Radial vs Bias Part 1 – Hot Rod Shake’n Fix

Posted by pikesan on May 2, 2012 in Featured, How-To & Tech | 2 comments

Hot Rod Tires How-To – Gotta Drive Fast!

Simple question: What’s wrong with this photo?

 

If you answered, A) Dude’s running Centerlines on a hot rod (What a loser); Well, you’d be part right. Why would I do such a thing? Does the car look better like this:

 

Take your time…. YES!! Much better. The bias plys on Bonnie make the vintage look, just like bias plys do on tons of other hot rods going for a straight out of the 50s, nostalgic look. (I’ll also agree the backdrop of the Bonneville Salt Falts doesn’t hurt!)

So why have I replaced my bias plys with radials? Simple: I want to drive… drive fast on the freeway.

 

I originally had a set of white wall, radial tires on my roadster. I dig the white wall look, but like I said before, I wanted my roadster to be more early 50s looking. Plus the blackwalls look more hard core hot rod to me, like my main focus is running fast, not looks.

 

Anyway, I had the radials on before, and when people asked, “How fast is it?” I’d say, “As fast as I dare to drive it.” I didn’t know how fast it would go cause I’d get scared long before I ran out of motor. Comparing that to the bias plys, I’d have to say… About 60-65mph. I was scared at 65 cause the front wheels would bounce or hop so bad I was afraid I’d lose control! Pretty much both wheels would hop off the ground if I went fast enough. The whole car, all 1475 lbs of her, shook. It sucked.

 

Now it’s time to figure out what’s wrong. What have I done so far:

 

• Proper tire inflation: 32 psi
  • I know some will argue this, but I tried low pressure and it was worse for the hopping
• I switched tires and wheels left to right – no effect
• I tried to re-balance the wheels – We could never get it right. Every time we’d add a weight, it’d say to add another one, then another in a different place.
  • no, I didn’t use a road force balancer but would like to
• I stripped off the balance weights and added Dyna Beads
  • A couple people recommended them. I think they helped, but not enough

 

So finally, I added the Centerline wheels and radial tires. Problem solved. This tells me I’ve definitely got a problem with my bias plys, or possibly the wheels are bent or damaged or otherwise no good.

 

Don’t Do it: Mix Radials and Bias Ply Tires

 

I’ll walk you through how I fix this problem, hopefully without buying new tires. I’ve recruited the help of Coker Tire expert Tommy Lee Byrd. The first thing I asked him was about mixing radial tires and bias ply on the same car. He said don’t do it! (And I recommend you don’t) He said:

 

It looks like you made the right decision with trying a different tire and wheel combo on your roadster, but it’s not a good idea to mix bias ply and radial tires, as you’ve heard.

The bias and radial mix is a definite NO NO. Coker’s stance on it is to never mix bias ply tires with radial tires….we definitely want to make that clear.

The reason behind that is the way each respective tire handles the road. Bias ply tires generally have a narrow contact patch with a criss-cross ply construction. This makes the tire stiffer and less forgiving, meaning that it’s more likely to follow the ruts, ridges, etc. in the road, while a radial tire conforms to the terrain. So, if your front tires are radials, they’re going to skim over those bumps and ruts in the road, while the rears (bias ply) wander around. As you can imagine, this makes for weird driving characteristics, which can be unsafe at high speeds or on wet pavement.

I should mention, I bought all four of these tires and wheels used off Craigslist. A risk, I know… probably didn’t work out so well, but I’ll fix it. Stay tuned!

 

Next step: Balance the bias ply tires and make sure the rims aren’t bent