Ok, i know I will get the knee jerk reaction from folk around here about never do it.

My question is- who has? I know of a few have mixed them. Like a BT45 with a BT021. But I am not gonna call them out. Even if it is in their sig.

Now what most don't know is that radial tires aren't really radial tires, they have bias. Just not as much.  Unless you have a very very vintage Michelin X on your 1950s Citroen.

As for motorcycle radials, as the front and rear are different size and load and loading is SO dynamic, I was wondering if this is a car rule passed over from the introduction of radials on to motorcycle tires. And with the modernization of radials to have bias, and the modernization of tires in general, if there was a really noticeable difference.

So if you HAVE done this, please respond.

And yes, we all know the rule is not to mix and match.

I've done it ... and I drive like a 50's citroen. So it works both ways.
Cool.
Buddha.

BTW biggest thing to remmeber about the radials vs bias ply ... the tar do the exact opposite things when you over/under inflate them.
Bias ply tends to get pointy in the middle with higher pressure, radials get wider and less pointy and have a bigger contact patch.
Less air and bias ply tends to get wide and cave in the middle. Radials relax into a pointier position.
Cool.
Buddha.

That's interesting. Makes sense now why a mixed pair would/could get you into trouble -- as temperature changes the tire shapes will change in odd ways, getting you into trouble if you're not paying attention.  Hmm. What about stiffness? I was told not to mix 'cause bias ply tires are more compliant and radials are stiffer, and this will affect handling. Yes, I accept that it will change handling, but on the face of it that doesn't seem like the whole explanation of why it's not a good idea.  The shape-change-with-temperature/pressure is a better explanation in my mind.

I know with CAR bias tires, you tend to get more squirm under the tread blocks as the tire deforms to meet the road. And original radials with no belts were quite compliant to bumps in the road. Modern radials have belts an some small bias in them.

I can't say a thing about bikes as that isn't what I studied, and car tires take lateral loads and bike tires basically don't. Other than the difference in rider lean angle versus bike wheel angle with respect to the road. Even when talking about a 155/80-13 car tire versus a 150/80-16 or whatever bike tire.

Quote from: 5thAve on May 08, 2009, 01:42:07 PM
That's interesting. Makes sense now why a mixed pair would/could get you into trouble -- as temperature changes the tire shapes will change in odd ways, getting you into trouble if you're not paying attention.  Hmm. What about stiffness? I was told not to mix 'cause bias ply tires are more compliant and radials are stiffer, and this will affect handling. Yes, I accept that it will change handling, but on the face of it that doesn't seem like the whole explanation of why it's not a good idea.  The shape-change-with-temperature/pressure is a better explanation in my mind.

No you run the right pressure (determined by trial and error) in both and inflate tires when warm. Which you do anyway.
Cool.
Buddha.

I talked to a customer svc rep at Pirelli mfg. facility in Rome,GA and if I recall correctly he said you could run a bias on the back and a radial in the front. Or it might be the other way around.  It can be done, now to remember which way is acceptable.  Gonna have to sleep on it, or just call the mfg. again.

Front radials with bias rear are still considered a no-no by motorcycle tire makers.  Back in the 70's when cars were changing over from bias to radials they told us to put the radials on the rear when mixing.  Same thing is true today.  A bias rear with radial fronts can cause serious oversteer when running  at the limit for either cars or bikes.

A bias front with a radial rear can be OK and is no longer frowned upon by the mc tire makers.  Metzelers reccommended fitment for the new Bonnies is a bias Lasertec front and radial Z2 rear and they also used this combo for one BMW F650 model.  A number of the newer Harler Models come with bias front and radial rear.

I have mixed them this way and like it but would never try the radial front/bias rear combo.  Here are the many mix and match tires I've run on the GSs:


http://img.photobucket.com/albums/v443/jcp8832/GS500tirelog.jpg

since I got called out, I will join, lol    I did alot of research on it before I purchased a rear radial. I didnt just happen to get lucky with it.