TOPIC:

I'm sure this has been covered somewhere, but nothing is coming up when I search the forum. Has anyone tried converting to radial tires? I am changing over to wider rims, front and rear, and was wondering if I should consider the radial type when purchasing the new tires??

The motorcycle in question is my '79 KZ1000 MKII. Thanks!

Motorcyclist magazine had a short tech article a while back about that. They said, definitely no for older suspension systems, but I honestly don't remember the exact technical reason. They said, basically, there are plenty of good bias-ply tires that are way, way better than the old originals, anyway. It's supposedly not safe, just don't remember why.

If I understand correctly: radial tires don't flex properly. There's a certain amount of "give" in a bias ply tire.

Kevin Cameron talks about how radial tires can help the handling of older bikes in his book Sportbike Performance Handbook on page 128:

"... With radial construction, the footprints become larger and longer, tending to increase stability. Perhaps this is why those who are restoring and riding late 1970s Superbikes --- which originally wobbled and wearved frighteningly on bias tires, even with braced chassis --- are reporting good stability today with radial tires on the correct rim widths."

I'm in the process of upgrading my '73 Z1-900's wire wheels, from DID rims (2.15" X 19", 3.00" X 18") and bias tires, to Excel 3.50" x 17" and Excel 4.25" X 17" rims and Avon radial tires.

Well, there are definietly some differing opinions out there. One thing I have read for sure is that you should never mix radial and bias ply tires, and this goes for cars too. I have also learned that proper rim width is even more important for radials because the side walls are not as strong. The minimum rim width I have seen for a radial tire so far is 3.5", and this is for a relatively small 120 front tire. The rim upgrades are a must, and since I am upgrading to wider rims anyway, I am considering the radial upgrade. I'll wait to see if anyone else has any input. Thanks for the info.

What’s the difference between radial tires and bias-ply tires?
The main difference between radials and bias-ply tires lies in their construction. Tires aren’t just toroidal balloons, they are reinforced with cords of steel or synthetic materials such as nylon or Aramid. In bias-ply tires, the fibers are wrapped in an X pattern between the beads; in radial tires, the fibers are wrapped perpendicular to the tread. Radial tires have more flexible sidewalls than bias-ply tires, and thus absorb road irregularities better and have a comparatively larger contact patch when leaned over. Because of the flexible nature of a radial, these offer higher mileage compared with a comparable bias-ply for a given rubber compound. Since they absorb small road irregularities better, they ride more comfortably and are less likely to be upset by groovy pavement.
While radial tires perform better than bias tires, some older motorcycles can’t be fitted with radial tires because of differences in rim profiles. You probably won’t notice much of a difference anyway, so stick with boas tires if that’s what the motorcycle was designed for.
Why can’t I mix radials and bias tires?
The different ways in which radial and bias tires react to sideways loads can lead to unpredictable behavior while cornering. It’s bad enough to do this on a four-wheeler, but it can be even worse on a motorcycle. If you need to replace one tire and the same type is not available, then go ahead and replace both tires with the same type.

Taken from www.timberwoof.com/motorcycle/faq/maintaining.html

With wider rims definitely go for the radials. Much better ride, grip, and stability.

Well, so far I am leaning toward the radials since I will soon have much wider rims. I love the look of the streetfighter type bikes that have the huge rear wheels. Radials are alot easier to find in the sizes I need. Has anyone ever ridden an older KZ with radials?

Post edited by: 79MKII, at: 2005/11/16 13:33