Bump steer question
I don’t know the exact alignment specs but they are somewhere in the range of
Toe in - 1/8
Camber - negative 1
Caster - positive 5
I don’t know the method used setting the strut bars. My plan is to find out how to set strut bars, double check alignment and check bumpsteer again.
Ok, so if those are the actual alignment numbers the shop that set them might actually know what they're doing. Again, what kind of shop is this? What did they say about installing the adjustable strut rods?
Has the ride height of the car been changed at all since you had the alignment? Because that changes the settings.
The process for setting the length on the strut rods is actually pretty much the same as checking the bump steer. Remove the shocks, remove the torsion bar adjuster and plates so the suspension can travel through its full range of motion bump stop to bump stop. Then raise and lower the suspension through its range of travel, seeing if there is any binding or resistance as you go. If the strut rod is the right length the suspension will move up and down freely, especially through the middle of the range. As you get to the extreme ends of travel before you hit the stops there may be some additional resistance, especially if you have rubber LCA bushings as the rubber in those is twisting to allow the LCA to move. If there's binding everywhere the strut rod is the wrong length. And if it's binding a lot at the extremes of travel its probably the wrong length. You want to start with the strut rods set so the LCA is perpendicular to the frame rail, if it's pulled forward or pushed back the strut rod is the wrong length. The goal of setting the length of the strut rod should be no binding of the LCA through its travel. Adjusting the length of the strut rod does change the caster setting, but changing the caster setting shouldn't be the goal of adjusting the strut rod, that should be binding.
There you go caster is way too high
Only for a drag race car. If this is a street car with the intention of having better than stock handling it's just about perfect.
If you read what I said that he needs to read the whole front suspension racing manual to understand what he needs to do and how to do it.
Oh BS. The front suspension racing manual is for drag racing. Pretty much everything it describes is for a drag car, NOT a street car, and some of what it describes would be the WRONG way to set up a street car. I mean seriously, /6 torsion bars, checking the toe pattern at 1" raised suspension so it's the same as through the traps, setting 0 toe to begin with, only checking the rebound toe changes. That's all great for a drag car, but none of it is applicable to a street car.
Zero toe change is also pretty much impossible. That's one of those theoretical deals for designing suspension, it's not something you get in the real world. And not on a street car. Even the graphs they use in the manual aren't realistic. 4" jounce to 4" rebound? Explain how you get that on a car that only has about 5" of total suspension travel.
And the front suspension racing manual doesn't cover what to actually DO about most of those changes.
72bluNblu
You can disagree all you want but the fact is when you change caster you change the height of the steering arm and that is what changes bump steer. I have never seen a mopar with a alignment spec that even comes close to +5* caster. I don't even know what kind of car he has so I can't tell him exactly what to do but the theory is the same for all.
Mine has +6.5° of caster. It's not possible with stock parts but with aftermarket suspension pieces it's not that hard.
When you run wide, modern tires on the front increasing the caster increases the stability of the car. All aftermarket UCA's have additional positive caster built in. Radial tires need more positive caster. The factory alignment specs are for bias ply tires, and are WRONG for radials.
Most aftermarket tubular UCA's have an additional +2 to +3° of caster built into the geometry for that reason.