gkmccready

For you guys running wings and splitters... how much did the aero change your suspension requirements? Because if you're using a 600#/in rear spring with no aero and then add a wing that gives 600# of downforce you're losing an inch of bump travel, right? Have folks found they need to run a stiffer spring to keep enough travel when adding aero bits? And I haven't really wrapped my head around whether aero would benefit from shock valving changes...

Just kind of curious how far the ST2 guys have gone with adding the aero because the aero alone seems to be dropping lap times like crazy...

wallyman424

Definitely need bigger springs and matching shocks to go w/ the aero.

John Shiels

Air never blows up and it works! Also helps braking as you have more stick. Adding a bunch of aero like my car works and you need heavier springs and re-valved shocks for sure. They was not that much when I did my car but there is tons of it now on HPDE cars. I went to aero early because I saw what it did on bikes back in 1975 when there was no such thing as a sport bike I had a full race fairing on a modded street bike. Back in 1975 a bike running 175-180 was real fast. There was a class for 100 CC bikes where adding a bit of masking tape on fairing edges gained you a mph and you only have to win by a foot.

davidfarmer

I personally don't think you need stiffer springs for aero. You'll go from having lift to possibly have 400-500lbs downforce (being optimistic) at TOP speed. In the corners, you'll gain a few hundred lbs of downforce.....basically like carrying a large passenger in the car.


I have the wind tunnel data from both C5 and C6 World Challenge tests, and while it certainly will gain a lot of track time, I personally don't feel you need a huge suspension change. If you are already running T1 springs etc (or similar) you will be fine. If you are running stock springs, well that's another matter.

I'm not downplaying the effectiveness of aero, just downplaying it's effect on the suspension at all but maximum speeds.

**** Wallyman is any exception with his 8' tall wing

drivinhard

good info, always wondered about that

I am not an expert on the matter, but I'd still set it up as soft as you can get away with, for mechanical grip (especially in slower speed stuff)

I'd love to see that wind tunnel data sometime

John Shiels

you can buy data. If you have your aero set up and you go hard into a corner and your car rolls you have just lost all your aero advantage from under the car. My opinion is from what I have seen is T-1 suspension rolls to much. That is also why cars have side skirts that flair out to keep air from under the car. Ever notice Rolex or other cars like C5 or 6R they keep the splitter right near the ground even in a hard corner? If they did roll their aero would be wasted when they roll low pressure under car is gone as air comes in.

If you are set up real low and rolll you would grind up your splitter too.

geerookie

Hmmmmm....... 600# of downforce from a wing on a Corvette.......that normal humans can afford!? Not Likely.
Of course, if you measure it at an unrealistic speed of 180mph or higher then maybe....
In ST2 wing downforce numbers really only count between 80mph and 130mph with top speeds of 140mph - 155mph.
Downforce of 600# is not needed in a straight line.
Realistically you can expect about 100 - 150 lbs on the nose and 200 250 on the rear. You could easily get more on the rear but it can't easily be balance on the front so why add the extra drag!

In your question above, the loss of 1" of travel is true but what is of more significance is, are you touching the ground/bottoming out yet? Compressing the suspension while going in a straight line at high speed isn't a bad thing. Don't raise your spring rates to maintain full travel in a straight line and then sacrifice mechanical grip in the corners because you can't get the tires "in" the pavement.
The other thing to consider is tire type and construction. Can it handle the extra load, do you need to add air pressure to support the load, how will that affect cornering, how much flex in the sidewall and could you hit the rim at higher speeds?

fatbillybob

Amazingly the sae report says chassis makes about -150lb front and -350lb rear at 120mph. Chassis rake has a significant effect. The apr wing for the vette on CFD makes another -300 at 120mph. I guess one would set the car up for max mechanical grip with just a hint of oversteer. Then at speed you would want safer aero understeer. I had a car once where I put a wing on the back and it worked so well the car was undriveable. I had to balance the new aero with a splitter then all was happy again. Even at our speeds you can feel the wings working. But maybe runing on the bump stops with lots of areo is not a bad thing? I don't really understand it but doesn't nascar run softer springs so that the scrutes sign off on the rideheight but then at speed the car drops and that increases the aero. The car run on the bumpstops and they add wheel rate with giant roll bars. Back to the SAE report they suggest more chassis rake that most T1 guys run. IIRC SAE said 1" and most guys run 1/4"-1/2" I think. So if you run the full 1" rake I suspect the rear end would be a bit loose which might be tightened up a bit by using a oem Z06 swaybar instead of a T1 swaybar. What do you guys think of that idea? The corallary to this question is does anyone run a T1 suspension and the stiffest setting on the rear bar? I wonder what the chassis rake is on that car?

