In Reply to: another view, Kevin K [Profile/Gallery] , Fri, 15 Jun 2001 10:32:45

Your first point is incorrect. Scrub radius ( the distance from the tire center contact path to the king pin at the ground) will have almost no effect on torque steer. I have modeled torque steer extensively and the parameter that matters is spindle length. Months ago I posted the governing equations and derivation. If you are interested I could take some excerpts from papaers and e-mail it to you. As far as typical values for spindle length, yes they are usually much greater than 20mm (55-70 mm for most strut cars) The reason that the 20mm number was quoted comes from a study done by toyota that showed an exponential increse in steerin wheel torque vs wheel torque imbalance, however with less than 20 mm SL and the torque levels they were using there was nopt an appreciable difference since other effects dominated.

Not trying to prove by intimidation but a little background about myself. I work for GM at the advanced chassis center. My title is "Lead subsystems engineer - suspension" I have done some extensive research and modeling in the field of torque steer.

There are lots of very smart people that think the scrub radius will effect torque steer but it is not the governing factor. Draw a free body diagram taking all the forces into account and you will see as well. People who come to the scrub radius conclusion miss a crucial force in their FBD. Not only do I have math, but also computer modeling and experimental data show that Spindle length is the key. (this is assuming equal length and stiffness halfshafts as well as a fairly rigid body)

Scrub radius is important for many other parameters such as brake loads and wheel feel, but does not affect torque steer.

The torsional stiffness of the halfshafts can have transient effects. They are reduced with an open diff, but a report I got from the proving grounds showed that the phenomenon is much more significant than I ever imagined it could be.

-Joe

• Viggen v. TT for Torque Steer, bob, Wed, 13 Jun 2001 16:13:03
  • Re: Viggen v. TT for Torque Steer, Increased Tire Pressure, Sat, 16 Jun 2001 18:49:19
  • Re: Viggen v. TT for Torque Steer (long), Dean, Thu, 14 Jun 2001 09:19:24
  • Re: Viggen v. TT for Torque Steer, 2Slow, Wed, 13 Jun 2001 16:55:45
    • another view, Kevin K , Fri, 15 Jun 2001 10:32:45
      • Re: another view, 2Slow, Fri, 15 Jun 2001 12:49:06 <-- Viewing This Message
        • Re: another view, Kevin K , Fri, 15 Jun 2001 15:03:41
    • Why then does the "torque steer" virtually dissappear, Talladega900, Wed, 13 Jun 2001 17:28:43
      • Re: Why then does the "torque steer" virtually dissappear, bob, Fri, 15 Jun 2001 11:41:22
      • Re: Why then does the "torque steer" virtually dissappear, 2Slow, Thu, 14 Jun 2001 08:39:43
        • Ahh. I see what you're saying. Really a matter of semantics, Talladega900, Thu, 14 Jun 2001 11:07:33
          • Perhaps this helps explain why "camber steer" is a misnomer..., 2Slow, Thu, 14 Jun 2001 12:51:54
            • I thought camber steer referred to..., LDH, Thu, 14 Jun 2001 13:17:22
              • Re: I thought camber steer referred to..., 2Slow, Thu, 14 Jun 2001 13:30:47
              • Re: I thought camber steer referred to..., 2Slow, Thu, 14 Jun 2001 13:24:50
      • Re: Why then does the "torque steer" virtually dissappear, Brad, Wed, 13 Jun 2001 19:25:01
      • It reduces compliance, Schu, Wed, 13 Jun 2001 19:15:02
    • Very good input Joe, Schu, Wed, 13 Jun 2001 17:10:52

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