FD Race Suspension Setup Thread
 

I'd like to make this thread mirror Howard Colemans thread, except be geared toward racing on R compounds, or slicks.

I'm looking for people who race on slicks or R compounds to share their setups and impressions. If you drive or race on street tires, this thread is not for you.

I'm trying to fine tune my car to handle better. I do a lot of autox, and occasional track day, and a small amount of street driving (on Hoosier slicks).

Here is the setup I ran on all year so far.
12kg/mm front springs
Tripoint 0.125" thick bar (middle adjustment hole)
Full soft on Tein MonoFlex dampers.
-2 deg camber
Straight toe
245/45/17 Hoosier Koni Challenge Slick, set to 30 psi cold (usually 34 hot)

10kg/mm rear springs
Stock rear bar.
Full soft on Tein MonoFlex dampers.
-1 degree camber
Straight toe
275/40/17 Hoosier Koni Challenge Slick, set to 28 psi cold. (usually 32 hot)

I have noticed that the car would really want to oversteer on corner entry (partly my over ambitious driving and coming in with too much entry speed and over trail-braking). The car would also not accept much if any throttle on corner exit, it would oversteer badly. The car was fast, on the edge, but I felt there could be improvement. I have been getting pretty close to full travel on the shocks, but not quite (I used the zip tie trick). When I say full travel, I mean hitting the bump stop. I guess I have more travel if I get into the bump stop. They're pretty soft and about 1" tall. It might be worth noting that I was on 14/12k springs last year, but found they were too stiff and lowered overall grip.

To improve on the rear grip I thought I could do one of two things as a first trial. 1. Move the front bar one hole stiffer. 2. Remove the rear bar. I decided to do something more drastic. I figured the car could maybe use a bit more roll overall. What I did was disconnected the rear bar and moved the front bar one hole softer. My impressions after driving are that I was able to produce a bit of under-steer, but that was only when purposely messing up the corner entry. The rear seemed to plant better with more power on corner exit.

Another thing to note is that at the autox the hottest I'm getting my tires are in the range of 120 deg outside, 125 deg inside, both on front and rear. Doesn't seem hot enough for my tires, but I have yet to confirm with Hoosier tech staff.

I'm unsure if it was better for me to make the car overall softer, or if it would have been better to leave the rear bar connected and just make the front bar stiffer. I'll probalby try it out sometime, but curious what other people are running.

I'm unsure that I'm running the right spring/bar ratio for roll stiffness, and traction. I'm half tempted to go even softer on springs, and move the bars back stiffer. I probably won't since I'm planning on using a 285/315 Hoosier A6 setup at the beginning of next year, and I think I'll need the stiff springs to keep the travel under control.

Anyone care to share what works for you, things you've tried, etc.

Really, nobody wants to share either setups to autox, or road course?

give it time. they will come. most of the real race guys aren't on very often. some of them have also posted their setups and experiences on howard's thread and in other threads in the race section. hopefully this thread will be able to consolidate that info.

I hope this thread takes off...

Objectively, I am not the fastest driver; therefore my settings may not be ideal - but they suit my needs well, given my limits.

In my case, the objective is to load the tires very quickly on transitions to make the car settle fast (autox) even though I am not that good at inducing smooth weight transfers (like anticipating early enough changes of direction and providing smooth inputs accordingly).

My settings are:

14 kg/mm springs all around
34 mm solid sway bar front
no rear sway bar
full stiff rebound all around
half way compression all around (if surface temperature, tires, etc. are good I do stiffen this as well)

Camber: -2.8 deg F and -1.5 deg R
Toe: 0 deg F&R

With R-compound tires, traction and braking are good and I feel the car is well balanced.
I was in stock class before and had stock springs. With stiffer suspension, the car is now much easier to drive or to recover from mistakes.

The front bias lessens the risk of unintended overstear on lateral weight transfer.
Yet, the stiff springs in the rear and full rebound in the front make the rear tires load quickly on acceleration, allowing to effectively put power down.
The use of stiff rebound all around effectively damps (maybe overdamps) spring oscillations, which are highly undesirable as they unload the tires with resulting loss of traction (ever tried driving a car with shot shocks?)
The stiff rebound in the rear, makes also for a better rotation of the rear on corner entry - despite the front bias
Disconnecting the sway bar in the rear makes the rear suspensions truly independent - again making for a better power down.

