Carroll Smith says that "The front camber curve should keep the laden wheel more upright in roll than the rear." Does he mean that the front wheel should be closer to zero degrees camber then the rear or that it should have less positive camber gain in roll?
Good question! Does Smith usually look at camber relative to the chassis or the road? For some reason, I think it's the former but it's been a while.
I would interpret that as less negative camber gain relative to the chassis in roll. Caster will add camber as the steering is turned.
So in other words, the front should gain less positive camber relative to the road in roll correct? That is what I was thinking, since it doesn't make much sense to me to have the front wheel closer to zero degrees camber in roll.
I believe what he is getting at is that the front loaded tire should be more square with the road. Negative camber is just pre-loading because you know chassis, wheel & other deflection combined with roll would push it positive otherwise. if you could magically have the tire at zero camber (to the road) 100% of the time that would be ideal.
Don't most race tires work best with some negative camber? I'm pretty sure some deDion and live axle guys try to build some negative into their axles, even though the tire's always going to be perpendicular to the road surface.
Since you don't want any tires going to positive camber in roll, I think Smith was saying that you want more negative camber (relative to the track) in the rear than the front.
Keith wrote: Don't most race tires work best with some negative camber? I'm pretty sure some deDion and live axle guys try to build some negative into their axles, even though the tire's always going to be perpendicular to the road surface. Since you don't want any tires going to positive camber in roll, I think Smith was saying that you want more negative camber (relative to the track) in the rear than the front.
What I was trying to say is that negative camber is not ideal... its how you make the suspension cope with deflection. After all the roll and deflection you want the tire flat on the road... since there is no perfect chassis you try to make them deflect to zero by preloading or using a "ramp" under compression. Any camber other than zero left in the tire under load is wasted footprint that isn't getting properly squashed into the road.
According to what I read, the Hoosier slicks that we would be using for the car work best in cornering at 1.5 degrees of camber.
What he means is that the Virtual Swing arm length (VSAL) for the front tires should be much longer than for the rears. You do this because the front tires gain camber not just due to body roll but also due to Caster, and to negotiate a corner and therefore initiate body roll you will have steering deflection. Front VSAL is in the order of 120-140" +. In the rear there is no steering change with cornering so all of your Camber change must come from a short (<80" or so) VSAL. Another reason to run long VSAL in the front and therefore low camber gain is during braking it keeps the front tires more upright to generate more braking force. In the back unfortunately with short VSAL you get a lot of camber gain during acceleration induced bump so this is why you run Anti-squat to keep the rear tires upright.
96DXCivic wrote: According to what I read, the Hoosier slicks that we would be using for the car work best in cornering at 1.5 degrees of camber.
Ideally you would have everthing in the suspension be fairly linear in nature, so say a 1g corner produces 1 deg of body roll and produces 1 degree of rear camber gain, and requires a steering angle that produces ~1 deg of camber gain. In this way you can just use static camber to optimize the tire cornering force. Where you run into problems and where tuning comes into play is that this 1:1:1:1 relationship will only occur at 1 speed on 1 corner of the racetrack, so you can really only optimize for a general behavior. This is why a properly setup AutoX car will be terrible on a road course and Vice-Versa. Suspension design is a horrible can of worms that can consume so much time. The good news however is that modern tires are much less sensitve then they used to be. That tire may be optimum at 1.5 deg, but it produces probably 98% of the max grip from .5-2.5 degress. This is to say that you can be pretty far off and still make a car handle good.
It's been a few years since I read Smith, like, 8 or so, but from memory, Smith almost always talks about the tire with respect to the road, not with respect to the chassis, because who cares about that anyway. Also, one of Smith's books has a chart of camber V. grip on a race tire, and there was a fairly broad band between about -1.5 and +.5 degrees camber, as nocones alludes to.
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