drivinhard

I will preface this by saying I am not interesting in trying to look cool or achieve any subjective tire/fender gap "look".

I am interested in opinions on lowering (or not lowering) the Z06 for track work.

Car is a 2001 Z06, '04 shocks, fairly aggressive alignment, 18x10.5 OEM rims w/ Nitto 285/35/18 555R2 at all 4 corners.

Obviously I'm running a taller tire in the front than stock.

I'm mostly interested in opinions on lowering the car

1.) for rake, for aero purpose (nose down)

2.) and/or vs putting the car lower (I'm thinking slightly) to get the 04 shocks in the sweet spot of their valving, and of course lowering the CG of the car. I've hear anywhere from 10-20mm is optimal, although I've talked to at least one T1 guy that said leave it as is.

Assuming the above car/context on the said wheels/rubber, how much would you drop the right height in front, and rear? (I don't want to be running out of travel on the shocks).

CHJ In Virginia

I dropped mine as far as it would go on the stock bushings. It ended up being about an inch all around. When combined with the track alignment, it made a substantial difference for the better in the way the car handled. In your case with the same size tires F & R, I would drop the front slightly more to keep the original aero of the car. Can't really offer any info on your shocks. I'm running the Bilsteins and do not have any travel or bottoming problems.

Casem1

My car was slammed when I bought it, all the way on stock bolts. Once I started some HPDEs I noticed a little harshness that I thought was bottoming out. When I got faster I was pretty sure i was bottoming out (the shocks). I installed the c6z shocks on my 99 and after another event (and bottoming the suspension again) I also raised the car. My rear has been raised about as far as the bolts let me and the front was raised so that the rear stood about 1/2" or so higher. I no longer bottom out but to be honest have no idea if my nose should be lower or not. I will not go back to a 'slammed' car, it was too low.

Somebody else may know the specifics of front vs rear and ideal rake, but not me but i will not be lowering my car any more.

AU N EGL

about 1" lower then stock is just fine.

NemesisC5

I do not know what the stock ride hight is supposed to be....About how far is that from the driveway to the front & rear fender lip?

AU N EGL

Dont use fender lips. They are uneven by as much as a 1/4" left to right

use the frame rails by the jacking puck holes for a quick measure. in front of the front hole, and behind the rear hole. or the lower a-arm attachments for the proper adjustments and measurements.

On our 04 vert with stock suspension stock wheels and tires.

In front of the front jacking puck holes the distance is 5 1/2"

just behind the rear jacking puck holes the distance is 5 3/4"

that is 1/4" rake at between those points.

My car with T1 suspension on 18x305/30 fronts ane 18x335/30 rears
and 200 lbs of me in the drivers seat

front 3 5/8" Left and right

rear 3 7/8" left and right

again a 1/4" rake

with out 200 lb driver

front
Left 3 6/8"s right 3 5/8"

So some place in those areas.

The front suspension adjustment is all the way UP

Corner weighting your car will help too

wtknght1

You have just royally screwed up the handling of your car - guaranteed!!!!

I've spoke about this many times, but if you change the ride height on your car without a good set of scales and THE PROPER KNOWLEDGE OF WHERE THE RIGHT SPOT IS, you will definitely be slower and the car will not handle properly. Suspension geomentry, shock travel, rake, etc, etc plays a HUGE part in these cars. The Corvette suspension needs to travel to be effective! Take it to a pro shop like Phoenix Performance and let them set the correct height, rake, cornerweight, zero the sway bars, etc, etc. I can't begin to tell you how much better your car will handle...and will bet my next paycheck it'll be better than slammed to the ground!

AU N EGL

Watch how much suspension travels http://vimeo.com/2198187

C5Z06 on Summit Point. Jack at the wheel

drivinhard

Chris, you were actually the T1 racer (or one of them) I referenced in my first post that said not to. I bought a seat from you several years ago, although I doubt you remember me. lol

My "home" track is road atlanta, which you are normally on the curbs pretty good at 3, out of 5, and 10a/b. 3 is probably the hardest, I don't want to be bottoming things out being too low.