Also, I replaced the stock torsen diff with a clutch type (OS Giken) which avoids the "uncertainty" of the torsen under acceleration, making the car feeling more "solid" and controllable with the throttle.

In the end, I realize that good drivers may prefer softer springs and compression damping for "better traction", but I can tell you that - at least in autox - those do make the car much more difficult to drive as they slow down the loading of the tires on weight transfer. Which actually reflects in poorer grip until the tires are finally fully loaded. Compare how you do negotiate a tight slalom with soft suspension vs. stiff ones and you know what I mean. If you are not proficient at anticipating steering inputs well in advance [compared to your speed and how tightly the cones are spaced], you may find yourself changing direction before the tires have had the time of getting fully loaded and you will loose the car at the third or fourth cone...

- Sandro

I find it odd that you'd have an oversteering car with the narrower front tires, and softer rear springs that you do. Have you plated at all with the dampening settings?

Old setup for autox

9.8 kg/mm front
7.15 kg/mm rear

camber: -1.7 front and -1.5 rear

Koni Yellow with Ground Control

Sway bar - suspension techniques front and rear.

Tires - 285/30/18 Kumho V710 on all corners.

With this setup the car would not turn until the tires were warm.
The ST sway bar is too stiff for autox unless you are in a warmer climate.
I am in Oregon - it is not warm most mornings.

The ST setup felt fine on track however.

Changed the Sway bars:
Tripoint .180 in front, stock in rear.
Better, still too stiff.

In addition, I was having issues bottoming out the suspension in a couple spots.
The nuts on the TP sway bar actually got ground off.

Latest setup:

.120 bar for the TP sway.
Raised the car from 25 to 25.5 ride height.

Changed out the springs:
Front: 12.5 kg/mm
Rear: 9.8 kg/mm

These changes made the car much easier to drive.
It works now on the rougher course without issue, and works fine on the smooth courses.

The additional spring has sped up the transitions a bit, and the softer sway bars have made it easier to drive in low grip conditions.

I had a co driver at a Porsche event last month with the current setup, and he was nearly able to match the times of race prepped 914-6 cars, so I guess the setup was working fairly well. :)

Bumping this back up for the new year.

This year I'm running on a new wheel/tire setup. I'm on an 18" setup with 285/30/18s up front, and 315/30/18s out back, on used Hoosier A6 rubber.

I have found that the A6s offer much more grip, and my suspension is traveling significantly more on the compression side. I've had to raise my ride height to 25.75" to keep from rubbing the tires on the upper part of the liners (plastic up front, and metal in the rear). I think I'm going to switch back to my 14k/12k spring setup to help combat that, and so I can keep my ride height down a bit more.

Does anyone know what kinda front camber the Hoosier A6s like on FDs for autox? Right now I"m at 2.2 (was at 2.5 before I raised my ride height), and the car oversteers badly and the tire kinda chatters. Does the A6 like more camber?

I come here to ask for some advice on suspension setup.

I have changed my wheel/tire setup a few times recently, and have some questions. First let me take you through the timeline of what I did so you can better understand.

In all of 2009 I ran a set of used road race tires, they were Hoosier Koni Challenge tires. The fronts were 245/45/17 and the rears were 275/40/17. Over the winter I did some upgrades and ran a halfway new tire setup.

For points event #1 this year I moved the 275/40/17 Koni Challenge tires up front, and ran a set of used 315/30/18 Hoosier A6s in the rear. This setup was amazingly better than the previous years setup. The rear grip was amazing, and my car seemed much more drivable and able to put some power down. Wanting to improve upon that, I made another change.

For points event #2 this year I changed the front setup to a 285/30/18 used Hoosier A6, and ran the same 315 rear. I fully expected the used 285/30/18 A6 to offer more grip than the used 275/40/17 Koni Challenge tire, but that was not the case at all. I ended up getting terrible understeer on corner entry and it was very hard to recover from it till the corner was completely blown. I already had the front shocks full soft, so I tired stiffening the rear shocks to help balance it out, but it didn't work so well, it made it understeer on entry, and oversteer on exit, it sucked. So, I have come to two possible conclusions:

1. The front alignment settings that each tire likes isn't the same. Possibly the A6 likes more static camber than the Koni Challenge tire?
2. The used 285/30/18 A6s are just plain heat cycled out. I'm not too sure about this because my braking grip was pretty phenomenal (the tires rubbed on hard braking whereas I never had the rubbage on braking with the 275/40/17 setup that was over 1/2" taller. So I can tell I'm getting good grip, just not laterally.

