fhturner

Hey Everyone--

I've tried to research this through previous threads, but keep coming up with conflicting opinions. Maybe I'm just asking for more of the same here, but I'll try posing the question anyway...

I'm thinking about aligning my C5 more aggressively for track days, primarily with more camber. I'm wondering, though, if I should consider lowering my car a bit first. I wouldn't want to do it too much, because I drive it on the street, too, and it already is tough avoiding scraping in some places.

Anyway, conventional wisdom seems to have always held that lowering is better for handling because it lowers the center of gravity. However, when I mentioned this to my instructor friend who has a T1 racecar, he said that the factory ride height is set where it is to allow the suspension the travel it needs to work properly. So, what is one to do?

1. Lower the car as far as possible to get down low with the Cg?
2. Leave it at the factory settings so the suspension can travel?
3. Meet in the middle by lowering some but not so much that the suspension binds?
4. None of the above?

My plan for now is to keep my F45 setup for a while longer, then probably go with Z06 and/or T1 components later.

Thanks!
Fred

yellow01

Others will know more, but I can share my experience.

I put on the Z06 springs, and based on recommendation from LGM lowered a bit. Exact amount I don't know, but I have a little more than 2 fingers in front, a little more than 3 in back. Running -1.5* in front and -1.0* in back and the car handles very well on street tires and I'm very happy with it.

Hope this helps a little bit.

tigerdrvr

For track use, I'd keep within the nominal amount (15mm) lowering GM suggest, based on everything I've heard and my own experience. Anything more is going to put the stock length shocks into the red zone (bottoming risk) and also may not be optimal in terms of geometry.
For autocross, the common wisdom has been take it as low as the bolts allow, but that seems to be currently under question. I know of one National/Pro champ who is a proponent of keeping the front a little higher than most. Not only to keep good travel and stay off the bump stops, but also to help weight transfer by keeping some of the rake out of the stance.
If you can engineer the whole package to work together, lower can be better, but I don't think so working with the stock parts.

AU N EGL

If you lower it too much and you driver over a gater you WILL notice it.

Lowering too much is a BLING factor not for real driving, especilly on the track.

fhturner

It has seemed that way to me at times, too-- many folks seem to want to lower their cars well below the stock adjustments just for looks (and never track those cars).

But, can you expand on your point here, AU N EGL? How much lowering is too much? None? Or should one lower a bit if improved track performance is a goal?

nassaufrc

I track my car a lot and I run the stock height. I need the height to clear certain combinations of tires. Cramming a 335 in the back and pulling over 1g in a turn will tell you really quick if your car is lowered for looks or racing.

AU N EGL

My understadning and I may be incorrect, but Chevy suppension engineers say the Corvette should not be lowered MORE then 15 mm that is 3/8" for optimal suppension travel and race performance. that is 15 mm in front and no more then 10mm in the rear. Keeping the 4-5 mm front to rear ride height difference rake for aerodynamics. ( undercar suction) .

Most race orginzation have a minium ride height ( ground clearance ) requirnemt of 4 1/2" for the class that corvettes run in too. ( I think I saw this one on the FIA / ACO Tech specs for GT1 cars )

Also think about when, not if, the car goes off the track and does a little agriculture excussion. If the car is lowered TOO much it will pick up more grass and dirt. or WHEN not IF you apex too tight and go over some very ruff gaters the suppenssion has room to work. If the car is too low the suppenssion will bottom out and toss the car sidways. I personally know this one.

When you look at some of the T1 cars with their 17" wheels, you would sware the distance from the top of the tire to bottom of the fender was 6" and the car looks like a 4x4.

Slammed cars look great, but functionality ?? NOT

AU N EGL

Look at nassaufrc blue FRC above. I would bet he is heavly weighted on the right do to the high speed left handed corner?? It looks much lower then it is because the suppension had room to move up and down.

yellow01

All these guys above know more than me but I would add one thing for the original poster. I would focus on ride height, not the actual amount lowered.

The reason I say this is I have seen signficant variation in cars from the factory. There's clearly a range of height settings that are acceptable from the factory.

So, if the gents above identify a good ride height, I'd focus on getting that. Focusing on the amount lowered may have you above or below that ideal height depending on how your car started from the factory.

quick04Z06

Good stuff.

Also, if you drive your car on the street, too, lowering is a PITA. You hit everything. I had my Z06 lowered a little just for DE track purposes by a professional and it reduced my street enjoyment considerably. Unless you are really racing, I say leave the ride height alone. Work on sways, shocks, alignment and corner weighting. You'll be plenty fast enough.

robvuk

The factory video tape that comes with the C5Z recommends lowering no more than 15 mm. or about a half inch. Any more and you risk hitting the stops and losing control.

