Bonneville America Forums Forums Technical Forums General Tech cyclic vibration

After i had new tires mounted i began to notice a vibration that was cyclic like a stretched chain would be. But the thing is, it never did that before the tires. They're metzlers same as the stock ones, and the shop that mounted them is a ducati dealer that knows what they're doing. they mounted and balanced them and the rotation arrow is correct as is the red dot metzler uses to show ehere the stem should be oriented with the tire. I did the removal and install of the wheels and even pulled the rear a second time to double check that i'd installed every thing right after i noticed this. Even took the sprocket hub out to make sure that spacer was in right and the cush rubbers too.

It only happens at very low speeds either when decellerating or going very slow such as 2nd gear holding at a steady 20 mph or such. If i pull the clutch and coast it goes away. The speed of the cycle of the vibration gets slower as i go slower. And again, above about 25 mph i can't feel it. Nor can i feel it while accellerating even from a stop. I only feel it at 25 MPH and below decel or held steady at 25 or less. Thats approximate, but it seems like around 25 mph. Oh, and the chain is adjusted as always with an inch of play in the middle and the axle notches the same as they always were and lined up the same on each side.

Anyways, it sure feels like a stetched chain but how can that be when it didn't do it till after the tires. I also don't think it's the tires because with the clutch in it's gone. Only with engin engaged mand 25mph or below. Any ideas what this could be?

Tires are seated properly? Was thinking out-of-round until you said the clutch thing.

yeah, only with the engine engaged. The tires seem fine even when i spun them to see how true the tires themselves looked. The chain is the only thing i can think of but why didn't it do that before? I figured either stretched or the rear wheel not being straight. But after checking and re aligning it that can't be it, especially considering it's all adjusted now to where it was before both alignment wise and chain slack. I keep thinking maybe i just didn't notice it before, but it's to obvious, and if i noticed it so easily now why not before? Bike is approaching 9k and i certainly hope i don't need a chain already after just spending $260 on tires. I never pop the clutch or do any of that insane stuff. the worse i do is wind it up thru the gears on occasion.

The engine engaged says it is a problem when it is loaded. Check the rear wheel alignment, then check it again. If the chain is slightly crooked this will happen, disengaging the motor lets the chain spin with no load.

I did that Pat. I've readjusted it several times with no change. at the moment the alignment is exactly as it was before the tire change. I might try the string method, but having adjusted the rear wheel for chain adjustment many times it's never happened before this so that would be a huge coincidence.

How do you do the "string method"? I tried to use a straight edge, but there is a raised rim around my rear sprocket that won't let it lay flat.

DO NOT trust axle notches. Measure from swingarm center bolt to axle bolt centers, or count the threads on the adjusters.
I was amazed when we did Matt's bike, that when we had it together and lined up, how far off to one side it really was. From behind, on the lift, you can see if you stand about 5 feet back. My notches are way off but the wheel is centered and spins perfectly. But, I also have the belt drive and it is much easier to see deviations from the rear now.

I am just thinking out loud here. Put your bike in gear on a long flat lonely road. Hold the throttle open exactly at 20mph for some time. See if the engine rpm or speedo jumps around after a bit.

May be the pilots having to work at low rpms and the mains for some reason are still shut down.

If it does that and you like the bike just the way it is, shim the needles one shim and all will be fine probably. I know you don't like the 45 pilots but it sounds like fuel to me.

********* That is if I am right******* Doesn't sound like tires.

I hope you figure out what it is... i've got a vibration as well and it's about to annoy me to no end.

Pat.....you may well be right and thanks for the suggestion....i will try that. i still doubt it could be the reaon because i've always used the notches. but i would like to see if they're off never the less.

Satxron.....good call on the on the pilots. Sounds like thats a possibility, tho slight. i say slight because again, everything is how it's been for a long time and has always worked. But i DID play with the screws not too long ago and it's possible i left them too low. I don't think so, but at my age i'm prone to spacing now and then. They've always been fine at 3 to 3-1/2 turns so if it's there then thats probably not it. But i'll check to make sure i didn't leave them at 2 turns or less where i had them at times when experiemnting with the 45's. (then again the question remains.....why didn't i notice it B4 the tires?) Thanks both of ya's.

