Caster setting

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Ceedawg

Ceedawg

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On a race car, what will work ok 0-1-2-3 degrees, 0 seems to work good for my toe in but open for sugestions
 
This gives a good place to start:
1677689253609.png
 
If you have a stock suspension:

@ +1" nominal ride height:

-.5* camber
+2.5-4.5 caster sweep
Toe 0-1/16" in

Send it
 
Just to be sure, positive is toward the back of car?
 
What kind of race car? Settings for a slalom car would be totally different than a drag car or oval track car.
 
1970 Duster drag car, hope it never does slalom
 
Reason I ask, with 1* I get almost no toe in (1/6”) change but with 3* I had 3/16. 0* camber change throughout rebound and jounce. As long as car don’t move around @ 125 mph it’s ok by me.
 
As the skosh chart mentions, try to figure out the ride height when the car is accelerating down the track, then jack the front end up to that height when making the alignment adjustments.
 
I have the frame set on stands and I move the spindles up and down and set at different heights, no shocks or T bars
 
On a drag car +3 degrees caster minimum. I like to drink my coffee in high gear.
 
:popcorn: :popcorn:
All ears as the lack of caster on my avatar is what is causing me issues. Not going back to the track until I can get some positive caster (I have 0 to -1* caster now and car is very unstable at speed). Waiting to install my new SPC fully adjustable UCA's to address the issue.

@LO23M8B - I like your analogy!!:rofl:
 
Demonx2 said:
:popcorn: :popcorn:
All ears as the lack of caster on my avatar is what is causing me issues. Not going back to the track until I can get some positive caster (I have 0 to -1* caster now and car is very unstable at speed). Waiting to install my new SPC fully adjustable UCA's to address the issue.

@LO23M8B - I like your analogy!!:rofl:
Click to expand...
I've got some aftermarket solid upper control arms that are a bit longer and helped with caster and bump steer. I'll try to think off what co. I bought them from. They were great to deal with.
 
I always liked more caster than the skosh chart shows on mine when I was drag racing.
 
cudamark said:
As the skosh chart mentions, try to figure out the ride height when the car is accelerating down the track, then jack the front end up to that height when making the alignment adjustments.
Click to expand...
The further the suspension extends, the LESS caster you can get.
In other terms, these cars can get the MOST caster the lower the front end is. If the front is cranked way up, positive caster may be impossible to get.
It is just how they are designed.
 
LO23M8B said:
I've got some aftermarket solid upper control arms that are a bit longer and helped with caster and bump steer. I'll try to think off what co. I bought them from. They were great to deal with.
Click to expand...
I believe that they were Magnum Force. They also power coated them for me.
 
Kern Dog said:
The further the suspension extends, the LESS caster you can get.
In other terms, these cars can get the MOST caster the lower the front end is. If the front is cranked way up, positive caster may be impossible to get.
It is just how they are designed.
Click to expand...
That's exactly what Peter Bergman explained to me when I bought the SPC arms from him. My car does sit a bit higher and lifts quite a bit on launch (pics suggest about 4" of lift) and down the track. But c'mon, there's cars that are a LOT faster than mine that hold the front end up and don't have this stability issue. So I am counting on the UCA's to give me some caster and address the stability concern.

One thing a higher ride height setting does do is cause more toe change when the wheels drop down. I've used the methods described in the Mopar Performance Chassis manual to measure this. The tie rod end "looks" longer and adds toe-in when the wheels drop. So it's all a balance that I clearly have wrong and will get after when I install these arms and set up the alignment.
 
Demonx2 said:
That's exactly what Peter Bergman explained to me when I bought the SPC arms from him. My car does sit a bit higher and lifts quite a bit on launch (pics suggest about 4" of lift) and down the track. But c'mon, there's cars that are a LOT faster than mine that hold the front end up and don't have this stability issue. So I am counting on the UCA's to give me some caster and address the stability concern.

One thing a higher ride height setting does do is cause more toe change when the wheels drop down. I've used the methods described in the Mopar Performance Chassis manual to measure this. The tie rod end "looks" longer and adds toe-in when the wheels drop. So it's all a balance that I clearly have wrong and will get after when I install these arms and set up the alignment.
Click to expand...
Do you work at a shop with an alignment rack?
 
i might be wrong

BUT as the front end of the car rises you have the droop of the suspension reduceing the castor some-what, but along with that you have the reverse rake of the car increaseing the castor. As the front rises and the rear squats the upper balljoint moves back in relation to the contact patch of the tyre, and that increses + castor basically if you had a kingpin instead of ball joints it would become obvioulsy more inclined.

The suspension travel aspect in relation to CASTOR should to some extent cancel itself out.
but you do need both wheels facing directly forward

i think toe in might be some of your problem

you need enough at rest to make the wheels face dead ahead at the ride height you reach at speed.

If you don't have enough
the positive castor goodness is cancelled by a car that wants to favour the direction of one or the other of your slightly splayed out wheels

makes for a hair rasing ride and an undesirably large underpants laundry bill

Dave
 
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Just finished up driver side, 5* + caster, 0* toe up and down, 0* camber up and down. Tie rod arm was a little long trying to center the length on both sides, Will do Pass side tonight. Once that side is right I’ll add the 1/8” toe in
 
Ceedawg said:
Just finished up driver side, 5* + caster, 0* toe up and down, 0* camber up and down. Tie rod arm was a little long trying to center the length on both sides, Will do Pass side tonight. Once that side is right I’ll add the 1/8” toe in
Click to expand...
I'm hoping I can get those kind of numbers!!
 
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