Don Terrill’s Speed-Talk

my car is an 81 malibu with a mish mash of different aftermarket front end components. Right now it has a cheap junk set of speedway upper control arms that require a ton of shims. The car is a little sketchy at 140 MPH. I just purchased a pair of Global west drag race uppers (TLC-88) that hopefully will allow me to get rid of lots of shims and align it properly. I know that for drag racing the caster setting should be changed from factory but i have no idea where to set it. Anyone have any experience with this ?
Brian

I don't really know but I grew up in my dads alignment and frame straightening shop.
Have the car in race ready condition. What is the stance of the car when the car gets into high gear.
I would set the camber at this ride height at 0 to 1/2 degree positive. Then start with the caster at + 3'.
Also be sure to check check the toe.
Hope this helps.
John

Try to get as much positive caster as you can get.

We run tall ball joints to cut down on camber change, and bump steer kits. As a rule, we run 1/8" to 1/16" toe in, and as much positive caster as possible of course, not using longer bolts or studs, or stupid amounts of shim). We align with the car raised in front around 2"-3" from ride height, with the weight of the driver in the seat. You can just about sit on your hands if you stage straight, and the track is decent.

I was told to get as much negative caster by a friend. Now i need to do some research. Positive or negative. I've been a mechanic for 15 years but i've never done a wheel alignment.
Brian

prairiehotrodder wrote: ↑Wed Apr 03, 2019 11:25 pm I was told to get as much negative caster by a friend. Now i need to do some research. Positive or negative. I've been a mechanic for 15 years but i've never done a wheel alignment.
Brian

Positive Caster is your friend at 150+ I run 8* with a straight axle and 1* negative Camber in case the car goes array.

prairiehotrodder wrote: ↑Wed Apr 03, 2019 11:25 pm ...negative caster by a friend.

Try driving at medium to high speed in reverse in any thing but a forklift & you'll get you a scary dose of neg castor.

Thanks guys, positive caster is correct. My new control arms which are on the way have extra positive caster built in so hopefully i can use far less shims for the alignment.

Those TLC 88 arms have 6 degrees of caster built into them so try to get the shims even to keep the caster from shifting as the wheels cycle up and down.. If its a track only car set caster even both sides. Set camber negative .25 with toe in 1/32 each side.

I would set it up like this;
Caster Positive +5 both sides.. The more caster you add above 5 the slower the steering will be..
Camber negative -.25
Toe in 1/32 each side..

Jack the car up with the front wheels off the ground and see what they look like. You might want to use limit straps if the camber is all out of wack. .9 and .5 tall ball joints would help this..

I would change the lower control arms or at least beef them up, they are known to crack and release the lower ball joint..

Back in the day we would take pictures of the car at several points as it went down the track, then one at rest. We would then figure out how high the front end was carried throughout the majority of the run and raise the car to that point when aligning the front end. That seemed to work fine. Hope that helps.

rather than using taller balljoints would the old school balljoint spacers work? Upper control arms with more positive caster must be designed with the upper balljoint location set rearward?

No one said it yet so I guess I will:

In drag racing, assuming we are only talking about front suspension alignment, the key is getting the least amount of rolling resistance as possible from point A to B.

where... reduced rolling resistance is the 'speed secret'.

This will be very different than the stock front wheel alignment specifications, mostly because there should be no, or very little, 'crown' on the drag strip lanes.

Since there is no crown (worth consideration anyway) basically you'll want both front wheels 'straight up' = zero camber... in theory.

Since there is no crown, desired steering wheel 'feel' is accomplished by the amount of positive caster (how much the lower ball joint is ahead of the upper) where, more caster = more 'feel' (where the steering wheel feels 'heavy') & less caster = less 'feel' (where the steering wheel feels 'light')

Another caution to adding unusual amounts of positive caster is how the kingpin to spindle relationship affects ride height as the steering direction is moved... whereas on many cars, when an inside front wheel is 'turned back', with lots of caster, the arc of the spindle will travel down, but the arc of the spindle for the outside front wheel will travel up.

...when one has to steer right and left rapidly to correct a fish tail due to excessive wheelspin; it'll only make the hair raising moment worse.

This is even a similar scenario on car that must negotiate corners at high speed on a road course and there is a 'point of diminishing returns' when dialing in more caster -when the car steers like it has a mind of it's own, it's out of control.

Too much caster places unnecessary strain on the front suspension parts also, where all parts are subjected to increased load due to increased geometric leverage. IE: when the 'kingpin' is straight up, it is applying the least amount of leverage upon the upper pivot joint/ball joint. (and you need ball joints in good condition especially if you're popping wheelies)

Just for a reference point, not to overthink it, don't even try to guess how many muscle cars have been modified to run 140 down the highway and 'feel like a dream' with only near stock front wheel alignment settings.

I'd say, reduced rolling resistance is the speed secret, not huge amounts of caster.

The ever elusive goal is to be able to push the car forward with one finger like it was a ten speed bicycle.

I'd say zero camber both sides, about 2.5 to 3 degrees positive caster both sides and 1/16" toe in -measured when the wheels are 'as they are' when the car is rolling forward, not 'as they are' when the car is come to stop using the brakes as this will load the front suspension differently.

-when the caster is equal on both sides/both front wheels, the car should 'run straight' down the track when one takes their hands off the steering wheel, not veer off to one side or the other.

(which is an incorrect setting for a car that is street driven; it should gradually veer off the crown of the road in order to avoid a head on collision if someone falls asleep, passes out from listening to the stereo too loud, smokes too much or whatever...)

The next chapter in this booklet would be on four wheel alignment -why not be smarter and check that too?

amcenthusiast wrote: ↑Sun Sep 15, 2019 11:20 pm

-when the caster is equal on both sides/both front wheels, the car should 'run straight' down the track when one takes their hands off the steering wheel, not veer off to one side or the other.

(which is an incorrect setting for a car that is street driven; it should gradually veer off the crown of the road in order to avoid a head on collision if someone falls asleep, passes out from listening to the stereo too loud, smokes too much or whatever...)

The next chapter in this booklet would be on four wheel alignment -why not be smarter and check that too?

Totally Disagree! The crown is for water run off period! Proof from a friend that is one of the head engineers for Cal Trans.
That other crap on head on had been around for years and is not the reason for the crown yet some people still believe it.

I agree with several here....although I have honestly never heard of the head-on thing in regards to road crown. I would keep it simple 3-6° of positive caster, zero camber, 1/16 to an 1/8 of toe depending on how the car goes down the track at speed......and definitely look at bump steer through the whole deal....especially if it has a lot of travel.

Not trying to ruin your post but you made me think about many people who told me I wanted the rear yoke pointed down 4 degrees to make it hook. I never did. Thanks for posting