Re: Radial or Bias Ply Tires???

Posted by PackardV8 On 2010/10/7 16:51:06

I read most of the Imperial Club post.

I have to agree with BH that the "radial Tuned Supension" is just so much gimmick.

Such points about shock absorber valving is again just gimmick. One can buy a variety of shocks for ANY ONE SPECIFIC car and get a wide variety of valving or other technical changes in the shocks. So shock absorber variation/valving is a moot point.

I'm not sure about the toe-in issue either. Most modern cars (rear wheel drive) run at least 1/16" toe-in spec.


What no one has addressed here is the foot print of the tire while under operation. Foot print of the bias ply tires tends to move REARWARD and further rearward as the speed of the car increases. Radials tend to move rearward much LESS than bias ply.
What this affects is the CASTER setting of the front suspension. The bias ply tyres tend to create THE EFFECT of more negative caster than the radials. Most cars built prior to the early 60's are spec'ed for neg caster. So the putting radials on a negative caster car will tend to give the EFFECT of zero or s0mething closer to positive caster.

The negative caster of pre-60's cars coupled with the rather large stering wheels was an attempt to make the cars steer ez at low speeds and parking. THE DRAWBACK is that negative caster creats alot of wander or hunt in the steering at higher speeds of say 45+ mph.

Most manufacturerss moved toward POSITIVE caster during the early to late 60's WHILE PROMOTING power steering and makeing smaller steering wheels because the car sihoutte was dropping. I'state hwy commision was born.

All of these 1965'ish driving environment and manufaturing evolutions allowed for and demanded the positive caster setting. POsitive caster alllows for a more stable high speed steering control.

So the so called "Radial Tuned" suspension is just so much nonsense. Makes for good coctail party buzz words but that's about all until someone can be more specific as to what changed in the radial tuned suspension other than a cheap pair of shock absorbers.