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    Results 1 to 3 of 3
    1. #1
      Join Date
      Sep 2007
      Posts
      419

      Are there any radial tires designed for smoother break-away traits?

      I never never heard or seen much discussion of this going on. The old bias-plys are inferior in most ways but the "hard" design makes them lose grip very gradually.

      Tires with a gradual loss of grip are more fun to drive. Screw the track times. I would readily sacrifice some ultimate grip for the sake of friendlier traits at the limit.

      (I'm talking street tires in old car sizes with some sidewall height. 15-17" rims, 225-255 treads, 50-70 series sidewalls, etc.)




      There also seems to be some difference in opinion about whether a tread that is more free to move (laterally) is better or worse for break away warning. I mean like when the sidewall is tall and/or the tread width is bigger than the rim width, the tread can move more. I've always considered that movement to be a negative thing and sought rims near the width of the tread.


    2. #2
      Join Date
      Sep 2017
      Location
      Silicon Valley
      Posts
      4
      Country Flag: United States
      @mikedc,

      Often putting modern high performance tires on cars from the 1950s-1970s is that because the tires have higher grip, the higher cornering loads stress the suspension more than the original tires. There several things that can be happening at once that would cause the car to be nervous and unstable. First, if suspension pieces are worn, particularly the steering linkage pivots and ball joints, the steering box, and the fabric joint in the steering column, then the front wheels won't stay exactly pointed in the direction you want, forcing you to make constant little steering corrections. Next, the rubber suspension bushing pivots, particularly in the lower control arms in the front, and the control arm pivots and the forward attachment to the body or frame of the leaf spring eyes will, even if brand new, will be compressed more than with the original tires that couldn't generate as high cornering force. The sensation for the driver is that as you approach the cornering limit, the car suddenly breaks loose because the compression of the rubber control arm bushings mean the angle of the tires to the pavement is no longer in the sweet spot of where the tires work best. As soon as the tires break loose, the cornering load goes down, and the rubber bushings are unloaded, which returns the tires to their sweet spot, and you build up cornering force again, until the tires break loose. All this happens a lot faster than reading my words, and for you the driver, you are constantly making steering corrections at the limit, and blaming the tires.

      There is one other contributing factor. Because the tires grip more, the car is rolling over more in the corner, which may mean the outside tires in a corner are leaning over (technically, positive camber) more than they were designed to, also resulting in the tires being outside their sweet spot.

      What's the remedy?

      Replace the joints in the steering linkage, and the ball joints, rebuild or replace the steering box, replace the rubber bushings in the suspension pivots with new ones. Replace the anti-roll bar bushings. If you really want to make the car easy to drive at the limit, you can replace the control arm bushings with high-quality parts from companies such as Global West. I would strongly caution against using polyurethane bushings, and also I would advise using spherical bushings in the front eye of rear leaf springs, and in control arm bushings on cars with upper and lower control arms. In the rear, the control arms need to twist as the car leans. The orignal rubber bushings are designed to distort when cornering, but tubular bushings won't, so it's better to use spherical bearings. Finally, you can replace the anti-roll bars front and rear. Notice I am not recommending to replace the standard spring rates with stiffer ones.

    3. #3
      Join Date
      Apr 2005
      Location
      Colorado Springs
      Posts
      760
      I seriously doubt there are any classic muscle cars being used for performance driving that still have original suspension and alignment specs under them any longer.

      Bias plays and radials simply broadcast their traction differently. Its because of their construction.