Tires, the round rubber things on the road

[Kaw-meister]

So, as i attempt to understand the differences between radial and bias ply tires on motorcycles. I have decided to ask the clubs opinions on this matter....that is of course if anyone has an opinion on this subject....how will it affect ridability to install bias tires on a bike that recommends radial and of course visa-versa....anyone....anyone at all...

[Hans]

I put radials on my FJ1200, it originally was a bias ply bike.  It was fine.  The sidewalls tend to be a little more pliable than bias play, so keep that in mind.  Also keep in mind rolling radius, radials tend to me lower profile, though you can find some the same or close profile.

[fast1]

   Steel belted radials claim to fame is that they generate less heat and dissapate it better ensuring longer life. Because of the steel belts they need fewer plys. They also flex. Push on the fender of an average passenger car and you can visibly see them move. This is why it took so long for them to make the jump to motorcycles and only in low profile sizes. Bias ply tires obviously don't flex and that is why it is illegal to mix them. Back in the 80's I did this on one my cars and it made for some downright scary handling, changed them back the next day. From a performance perspective bias plys actually handle better in agressive cornering. Now you know why the hot rodders all run lo-pro tires. The shorter the sidewall the less flex there is. Tire flex is deadly on a motorcycle as anyone who has thrown a bike into a hard corner with low pressure can attest. CHEERS.

[Dennis]

Tire flex is deadly on a motorcycle as anyone who has thrown a bike into a hard corner with low pressure can attest.

My Ironhead Sportster in a rigid frame always felt a little nicer running at low pressure (16 lbs) with radials, 140/90s.  I never used to really hot rod that bike except in a straight line.  I was riding through the Fraser Canyon one time and noticed that on perfectly dry pavement, I was getting a very nice and controllable drift.  It was fun for a while and then started getting really bad and scary.  I pulled over and found the tire pressure just barely enough to hold the shape while sitting still, and one push on the seat and the tire would squish.  A quick inspection determined I was leaking air around the valve stem.  I guessed I was about 4 lbs pressure at that point. 

I road fixed the leak with Teflon tape squeezed under the valve stem nut, and pumped it up with a trucker's built in air compressor.  I didn't properly fix it for weeks after that since the Teflon tape worked fine.

I run 20 lbs now on the Smithers XS650 and the EBay Bobber (both hard tails), but with old school bias ply tires.  However, I run the XS650 tubeless.  Seems fine.

Peace & Grease, Dennis.