Mixing Radial and Bias Ply Tires

[Rick62]

I have 31-18.5x15 M/T bias ply tires on the back of my pickup. They are old but have plenty of tread. The front tires, also bias ply, are shot. I'm considering replacing the fronts with radial ply tires. I know mixing bias ply and radial tires can be a problem. Can anyone speak from experience?

 

[WileERobby]

Tread depth is not the "only" measure of the life of a tire. Since you say they're old, they're likely no good. Rubber deteriorates over time. Replace ALL with a new set of radials.

 

[Rick62]

By old I meant five years. The truck has always been in a temperature controlled garage so there are no signs of cracking. I think I'll try to get another year or so our of them before I replace them as the new ones are close to $400 each.

 

[bm02tj]

It is the side wall flex difference that makes this unsafe at speed with under and over steer

 

[YY1]

By the book you're supposed to put the bias on the front if mixing.
On account of the bias breaking traction sooner IIRC.

However, in reality that is a nightmare handling situation, as the bias will wander and track pavement irregularities.

If you know anything about performance driving and skid control, bias on the rear actually creates a rear steering opportunity via a controlled skid.

Radial tires hold grip evenly until a sudden break occurs. At that point recovery is questionable at best.

Bias ply slowly lose grip and can be brought into and out of grip by feel of steering and or accelerator.

I ran radials on the front of my Super Bee and 12" bias on the rear.

"Go cart" best describes the handling of that car. The front went where you aimed it, and the rear could come around (or not) at will. Holding the wheel part way through a turn and slowly relaxing my grip while adding enough throttle to let the rear end finish the turn made drivers of LOTS of "handling" cars very envious.

The un-savy motorist could have their rear end come around unexpectedly- is the reason for the book specifying bias on the front.

 

[Rick62]

By the book you're supposed to put the bias on the front if mixing.
On account of the bias breaking traction sooner IIRC.

However, in reality that is a nightmare handling situation, as the bias will wander and track pavement irregularities.

If you know anything about performance driving and skid control, bias on the rear actually creates a rear steering opportunity via a controlled skid.

Radial tires hold grip evenly until a sudden break occurs. At that point recovery is questionable at best.

Bias ply slowly lose grip and can be brought into and out of grip by feel of steering and or accelerator.

I ran radials on the front of my Super Bee and 12" bias on the rear.

"Go cart" best describes the handling of that car. The front went where you aimed it, and the rear could come around (or not) at will. Holding the wheel part way through a turn and slowly relaxing my grip while adding enough throttle to let the rear end finish the turn made drivers of LOTS of "handling" cars very envious.

The un-savy motorist could have their rear end come around unexpectedly- is the reason for the book specifying bias on the front.

I guess you could say I drive my truck like an old lady. Will I notice a difference if the tires are mixed?

 

[oldbee]

YY1 nailed it. Mixing is the weirdest feeling you'll ever feel.Scary too, no matter the speed.

 

[Homstead]

The size difference would come into effect here. With the skinnies on the front and those big tires on the rear the slip angle ratio is so out of proportion that its doubtful a radial or bias ply tire would make it worse. Just my .02 cents.....

 

[oldbee]

Homstead-- beg to differ. big slicks and skinny fronts still work-- if all bias or radial. Normal street tires with bias&radial are way different. Scared me the one time I tried it.

 

[YY1]

If you know anything at all about controlling a skid, put radials on the front.

Done.

 

[oldbee]

YY1- yes, you feel like you're in a skid all the time!!! lol

 

[68 HEMI GTS]

I run radials on the front of my rr. I've ran both radials and bias on the back. No real issues that I've ever noticed. Radials do drive a bit better, but didn't hook as well on my application. I drive it all over the place with the bias on the back and radials on the front..

 

[HEMI-ITIS]

I alway heard that it normally does not work well.I am old skewl to E/t streets all the way around.

 

[YY1]

YY1- yes, you feel like you're in a skid all the time!!! lol

NOT true.

Only starts breaking traction if you are 1- HARD cornering, or 2- panic stopping and not real straight.

...and #2 doesn't happen all the time, but you need to be aware of the possibility.

 

[Rick62]

I have 31-18.5x15 M/T bias ply tires on the back of my pickup. They are old but have plenty of tread. The front tires, also bias ply, are shot. I'm considering replacing the fronts with radial ply tires. I know mixing bias ply and radial tires can be a problem. Can anyone speak from experience?

Just as an update, I replaced the bias ply front tires with radials. The rears are still bias ply 31-18.5X15 M/Ts. The improvement in handling compared to the M/T 28-7.50X15's is unbelievable! Had I known those front tires were causing the horrible handling I would have dumped them a long time ago. With the new fronts panic stops seemed fine but I only did them going in a straight line. At interstate speeds going around curves nothing seemed unusual. Admittedly I do not drive this truck like and autocross vehicle. Those circumstances may in fact be different. I do plan to replace the rears with radials of the same size in the near future. I don't drive the truck often enough to get $800 tires to the top of my priority list.

 

[khryslerkid]

Nice looking truck!

 

[YY1]

See, told ya.

 

[Rick62]

See, told ya.

Yep, thanks!