My alignment specs for the front are 2.2 deg camber, 5.5 degrees caster, zero toe. I was at 2.5 deg camber up front, but I had to raise my ride height to keep from rubbing the fender liners.

Any ideas on things to think about or try? Thanks in advance for any guidance you could give.

Hoosier recommends -3.0 deg
http://www.tirerack.com/images/pdf/warranty/HOOSIER.pdf
but you probably won't be able to get it in the front unless have adjustable arms. I am lowered and max out at -2.75 -2.80. I use less neg camber in the rear.

Use skid pad and take temperature measurements to find out optimized camber.

But understeer/oversteer has little to do with a less than ideal camber; it's something else. Generally it's tire problem or severly screwed up toes. Corner entry understeer is normally driver error --- with all due respect... --- or worn out tires. If the latter, you would also notice weak braking.

- Sandro

I would normally suspect driver error, but I didn't notice any understeer with my other fronts (the harder Koni Challenge tires). Maybe its that the A6s don't mask bad technique as much. Hmmmm.

Then, it is likely those tires are done.

Start with good references:

- Make sure all your suspension bushings are tight are not worn out
- With those heavy tires/wheels... put back the 14k/12k and make sure your dampers are working and are properly matched to the springs --- find a place to dyno springs and dampers to make sure they are OK
- Get a fresh set of tires
- start with a ball part alignment, max out front negative camber (most likely you will have to sacrifice some caster for that) and use -2 deg in the rear; 0 toe all around

If you don't do those first, you will never be able to set your car properly.

Go to a skid pad to check the cambers are OK and car is balanced (most likely it will be) or adjust those accordingly.

- Sandro

Update from last time, I forgot about this thread.

I put on some new tires (285/315 A6s), huge improvement in grip over the used ones I had.

My setup is currently sitting at this:

Springs: I'm running 16k front, 13k rear springs (Its actually a 14k spring, but the rear lower shock mount is moved inboard, so effectively a 13k spring in comparison).
Alignment: -3.2 degrees front, -2.5 degrees rear camber. 0.0625" toe out front, 0.03125" in rear, 5 degrees front caster. I think I'm going to try less camber in the rear, maybe -1.8 or -2.0 in order to obtain more forward grip on power.
Anti-Roll Bars0.125" tripoint front bar, in middle adjustment hole. Stock touring rear bar.
Tires/Pressures 285/30/18 front, 32 psi. 315/30/18 rear, 30 psi.
Ride Height 25.25" front, 25.625" rear.

This setup is working very well thus far this year. I've been finishing much better in my region (with some very fast drivers, Danny Popp, Greg Llyod, Brian Shaffer, Tom O'Gorman, etc), with an FTD the last event. Others autoxing please share your experiences.

the definitive setup is of course Eric Strelnieks. He runs 950/750 springs with 305/315 A6's. he also has drop spindles, but whatever..

are you still on the torsen kevin? all the top FD guys complained that the torsen cant put down power well enough with high grip (not enough load on inside tire to work right). a clutch diff will make the car a lot more stable on throttle and inspire confidence. Eric says his Kaaz didnt affect his turn-in like most would expect.

I'm actually using a cobra diff with the stock ford clutch type LSD.

Anyone know more than just spring rates on eriks car?

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i know this had been ongoing for a few years, but have you thought about going thru the various suspension setup sheets around? this is one Autocross to Win (DGs Autocross Secrets) - Dynamics Calculator we have tracked yaw and lateral G on our car, and we played with the spring rates, and it actually has worked out to 2 and 2.5! keep in mind we got the springs empirically, and use the spreadsheet and the data to confirm.

second rear toe might be worth playing with if you haven't already it actually does a lot!

Yeah I was just reading this and noticed that you never mentioned changing the toe on the car. Toe makes a HUGE difference. If the car is pushing you can try taking toe out of the rear or adding toe in the front. Keep in mind though if you take toe out of the rear you will lose some highspeed stability. If you add toe on the front the car will turn in quicker but be a bit twitchy. When messing with the toe keep track of your tire temps as they will change a bit as well.

