[Dylan Savage]

Those of you with coilovers, what spring rates are you using? I know several people are using Teins, some intrax.. what else ? Anybody using the GAB revolution Stroke coilovers? They look comparable to the intrax/teins.

Thanks all.

 

[Andi]

Here's an email I got from Kent Rafferty back in '99 on this subject..

Hi Andi,

Here's what I have - most are from the source, although I had to
get the Stock rates from Eibach since no one at TRD knew what
they were :-(


Specs are in lbs/in:

Manf.               Type                              Front          Rear
------------------ ------------------              -----------     ---------
---
Stock             linear                              430              219
Eibach          progressive                   370/510      180/263
Intrax             progressive                   559              285
H&R              progressive/linear        470/495      250
Grnd Cntrl    coilover                           950*            600*
Tein               coilover                           780*            450*

*I have not confirmed the coilover numbers - they were given to me
 by others.  -call to confirm!

Andi, let me know if this is unclear or if you have questions.

Kent

I've confirmed that the Ground Control and Tein numbers are correct.

Regards,
Andi

 

[Andi]

BTW, a while back somebody posted some supra suspension data on the mkiv list. Included in this data was:

front wheel rate: 222 lbs/in
rear wheel rate: 204 lbs/in

From this, I've calculated that the Tein wheel rates are:

front wheel rate: 403 lbs/in
rear rwheel rate: 419 lbs/in

Let's analyze some other from Kent's email... Let Z be the spring rate ratio front to back... and let Y = the wheel rate ratio front to back.. i.e. Y = Z * 0.5543. I believe that, not considering swaybars or different tires front to back, it is this value (Y) that determines the car's balance, and ideally would be set to 1.00. Less than 1.00 would dial in oversteer, but the MKIV has bigger tires in back as well as swaybar differences so I personally thing slightly less than 1.00 is optimal. Jeff Hood said that he loves the balance of his Ground Control 950/600 setup with the regular TRD 27/27 swaybars, and 275/315 tires (which have about the same tire grip balance as the stock 235/255 combo).

Stock Z = 1.963
Stock Y = 1.08
Eibachs Z = 2.1155 to 1.9392 as they compress
Eibachs Y = 1.17 to 1.07 (again, Y = wheel rate ratio, front to back)
Intrax Z = 1.9614
Intrax Y = 1.09
H&R Z = 1.88 to 1.98 as they compress
HYR Y = 1.04 to 1.10
Ground Control Z = 1.58
Ground Control Y = 0.87 (Whoa.. front wheel rate only 87% of rear wheel rate!)
Tein Z = 1.73
Tein Y = 0.96 (Hmm.. front wheel rate is 96% of rear wheel rate).


Regards,
Andi

[ August 18, 2001: Message edited by: Andi ]

[ August 18, 2001: Message edited by: Andi ]

 

[Eric]

Intrax has a variety of spring rates depending on what you're planning to do with the coilovers (Ground Control does too, although Jay will steer you to something in the 1000+ lbs. range up front if you're planning to spend time on the track). I got their street/track compromise setup, which uses progressive rate springs front and rear. The odd part is that they use the same spring for both ends of the car. I assumed it was a mistake, but both Intrax and Rod Millen Motorsports, who actually came up with the spring rates told me it was supposed to be like that. The balance of the car was actually fine with the stock sway bars, despite the big increase in rear roll stiffness relative to the front. When I put the TRD sway bars on, it became a lot harder to put power down at corner exit because the rear end would come out easily. Since the TRD bars supposedly increase roll stiffness by an equal amount at both ends, I'm not sure why it happened, but it was a very noticible change, and slowed the car down a lot since I had to tippy toe at corner exits. I ended up keeping the Intrax rear springs, and putting a linear 750 lbs. spring on the front, which is probably about the minimum rate for a car that sees track use. I've never gotten a consistent answer on what the rate of the Intrax springs is, but the answers are usually around the range of 400/550 progressive.

 

[wizard_of_oz]

My current setup: Teins (standard springs, set 10 from hardest, 6 from softest all around), TRD 27% stiffer bars, and Hoosier 245/40/17 fronts and 275/40/17 rears on stock wheels. Tire pressure adjusted until there was proper tire scrub on both ends (I think 37 psi front 32 psi rear). Stock twins, exhaust, downpipe, boost controller turned OFF, still seeing 10 psi/15 psi.

When I went to Blackhawk Farms on Friday, I could not keep power out of the corners because the line between not enough weight on the rears and too much power to the rears was too fine. I'd oversteer if I didn't push it enough and I'd power oversteer if I pushed it too far. The problem is, not enough and too far were too close together to hit reliably!

I'll be doing TTC for my next track day this Thursday, maybe that will help...

If it doesn't, I guess I need stiffer springs in the front...

 

[Grant]

Oolan, your saying your car oversteers during steady cornering??? Although I have stock suspension, mine certainly does not at all. What changed it?

I haven't done much high speed stuff, but I know my car understeers unless I give it a decent amount of gas. In 1st or 2nd gear corners I can plow all the way off the course if I try and apply much throttle at all on exit. I've got 275/315 BFG KDs.

