Mixing bias plys with radials, oh my

OK, i dont understand the logic behind it, but ive heard it several times-- "it's dangerous to mix bias ply and radial tires on a car."

is this an old wives tale, or is there something real behind it? logically, i dont see why it would be a problem.

on my cadillac project, im thinking about leaving the radial white walls on the back (it's so low you cant see a difference,) and putting bias plys on the front where i appreciate the square, old look.

by the way.... i'll be posting an update on the Noteboom / Gambino Kustoms '60 Cadillac soon. Lots of great stuff going on.

-scott noteboom

 

well, if you mix bias ply tires with radials, it will feel like you are driving on ice (i've done it before). the bias ply tires track one way, while the radials will be trying to track a different way. the end result is a car that wonders all over the road. i ran a set of bias ply skinnys on the front, and a set of m&h drag radials out back on my nova for awhile. if you can get used to the way the car will handle, it can be done. but, like i said, the car will wonder from side to side. it has to do with the way the steel belts are inside the tires. i think the steel belts in bias ply tires (hence the name "bias") only go go across the bias of the tire, while the steel belts in radial tires (hence the name radial) go around the circumference of the tires. i'm not a tire expert, but i think that since one set of tires has the belts across the tire(bias plys), while another set of tires has the belts around the tire (radials)...makes them track differently.

 

i found this by doing a google search for bias ply tires
Radial Tire - A radial tire has the plies running perpendicular to the bead and to the ground. This gives the chords, which make up the plies, a radiating look giving the tire it's name. Radial tires generally are made out of softer materials than their Bias-ply cousins. Normally the plies are made of polyester with steel belts over lapping on the tread section forming a damage resistant tread and very stable tire. However, the side wall is generally weaker on Radial tires than on Bias tires when it comes to puncture resistance. Part of this is due to less rubber being needed as the radial cords give the tire it's strength and low bearing ablity. With a radial design there is better handling, mainly due to the tread being independent from the sidewall so side wall flexing does not alter tread pattern. This leads to better traction with less heat build up resulting in greater tire wear with better fuel economy.

Bias-Ply Tire - A Bias-Ply tire has criss crossing layers that are generally 32 to 40 degrees from each other from the center line of the tread. Each layer is only strong going one direction, so the criss crossing pattern gives the tire it's strength in both directions. Bias tires are generally made from Nylon chords. Nylon is very strong for load ratings but is also very stiff. As the tire is loaded by the vehicle the chords are stretched and the entire body supports the weight. Since there is no other layer to the plies for the tread the tread tends to be round. If you look at military truck tires from the past they appear to be rounded. This is due to their bias construction. This creates a smaller tread pattern for contact to the road hindering handling. The bias tire also creates more heat as the cords flex and stretch. This heat is retained and degrades the tire over time. However, the bias design does have a very strong sidewall and can more easily withstand trail hazzards than a radial design. Due to their weight and less ease in rolling Bias-Ply tires tend to be less fuel effeciant for highway use than Radial tires.

hope this helps..

 

you cant mix them on the same axle - as beetlejuice says it will be like driving on ice, however it is OK to have them like you are planning, radials on one axle, bias ply on the other.

 

I ran bias plys on the front, and radials on the rear...the car still wondered all over the place. i took the bias plys off the front, and put a set of radials on, and the car quit wondering...so i know it wasn't a steering or suspension issue...it was the tires. who knows, maybe the bias plys that i had, were bad ? i did have them balaced, so i know that wasn't it. my nova had manual steering, and i don't know if that aplified the tracking of the bias plys on the front or not. it was driveable, and i drove /drag raced it like that for a long time...it just took some getting used to the way the car would react.

 

radials to the rear as the old tv advert always told us. Why? If you put them on the rear you will be able to out drift any ricer wheather you want to or not. Big Mickey T and skinny radials in the wet do wonders for your pucker factor.

 

I know of two instances where someone has lost control of a car with a mix of bias and radial tires with disastrous results. One was a 73 Monte Carlo that a friend of my dad's lost control in which resulted in the death of one person. I witnessed a buddy of mine who lost control of his 71 Cutlass on wet pavement and nailed a telephone poll head on. I'll never forget seeing that one...
Todd

 

Danger! Danger! Will Robinson! Bad idea.

 

Made that mistake once with my Challenger,,took a turn a lil fast and well,,,in just my understanding,,1 tire flex's alot more ( rolls or whatever the real word is ) I forget what the set up was bias on back or radial on front,,but I belive they both hold the ground differently so if the front of your cars doing 1 thing and the back another,,then somewhere in the middle you get screwed

 

I seem to remember Ryan saying he mixed bias and radials front to back and it drove fine. It was along time ago.

