Re: Radial or Bias Ply Tires???

Posted by Highlander160 On 2010/10/28 11:46:15

I didn't read every reply and it seems to have taken the "scenic route" with regard to dates and safety beads which is just fine. Any tire discussion could lean to many aspects on the topic (no pun intended for you that are well versed in tires).

My input is related to the original topic, radial or belted. Simply adding radials may indeed lend some improvements but it can also lead to things not considered. A radial tire will add another function of sorts to the suspension. You will get the side-to-side motion that makes a radial a superior tire. A good thing? Maybe, maybe not. What I find from our customers with tire complaints is that we've all developed certain automotive habits over the last 25-30yrs. Radial inflation can be as high as 32-36psi in modern cars with low aspect ratio tires as OEM equipment. Many cars are intro'd with 60 series tires and additional inflation is required to maintain handling and ride quality. Over-inflate a belted tire and the car will wander following any tar strips or grooves in the road. It's effectively "thinner" at the all important contact patch or "where the rubber meets the road" as the ol' cliche goes. 30psi is a lot of air for a belted tire. I personally like 28 in some of the 700 or 750 17s on so many of our customers cars. Newer 16s and even 15s, same thing. The handling difference is sometimes just short of amazing just with proper inflation. Another thing that a radial can do is mask the real problem. I took a 160 for a ride recently that hand the dreaded wander lust. A full set of kingpins and some shock oil later, just what I've come to expect from such a car. These cars are old and in their day they were almost always at the top of their game in the industry, and while not sportscar handling would out perform most other makes in ease of driving (why we all like em so much!).

Those points aside, is a radial a bad thing? No. But in order to gain the full benefits of radial tires I'd recommend some add'l changes. Higher shock rates are a good start. Heavier anti-roll bars or at a minimum more solid mountings for the bars would also be a good thing. Since a radial can introduce lateral motion to the car's platform suspension changes should follow up their use. That lateral motion can serve to enhance the natural roll of the car's OEM design by getting it started before the suspension reacts. Consider how the car as a whole can be bounced from side to side just on the tire's sidewall when it's sitting still. Certainly belted tires have a similar motion but not as easy and less total movement. In motion you can feel this effect of the car 1st, then the suspension does it's thing. Bad? Dangerous? Maybe if things aren't up to par before installation. Radials offer less rolling resistance, a softer ride, lateral control and long life. All good things but like anything else the rest of the system needs to support those benefits. I'm adding radials to a 61 @#&^% that was originally eqipped with belted tires. The power steering box was upgraded to lose the slave cylinder system, a heavy duty sway bar is being installed, HD gas shocks on all 4 corners, and the alignment settings will be changed, the biggest change being another degree or 2 of caster to slightly increase the initial effort of the steering from straight on. I'm confident that I'll get the full benefit of the tires with those changes. On the other side of things my 160 will have belted tires. I'd rather have it "as it was" on roads that are generally superior to what they were back then.

If some of those ideas were covered and I missed em, sorry for the repeat, but these are the things I see in the continued discussion (debate?) of radials/belteds. Hope it helps.