[eddie]

I've always been told one should never mix bias-ply & radial constructed tires on a motorcycle.
Why is it I've had the SCR950 since September and only noticed today while cleaning the bike that it has a bias-ply front tire and a radial rear from the factory?
This may be part of the reason they call for 42psi in both tires.
I don't know.
Comments?
Thoughts?

 

[Cruze]

That's really odd... I would have to do some research to see what the benefits/drawbacks would be to run a setup like that. I'm sure they wouldn't do that from factory for no reason at all, it's just figuring out why...

 

[OpenRoad]

Did a bit of research on this and I think the reasoning behind the idea of never mixing bias-ply & radial constructed tires originally came from cars because you have 4 points touching ground at once and with different rebound rates. Doing so will give you horrible results, but there's apparently many different bike models that mix bias and radial from the factory. Most of them are cruisers, but the bias-ply is always in the front.

 

[eddie]

The 1st photo is of a used SV650 I bought ten years ago right after I got it. The original owner was the prop. of a m/c repair shop.
He was going to take it to the mountains and realized the rear tire was worn out. So, he grabbed the closest fit he had on the shelf and stuck it on there.
That's a Metzeler ME880 Marathon, bia-ply touring tire! =O
The aspect ratio was wrong, resulting in a slightly taller tire - tall enough to alter the gearing. It got 60+ mpg!
The front was a regular 120/70/17 radial sport bike tire.
I rode it that way for a few days before I noticed and it handled perfectly fine.
As funds became available, I did put on a proper matched set of radials, though.
The second picture is after I got through adding the new tires and a Leo Vince exhaust.

 

[OpenRoad]

Sounds like it really doesn't matter if the bia-ply is at the front or back so long as the size is similar. Or maybe you lucked out and the Metzeler ME880 Marathon just happened to work and give you a boost in fuel economy. Makes you think if the same can be done on the SCR950... Hmmmm

 

[Cruze]

Did you notice a change in mpg after changing the tire?

 

[YamiGuy]

Did you notice if they take longer or don't take as long to get to what you might feel is a rideable state? some riders I know like to take it easy during the first bit of their riding of the day just to let the tires break, once they "feel" it, then they proceed however they like

 

[eddie]

Did you notice a change in mpg after changing the tire?

Oh, yea. MPGH dropped a bit, but not as much as when I rejetted for a Leo Vince slip-on. Stock with a weird tire was well over 60mpg. After the changes? 50mpg. LOL
It'd run like stink and sounded great doing, though!

 

[eddie]

Did you notice if they take longer or don't take as long to get to what you might feel is a rideable state? some riders I know like to take it easy during the first bit of their riding of the day just to let the tires break, once they "feel" it, then they proceed however they like

I didn't have the ME880 on there long enough to notice, honestly.

 

[Cruze]

Oh, yea. MPGH dropped a bit, but not as much as when I rejetted for a Leo Vince slip-on. Stock with a weird tire was well over 60mpg. After the changes? 50mpg. LOL
It'd run like stink and sounded great doing, though!

Well then... that was a lot more significant than I thought it would be hahaha :|

 

[OpenRoad]

In Cycle World we trust:

Years ago, back when radial motorcycle tires first hit th market, tiremakers strongly advised riders not to mix radial and bias tires. Radials were new and offered significantly different handling characteristics than bias rubber, and neither the bike manufacturers nor the tire companies yet had enough model- and tire-specific data to predict how a combination of the two would affect the handling of any given motorcycle. So the best policy was to discourage mixing radials and bias tires.

Since then, radial technology has evolved dramatically, and the manufacturers have had years to develop a better understanding of the effects of mixing tire types. As a result, numerous production bikes, including two new models tested in this issue - the Harley-Davidson Rocker and the Yamaha Star Raider S - come from the factory equipped with a radial on the rear and a bias-ply tire on the front.

So that's where the mixing tire warning stemmed from, but that should no longer be the case with newer tires so we can go nuts, within reason of course.

 

[Cruze]

Sweet, thanks for finding that piece of info. Guess all is well and this makes sense as to why the bike comes like that. Hmm.. time to experiment?

 

[OpenRoad]

If you have the funds, by all means go experiment. Maybe you can get a wider radial rear tire for a smoother ride and more traction.

 

[ChopperCharles]

The reason is for the different contact profiles front and rear. Running a 60 profile front and a 90 profile rear makes the handling a little... odd. Or a 90 profile front and a 70 profile rear. Once you get used to it though, it's not a big deal. There are other issues too, though. Radial tires have a significantly stiffer sidewall than bias ply tires, and radials generally are a lot stickier. All of these issues together can make for some strange handling characterists. Honestly, you're not even supposed to mix brands or even series within a brand... but many do and have no issues at all. I will say though, I've made some strange combinations over the years, and handling is definitely different from tire to tire.

Charles.