I read a article about aligning the wheels by useing 2 8' flourescent light bulbs. He attached them to the rear tire with bungie cords and measured the differance at the front tire. Approx. $8.00 for the tubes. Beats buying a straight edge or two, and easier to use than a string.

How to count the threads (got this from Bluebass a while back): Use a toothpick and count by feel.

Put the bike up on a lift and spin the rear wheel. If it's the chain or an alignment problem that you can feel up to 25 mph, I bet you can see it too.

Quote:

---

It only happens at very low speeds either when decellerating or going very slow such as 2nd gear holding at a steady 20 mph or such. If i pull the clutch and coast it goes away. The speed of the cycle of the vibration gets slower as i go slower. And again, above about 25 mph i can't feel it.

---

My SM did this as well - feels like a low frequency (2Hz) "surging" vibration at about 2500 rpm/2nd gear. I just assumed it was some kind of harmonic vibration in the drivetrain or even a resonance effect in the intake tract. I know the wheels etc were correctly adjusted. Very noticeable when riding in slow-ish traffic but as you say, disappears once you speed up. Did not seem to do any harm and it didn't seem to get any worse over 7500 miles so I just ignored it.

I did spin the wheel but i felt nothing. I think it has to turn faster than i can turn it.

If you have a friend who rides well enough that you trust him to ride close, ask him to keep an eye on your chain while this is happening. If the bottom of the chain (should be pulled tight when decellerating) flops up and down, There is a stretched section, a sticky link, or a problem where the chain engages one of the sprockets.

I'll be purchasing a 2006 SM very soon, and have been doing a lot of research at all the Triumph forums, etc...I'm certainly no expert, but I'll throw in a thought or two, maybe it'll help. This premature chain wear is a concern...perhaps dazco's experience is somewhat isolated as I've read of some riders that are getting 30-40,000 kms on their bikes without chain stretching, but maybe THEY are the exception. Anyway, proper regular lubrication of the chain aside, I wonder if anyone posting that they are getting this vibration had also earler switched their front sprockets to a higher tooth-count, and if so, was the rear wheel aligned using the notches (inaccurate), or by measurement from the swingarm center bolt (accurate)? This vibration may not be noticable until after a few thousand kms, which would allow the wear of the chain and sprockets. If I am not mistaken, Triumph uses X-ring chains as stock equipment. There are obvious benefits, however, X-ring chains have flat-sided seals, as explained at http://www.quality-cycle.com/truth_about_motorcycle_chains.htm . I quote,

"Is a X-Ring Type chain better than a “standard type” O-ring chain??? Much, much better because it’s seals are flat sided, which means the seals have a much greater “contact patch” with the Side Plates. Since the seals are flat, it allows for multiple “sealing lips”......each one acting like a separate seal. As one “Lip” starts to leak the lubrication the 2nd lip seals it in....& because X-Rings are flat shaped on the top & bottom too " .

I would reason that because the flat-sided seals provide greater contact area, these X-ring chains would be more prone to failure from a rear wheel mis-alignment. In other words, the chain will wear/stretch along one edge quicker than the other, and the chain could seize, break, and cause extensive damage to the bike, if not the rider. An O-ring chain might be more forgiving, but there are inherent problems with their design, too. I used to ride a lot of bikes with O-ring chains in the past, and never had a stretching issue.
And, since I mentioned lubrication above, what chain lube do you prefer? Is a chain wax better than than a chain oil?
Your experience and advice is appreciatted.
thanks

In the long term, a misaligned chain will wear about equally on each side because the chain bends one way at the top of the sprocket and the other way at the bottom.

Properly applied, there is little difference in wax vs oil as far as chain lubrication. The wax lubricants stick to the chain better, so they are less messy and might not have to be applied quite as often. They also tend to be a little dryer so they might not collect as much dirt.