 

Positively! I had a street car, that I used to take to the track also, Once I threw my slicks in the back, and put 'em on with the radials on the front. Before the the car was at the traps, I had to get out of it...it was undirectable! ALL over the place...It was worse and worse, the faster it went, so...One might not notice it as much at lower speeds, but, I would not do it again...that was uhh...unpleasant!
went back with drag radials next week...straight as an arrow.

 

I've mixed and matched before, and had no problems. I know "they" say not to do it. I never had a problem.

 

Not only should you not mix radials and bias together, it is not recommended to run radials of different speed rateings together. Play it safe.

 

You will be all over the road, and hard braking will be a whole new animal. All I got to say is good luck but why would you want to do that anyway?

 

I wonder why mine doesn't wander(just had to mess with you a little)a signifigant amount, I have radials up front and very large Mickey Thompsons on the rear of my 120 mile per day driver(their website recommends against it, too.). No problems in rain, either.

 

i've done it, and it made the car almost undriveable.

then you got people here that say "no problem". makes me wonder how unsafe their car was before the mismatched tires.

 

what about the guys runnin recap slicks and bias in front?

 

In my experience (as limited as it may be) I've found that although mixing tires axle to axle may not be reccomended, I have never had a problem driving lightly. I havent raced around and pushed the car to its limits. I wouldnt with that setup, but I dont feel unsafe driving with the mix. I would not drive with radial/bias in the rain though.

 

I have Radir cheaters on the back and radials on the front, today. I also have a pair of radials for the back for potential wet weather days. I can't tell the difference.

Now, granted, the highboy with a mini spool isn't a cornering monster, but I drive it where I need to go just fine. Maybe it's not up to Ray's standards, but I'm fine with the car. It's been on the road for years, and down the track many times. Maybe I'm just a better driver than he is.

Even if it was "unsafe", shouldn't I be able to tell a difference between a trip down the highway with radials and then bias?

 

I'm running tiny 450-475 bias on the front and 8" Hurst cheaters (on radial casings) on the back. My car handles extremly well. It runs straight and true, brakes straight and I can hook neighborhood corners at 35 (not that I would....that would be wrong).
But I also new I was going to run this tire combo so when I put the new front end on I layed the axle back to 9 degrees instead of the normal 6 degrees.

 

After rolling a car on the LB freeway at rush hour, I'd recommend against mixing bias and radials on the same axle. But then I'm perhaps a little more performance oriented than I'm concerned with looks. If I can't haul ass in a car, I don't want it. That said, I'll most likely run bias plies on my roadster project. But on a heavy car like my Olds, NEVER.

 

You are making a highway cruiser that will haul your wife and daughter. Do you really want to take the chance?

 

my first reply that was 'it sounds like it could be dangerous-- but hey, i'll go for it.'

but Denise pulls me back into my responsible family guy role and it reminds me that i could afford bias plys all around instead (and sell the radials or use them elsewhere,) and not take any risk.

not fun, but yeah... the right thing to do.

these details about steel ply angles, etc is awesome. thanks folks for taking the time.

-scott noteboom

 

We respect you opinion here, Scott. Try each set of tires for a week and report back. Nothing like real world experience. That's a pretty heavy car. My money will be on the radials for long trips. Bias for profiling around locally.

Denise, as usual, makes perfect sense.

 

It is called "slip angle" which is the term used to describe the angle that the tire needs to be turned to develop a turning force. There is a BIG difference in the slip angle between a radial and a bias ply. So if you mix them when you drive down the street one end, usually the radial end, is much more sensative than the other so it is responding to much smaller steering and road inputs than the bias end and when you get the right combination of tires, suspension, alignment, wheel base etc you can get a car that is undriveable or you can get one that is no problem. The undriveable one is much easier to get. Don't do it, continous white knuckles can be painful.

Rex

 

X2

I ran radials on the front with bi-ass on the back; didn't drive too funny. And we have some pretty healthy ruts in I-5 going thru Seattle. Shoulda' showed up there.

I suspect it may vary significantly between make/model of tires in question. Just because it worked okay with my particular mismatched set of crap tires doesn't mean it'll work okay with yours.

-bill

 

this is the reponse i was looking for as im runnin hursts and bias in front (although im runnin 5.60s so im a lil better off)

sorry to hijack the thread

 

I did it with radials out back and bias'd tires up front in my Galaxie. Drove to San Diego from Phoenix, it SUCKED. I even got pulled over for suspicion of drunk driving. I wouldn't, now that I'm older and uhh, wiser(?).

 

Except for I was hoping he would choose the radials all the way around.

Experience talking here. Same car, radials for 40,000 miles, drove/rode GREAT. Roadster had a brand new set of bias plys we stuck on Big Olds in the spring two years ago I think. Took them off in less then one summer cruising season cuz they rode/tracked so bad. I didn't feel like I had complete control of Big Olds.

Scott, your Caddy is large, just try both types before you make a decision on what your going to drive cross-country.

 

No problems for me. Bias ply firestones on the front and good year radials on the back. I been driving it rain and shine for five years now.