rubbing top of swingarm

nizfiz · March 15, 2013, 09:20:31 AM

Last summer, after a 2 hour ride w/ my girlfriend on the back of my 2004 S4R, I noticed black gooey stuff splattered all over my swingarm. It looked kind of like tar, but it obviously came from the chain. I thought because of the passenger weight, the chain was rubbing against something it didn't normally come in contact with. Then it kept happening in subsequent no-passenger rides.

I worried about many things, and thought it might be the chain guard, which I took off.

Eventually, I found that the chain was actually rubbing against the chainguard rail on the top of the swingarm (near it's pivot point). You can see that in the image below:

To get it to clear that, I realize that 3 things need to be more or less in a alignment: front sprocket, swingarm pivot point and rear sprocket.

This does not seem possible w/o messing up the chain tension or changing suspension settings.

Why did this happen when I didn't change the ride height in the rear in any major way? Solutions?

TJR178 · March 15, 2013, 09:58:32 AM

This happened to me when I put my 14T on, and raised the ride height years ago. I never really worried about it. I replaced the guard a couple years ago when I had the swingarm off for powdercoating. Chain still rubs a bit, again, not worried. I'd worry if the chain started hitting the swingarm itself.

stopintime · March 15, 2013, 10:29:19 AM

With a passenger the bike will ride lower and the chain will, in some situations, have more slack - hitting the swingarm protector harder - more efficiently pushing/beating the grease and dirt out from under the plastic piece. That's my theory - does it sound logical to you?

FWIW, my plastic piece has been punished hard for + 50K miles and still looks fine. Always a lot of dirt under it though.

Howie · March 15, 2013, 01:07:48 PM

Are you seeing excessive wear on the chain guard? Does it rub under load?

nizfiz · March 15, 2013, 01:50:53 PM

Yes, the chain has dug grooves into the guard on the top surface of the swingarm. Now, it seems to rub LESS under load. This is because as the swingarm comes up relative to its pivot point, more room is created between the chain the top of the swingarm. I don't know how this happened, but I want to stop it without messing my suspension settings and ride height too bad. I suppose I need to lower ride height in the rear. I also want to make sure there isn't something else wrong.

ducpainter · March 15, 2013, 03:11:48 PM

If you raised the ride height and or changed to a 14T front sprocket it is typical for the chain to rub on the protector.

BK_856er · March 15, 2013, 03:24:13 PM

Some wear on the slider is normal. Will depend on lots of things, like your chain adjustment habits and chassis geometry settings, how you ride, etc. If you go down a tooth on the front sprocket the chain will come closer to the slider and wear it faster. Are you running a 14T front sprocket? I used to, but then went back to 15T and added a few teeth to the rear sprocket for similar overall gearing and better chain geometry. Never hurts to make sure you have a proper ride height baseline (ie swingarm angle), but I wouldn't tweak the suspension just to lessen wear on the slider. Replace the slider before it wears through completely - you don't want the chain rubbing on your aluminun swingarm!

BK

Howie · March 15, 2013, 05:13:15 PM

Post a photo showing the wear and mileage on the chain guard. It is possible the situation is normal. As BK said, check ride height and sag.

Speeddog · March 15, 2013, 06:33:19 PM

He's got a 14 on there.

nizfiz · March 15, 2013, 06:53:35 PM

Quote from: Speeddog on March 15, 2013, 06:33:19 PM
He's got a 14 on there.

how'd you spot that?

I'll get a pic tomorrow of the wear. I dunno the mileage on it though. I bought the bike a year ago

Howie · March 15, 2013, 10:01:07 PM

A whole bunch of folk asked if you were running a 14, that is why I didn't ask. though it m 14 will increase contact on the guard, but, if the rear is not raised, wear should not be a problem.

Heath · March 17, 2013, 12:48:27 PM

Quote from: nizfiz on March 15, 2013, 06:53:35 PM
how'd you spot that?

I'll get a pic tomorrow of the wear. I dunno the mileage on it though. I bought the bike a year ago

You can count the teeth off of the pic. My chain rubs on the guard but I've never been worried about it. If you have a build up a black gunk to the most likely from your chain lube.

cactus-pits · March 17, 2013, 06:18:50 PM

I've always been concerned about my chain...it basically lays on a groove on the swingarm..(2009 696, double sided) when parked and when I grab it from the bottom and wiggle up and down it travels almost 2".
is this normal? I've had the bike for a year..I've been a bicycle mechanic for half my life and ime that's a loose chain..??

BK_856er · March 17, 2013, 06:30:53 PM

Quote from: cactus-pits on March 17, 2013, 06:18:50 PM
I've always been concerned about my chain...it basically lays on a groove on the swingarm..(2009 696, double sided) when parked and when I grab it from the bottom and wiggle up and down it travels almost 2".
is this normal? I've had the bike for a year..I've been a bicycle mechanic for half my life and ime that's a loose chain..??

Loose = good. Tight = bad.

Shoot for the loose end of the spec with the indicated technique (varies with bike). Check a few spots along the chain, as it can vary.

With all your weight on the bike you want at least 3/4" inch of slop in the chain (might take two people to do).

Tight chain = bound up suspension and fried output bearing (split the cases to repair - not cheap!).

BK

cactus-pits · March 17, 2013, 06:42:15 PM

it's never sounded or felt bad..but I'll check next time I got my old lady in the garage..which is rare!

News:

Chain rubbing top of swingarm