I have not (yet) invested in a set of longacre's for corner weighting, although I plan to in the near future.

For the short term, I was sorta leaning on keeping the same OEM rack delta (WITH the taller front tires). I would guess that would mean dropping the rear maybe 8-10mm and the front 12-15mm. I would tend to think one full inch (about 25mm) would decrease usable travel on the shocks a good bit. However, I'm

(I also realize there is no perfect setting for all tracks/situations, I would tend to think based on prior track experience, you could get away with lower ride height on a pool table smooth track vs one that isn't)

Bill Dearborn

I left my ride height at the stock settings as I bottom too many places already (scraped the floorboards on a speed bump a couple of weeks ago). In the GM Z06 tape that comes with the car they recommend no more than a 15mm drop. That is a little more than a half inch. If you decide to lower it though I would do as Chris recommends and let somebody who knows what they are doing set it up.

Bill

wtknght1

Hey Mark! Yep, I remember you. Cornerweighting is only part of the equation. Before knowing anything about Corvette's suspension, we slammed my C5 down to the lowest possible setting too. Then, we adjusted each one slightly until the cornerweights were good ensuring that the sway bars were zero'd as well...and I raced the car and won a few...and even the 2003 Southeast Division Title. I thought that's just the way the car is.

Then I took the car up to Joe's shop and Mark set everything CORRECTLY and what an improvement!!!!! It was sooooo much easier to drive and the suspension was actually doing what it was designed to do - and ultra predictable - no surprises. I was 2-4 seconds per lap qucker than before! That convinced me ! You just don't know how good these things CAN be until you let the pros go thru your car.

Anytime I see a car at the track that's slammed down to the ground, I know he's not going to be anywhere near me.

NemesisC5

Thanks Tom

AU N EGL

That is only A STARTING PLACE.

Having your car professionally corner balanced is the proper way.

YES slammed cars do look cool. but handle like chit.

gkmccready

Before I mucked with my '06 Z51 car it was 5.0" Front/Rear & Left/Right at all four jacking puck holes. 0 rake. Just to add another data point.

gonzalezfj

3/8" to 1/2" rake is highly recommended for high speed track use. It helps keep the car planted at high speed and tends to negate front end lift.

Frank Gonzalez

froggy47

I have also "heard" that if you get really low in front that for serious high speed work you need to trim up the front spoiler so that "some" air can get under the front. Otherwise the air sort of "dams up" in front & can cause some lift (talking 140 & more). I don't know this for a fact, it's value may be what you paid for it.

gonzalezfj

I don't know where you heard that, but it is incorrect. Every effort should be made to keep air out of the bottom of the car. Air under the dam is high pressure and tends to lift the car, a very undesirable trait at high speeds.

This is the reason why you see chin spoilers in every modern car, even sedans.

Frank Gonzalez

davidfarmer

I have to disagree with Chris on this......slamming is bad if you CUT anything, but lowering on stock hardware is fine. I lower cars as far as they will go with not mods (ie, find the adjuster with the LEAST adjustment left, and adjust them all that amount). THEN, I put them on the scales and propperly adjust corner weights.

If you adjust without cutting or using longer bolts in the rear, you will still have ample travel, and should not bottom anything out.

wtknght1

The shocks bottomed out and the suspension geometry changed enough to make 2-4 seconds worth. We didn't cut anything...just lowered it. And OBTW, my first three years and more was done with just the stock Z06. The only thing different I had on there was/were the T1 bars. The springs and everything else was stock.

The only way to know for sure though is to try both and see. One good test is worth 1000 opinions.

fatbillybob

Is anyone willing to tell the secret Pheonix C5Z ride height and referrence point for those measurements? From the zillion posts it seemed unclear where the ideal is from a pro tuner's point of view.