Looking for spring rate recommendations for my car. I’ll be adding the full NLR aero package for this coming season. I will be using one of the 200tw UHP tires per classing rules/points and the car weighs about 2400lbs race weight. No power adders, just bolts on and a tune on my MS3. Thanks in advance

 

I love the 1200/600 setup on my Xida's...

 

what tire and setup are you running? 1200 seems high for a 200tw tire.

 

Full 9 lives setup(carnards, splitter ramps, end plates, big gurney, CFD end plates, etc...)

RC1 which is 100TW, but supposedly some of the fast super-200's are on par or better than the RC1 so I dont put to much faith in TW ratings anymore. Probably swapping to P1's next go-round.

Everybody who has driven my car has absolutely loved it.

Not saying this spring rate is for everybody...dont know what your base damper is if it can even tolerate that much spring.

 

Maybe the better question is what do you guys think the spring rate should increase on a aero vs non aero car should be. These cars are pretty slow let’s be honest so the aero load isn’t that substantial. Atleast not c6 z06 loads which is what I’m used too. An extra 100lb worth of spring rate maybe?

 

Only an extra 100lb is probably a little on the low side.
NLR quotes the medium **** kit as 140lb downforce at 80mph and just under 500lb downforce at 150mph

not sure what your max velocity would be but bolts ons and a tune would still get you you 125 ish I imagine so you’d be getting something like 250lbs downforce.

 

Interesting question. Bear in mind that the DF is speed related. You may be compressing the springs somewhat at the end of that straight, but as soon as you touch the brakes you bleed DF big time. Just look at the l/d curves, and think about where you sit when you are exploiting that DF the most (ie where is it you want the aero to give you the biggest benefit). Are there many circuits/corners that you take at Vmax? Probably not. So tradeoffs might include riding the bump stops sometimes. If you are going to run super stiff springs, think about the tradeoffs there, possibly excessive ride height in the slow stuff unless you use short springs with helpers.

I would approach it this way: fix the problem that exists, not the one that is yet to come.

If you are happy with the suspension sans aero, run the aero on that. Then fix the problems that emerge, if any. This is where you will be doing some testing right, so that when you front up to a competition you are ready to rock?

 

Can you come tell my 98 mph car that it should be doing 125???

 

My vmax on our longest tracks is approx 110mph on the main straight, give or take 1mph. The long fast sweepers where aero would most likely be working the car is doing about 85mph. Both mph numbers taken from my AIM data. So as a rough estimate using the NLR CFD I might be making a total of 150lbs down force while the car is loaded up. Im only looking for drag reduction on the straights as the car is very stable with 7* caster.

 

Smart approach but yes the car handles pretty well as is although it does tend to push the front end on some sweepers. Unfortunately these sweepers are also the turns right before the main straight so they're crucial for vmax mph. I have a few different damper options im considering but trying to do it once, do it right sort of setup but any of the options would need to be revalved accordingly. While I love my Hoosier SMs I need to stick with a 200tw for this class and dont want to overspring the car if not needed. NVH is not a consideration for me as the car lives on the track only.

 

NVM

 

Aero is a trade-off, and the trade-off is calibrated by lap time. Never mind Vmax, what does the lap time say? Sure you lose Vmax, but is the time lost on the straight(s) greater or less than the time gained in the twisties - are you faster measured in lap time with aero, or slower? If slower, have you tried backing off your AoA on the airfoil? Look at the l/d curves, you can still get some DF even at low to negative AoA, you lose DF but gain in straight-line speed, and if your circuits are dominated by long straights high DF will not be the advantage.it will be on shorter/slower/twistier circuits.

If you are just looking for higher Vmax on the straights, forget a wing (too much drag), maybe add a small MSM style boot spoiler instead, and focus at the front, Crusher-style: bluff front, small splitter, spats, reduce radiator opening, minimise window openings. These are worthwhile adds in any event, and can be adjusted with bigger splitters as you add rear DF.

 

Great question but I have no data to say either way whether the aero will be faster or slower in total lap time. I still can’t wrap my head around utilizing the aero on slower technical tracks. The air isn’t moving fast enough over the foil to actually make a difference. I was always under the impression that aero works best on long fast sweeping turns where you gain stability and traction ala DF thus allowing you to push even harder through said turns. I do understand there is a big time delta by carrying a few extra mph through sweepers down the main straight which I’ve seen with my own eyes.

 

You are reducing drag vs. increasing downforce...

I dont have A to B comparison as my car has always been an aero car, but my buddy dropped I think it was 2 seconds at Hallett post aero... and thats a short, fairly technical track where you arent taking advantage of the downforce component very much.

 

A wing is adjustable. On a slower track, by implication where mechanical grip plays a big(ger) part in generating lap time, you crank UP the aero (increase wing AoA) - increase the DF (and drag), but the DF increases faster than the drag and enhances the mechanical grip. Because it is a 'slower' track, the drag penalty does not hurt straight-line speed so badly and anyway straight-line speed is not that important here. That is just physics, how that plays out in lap time depends on the tracks, the cars, and the drivers.

Yes, carrying more speed onto a long straight is better than carrying a lower speed, and if lap time is heavily dependent on straight-line speed, we can see which is best - maybe. The maybe is the drag question, so it is probably better to look at the Vmax at the end of the straight, AND the lap time. If you have the AoA craked up to maximise exit speed from that sweeper, you are carrying a LOT of drag down the straight, hurting acceleration and therefore speed, particularly near the end of the straight where speed and drag are highest. That's basic aerodynamics. After that it gets down to specifics, and that is just what works best for lap time. If you run aero, you better be prepared for some 'scientific' testing - it is not 'set-and-forget', or one setting fixes all your needs.

So get your data. At least a Solo2DL-type laptimer/datalogger, learn to use the software (looks like you are already at least somewhere down this path already). Get yourself a notebook, and start recording tyres, tyre pressures, shock settings etc etc. Importantly, record your wing data (AoA) (use a level, and make sure the car is on a flat level surface), splitter length, and all changes you make before the meet and during it. Then look at your lap times, and in the context of this thread, wing AoA/splitter width. Not only will you know the end result, you will know how/why you get that result by looking at your sectors, especially corner speeds and straight-line speeds, and the effects of making changes to your set-up.

Finally, don't be hung up about being fast on the straight. As you know lap time is what counts when the trophies are handed out. Maybe not great for bragging rights, but if you want your name in the record books lap time rules.

 

Great info appreciate the help. I probably under estimated the combo benefit of DR and DF.

 

1200/500
1-1/8x 1/8 wall front
9/16 (14mm) rear

 

Awesome thanks