My 7 isn't on the road and I don't auto x but I play with supspension settings all the time till a car handles just like I want it to.

i should say the natural frequency of our spring rates has actually worked out to be what the formula says, if that wasn't clear.

also once the car is balanced, rear toe made a HUGE difference, and we only moved it 1/16" and its a FWD car.

i was going to say, the front toe on the honda did nothing, but actually the bigger piece is that we've tried toe in, toe out, and zero in the front. and we've tried different ride heights and spring rates, and we've tried different camber angles, and such. it took a season, but we the car is dialed now, and if we need it to make changes we know what value does what, so its really quick and easy.

so play with the adjustments!

Very interested thread.
How to calculate the front and rear spring rate to start playing for a 1994 rx7 race only total weight w/driver 2,450lbs (47%f / 53%r) 13b NA semi peripheral 265whp. Track is a paved circuit with 11 turn, 1.6 mile road course, top speed 120mph with almost all 50-90mph turns. Asphalt quality is not good because 12 years old and close to sea. Using 4) toyo r888 235/40r17.
From what I had read before from Howard Coleman suggestion is 448lbs F and 336lbs R for a dual purpose (street and race) 3,100lbs fd3s ... ....
Our plan is to use an independent bound and rebound coilover like penske or similar.

The premise of the thread, seems a bit misguided I think, unless everyone's running the same track and tyre, aim is, softest spring you can get away with.

Running R888s in the past in a bumpy tarmac rally - 2 people, usually in the 5/600 lb range up front, 4/450 rear, if you went to a better tyre or the higher speed corners you mention, you'd probably want to bump the spring rates. Same combo on a slow speed circuit was too soft - 1 person......but the car's a couple of hundred pound heavier with the turbo stuff.

With medium to high speed circuits, slicks, usually running in the range 750/1000 lb in front, 550 to 850 in the rear....pity swapping springs in the front takes so long.

many thanks we wil go with 550 front and 450 rear to start playing.. :icon_tup:

there are two ways, you can try stuff, or look at what other people run or you can do the math. its also perfectly acceptable to try both approaches too.

the math part is kind of newish, but you need the car weight and a bunch of measurements, including motion ratios. this approach is actually best on an unfamiliar car, because you can take measurements, and do the math, and be in the ballpark without doing any testing.

that being said 550/450 is a proven spring rate that works really well, and its actually soft enough to street, so it should handle bumps really well.

I'm on Toyo R1R's. Do they count?

Zeal B6 10k/10k
Modular Tripoint front swaybar, stock '93 rear.
245 and 255/40 R1Rs wrapped around 17x8 and 9 RPF1s
My alignment specs can be found in Tripoint's site for a 'long track'.
My car is also corner-balanced before every trackday

I live about 30min from laguna seca and go there a lot to play. With the Tripoint bar set on its 'softest' setting my FD is still a tiny bit tail-happy, which is actually a good thing, for me anyway. The R1Rs do grease up a bit after a lap or two, but they let go very predictably and haven't surprised me yet.
I couldn't be more impressed with the ZEALs. Comfy yet fast, and damn near bulletproof.

Some kid of cheap BBK is next on my list, as the brakes are definitely my weak point. Porsche Big Reds? Show car part out? I'm on the hunt. :)

Alignment(this is a little old):
Attachment 695312

Coilovers:
Attachment 695313
Penske 8665, dual bleed shaft, triple adjustable(low speed compression, low speed rebound, high speed compression) setting depend on what track I'm at.
Shaft size:
Attachment 695314
900lb Front
750lb Rear

Tires:
-315 A6 Front(on a 11in rim, 7.5 backspacing)
For tire pressure, I start at 25psi cold for a flyer TT lap

-335 A6 Rear(on a 12in rim, 7.5 backspacing)
For tire pressure, I start at 23psi cold for a flyer TT lap

Sway Bars:
Tripoint .188 Front on middle hole(5 holes)
Racing Beat or Stock Rear Bar

Rotary Extreme Trailing Arms and Toe links

Stock bushings minus diff

Stock FD diff.

I still have some more things to tweak, but it's pretty close to where I want it.

Plenty of ways to skin the cat depending on what you are wanting to use it for.