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I just got my son a 1995 750 Nighthawk. The front tire looks new but on the edges the tire is feathered on one edge of the water groove. Is this due to aggressive cornering or could it be caused by another problem? Thanks.

Here in the U.S. we obviously ride in the right lane. If you look at an overhead view of any intersection you'll realize that a left turn is roughly twice the distance of a right turn, and even further in the case of a multi-lane road. Because of this, the left side of your tire will have upwards of twice the mileage on it than the right. In addition, people tend to take lefthand curves faster and more aggressively than righthand curves because they're easier to see around and because it's easier to imagine hitting a ditch than an oncoming car.

So, due to the additional mileage and aggression applied to the tread on the left of the centerline, you'll end up with a tire that is scalloped/cupped/feathered on one side and not the other.

The dunlop website says overly aggresssive braking can cause cupping...sounds pretty aggressive to me.

The BMW K1100RS I once had would cup both sides of the front tire in as little as 1700 miles. No other bike I've had has demonstrated any cupping tendency whatsoever, in spite of much more aggressive riding than I did on the BMW. I would suspect other causes in addition to hard braking, such as misalignment or other anomaly.

should you flip your tire after soo much usage then?

Motorcycle tires are not multi-directional, so flipping, or reversing, is not a good solution. The grooves are designed to dispurse water in rainy conditions, and if the tire is mounted in the wrong direction, control issues can arise in wet weather.

Another possibility is old, or enequal amounts of fork oil. I think I'd change that first, as it's a real cheap thing to do and probably needs it anyway.

Okay, thanks for the advice. I take it from most of the info here that more than likely the cause is due to wear and tear. I will look into changing the fork oil. I'm sure he did not do it and the bike is 10 years old.

Under-inflation is one of the most common causes of cupping a front tire. It doesn't take many miles before the damage is done....

My FJ cups the front tire and it is apparently a standard issue with the bike. All my research has lead me to believe that it is a normal function of the tire doing it's job, combined with carrying alot of wieght on the front. The grooves in the tire are a weakspot in the rubber, and when the tire is loaded suring cornering, the rubber flexes as the groove passes over the pavement. This flexing is what causes the wear, but is also a sign that the tire is gripping while loaded.

Some bikes eat only one side of the tire(Valkeries are known for this) but no one has come up with a satisfactory answer as to why.