sothpaw2

Hi,

Recently in reading threads here about suspension mods, it sounded like some had implied that it was ok to lower the C5/C6 on it stock bolts (no cut bushings etc though) all the way for use on track.

I had been under the distinct impression that the shocks/suspension travel would be insufficient if you lowered the C5 (at least) more than 1/2 way or about 1/2 inch. Lowering it the full 1 inch was supposed to ruin handling etc.

So is the above 1/2" recommendation an old wive tale? Will the suspension/shocks work just was well if you lower your car all the way on stock bolts (no mods to bolts or bushings, etc).?

Thanks

autoxer6

I like to see my competition with the car all the way down. It feels fast, with awsome turn in, then pushes and makes it hard to get in the power.

I like it about half way between stock and all the way down.

Shortened shocks would allow you to get closer to fully lowered but I still wouldn't go there.

drivinhard

In my experience, the rears are more sensitive than the fronts. The fronts seem to be able to not change much if you go fairly low, the rear will get pretty unsettled if it's really low, especially if you are banging curbs, etc. car seems to have better bite on exit if you get the rear up a bit.

0RAAMaudio

I would not lower it much at all, the geometry gets all screwed up, if you study such things it starts to make a ton of sense, glad I have some great books like the one from Herb Adams.

If you lower the car to much you put a great deal of leverage on the outside tires basically making the car a two tired vehicle(extreme example but pretty accurate way to describe it)

Some misunderstand the idea of the control arms, stock they point down from the mounting points on the chassis towards the outside, wheels, etc...if lowered to much they point up, bad news.

But, the actual angle from pivot point to pivot point is what matters, not the arm angle, I have seen cars setup wrong because they misunderstood where to measure from.

I normally draw it all out in full scale and do very setup to ensure I am getting it right.

Of course I know and use all the terms, just keeping it basic here, my car has just about every suspension mod I can do for handling and it is not lowered much at all (ok, bushings instead of monoball pickup points, mid size not massive sway bars, single not dual, etc coilovers, but it has the DRM rack bushing and a camber kit, etc.....and a very very good alignment)

Low looks cool but is not, unless you want to spend the money on the LG uprights, $$$$$$$ but dang sweet!

Rick

yakisoba

Conventional wisdom is to lower it about 20-25mm and call it a day.

sothpaw2

How low do you think is too low in front? I had dropped it about 1/2 way, or 1/2", all around. I think it still handles very well. Do you think I could drop another 1/4-3/8" in front? The gap looks a little funny. The newer sports cars don't have big tire/wheel well gaps.

davidfarmer

I don't think I've really ever had a c5 drop more than 1/2" when dropped all the way. Without cutting or modifying, there is usually only about 2 threads or less in the front adjusters. In my experience, dropping the fronts all the way us a good starting point, then use the scales to raise if necessary to adjust corner balance

VetteDrmr

Are you going to track your car or take it to a car show? Those two are usually mutually exclusive.

I wouldn't go down all the way on both sides because that can really screw up the cross weights. Going down an equal number of turns on both sides should be pretty safe. Only you can figure out if the handling gets worse or not.

Have a good one,
Mike

0RAAMaudio

I never measured mine for fender gaps, just the frame rails for a reference point(cars are not made perfectly aligned, tire diameters may not be stock, air pressures uneven or different preferences set, etc....to many variables to be accurate)

Though a pain since I do my alignments on the ground (suspension has to be totally settled) it is hard to get close enough to get the right measurements. My next place will have a second lift, maybe a third, one with alignment capabilities!

I measure all the important points and then draw it out in full scale to see just where everything is when setting my ride height, again to low, you are not using all the tire you have on the car.

Another aspect many street tuners overlook is when going to low you induce bump steer issues caused by the control arms and tie rods no longer on the correct plain. This causes the wheels to turn when hitting a bump.

Now we have two major issues in handling when lowered to much, bump steer and nearly all the weight on the outside tires for less grip.

I imagine many ricer wrecks and more than a few Vette wrecks could of been prevented it the car was setup to be fast instead of look fast.

I love lowered cars as well as anybody but I love real performance more and the safety factor.

To properly lower a Vette very much you need new uprights ($$$$$) and bump steer correction kits, LG has them both, plus a real alignment, not something you get at very many alignment shops.

