Is there an actual advantage to lowering in terms of handling? Lots of info on how to do it here but seems to be mostly for esthetic reasons.
I know, thororeticly the lower COG and all, but balanced with the changes in suspension geometry and reduced suspension travel? And potential tire rub?
Anyone do comparison in terms of actual track/auto-x times, skid pad Gs, or slolum times?
Considering lowering on stock bolts ~1" or less. Easy enough to do, and I can change back. Just wondering if its worth the effort...

 

According to GM a slight drop (3/4 of an inch or less) is goodness.

We tested lowering down into the weeds (max allowable on stock bolts) and that was slower than lowering it 3/4 of an inch. If you take your car to Phoenix performance and tell the to "set it up for best handling" the car will come back a bit lower than stock, but not lowered all the way on stock bolts. That pretty much says it all. We tested fully lowered, a bit higher and back up at 3/4 of an inch from stock, and that was what we found gave the best autocross times. We didn't test at the stock height since my sources inside GM said that a bit lower was better and too much was not.

This was on Hoosier A6 tires, an autocross alignment and Koni double adjustable shocks that were 1 inch shorter than stock. With the car lowered to the max on stock bolts our shorter shocks didn't have a lot of travel. The stock shocks would have had less than a half an inch of travel, and with the A6 tires you would almost be on the bump stops in a high g corner from just the cornering forces alone. Any small bump would have been into the bump stops.

We also found that if you lower it a lot the car doesn't put down power as well coming off of corners, or in a straight line either. The higher CG lets the weight shift aft and that is a big improvement in acceleration.

Bottom line is that a bit lower is faster, but don't get greedy.

 

LG makes lowering spindles for those who need to be really low without compromising suspension geometry or travel, but the price will keep this mod out of reach for most.

 

I followed this advice (5/8" & 3/4") on uncut bushings/oem bolts on my car. It is strictly a street driven car. Then an alignment after everything settled a bit. No loss of handling, no loss of ride comfort and better looking.

Unfortunately, to many C5/Z06 owners chose form over function. That might come from their import background...

 

There is probably also a slight aerodyanmic improvement if you lower it a bit too. This gets the spoiler closer to the ground and less air under the car at speed. There was a SAE paper on the C5 aero when it came out. I think they talked in there about the effects of lowering on the aerodynamics, but a bit lower would likely reduce drag and increase downforce, something that's a 2fer...

 

I believe you can also increase the maximum amount of camber that can be obtained when the car is lowered from stock.

 

Parking Lot Queens

 

Looks alone are reason enough!

 

What is the recomended OEM height. Mine is sitting @ 27" on the front from the top of the fender.

 

The fender is not a reliable place to measure these cars. To properly measure ride height you should actually use the factory tools and measure from the distance from the lower ball joint to the suspension pivot point. Here are the proper dimensions for ride height as measured this way.

http://forums.corvetteforum.com/1575382403-post32.html

Assuming that you have the original tire sizes then you can measure from the ground (ON A FLAT SURFACE!!!!) to the points on the frame as shown in this post.

http://forums.corvetteforum.com/1578180112-post18.html

These are from the shop manual for the 1999. After that point the manual only shows the trim height as measured by the first method. I know it's a PITA to try to measure it this way, but the idea is to get the proper trim height and setup regardless of the tires that you have on the car.

 

I know I've seen it somewhere but is there a ratio of bolt turns to lowering amounts?

Solofast, that is some of the best and practical info I've read.

 

No offense but handles poorly

If the car is lowered no more then 1" in front, the 3/8' to 1/2" rake is kept, and the car is re aligned you will be good to go.

Good Luck

 

Any idea what this translates into for the bolt to bj measurements as spec'd in the GM manual?

Thanks.

 

When I first started to lower mine, dropping it all the way on stock bolts in the front was equal to a frame measurement of a little over 4 inches.

If you did it about half way between as delivered and fully lowered in the front you should be good. Count the threads below the spring in the front and go about half way, turning each side the same amount is probably darn close.

The rear is so easy to reset but the same thing applies in the back. Count the threads above the nut and then back each side off about half the number of turns and you should be close.

Let it settle and then check heights and rake, tweak the back as necessary to get the rake right.

 

If you have the C5Z Owner's Video there is a section that discusses Racing Setup where GM Engineers recommend lowering in the range of 10 to 15 mm below the nominal suspension ride height. Each turn of the spring adjuster bolt is equivalent to 2 mm of trim height adjustment. This is measured on the suspension using the proper tools.

Bill

 

Just to clarify - the 10-15mm lowering is with respect to the lca bolt to bottom of bj measurement?

 

great thread