Solution for chain rubbing on swing arm (SSSA models)?

[czen]

Hi All - I know this has been covered, but I can't seem to find a definitive answer: what exactly is the solution/remedy for a chain rubbing against the top of the swing arm on single sided swing arm models? My S2R1K has stock gearing with 15/41 teeth, but at some point the chain was (or perhaps still is) making sufficient contact with the swing arm as to cause the rubber chain guide to get chewed up, and is also leaving some groove marks on the aluminum (not too deep, fortunately).

I'm not sure if this happened with the previous owner (probably), or after I got it 3 months ago. I'm only about 150lbs, so perhaps the suspension was too stiff when I first got it. So I lowered the pre-load tension on the suspension (and also softened with by turning the large screw thing at the bottom of the spring) ... but then I read somewhere that this does not actually have any relevance to chain height. ()

So now I'm not sure if contact is still happening while riding; when I sit on the bike when stationary, the chain lifts off the swing arm just slightly, but keeps contact for a good portion. When I'm not sitting on the bike, a good portion of the chain is touching/resting on top of the swing arm.

In a separate post I theorized that one could adjust the chain height by adjusting/turning the eccentric hub in such a way and enough times so as to bring the rear axle to a higher centre point within the hub (hence raising the rear sprocket relative to the swing arm), while returning to an appropriate chain tension point at the same time. I didn't get a response on this idea, so I just tried it but couldn't make it work as the hub adjustment (using the c-spanner) seems to be limited to a narrow range, i.e., it does not seem to be free to turn 180 (or more) degrees. At least on my bike.

So if neither of these are the solution, what is, exactly?

I really need an answer as I'd like to install a 14 tooth front sprocket, which might make things worse if I don't figure this out.

Many thanks!

[stopintime]

If the suspension is ok, the chain slider won't wear (mine is fine at 80,000 miles).

If the previous owner changed the spring for a heavier one OR added a LOT of preload, you won't 'push' the bike low enough to get the correct geometry.

The 'large screw thing' is rebound damping and has nothing to do with this problem (although maybe a good idea to have sorted anyway).

Your theory about djusting the eccentric hub is correct, but have in mind that it changes the ride height and/or changes the wheel base. It's not the correct way to fix your problem. We use slight adjustments to get the chain right. (from the factory the axle sits at about the 5 o'clock position)

So, get help to dial in correct sag numbers - if neccesary by changing the spring. That'll fix your problem.

[czen]

If the suspension is ok, the chain slider won't wear (mine is fine at 80,000 miles).

If the previous owner changed the spring for a heavier one OR added a LOT of preload, you won't 'push' the bike low enough to get the correct geometry.

The 'large screw thing' is rebound damping and has nothing to do with this problem (although maybe a good idea to have sorted anyway).

Your theory about djusting the eccentric hub is correct, but have in mind that it changes the ride height and/or changes the wheel base. It's not the correct way to fix your problem. We use slight adjustments to get the chain right. (from the factory the axle sits at about the 5 o'clock position)

So, get help to dial in correct sag numbers - if neccesary by changing the spring. That'll fix your problem.

This is great, many thanks for your response!

So basically, make sure the suspension is correct and the chain height will be correct. Glad to know this; I probably read some bad info somewhere re relationship between suspension and chain height and/or misread something.

I already eased up on the pre-load a bit since the previous owner was much heavier than me (I used a smaller diameter c-spanner to turn the adjuster and stop nuts upward) ... but I should probably do a proper/thorough suspension adjustment to make sure it is truly correct.

Thanks again!

[He Man]

Check if your chain is out of spec (stretched) and then adjust your chain to meet the manufacturer's specifications.

[stopintime]

 

You could start (and come close) by visually see how far down the bike sinks when you sit on it. Monsters have progressive springs which allow generous 'rider sag' (movement when the rider sits on it). You should be able to see the movement clearly - probably ~2 inches. Maybe a little less at 150 lbs.

A semi competent mechanic or suspension shop can dial in the rebound accordingly (should be done when the spring is adjusted)

[czen]

You could start (and come close) by visually see how far down the bike sinks when you sit on it. Monsters have progressive springs which allow generous 'rider sag' (movement when the rider sits on it). You should be able to see the movement clearly - probably ~2 inches. Maybe a little less at 150 lbs.

A semi competent mechanic or suspension shop can dial in the rebound accordingly (should be done when the spring is adjusted)

Yeah, it's probably still too stiff as I don't see much movement. Also, riding on bumpier roads I feel as if I'm doing a rodeo "hold on for dear life for 8 seconds" thing!

[czen]

Check if your chain is out of spec (stretched) and then adjust your chain to meet the manufacturer's specifications.

Yup, checked chain and it's good and adjusted/tensioned to spec.

I don't think the rubbing is getting worse, but I doubt I've eliminated it.

[stopintime]

You'll enjoy your riding much more when this is taken care of 

Any mechanic/suspension guy should be able to sort it out in half an hour or less. The axle position in the eccentric hub might require a mechanic with some basic Ducati experience, but shouldn't be impossible for other mechanics.

[Howie]

After you set rear sag make sure your ride height adjustment is correct, you should have an adjustable link on your SR2 1K

[S21FOLGORE]

After you set rear sag make sure your ride height adjustment is correct, you should have an adjustable link on your SR2 1K

+1
Make sure the previous owner didn't screw up the rear ride height with this one



(The photo is the link for 848, but yours should look similar. If the previous owner is really heavy, he might have tampered the ride height with this one.)

What this actually does is "changing the swing arm droop angle" (as a result, rear ride height gets changed).
So, if the PO messed up with this, trying to increase the ride height, what he did was actually making swing arm droop angle steep, which will cause excessive contact of the drive chain and chain slider on the swing arm.
(Get a pen and paper, and draw a picture, you will know what I'm talking about.)

[czen]

+1
Make sure the previous owner didn't screw up the rear ride height with this one



(The photo is the link for 848, but yours should look similar. If the previous owner is really heavy, he might have tampered the ride height with this one.)

What this actually does is "changing the swing arm droop angle" (as a result, rear ride height gets changed).
So, if the PO messed up with this, trying to increase the ride height, what he did was actually making swing arm droop angle steep, which will cause excessive contact of the drive chain and chain slider on the swing arm.
(Get a pen and paper, and draw a picture, you will know what I'm talking about.)

Ok, so yes, the link is fully wound in; there virtually no threads showing. I assumed this meant that the the rod is at minimum height, so the bike is as low as it can go with this rod, which is just the stock rod as far as I can tell. (I gather one can purchase rods that allow even further lowering.)

I kept it like that since I'm not a very tall guy either (5'9") ... was I wrong to keep it that way? Should I wind it out? But does that not increase the height? (I don't like being on my tippy toes when stopped at lights, etc.)

Many thanks again!

[stopintime]

Stock height is about one thread showing, so that takes this very relevant issue out of the consideration 

[S21FOLGORE]

I kept it like that since I'm not a very tall guy either (5'9") ... was I wrong to keep it that way? Should I wind it out? But does that not increase the height? (I don't like being on my tippy toes when stopped at lights, etc.)

No, you are not doing anything wrong. The PO probably didn't mess up with the rod (rear ride height), then. (Which is a good thing. One less thing to worry.)
To clarify what you're wondering about, to raise the rear ride height, you need to make eye to eye length of the link (rod) longer. To lower the bike, you make the rod shorter.

Maybe all you will need is setting up the suspension properly.

[Howie]

If the spring is not stack and the PO was notably heavier you may need a new spring.  You will know this if you cannot adjust for proper sag.

[czen]

Thanks guys, all this is very helpful indeed!

Cheers!