95jersey

Originally, I lowered my car as far as the stock bolts allow (01 Z06), which came to about 15mm or the GM recommendation. I was told that setting ride height depends on the suspension your car has. I have been told that the base suspensions will not take well to lowering. This goes for the base and electronic suspension, primarily because their too soft and won't hold up to bottoming under load. For the T1 and Z06 suspension, I was told they will hold up much better to heavy load, and can handle being lowered. This does not mean buy the long bolts and slam the car, but I beleive it does mean lower to the recommended ride height.

Now, with all this said. I took my car to Phoneix Performance (who have won the national T1 title for several years now). There are a lot of opinions about these and other tuners both good and bad, but you have to admit that their track record means something, and the fact that a top GM engineer (Heinricy) leaves his car in their shop to be prepped before every race says something..who knows.

They measure ride height from the lower control arm joint and not by the fender. They set the ride height for my car based on the suspension it has, the track I frequent, and the tires/rims I use. It was just a tad higher than the GM recommendation or how my car was previously set.

Now, when I look at their T1 cars in their lot, they look much lower than how they set up my Z06. But the T1 suspension is also much stiffer and comes with different control arms to handle the modified geometry and they use 18" rims which fill out the wheel wells even more.

So...from deductive reasoning, it seems that if you have a non Z06/T1 suspended car you may want to stay away from lowering your ride, if you have a Z06 suspended car, you can go a little and if you have a T1 car, you might have even more room. I am no expert, but rather just paying attention to all the advice I hear, and finding some more frequently than others.

tigerdrvr

that about sums up what I was trying to say.

2K3Z06

Use a marker and mark the front edge of the bolt. Count the # of turns. That way you can put it back if needed.

My car seemed to corner just a little better when it was lowered. But, it scraped on my driveway and at the dip on the end of my street, and everywhere else. So, I raised it 2 turns.

Also, after I lowered my car. TMS has slight hill, which really compresses the suspension. And was causing a small wiggle at the bottom of the hill. Possible bump stop issue. I didn't have a transponder that day. But my lap times were probably a little quicker, than previous days because my car was lowered. Which in turn, use's more suspension travel.

Lowering is great for Solo2, and gives the car a lower center of gravity. The lower CG doesn't transfer as much weight to the outside tires of the corner, allowing the suspension to work better. (more grip)

Like every street/track car its always a tradeoff........................



Count the turns, and if it scrapes to much on the street. Raise it a little.

95jersey

Yeah but it only scrapes some cheap peice of plastic that was meant to be scraped under the car. I have never had the paint on the nose scrape the ground. All you hear scrapping is the plastic lip that is mounted on springs to move for that reason. The sound is bad, but it's really nothing. That thing is meant to scrap the ground. Mine has scrapped the ground a hundred times and looks absolutely fine.

This truly is a non issue, unless you are the type of person that hates dirt in your wheel well or something

tigerdrvr

I wouldn't worry about the plastic, I'd worry that I was basically on the bump stops...you aren't going to hit the spoiler on a smooth track unless you're too low and bottoming the factory shocks, based on my car and different ride heights I've experimented with...

taaz024

I spun my front down all the way to the stoppers, and the rear just below the maximum thread distance your stock bolts will allow by using longer bolts. Alignment is -1.5 front, -1 rear. 1/16 toe in on rear, 1/16 toe out on front. This set up was recommended by many that track professionally and I love it. car is on rails. I also added Hotchkiss swaybars and Bilstein shocks. I don't have any problems at Sebring or Homestead with bumping and loosing control. I think you guys need to stay on the track and out of the dirt. I would recommend this setup to anyone, in fact have set a few cars this way and they love it. Oh, my car is a '98 coupe too, not a Z06. I stick with and beat Z06's on both tracks. I am running Nitto 555r2's for tires.

rbeckham

Fred - there are lot of things working here, and I say up front I don't know which is the most important.

I run a C5, and it is lowered a lot, but I also run different springs and Koni yellow DA shocks which are shorter than stock. This seems to work OK for me, but even so, I have come around to the thinking that the fundamental suspension geometry of the C5 might not like being lowered very much.

As several people have mentioned, the Phoenix T1 cars are not real low, plus I have been on the track with C4s which appear actually to run higher than stock, and which I believe (with pretty good reason) cornered better than my (former T1) car.

I no longer run the T1 shocks because they were so harsh (and non-adjustable), and I have lightened up my springs somewhat with VBP pieces, but I have to wonder if the C5 control arms and originally designed Corvette suspension geometry limit the C5 to a pretty narrow range of ride heights to perform well. (BTW - the GM T1 control arms are the same pieces as stock except for the bushings).

Mine is a street/track setup, so I do not have the resources to test all of this out, but if I had not just had my car corner balanced, I would like to raise it back up a little to experiment when I get back to Watkins Glen in September.