Right now my car is at 5 1/8" front, 5 3/8" rear frame rail height off the ground, +- a bit, not totally even floor and I have different tires, bigger radiator, accusump, oil and trans coolers added, 6 lb trailer hitch out back and I always carry quite a few tools for sometime after doing so many mods(far more than just that have been done) since I last did this from the ground up. It feels great, no bump steer at all, feels the same left and right turns, very stable, etc.....

I know it is not perfect but it is very very good, if I was trying to win a race I would have to spend much more time on it, not to mention corner balancing, again, etc.....

It is far better to be on the higher side of things than the lower side, once you cross the threshold things go bad very very quickly.

I have seen 2 second lap time improvement on a short course from raising a car that was to low by just .25".

Rick

sothpaw2

Trying to balance both with performance as the driver.

Not sure what you mean by both sides--front and back? But yeah the shop initially lowered all the way (not my instruction!)and I had them put it back up evenly on all sides about 1/2 way on all 4 corners. There's still quite a bit of gap on the fenders but it's noticably less than stock.

Doesn't sound like lowering it full way in front is what most are doing.

Thanks!

0RAAMaudio

To make on issue here very clear, handling gets worse or it does not get worse, pure physics. If the geometry is incorrect the handling is worse, if correct it is better pure and simple.

The drivers experience level, driving style, etc will determine if they can tell the difference, it is there whether or not they can tell. It may never be an issue but what happens when somebody runs out in front of you and you jink and jive to miss them and your handling is not what it should be?

In a car as fast as these compromising the handling for looks is a bit of an odd thing to do in my opinion.

Rick

Bill Dearborn

The owner's manual in my C5Z indicated no more than 15mm which is a little over a half inch. On another now defunct forum a long time ago Ken Brown from GM Engineering posted that the early C5 Z51 cars shouldn't be dropped more than a half inch.

One well known T1 racer who is part of this forum told me he doesn't lower his cars at all. He didn't find any advantage to lowering them.

Bill

minitech

Would someone post up that table with alignment specs including ride heights for C5 and C6? And the drawing of the car with location of where to measure the right place at the frame?

I've seen both here but not able to find them after searching to bring back out.

RX-Ben

+1 for not dropping all the way. I thought that would be a good idea (for some reason I thought I read here that it was a good idea, obviously not) - terrible results. It didn't seem extreme since there was still plenty of gap, but the unsettling results make sense after reading this. At WGI on crappy (nitto 555, 300 wear, 245/275) street tires, the C5 was slower than my S2k. The place felt like an ice rink in the C5, felt like a velodrome on the S2k.
So, halfway on the bolts sounds good.

Does anyone have any corner weight vs. thread data?

Thanks.

sothpaw2

Great comment! What did you put it back up to--how many threads show front & back?

Would be great to have a diagram showing how to measure the ride height to some hard pts on the frame so we can compare.

sothpaw2

+1 A drawing w/ reference for a stock suspension car would be great!

RX-Ben

I need to adjust the bolts again (once I get replacement axles since the NAPA rebuilds I put it at the wheel speed wiring, sprung a leak and vomited grease everywhere).

I have scales, but they are a pain to setup and I am still working on ramps and a leveling system since finding a flat pad is tough.

0RAAMaudio

Corner weight is measured with you in the vehicle and everything setup exactly like you will have it on the track. There are no real close numbers to give as each car will be a bit different even stock and then add in all the other variables......

RX-Ben

Right, but the %s should be pretty similar (at least ballpark) with the typical non-caged car. I am more interested in how far the weights are off with a full drop to put some data behind the evil handling I encountered (with Z51 springs, sways, gary's delrin shock tops, Bilstein Sports and poly bushings). It could've just been the tires (that was prob my last event with those), but the car was a ton of fun at Pocono North before the above changes on totally stock base model suspension and the same tires. As stated, the ride height could also screw with the suspension geometry, but I've seen some pretty dropped track cars (with coilovers) that I assume had some grip.

redtopz

My car consistently pulls 1.5 G's on A6's without aero and is pretty much slammed on G2 coilovers. No problems with bump steer on curbing. I did my own install and car setup/alignment. Checked corner weights last week out of curiosity and they were 50.2% cross balanced. I guess I was lucky with my ride height adjustments using my fingers between the tires and fenders to set the heights.