For the sake of argument we'll assume your bike is in perfect mechanical trim-both wheels properly aligned and so forth. So why does the tire wear more to one side? Even though you didn't state which side of the tire wears fastest, I'll guess it's the left side (if it isn't, then either you've got wheel-alignment problems or you live in England). There are two schools of thought as to why the left side wears fastest.
School A says it's because in the U.S., we drive on the right-hand side of the road, and since the majority of roads here are crowned, tires wear faster working against that slope. There's a ring of truth to that, though usually the crown is so slight it's hard to imagine it could scuff a tire badly. In fact, the scuffed area of the tire doesn't contact the road until the bike's tilted considerably. In my opinion this explanation is a case of right church, wrong pew.
School B also says the reason is because we drive on the right. But it's not the crown that wears the tire; it's the fact that left-hand turns have a larger radius than right-hand turns. Because left-hand turns are longer in length and can be taken at faster speeds than right-handers, it means the left side of the tire gets used harder and more often than the right, thus wearing it quicker. Of course if you live in England or Singapore, the situation is reversed. That's the explanation I accept.
Toothsome ProblemQ I have an '02 VN 800 with 19,000 sweet miles on it. I'm interested in reducing the rpm at highway speeds and have found some options, but I am unsure which one to take. As you know, it has a stock gearing of a 17-tooth counter shaft sprocket and a 42-tooth driven sprocket (2.47:1). I have located a 38-tooth driven sprocket. My questions are: If I change my 42-tooth to a 38-tooth, will it cause excess lugging on the engine or wear out the clutch too soon, or would this be an insignificant change that would create no noticeable rpm drop? The only dealers around here either admit they have no idea or respond by trying to sell me a new bike.Reagon RichBurleson, TXVia e-mail
A A four-tooth drop at the rear sprocket is a roughly 10 percent difference. Although the speed will increase by a corresponding amount (assuming the bike reaches redline), the engine will be lower on the torque curve for a given mph. So dropping four teeth might be a little steep, although a lot of it depends on the type of riding you do down there in Burleson. If it were my bike, I'd run a 39- (8 percent drop in rpm and a corresponding increase in speed) or 40-tooth (5 percent drop) rear. Or better yet, see if you can find an 18-tooth countershaft sprocket. Not only will it be cheaper to install, but it also splits the difference between the 39- and 40-tooth sprockets by changing the ratio by 6 percent. You should find it easier to install, and it shouldn't require more than a chain adjustment to make it fit, whereas altering the rear sprocket by more than two teeth usually means a new chain is in order.