I‘ve noticed a lot of motorcycles are running car tires on the rear. I have a 2003 Honda VTX 1800 Retro with a rear tire size of 180/70R 16. What size car tire could I run on my bike?
They are better for dirt, but the taller tread blocks move around too much for the best traction on the road. They often make more noise than street tires and the wear much too fast for street use. Street tires are amazing in their ability to handle traction on hard surfaces.
Slick tyres are for maximum traction, they have more contact area with the road surface. Slicks are used only for racing, they are not road-legal. Off-road knobbly tyres can be good on poor road surfaces but they have less contact area and a less regular grip. They aren't so great at high speeds either. If you tried riding a dual-sports or off-road bike and compared it to a road bike you'd instantly feel how different they are; the road tyres give a smoother ride and better grip on well maintained roads.
There's no way I'd do it. First of all, with the more flexible sidewalls, it will be like having a water balloon for a tire. Second, the bead (the part of the tire that fits on the rim) on a car tire is deeper than on a motorcycle tire, so sealing may be a problem. Tires are made to conform to the side and shape of the rim for sidewall stability and sealing and a car tire isn't going to do any conforming on a motorcycle rim. I know a car tire 1/3 the price of a motorcycle tire looks good, but how far will the $100 you save go toward replacing the scuffed up chrome and the ER visit for the hide taken off your butt after you have a catastrophic loss of aire pressure of it bucks you off in the first sharp curve?
As others have said, running a car tire on a motorcycle is a really bad idea. The construction is very different because the forces exerted by a motorcycle are totally different than the forces a car demands. I have heard people say things like, it's just a cruiser - i'm not dragging my knee around corners. Okay, but you're still leaning the bike at anything over parking-lot speeds. That's a force that the car tire is not meant to cope with. I have heard, my friend did it for 60,000 miles, and it was fine. Your friend got lucky. Motorcycles rely on 2 tires to provide traction. If 1 fails, you're in a LOT more trouble than if 1 fails on a car. Why risk your life to save a few dollars? a decent set of motorcycle tires is under $200. How much is it going to cost to repair you and your bike if the car tire fails?
