13x12 tire on 13x11 rim?

[mikey]

Anybody have experience or good knowledge about running tires on narrower than recommended rims? I'm trying to find a bias ply that I can use with my PFM but Goodyear no longer makes them. Nobody else seems to make the 13x11 size for the rear. Hoosier has 13x12 but the recommended rim states 12-15" wide. I don't think going down to 10" wide tire would be desirable either..

Or if anybody knows a manufacturer of bias play 13x9 and 13x11 please let me know..

thanks,
mike

[Brian]

Avon makes those sizes in their vintage/historic series. They call them "cross-ply". They are quite tolerant of rim width variation. Why do you want to go to bias ply tires, rather than the radials the car was designed for? Do you have enough suspension adjustment? Just curious.

http://www.avonmotorsport.com/histor...istoric-slicks

Very popular in vintage racing, easily available. They last a long time, too. I ran their Atlantic sized tires on my historic B-SR, and after I found them (tried Goodyear and Hoosier first) I only ever had but one set on the car.

Brian

[R. Pare]

Running a bias ply tire on a narrow rim will decrease the tire spring rate and make the walls less stable - lots more lateral movement under cornering loads. You would need stiffer springs to compensate to get your wheel rate back to the same. Also, the bias ply tires are already most likely a lot softer vertically than the radials, so the problem will be compounded even more.

Best to stick with the radials unless you plan on doing a lot of re-tuning.

[mikey]

ok thanks guys. it was my understanding that the '04 spec PFM was originally designed for bias ply. my car has never been updated. goodyear quit making the original tires.

[Brian]

I was told the same thing, originally Goodyear bias ply then changed to Cooper radials. The Avon 10.5-23-13 is designed for an 11" wide wheel, fwiw. 23" tall at 20 psi on that size wheel.

Brian