In Reply to: Three wheel turns, MTAERO [Profile/Gallery] , Sun, 30 Nov 2003 22:50:32

I get this in my SPG in corners where the corner-entry favors trail braking. Going up on 3 wheels is a suspension failure, but I don't know how to "fix" it!

I see it like this:
Typically we make the rear suspension stiffer to get more responsive turn-in and less understeer. Works great. At the front end, making it stiffer will reduce traction & increase understeer, so most people setup their cars with the front end relatively softer than the rear - this keeps your understeer in check and also the traction will let you put the power down more effectively.

This mismatch in roll stiffness front-to-rear is what gives you this raised rear wheel syndrome. When the body rolls, that rear sway bar resists it, even to the extent in the picture (picking up the inside rear tire). When the body rolls, the front just lets it roll. It is trying to keep some weight on both tires so that you can maintain traction with both tires. Presumably you need that for the braking and/or cornering and/or acceleration you are trying to accomplish.

You could make the front/rear roll stiffness exactly the same, that would eliminate wheel lift. And in a race car with 50/50 weight balance, this is definitely the goal. But this would turn a nose-heavy FWD Saab into an [even more] understeering pig! It is all about compromise.

Question for you MT AERO, did you know the car lifted at the time? Or did the pictures surprise you? I could not tell until a spectator told me, and even then it was hard to notice.

posted by 63.207.93...

• Three wheel turns, MTAERO , Sun, 30 Nov 2003 22:50:32
  • Re: Three wheel turns, RobInfo, Wed, 3 Dec 2003 03:57:11
    • perfectly natural, MTAERO , Wed, 3 Dec 2003 19:48:50
  • Re: Three wheel turns, gorper, Tue, 2 Dec 2003 11:01:42
  • Viggen will do it too, CFishgo, Tue, 2 Dec 2003 08:17:39
    • I think it has to do with the non-independent, nickR, Tue, 2 Dec 2003 18:32:53
      • I saw pics of a vw Golf flip on a turn on dry pavement, Steve88SiS, Sun, 7 Dec 2003 10:31:22
  • Re: same here, damien, Mon, 1 Dec 2003 12:05:59 <-- Viewing This Message
    • Don't fix it, MTAERO , Mon, 1 Dec 2003 20:05:35
    • no understeer here, MTAERO , Mon, 1 Dec 2003 19:56:38
  • Impressive - ABS defeat?, Chris, Mon, 1 Dec 2003 08:37:48
  • Re: Three wheel turns, jp, Mon, 1 Dec 2003 07:06:30
  • bigger photo, MT AERO, Sun, 30 Nov 2003 22:54:23

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