Spring Rates - Track / Autocross
 

So I haven't seen a dedicated thread yet so I wanted to start one.

Basically I'll be switching over to coilovers in the next month or so and wanted to see what you guys are running for rates for track/autocross use. I think I saw that RCE was running 400/400 but I was wondering what others were running. Also include sway bar setup (stock, aftermarket, just one aftermarket, stock removed from one end, etc).

This is for a DD/HPDE car but I've run very high spring rates on the street so I'm not opposed to that, that just requires good dampers. :shrug:

Thanks!

^ For reference, we're using 400/400 with the Whiteline 20mm front and 16mm rear bars.

Tires are michelin pilot super sports 245 width.

It's very nice...still easy to get it to rotate but very controllable. Ride quality is good on our RCE T2 prototypes (modified KW V3).

Myles has done some testing with firmer rates but I don't have the feedback on that.

- drew

I'm using out of the box KW's with the front/rear springs swapped.

I will most likely add a front bar and possibly adjust rates. I've been waiting for other mods to be installed before I corner balance the car again and give it a full eval, not to mention it's winter.

On a side note, I ought to visit RCE one of these days.

What are the stock KWV3 rates?

From what I recall (don't have the manual near me) they are 6.1k F / 7.1k R.

Any input on staggered? ~ 235/255

Yeah I just spent some time searching and found an old post saying 6/7. Round up say 340/400.

It seems like unlike the stock setup people are choosing to run higher front rates, or equal.

Looking forward to everyone elses response, kind of thinking about trying an even setup first, maybe 350/350 or 400/400. No idea on sway bars, I'll worry about that later.

I'm going to go 450/400 to begin with. Solo STX setup on 245/9" R-S3s.

I'm running 8/8 and I would that say that I would have gone with a 7/6 or tad lower for the streets, but then again that wouldn't have been the best for the track. I'm happy with that I got and the car handles very well. Some people don't even know it has aftermarket coil overs.

Which dampers? Sway bars?

Thats right you did as for that info, im running Fortune auto 500 8/8 with swift springs and rear helpers, all other suspension components remain stock.

I'm also running the flipped KW set-up which is about 340R/400F on stock sways. With 245 R-S3s I've found it pretty hard to overwhelm the rear tires with power.

we run 7k front 8k rear with no rear swaybar stock front sway and with the COG 3" lower than stock car works very well (a bit firm for my DD tastes). We have FLAT cornering (about 3 degrees at full yaw) with the ability to throttle steer the car in 2nd and 3rd gear if you keep to the tq peak when you add power.

as you can see LOW lol
http://www.ft86club.com/forums/showt...light=robispec

Robi

I think we'll be starting with 10k/12k (560/670 for you lb/in people)

Robi, we may need to consult with you at some point in the future for some geometry corrections :)

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.

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.

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

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.

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.

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.

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

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. :(

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.

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.

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.

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...

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.

I prefer my cars like Switzerland... Lol

Coming from my FWD experience, a loose car was a fast car in my opinion. I've been more consistant and fast in a car with stiffer rear springs/sway bar, that but's FWD. I can imagine with RWD I'd have a different opinion, the car stock is pretty neutral IMO so I'd be fine with keeping that balance, but that seems to include higher rear rates. I could see that being a bad thing too on some tracks, Perhaps I just need to switch it around to a heavier front setup and learn to drive again :)

My RWD experience is more limited to stock, or lightly modified setups (coilovers/swaybars) and I've never had to spend the time really sorting it out.

FWD and RWD are not the same. You can drive a loose FWD fast because it turns in better, but you can literally pull is straight with throttle (especially if you have a limited slip).

If the rear of a RWD moves around too much, that option is not there. Now I'll happily admit that you can get away with one of these cars looser than say a Corvette. Not as much power to get you in trouble. However by the same token that lack of power means if you get sideways it's speed scrubbed you can never get back. What you want is balance, pure balance. This is something that has been a problem getting the "subaru" guys to understand. While the car is a Subaru mostly, it's not like a WRX or an STi, or what have you. It's not super nose heavy, it's not AWD.. no front wheel drive to help fix things.

We successfully tested 10/12 springs this weekend. We're going to test 12/14 next weekend, but we're worried that it may overload our skinny street tires...

Car was very neutral after the dampers were dialed in; I can cause under/oversteer with purely steering and/or throttle input, with zero power adders.

What do you guys feel the limit of the stock dampers, performance wise, is with springrates? Most aggressive I've found is 250/250 from RCE. Debating between that Swift's springs but they have stiffer rear and softer front than the RCEs...

