BrianCunningham

Got my alignment finished today over @ FasTrack

Great place, a pro shop that can deal with custom suspensions no problem.

Car was aligned weighed, so it would be correct with me in it.

Set the ride height 1st.
Stock is
7.8in front & rear
I set mine @
6.25in front
5.75in rear
which actually makes the wheel lip clearance even.

Camber, I decided to go ahead and crank up the camber since I have my truck for a daily driver, and I like to autocross.
Front
2.5 degrees
7.0 degrees caster
0.05 degrees toe out
Rear
2.0 degrees
0.20 degrees toe in

I managed to get that much caster & camber with the much ride height because I have adjustable a-arms on the front.

Previously, I had the car 'in the weeds' but this made the top a-arms angle UP, stock they angle DOWN, so I knew that couldn't be good for geometry.

dizwiz24

i was just going to ask how you got that much camber up front, but then you answered my question.

you said you have adjustable a-arms.

Thanks for the specs.

Werks

I'm not the most knowledgeable about set ups for autocrossing but doesn't having the rear end of the car 1/2 inch lower than the front throw off the rake and affect the overall weight distribution? I would think that this might also negatively affect on power steering? Again not the the most knowledgeable about this so just trying to pick your brain a bit about this.

BrianCunningham

I've got a supercharged 383, so the more weight in the back the better.

The weird part is that it looks level

the lip is higher in the back so you can put a load (luggage) in it

BrianCunningham

BTW I still got 0.75in of washer left!

Solofast

Even with our BSP car we never ran quite that much negative camber in the rear. Our testing gave the best tire temps (equal across the tire) with about 1.6 to 1.75 depending on the tires we were using, but this was on A6's.

We found that overdoing the rear camber reduced the amount of power we could put down on corner exit. We were using 335's on the back.

In stock class cars we typically ran -1.5, but with tires like the A6 with a flatter tread radius we ran as much as -1.75, but never more than that.

Just our experience.

Crepitus

SoDiezl350

Any improvements in steering response? How's it drive?

BrianCunningham

I put a fast ration rack in at the same time, (which I really recommend), so it's hard to tell. I mean it's a lot better, some due to the rack, some due to the alignment.

bsalie99

That much rear camber will limit how much power you can put to the ground. Are you going to run at corvette club event at devens?

froggy47

Ditto what the guys said about the neg. rake and the rear camber,

FWIW My car likes about 1/4" rake (rear high) and about 1.6 to 1.7 rear neg. cam. big tires.

Let us know how it works.

RacePro Engineering

Gentlemen,

For whatever it might be worth in terms of technical info, ride height (and therefore RAKE) should be measured from fixed points on the chassis (not the body), to the perfectly level horizon. The C4 chassis and suspension prefer forward rake. If anything, having a slightly heavier motor would increase this need.

Adjusting the ride height in just the front, or in just the rear, or in BOTH front AND rear of any car, has no effect on static weight distribution.

Ed

froggy47

So if I have my prelim ride height set & I roll onto the scales and I turn the RR spring (height) adjuster on my C5Z,

I am changing both the ride height (2 opposite corners - think of a 4 leg chair) and the weights on those corners.

Yes?

No?

I thought I had that figured out.

Now if I have a race car with stiff springs & I move a lead plate around I may be changing corner weight & not ride height (depending on the #lbs of weight.

RacePro Engineering

Sorry, Bob,

I should have been more specific about "front" and "rear". And you probably DO have it figured out.

When we speak of "changing front ride height" we are assuming the same height change on both front corners. Likewise, changing rear ride height means effecting the same height adjustment on both left and right, equally. These equal-side-to-side changes will not change corner weights. The only reason I bring this up is that common misconception that simply raising the "front" shifts weight to the rear, and visa versa.

To make any adjustment in corner weights, side-to-side, front-to-rear, or diagonally, one must either [1] physically remove (or add) weight from/to the car, or [2] physically move weight from one place to another, within the car, or [3] adjust the height OF A SINGLE CORNER (ala your RR spring perch).

This is not to imply that setting up corner weights properly can all be handled from a single corner. That would be rare! But it is the raising or lowering one corner at a time that makes the weighting difference.

Hope this is more clear.
Ed

BrianCunningham

Guys remember this is a C4

totally different animal

I do need to scale my car
I added a supercharger
lost the AC
put an oilcooler w fan, accusump and oil filer in the BACK

Yes this will be for Devens

If I can get it dynoed next week I'll run it at this years final BSCC autocross

shakedown067

Man, that's going to be a BLAST at the autocross. I dig the alignment settings! Would like to add more camber, both front and rear, but I still drive my car on the street too much.

Werks

Sorry, I was being a little non-techie in the wording of my question lol ;-) What I was getting at was running a car with a negative rake (nose higher that rear) will generaly result in a reduction in on power steering. Being nose high already, under acceleration the car will squat down even more in the rear unloading the front tires, which reduces front end grip causing the car to push. That is not really something that I would think would be beneficial on the small auto cross type tracks which is why I was asking about that. Being candid though I know zero about set up on C4's just curious that's all.

USAsOnlyWay

With my setup (c4), zero rake hurt turn in. I guess we'll find out how yours likes it.

Kubs

My car liked at least 3/4 - 1" of rake. It felt better in high speed corners as well.

BrianCunningham

with 1" of rack, what was your ride height set to?

Where the front upper a-arms still pointing DOWN or were they UP?

That's a BIG change in the roll center.