alignment specs?

[bigcat]

for those that have lowered, please post your pre alignment specs and how much you lowered the car. i see camber mentioned often, but dont hear much about caster. i have the option of adding an additional 0.5 degrees of caster. i dont want to take apart the lower control arm to add it later.

additional caster should help the high speed straight line stability, but are there any other benefits? how will it affect tire wear? i dont see it doing much for tire wear, but would like to hear from others.

any reason for or against adding the extra caster?

 

[Jenns01TA]

I don't have numbers for ya' bigcat. But can at least chime in to agree with what you have said.

Caster has little affect on tread wear and everything to do with straight line handling and steering. Adding the 0.5 will do exactly as you said and really no more. The alignment specs are set so tight these days and dialed in that it is not an issue.

I would be more focused on the Toe value now that you have adjusted the ride height.

How far of a drop are you looking to get with those fancy German Vogt's you have? As long as the Toe/Camber and Thrust Angles are within spec. compensated for ride height you should be fine.

 

[bigcat]

its a 1.5" drop.

i am going to call a few alignment shops to see any advantage of adding the extra caster. adding the shims wont cost me anything to do, or take any longer, but i would like to know exactly why i would want to add it.

 

[Jenns01TA]

Yes, the alignment shops are always a far better and more accurate resource then me. Let me know what you find out.

If the caster/camber plates are designed for track/road then my uneducated guess is that the 0.5 caster plate shim would primarily be used for vehicles with a lower dynamic running off and on-road events where the contact patch/footprint of the tire will be prone to wander and change based on speed and road conditions. Therefore, the positive caster will prevent irratic wander/axis pull and handling issues under these circumstances.

 

[bigcat]

after calling a few alignment shops, i could not get a good answer. i contacted the manufacturer directly, and got this response.

Adjusting caster to be more positive (moving the lower control arm forward in car) has two major advantages. While steering through a corner the positive caster will cause the outside wheel to have more negative camber, increasing cornering grip without the negatives of static camber changes. Second it will increase the vehicles "self aligning" ability, causing the car to snap back straight after going through a corner. The trade off for all these positives is a slight increase in steering effort, but with a 0.5 deg change the effort will not be greatly noticed.

 

[Jenns01TA]

See Post #4 above.



Glad you got your answer J.

 

[bigcat]

i cant believe that i kept forgetting to post the reply for so long. i always remember i need to do it, but kept forgetting when it came time to actually find the thread and post the results.

 

[toolttime]

positive camber makes harder to turn as the car is being raised slightly up that's why powersteering is used.The negative caster is used on cars with no powersteering to make it less effort to turn.

 

[toolttime]

Here are the specs that roush supplied for their kit.

I did a 4 wheel aligmnent as I had installed a adj panhard bar. inputed the roush specs
View attachment 431968

The rear end I had adjusted . using a plumb line and it was dead on

View attachment 431974

All it needed was a half turn for the toe in no camber bolts needed camber and caster ok

final reading perfect!!!!!
View attachment 431980

 

[bigcat]

how much does the roush kit lower the car?