How does the caster setting affect an AutoX car.

What is the best, and why.

Rich

The more caster one has, the more it effects an AX car in a positive manner....2 areas.

The first is as the wheel turns, the caster causes an increase in the negative camber on the outside wheel. This helps counteract the positive camber caused by body roll....if you have any

Second is the steering centering effect.....big deal, one might say....what's that good for? The answer is catching tank slappers or limiting them to one "slap".
I don't recommend letting go of the steering wheel (actually, letting it slip thru your hands) to novices, but the wheel will spin a hell of a lot faster than you can turn it.....ya just gotta grab it again at the right time. It takes some practice.

5-6 degrees is good....I run close to 6. I understand more than 6 is not better, but dunno why.

so, more caster would mean that the top of the strut would be as far toward the rear of the car as possible??

R

Ayup. That'll be right around 6 deg.

Would it be recommended to do the 6 deg to a street car?

6 +/- 0.5 degrees is the stock setting.

Ah, simple enough I guess I would have figured that out once I got to that part of my operation.

A rule of thumb we use is for auto-x, DE and other stadium events we would take caster out as the car turns quicker, sort of like toe out. On road racing course such as the CA Speedway, we put in as much caster as possible since we want the car to be stable on the high speed banking portion of the race track and the turns are not nearly as tight as an auto-x course. When I was racing bicycles, my road racing bike had more caster or rake in the front forks which made it easy to ride in long road races but the criterium and track bikes had very little rake or caster since they needed to turn very quickly in short races.

I am of the same thought as John on this one.
I used to have a lot of caster in my car. did not turn in as quick. much more stable at high speed.
the one road course I run has tighter turns where I can excel so I keep the caster less than full.

I'm pretty firmly in the camp of caster is good for autox. And more is better. Granted, there's such a thing as too much of a good thing. But the dynamic camber gain more than makes up for the reduced turn-in if that is the ONLY thing you're doing.

But it's all a system. Caster alone is not the end-all-be-all. You need to dial the rest of the car in around it. And a truly hot setup for autox, is not going to be a hot setup for track or street.

Having a lot of caster allows you to run less static negative camber, giving you a better contact patch for braking. Turn-in won't be as light, but the car will have more front end grip when you need it (mid turn). Turn-in then can be played with by toe, or spring rate, or just compensating with the steering nut. I think I'd rather have a little more effort for turn-in if it meant I could carry an extra .15 G around a turn.

-Josh2

You had me right up to the point where you say you set up with less negative camber and have more grip in a corner....not in my experience...but I also don't run max caster on my race cars...I do use a pyrometer to maximize all test set ups though....I'm also not sure your more caster/less neg camber theory is correct...but if it works for you...who am I to argue.

F=uW

Whatever makes the tires stick best.

Absolutely. The pyrometer tells all. With more caster, you don't need radical amounts of static negative camber. The negative camber grows as the wheel is turned. Now, a track car doesn't see as much steering angle as an autox car does, and as such, you don't get as much of a camber benefit from caster.

For a fictional example: You have a 1982 hupmobile.

You can, fictionally speaking, come off a hypothetical skidpad with identical tire temps. Two different setups.

Car 1: 6 degrees of caster, -1.5 degrees of camber.
Car 2: 4 degrees of casetr, -3 degrees of camber.

Car 2 will have lighter, more responsive turn-in, but will be more prone to locking up a tire under braking, and if there are a lot of high speed straights, the inner edge will wear more.

Car 1 will have heavier turn-in, but will have more contact patch on the ground when the wheel is straight.

What's good on the track, is not necessarily good for autox, and vice versa.

-Josh2

And if you've ever driven a Hupmobile, you know how important this can be!

Like Josh said it all about the whole set up.
Since I run 11" wide slicks up front and they don't like a lot of camber my set up is going to be different.
Tire pyrometer readings vary as little as 5 degrees inside to outside when up to temp of 120 degrees.

Lots of caster makes them big tires a real bear to turn. If I remember right John Rogers runs slicks too.

And slicks require a LOT less camber than radials do. So caster is no longer the "big thing" once you start running on slicks.

-Josh2

OK I am almost to a point where I will need an alignment.....can I do this at the shop (mine!) or do I NEED a alignment machine??

Sorry to hijack but.....