Grinding vibration on left turns

[cswett]

Lately I've been sensing a slight grinding vibration in slow left turns, but it really became apparent yesterday when I was coasting in neutral down a gentle incline and was making shallow S turns. With bike just idling, there was less engine vibration to mask the grinding. Vibration is subtle but definitely there. not sure i can feel it when going right. Bike is a 2004 with about 17,000 miles. Tires are in good shape with only about 3,000 miles on them.
Thoughts?

[tiPirate]

Does the vibration change with variations in wheel or engine speed? Clutch engaged, disengaged?

[cswett]

Just went out to try the different scenarios . Vibration is most pronounced at low wheel speed, 10-15 mph. Much less vibration at 25, which is fastest I got it for test. The vibration also now seems same, whether going left or right.
Engine vibration masks turning vibration, so can't tell what happens when the engine revs past idle.
Vibration seems pretty much the same in neutral with clutch lever let out, in first with clutch lever pulled in, and in neutral with the engine off.
Vibration also seems same whether I am turning with handle bars, or just using my weight to lean bike over.
That about covers it.

[tiPirate]

Caveat: I'm not a mechanic, but here's where I'd look.

Sounds like something is binding in the drivetrain if you still have vibration with the engine off. Can you reproduce the binding on a center-stand in neutral? Is there any slack in the driveshaft? With the bike on the center-stand and turned off, how much can you turn the rear wheel back and forth with the bike in gear? Any lateral play in the rear wheel at 12-and-6 or 9-and-3?

Are the brakes dragging when the wheels are turned on the center-stand? Does the front wheel spin freely on its bearing?

[Sunbeemer]

Those are good things to check, but this kind of noise can often be tire related. Some tires seem more prone to it than others, but all the tires I've used (Pirelli Diablo Strada's, Bridgestone 023's, Z4 & Z6's) have done it at some point in there lives. I've heard PR2's are also prone to it.

It's usually more noticeable on left turns at first because of increased wear on the left side of the tire due to road camber and wide left turns, but eventually becomes noticeable on right turns too.

What kind of tires are you running?

[cswett]

TiPirate - thanks for the suggestions. Will be hard to recreate binding on center stand because it only seems to happen when bike is turning left or right, but I will check for play. I've had what sounds like very light rubbing from front wheel (like disk pads are touching disks momentarily) since I've got the bike 15,000 miles ago, but none of my mechanics have ever mentioned it as a problem.

Sunbeemer, I'm hoping it's a tire issue, which would certainly be cheaper. I'm running PR2s.

[Sunbeemer]

PE2's have been mentioned as being notorious for doing this, especially the fronts.

Another valuable check can be done while your bike is on the center stand and in neutral by slowly rotating the rear tire to detect any roughness in the rear bearing. It should turn smoothly.

Any play detected at top and bottom of the rear tire is often related to worn or loose parelever bearings. They can be retorqued, but will eventually need to be replaced.

[cswett]

Thanks, all

[wncbmw]

I am going to suggest you check for play with your hands on the 3 and 9 o'clock positions on the rear tire while it's on center stand. If there is any play, I would then suggest you drain the final drive oil to check for metal.

I had a grinding sensation during turns while on a trip and the tire had some play. When I got home, the final drive oil was drained and full of metal shavings. Final verdict was a bad final drive bearing. However, by catching it in time, it saved having to replace the whole final drive. Only the bearing went bad. Not cheap but definately less expensive than a new final drive!

And if the final drive oil is OK, then you are only out the oil for a refill! Cheap way to check.

Of course, any of the suggestions might be the problem and any of them are an easier fix.