Mixing bias plys with radials, oh my

Since I've been in the tire business over 30 years, I'll pipe up.

The problem that CAN arise with mixing the two types of construction results from the "slip aspect" being different, as LATERAL force is put into the tire(s).

The more compliant radial sidewall lays over more, maintaining the tread patch, until lateral traction is suddenly lost. The bias sidewall flexes less, and the tread lifts sooner, but gradually.

Bias/rear-radial front can result in the rear end coming around, but usually with some advance notice. Bias/front-radial/rear results in plowing or understeer, with sudden loss of traction in the rear.

Different tread widths, design, size and air pressure between the two types can compensate or deteriorate the imbalance, due to contact patch size and traction coefficient. In other words you can get away with it.

Both exhibit different behaviors with steering input for the same reasons. "Road walk" is different, and caster angles can compensate.

BUT, throw in some wet pavement with a sharp turn, and the pucker factor increases.

As the Sarge said "let's be careful out there".

ps: REX (above) is right

 

I noticed the people having trouble the the bias in the front are doing it on 70's vintage cars. Isn't there a difference the required toe setting for bias vs radials. I suspect the 70's cars have toe settings for radials.

My 2 cents.

 

If it's a matter of money, wait until you have enough to buy four (bias are cheaper than radials anyway (WWW)). If it's a matter of trying to change the quality of the ride, it would appear that you only stand to lose by mixing.

 

that makes sense. i never had the front end aligned on my 70 nova (which could have been part of the problem). it drove fine with radials all the way around, but was squirrly with bias in the front/ radials in the back. it was tolerable, and it never got out of control...it jist wandered (which i got used to).
on the other hand, my friend had an 87 buick grand national (that he bought brand new in 87). he bolted a set of bias slicks on the rear (with the original m.f. goodbitch radials on the front) and that car was un-controllable. i remember the term "radial tuned suspension" but i think that was a pontiac thing ??

 

So 25 people say don't do it, then the 26th said it was ok so your good?

 

Been doing it for 4 years now on my RPU...... only problem is when you "punch" it.........

 

to respond to a couple people:

1) yeah, ive run bias plys on many cars. the big, heavy cars are noticably worse-- as they track all over the place and are much more sketchy than the light cars (which arent bad at all.) That said, i just love the look of the square looking bias plys with a pie crust outer pattern.... love the look, even though it doesnt fit a 1960 Cadillac era so much (im thinking about that.)

2) One of my good friends runs mixed bias plys on front and radials rear on his 1949 Chevy. Just went on the Pacifica - Santa Cruz run with him today. He says he cant tell much of a problem. But, the car is much lighter and he hasnt run it long enough to have an opinion in rain, etc.

3) I (not family) may try to see how it rides with the mix-- being that it takes MAJOR EFFORT to change my rear tires (wait til you see it-- (i'll give you a tease...) the '60 Caddy project now has the skirts welded to the body. Yeah, i know it isnt sensible-- but you gotta pay a price to look good That said, i gotta drop the rear end to get the tires off!

4) When i drive across country with the family-- it'll be on radials, which i have on the '62 Lincoln.

thanks again for all the input.

-scott noteboom

 

Had radials on the front and bias-plys on the back in my beater 1980 Toyota pickup.

It was scary as hell in the wet weather, the rear end would slide out very easily with very little throttle in a corner, way worse than a full set of radials. I almost hit another car a couple of times before I got rid of the bias-ply's.

I won't tell you what to do, but I'll never run mixed radial and bias on my vehicle again. One or the other, not both.

Shawn

 

I've heard that just running differend size tires frontand back can take away from the handleing of a car.

 

-I agree with the above posts... It would be similar to me being warned to NOT run different brands of tires front/rear on my 4wd. I didn't believe the wise man at the tire store, and figured I knew better... Same as what other's describe...felt like I was on ice, as I was swapping ends, so I imagine bias ply, radial mix would the same... Just doesn't sound like a good idea... -Tony B.

