Spring Rates - Track / Autocross

[whataboutbob]

I'll be running the 4/4 RCEs with 20/16 Whiteline sways in the near future. For reference I'm running 1st gen Michelin Pilot Sports 225/45R17 on the stock wheels.

[gmookher]

375lb front spring and a 430lb rear spring come with the gc setup, should be fine for street/track/DD.
I plan a set of stiffer front coils for dedicated track use, but may go with a set of 430 fronts 1st and see where we are.
GC sells coils at $59 each, so it was a easy choice to shop with them...

a 22/16 sway combo will be interesting with that setup.

[Dave-ROR]

Damn this is like the Honda world all over again, some people running heavy front, some heavy rear setups ..

[mla163]

I've been messing around with suspension calcs and measurements. Obviously, there are a lot of opinions and factors with respect to spring rates.

Based on

http://farnorthracing.com/autocross_secrets.html

The ideal spring frequency should be right around 2.2Hz front and 2.5Hz rear (I know, it's not that simple). Based on the following

Weights (est'd)
LF+RF = 0.55x2645 = 1455 lb
LR+RR = 0.45x2645 = 1190 lb

Motion Ratios (approx.)
F 1.0
R 0.75

The "ideal" spring rates would be
375 lb/in F
646 lb/in R

The front rate is close to what people are running. The "ideal" rear rate is much higher than people seem to be running. Again, there are a few assumptions here, I'll dig through this a little more over the weekend to double check and develop a little further.

[Sam Strano]

An perfect case of numbers lying...

I've run front engine/rear drive cars for years. It's what I know, it's what I prefer. I also own an FR-S, had one of the very first ones. I read this stuff and wonder how some people get to where they are getting.

I'd not run a stiffer rear spring that front. I do run more front sway bar, I would NOT run more rear swaybar. I have reasons for all of this, I've tested my car various ways. Others have driven it both at autocrosses and on the street and very much liked it.

I am a parts vendor. I can't give away all the stuff it cost me a lot of time and money to learn. Some of it isn't news to some folks, but the reasoning behind what I do is what I can't let get out on a forum. If you guys would like to discuss, I'd be happy to in person. However, I do need to ask that if you call me to talk about this stuff, you give me a fair shake at your business. After all, I've got a pretty good track record over the years, which is more than I can say for some of the sources of information listed above. I'd like to think proven results trumps hypotheticals.

[Sam Strano]

Originally Posted by Dave-ROR

Damn this is like the Honda world all over again, some people running heavy front, some heavy rear setups ..

which makes perfect sense since you know, this is a nose-heavy FWD car. Oh wait... it's not.... And it's not a BMW which has a crazy motion ratio in the rear either.

If anyone finds themselves in Western PA, you are welcome to stop buy and take a ride in my car. You'll find that having stiffer front springs and bar than rear doesn't make for a understeering pig, even on Blizzak LM60 winter tires. Balance is about the same, but the car does move around laterally a lot more and if you transition more than 3 times it gets really lively on the snows due to the huge tread squirm. Slap the Hankooks on it, and it pretty much does whatever I want, whenever I want.

[GTB/ZR-1]

Agree w/ Sam. That kind of rear spring rate will render the car almost undriveable...

[FT-86 SpeedFactory]

Originally Posted by Sam Strano

which makes perfect sense since you know, this is a nose-heavy FWD car. Oh wait... it's not.... And it's not a BMW which has a crazy motion ratio in the rear either.

If anyone finds themselves in Western PA, you are welcome to stop buy and take a ride in my car. You'll find that having stiffer front springs and bar than rear doesn't make for a understeering pig, even on Blizzak LM60 winter tires. Balance is about the same, but the car does move around laterally a lot more and if you transition more than 3 times it gets really lively on the snows due to the huge tread squirm. Slap the Hankooks on it, and it pretty much does whatever I want, whenever I want.

We're running stiffer fronts then rear as well, probably for the same reasons I believe you are.

I'm not sold either on the stiffer rear, need to try it though but it's now to cold to test.

