Race Cars and Motorsports

No not drag racing, but as pertaining to sports cars with doors(production derived). Perhaps we can chat, in depth, about production suspension settings,(static), how they change,(dynamic) and how/why the modify. As I understand "some" of this, I'll try to start something. Ackerman, makes sense in theory, but in hot pursuit-maybe not.Considered at "zero" slip angles of tread and chassis, so tires woun't scrub/squeal while turning around slowly,(street theory).Dynamically, not so good, short sidewall tires with reduced slip angle tolerance,(quicker steering response), at speed, inside tire ,more lightly loaded, will be forced past it's maximum usable slip angle,(too much Ackerman/toe-out of inside tire), reducing effective ness. Correct amount of Ackerman, can assist on initial, "turn in".I suspect, "tires" like stagger better, as the hot set up through the turns,( one way) ? Discussion ? roverman.



Edited 2 time(s). Last edit at 05/27/2010 10:49PM by roverman.

Simple example of Ackerman steering: when you crank the steering wheel to the right, the left (outside) wheel turns at one angle (for example thirty degrees) and the right (inside) wheel turns at a somewhat greater angle (for example thirty-five degrees).

Without doubt, Ackerman steering is helpful at low speed. The front tires are inevitably traveling on two different radii, and Ackerman reduces friction. As suggested above, at higher speed things are different for many reasons including (a) weight transfer unloads the inside tire, and (b) we don't turn the steering wheel nearly so far.

I'm not certain, but I believe it's accurate to say that Ackerman steering is built into almost every production car and truck, and has been since beyond memory. But many people, including I believe Colin Chapman, have questioned whether Ackerman steering has any benefit for a racing car. Carroll Smith discussed Ackerman briefly in "Tune to Win" (~1978) and in detail in "Engineer to Win" (~1984). Between the two books, based on testing with a Formula Atlantic racecar, Smith gave up on parallel steering and became a believer. As I understand it, the key certainly isn’t in maximum cornering force – it’s in getting the “right” (small and predictable) amount of understeer during transient corner-entry situations without resorting to static toe-out. (In the late sixties and seventies, it was common for racing cars to be set up with slight static toe-out.)

That said, there are so many other suspension variables: static weight distribution, tire inflation pressures, tire size, tire compound, spring rates, shock valving, camber, caster, king pin inclination, toe-in or toe-out, bump steer, anti-sway bar stiffness, roll center height relative to CG (i.e. roll couple), anti-dive, etc. - If we could only survey suspension designers and learn how they prioritize these variables!

One of the most interesting conversations I've had about suspension set-up this past year was with Jerry Richards who is exceptionally quick in his MGB GT V8. More often than not, Jerry races on clockwise tracks and particularly on tracks that have a righthand turn before the main straightaway. So, guess what? His car is weight biased (heavier on the righthand side) and he also typically runs different tire inflation pressures left vs. right (depending on tire temps, etc., and specific tracks/conditions.) He rates the importance of correct shock valving VERY high in relative priority. Or maybe not. He might have been pulling my leg.



Edited 1 time(s). Last edit at 05/28/2010 07:10PM by Moderator.

"Full Ackerman", as I was taught, rear steer, steering arms angle inward ,towards rear, and their certerlines intersect the equal distant centerline, between rear wheels. Altering this angle,(moving centerlines outward), is called anti Ackerman. Formula 1 and sprint cars, run very little to none,( go figure). Front steer is tougher to get anti Ackerman. 3 wheelers, no clue. Any Morgans in the forum ? Obviously, there is much tunability , between full and zero Ackerman. Your results may vary. Tune in next time, maybe we'll discuss, "anti dive providing dynamic roll caster gain and negative camber gain." roverman.