John Shiels

What is the force on a car with 200 lb aero down-force on the nose and under hard braking? I have one of the earlier T-1 bars on my C-5 (no adjustment) and run 1100 & 900 on the VBP springs or close to it I would have to look under the car again. I may have 5/8 or 3/4 rake on the car also. Splitter is 4" past the nose. I never had a tire problem and I am sure I have loaded them nicely on Turn 1 banking at Pocono or even the other slower corners. I never ran the lower 20 lb pressures I see some have run on my Hoosiers.

If you click on the sig pictures you can see what happens on the banking vs the straight at Pocono in relation to the splitter height. If I didn't have the heavy springs where would my tires be or splitter on the banking picture? click on the pict again after it pops up and it will get bigger. The corner workers at Pocono often told me my car was glued to the road more than any other car coming down the straight at Pocono where you can hit 165 with my car. Even going over the infamous Pocono tunnel turn my car stuck when I saw others drop back in the mirror for that bump I could hit at 120+. To bad they took most of the bump out.

geerookie

These are real numbers. But the original statement was about 600# from a wing...in addition to what the chassis already provided.

I have the sae report and I'm not seeing the 150/350 numbers you are quoting...at least not stock. After mods?

gkmccready

It was a hypothetical, I had no data and was just curious what folks were doing when adding all the aero mods...

Solofast

Remember that most people are quoting a one wheel rate, and not an axle rate. That is, the axle rate is twice the wheel rate and with a 600 pound wing you are going to see a half an inch of lower ride height..

A half an inch isn't going to be a big deal so long as you aren't too low already, or just raise it up a half an inch and you should be cool.

Wasserott

I added my wing/splitter combination while running on a T1 suspension setup. I saw overall lap time improvements and the car was faster but i had problems in high speed corners and braking. I would seriously drag the nose under braking and rub the tires on the rear fenders coming out of the corners. My buddy "Woods" also installed the splitter/wing combo and although he had moved up from a T1 set up to bilstein C/O's, his front spring rate wasn't increased. As soon as he put the aero devices on the car, he would drag the nose as I had. He and I both now run about 700+ and 600+ plus equivalent C/O setups Fr and Rr respectively and I believe those are minimum rates for these aero devices.

Sorry Dave, i usually agree with you 99% of the time, but i've got first hand "transitional" experience on this one so yes, it does matter.

fatbillybob

I could see how you could have your problem. But the solution might not always be heavier springs because doesn't your non-aero mechanical grip go all out the window? I'm not saying I have a solution just more questions.

John Shiels

with the down-force you keep you grip. Never had a problem on tight infield with my car and heavy springs. Look at real race cars and the spring rates which they run and their light weight to boot.

redtopz

Where do you see aero dropping lap times significantly? I just started playing with some aero, but it opens a whole new can of worms that may not be worth it for most drivers. A wing alone puts the car way out of balance (understeer) as mentioned above. A splitter is a major pita and probably not practical on anything but a designated track car. My wing resulted in a 1 second lap time improvement around T-hill compared to no wing tested back to back and a 0.7 lap time improvement at Laguna Seca. However, in a race the wing caused my front tires to heat up and lose grip which seems to hurt in the long run. Full aero is optimal, but takes time and $$ to setup. And I'm not looking forward to dealing with broken splitters.

gkmccready

Watching Wally and the other ST2 guys take seconds off their laptimes...

John Shiels

putting a wing is a job half done.

redtopz

How much time did they cut off?

gkmccready

Have to go back and look but as Wally improved his car (and added aero) I think he's dropped seconds from what he was running. Just check the last few years of results on the NASA sites to see...