Obviously there is a lot of personal preference in this stuff. I'm not saying you are wrong, if that's what you like best then ok.

I am a pretty firm believer in not making the springs any stiffer than necessary. The best mechanical grip comes from having the car softer... until you run into issues with a poor contact patch, etc. Once I get where I've got a really good loaded contact patch that spreads the load across the entire tire, I don't want the car any stiffer in spring rate.

I'm sure what I find tolerable is different here in Western PA than what you might in SoCal given the climate and the roads.

To each his own. I know that I've run against cars with double my rates and sometimes more, and came out the winner. They clearly thought they needed more rate, I didn't. YMMV.

Considering that the car rides better and is much more planted with upgraded dampers and much higher rates, I'd say that the stock dampers aren't great for anything, and more and more less so when you ask them to do more work via a higher rate and shorter spring.

Nobody will have a for sure answer. Lots will tell you that the stock stuff is fine to X, but not have anything to back that up other than "it drives fine". And being honest, that's the trouble here. I think a lot of stock cars had dampers that were severely lacking too, even brand new (this isn't *that* bad mind you), but the OE thought they were fine.

What a shock can "handle" is largely a matter of when you the owner considers it to be out of whack. Trouble is most folks don't know a lack of damping when they feel it... until they feel what something better is, then it's very clear.

Our application is strictly for track use; I wouldn't recommend our setup for AutoX. Likewise, the majority of our tracks are unbelievebly badly maintained, and as a result, very bumpy.

Different environment, different recommendations. Perhaps we should split the discussion into a AutoX and Track thread, as the setups will diverge more and more as cars are developed.

I'm frankly surprised that so many other companies went firmer than us in the rear. We thought we'd have one of the stiffer rear rates but that doesn't appear to be the case. From the shock dynos we did for both BRZ and FR-S we weren't comfortable going past 250 in the rear. I guess other companies had other ideas. Also surprised everyone went soooo soft up front compared to us. The 250/250 with mild drop and shortened bumpstops works out very well in controlling body roll, soaking up bumps, and keeping a good balance with good turn-in. I just can't get over why everyone wanted a super soft front (that rides on the bumpstops) on this RWD car with a macstrut front. But hey, a lot of companies just take stock and multiply by 1.15 and call it a day.

For an OE shock they aren't bad. With Subaru we're used to complete crap, so we can tell when they put even a little more effort in which they have done for this car and to a lesser extent the most recent STI.

To be clear there is tons of room for improvement from a Koni or maybe a Bilstein sport later. But with just our springs and shortened bumpstops, it's a good match to the valving. Not bouncy or harsh, and around 65-70% critically damped. A little more low-speed damping would be nice, but with our springs vs. stock on OE dampers you'll come out ahead with our springs.

- Andrew

RCE: Most tried to stick with the stock softer front/stiffer rear setup would be my guess. I found stiffer than 250lb/in rear springs to work fine, no damper issues at all and the dampers handled the rate well enough (as well as I'd expect them to).

I'll be done with my stock dampers soon :)

I know, I just think it could be a lot better than stock. ;) The eibachs you have are one of the other better springs out there right now IMO.

- Andrew

250/250 is fine with stock tires. What are they 500+ treadwear? Sure stock dampers work.

Even as you go to a 200TW tire, you start to really lean into things with stock coils. Dampers get worked harder. They work fine, tho.

Just by going to a stiffer coil theres lots to be gained, especially if you keep the same exact bias front to rear, as was the case with my BRZ and H&R. Fine for DD.

But in HPDE< you can feel the under dampening with stiffer coils and realize there is more to be gained by modding past the stock point, it means committing to the next class up, but oh well. If you must stay with stock dampers, I see RCE as a no brainer, if coils are what you want for track use. If you want a DD, you may consider the HR option, the supersports are fun, and handle great.

As you add FI power, I think brakes, and stuff like squat and dive need to be addressed a bit differently. Hard to compete with a well designed coilover solution if you ask me, spring versatility is key for me.

Once I go to something like a stickier R-DOT tires, I will take a whirl at 440 front 430 rear for driveable track setup. I am sure there may be benefit stiffer still, but I wanna keep try my fillings in my mouth before going any stiffer, should not really be required at my recreational level.

My earlier post is a great departure point for most folks, 375/430 allows for DD more comfortably, where youre not standing on the brakes just before going into a hairpin corner at full speed all day.

Stiffer front sway bar, rear sway set on softest setting or may even need to redrill a hole..
Welcome feedback from the vendors posting above

Yeah I think I'm going to test 350/400 on Multi Pro R2's as a first attempt. ERS coils are cheap so I can test more options as needed :)