[CSG Mike]

Originally Posted by Sam Strano

An perfect case of numbers lying...

I've run front engine/rear drive cars for years. It's what I know, it's what I prefer. I also own an FR-S, had one of the very first ones. I read this stuff and wonder how some people get to where they are getting.

I'd not run a stiffer rear spring that front. I do run more front sway bar, I would NOT run more rear swaybar. I have reasons for all of this, I've tested my car various ways. Others have driven it both at autocrosses and on the street and very much liked it.

I am a parts vendor. I can't give away all the stuff it cost me a lot of time and money to learn. Some of it isn't news to some folks, but the reasoning behind what I do is what I can't let get out on a forum. If you guys would like to discuss, I'd be happy to in person. However, I do need to ask that if you call me to talk about this stuff, you give me a fair shake at your business. After all, I've got a pretty good track record over the years, which is more than I can say for some of the sources of information listed above. I'd like to think proven results trumps hypotheticals.

I do believe that part of this is also driver preference, as well as the specific tire being used, aero setup, and power output.

I've noticed I like looser setups than most, but I also acknowledge that a slightly pushy setup is far more consistent with very little sacrifice in absolute potential.

We'll be testing combinations of 9/10/11k front springs, as well as 11/12/13k rear springs this weekend on track.


Another thing to keep in mind is that you cater primarily to an AutoX market, while we cater to a track market. The setups are vastly different.

[Sam Strano]

They shouldn't be vastly different. I run the same stuff both places. There is footage of me running the FR-S and my old Camaro @ BeaveRun (not PittRace) here in PA where folks can see how they work.

Both things require balance. Both require placing the car. Lap times at a track are largely influenced by power, at an autocross it's a more basis suspension question. Corners tend to be the same radius or larger on a track, and there are fewer of them. In fact typically I find cars loosen up as speeds climb, meaning I want typically a setup that isn't stiffer in the rear, but the same or softer even at times than autox.

Personal preference is true. But I don't want an imbalanced car either place, and the car weighs what it weighs. Basically, folks tend to be more careful on a track, which makes the car move around less (not being driven as aggressively as there is stuff to hit), which tightens it up. So some choose to stiffen things up. I'm typically not one of them.

I don't mind a little roll in a car. It's not bad at all as long as the tire's contact patch isn't screwed over it, and great damping is what makes the car respond and turn in, not high spring rates. So I tend to not go nuts on springs, let the suspension work and use the dampers to tie it down. I also I like to use some more front bar (but not as much on this car as some others) to help with roll but not at the cost of ride/impact harshness. It takes a lot of spring to counter a little more swaybar.

[CSG Mike]

I sort of agree and I sort of disagree.

Aero is generally not a factor at AutoX except in the crazy $$$$$ classes, as the aero needs to be pretty extreme to have an appreciable effect at AutoX speeds.

The fastest track cars tend to be the ones that rotate well at low speed, and understeer at high speed, whereas AutoX rewards cars that respond quickly to input and make fast small direction changes. Although experiences vary, and admittedly my AutoX experience is minimal, stock/STR/RTR cars tend to have ultra fast transitional speed, but push in sweeper type corners (unable to power out without push), whereas a track setup on an AutoX course would transition much slower in a slalom, but make up time in sweepers and boxes.

As you stated, cars tend to rotate more at speed, and this car is no exception. However, it's not as drastic as most cars in the past; the front gives out before the rear even at 100mph in a steady state turn at terminal on both the FRS and BRZ, both with stock suspensions.

To me, the two setups are mutually exclusive without at least SOME changes.

[GTB/ZR-1]

Sounds like Sam & I like similar setups. Also, my autox & road course setups are very similar, just a little bit of fine-tuning. The car should be comfortable & instill confidence in general; and it should act similarly in both environments with like settings, IMHO...

[CSG Mike]

I wish there were a way to do an apples to apples comparison. The tracks in socal tend to bring out understeer in cars, so a lot of setups here are slightly biased toward oversteer.

It probably doesn't help that I prefer a looser car.

[GTB/ZR-1]

I prefer my cars like Switzerland... Lol