 

Old wives tale running bias plies on the front will make anything wander don't matter what you run on the back. Radial tyres are much more forgiving of heavy negative camber thats the real difference .

 

I have M/T N50 15 on the rear and 225 70R 14 on the front of my 73 Sat and drives fine. Handles good in wet weather as well. Handling never a problem. But I am curious if vibration I have at 65+ could be a result of mix?

 

As an example imagine this.....
Ya have cushy low air pressure radial tires on the front with their sidewalls squirming left and right as you encounter the dips and curves in the road......
Now on the rear you have solid steel wheels that would have to slide to give any amount[in side to side motions].....
see where Im headin here?
one end will be pinned in plase rolling straight forwards and the other will be squirming slightly left to right at will.....
Not a very apealing thought at 70 MPH...even when the road is dry muchless on wet pavement....
I never could drive any car with them mixed,and feel good about it.

 

Not at all an old wives' tale. I did this once and my Impala handled like I was driving on ice. Lesson learned.

 

I drove my old T roadster with 5.60-15 bias plys up front and 235R78-15 radials out back for several years in rain and sunshine and never had a moment of anxiety due to the tires, I did have a few due to traffic and personal loss of sense.
I think light cars, under 2000 lbs or so probably don't exhibit the nightmarish behaviour that heavier do when mixing B&R tires.

 

You probably would notice it less with the radials on the back rather than the front..I had the opposite on a 35 coupe and I suppose maybe a little slack in old steering components, added to the extremely squirmy road feel.....

 

before there were wide radials we all ran radials on the front and bias 50's on the back, this was in the 70's, when radials became more common i put lots of radials on the front of cars with bias on the back. if you put bias on the front and radials on the back they were squermy.

 

Why would you want to do this. Go with Bias or go wiith Raidal, no reason to mix.

Post photos of said caddy

 

I think HOTRODA has it right , i tried it on a early nova with mixed results, but my GTO has went 131 mph thru the traps with 175/80 bfg radials up frt, and et streets bias plys in the rear, and drove good on the highway too. but then it has a bunch of caster in it .

 

Dont mix your tyres (Aussie spelling) Very bloody DUMB. not an old wives tale.Read up or ask your tyre man why radials were ever invented and you should understand.Would any of you drive with1900s solid rubber tyres mixed with cross plies???

 

A story I've told before, but...

When I bought my '60 Pontiac in 1994 it came with these shitty nearly worn out bias snows on the back and new, although older, General radials on the front. I drove it like 75 miles up the interstate to come home and every ridge in the road - every place they'd sealed up a crack with tar - the back of the car would try to follow it. It handled terrible that way. Wet road didn't seem to be any worse.. it would just follow any sort of line or crack and feel like it wanted to swap ends, you constantly had to correct the steering.

So I went to a tire store and tried to buy two new tires. Of course, they didn't have the same size as the fronts, they were an oddball size. Well, the car drove terrible, and I didn't care if they were a little bigger in the back. The dipshit manager there wouldn't sell me just two for the back, he told me it wasn't safe to mix & match tire sizes. Never mind that I'd passed someone in a pro-street '70 Camaro on the way there - the only way it could have had more difference in size front to back is if they'd put riding mower tires on the front and monster truck tires on the back - this prick just wanted to sell me four tires. I said "screw this" and went home and had a pair of 235/75R15s off a '79 Buick that weren't quite worn out and had some dry rot cracks and slapped them on.

The difference was like night and day and I drove 'em until I wore them out. That car would handle like a racecar with the long wheelbase and wide track, I really found out what that old sedan could do.

It could be you don't notice it as much on a lighter car, but I sure as hell wouldn't mix and match again. I'll buy wrong-size rims with good tires at the u-pull-it if I have to.

 

my followup to this post that i started: thanks much for all this good info. ive decided against mixing my tires

-scott noteboom