 

[Eric]

Originally posted by Oolan Zimmer:
<STRONG>Oh, and when it oversteered it was always most of the way towards the track out point, not near the apex. It was very consistent, so I learned to apex really late and leave an extra foot of pavement to catch the oversteer. Not the fast way around the track.</STRONG>

Are you unwinding the steering wheel at the corner exit? Oversteer that late is the corner is often caused by keeping the wheel cranked over to the track out point. You shouldn't have more than a little steering input going by the time you get there on most corners.

Also, you need more than Lance's recommended amount of negative camber for track use. Borrow a pyrometer from someone and check your tire temps next time out. I'd bet the outside edge of your tire is quite a bit hotter than the inside edge with -1.

 

[wizard_of_oz]

I'll check temps with a pyrometer at this track session.

I let my instructor drive my car for one of his time slots, and he had exactly the same problem. It is possible to get it to do just the right thing, but it's a very fine line and the acceleration felt too sudden to be fast. That might just be the way this car is; I might be able to learn to live with it and be fast on the ragged edge. I know there's time to be had if I can make it more stable leaving the corners.

Now that I think about it, it also just might be the 1->2 transition. I at least was dropping to 3500 rpm in some of the corners, and it was the slow corners that were the problem.

 

[Andi]

Originally posted by Oolan Zimmer:
<STRONG>I'll check temps with a pyrometer at this track session.

I let my instructor drive my car for one of his time slots, and he had exactly the same problem. It is possible to get it to do just the right thing, but it's a very fine line and the acceleration felt too sudden to be fast. That might just be the way this car is; I might be able to learn to live with it and be fast on the ragged edge. I know there's time to be had if I can make it more stable leaving the corners.

Now that I think about it, it also just might be the 1->2 transition. I at least was dropping to 3500 rpm in some of the corners, and it was the slow corners that were the problem.</STRONG>

If that's the case then DEFINITELY go TTC. It's way more predictable.

Andi

 

[Grant]

Oolan isn't TTC? Damn I just lost some respect for him... j/k

The car won't switch back into the 1st turbo till the revs drop below 3k, not 3.5k, so that may not be the problem. I tried sequencial once, and immediately switch back to TTC. Almost hit a wall. OTOH boost at corner exit does take some getting used to, I don't even notice the torque spike anymore. I do know tires make a big difference, my KDs are way more predictable than anything else I've driven on.

Eric what camber do you run in the back for good tire temps? 1.5? Best I could get out of my stock ride height was -1.8 in the front, and with little caster.

 

[jkbrauch]

This is good suspension info, guys, keep up the good work. FYI - I ran a Solo II autox (my first) 2 weeks ago with this setup:
Eibach/Koni (Konis 1 click from soft, F&R),
BFG R1s on stock wheels 255/275, 44f,42r pressure, camber -1 F, -1.5 R, toe 0 F, 1mm total in R, caster 5. TRD front strut bar, no rear (now have one), stock sway bars. My car is a 97 6 spd. with 35K, BPU. I was understeering badly in the slow corners especially, partly because I thought the turn-in would be better than it was. Surprisingly, the tire temps in front were very close to even. I'm going to experiment with sway bars now and hope to avoid the coilover route. I'm used to driving shifter karts with neutral or oversteer balance, so this was an eye opener. Nothing like starting over. Any comments on getting by with Eibach/ Konis? I now have TRD sways and the heavies on order. Money's not the issue, daily drivability is. Thanks, Jeff B. in Colorado

 

[Grant]

Yeah I know all about understeer and Solo 2. Got to brake way into the corner to get it to turn. Andi and Phil's larger front bar and the TRD 54% rear should help a little.

From riding in a Tein car set at the stiffest and my '97 Lexus suspension, I say go with coilovers. Its really not all that stiff, some people are just pansies I'd gladly drive it everyday.

Kent Rafferty is the one to talk to about autocrossing, hes on the www.mkiv.com list.

 

[Eric]

Originally posted by Oolan Zimmer:
<STRONG>My current setup: Teins (standard springs, set 10 from hardest, 6 from softest all around), TRD 27% stiffer bars, and Hoosier 245/40/17 fronts and 275/40/17 rears on stock wheels. Tire pressure adjusted until there was proper tire scrub on both ends (I think 37 psi front 32 psi rear). Stock twins, exhaust, downpipe, boost controller turned OFF, still seeing 10 psi/15 psi.

When I went to Blackhawk Farms on Friday, I could not keep power out of the corners because the line between not enough weight on the rears and too much power to the rears was too fine. I'd oversteer if I didn't push it enough and I'd power oversteer if I pushed it too far. The problem is, not enough and too far were too close together to hit reliably!

</STRONG>


What kind of alignment do you have, specifically, how much camber do you have up front? Before you start fooling with spring rates etc, make sure you have enough camber up front to get good tire temps. It will probably take about -2 degrees to get there. On race tires, power oversteer shouldn't be a problem on anything but the slowest corners if you're doing the corners properly.

<STRONG>
I'll be doing TTC for my next track day this Thursday, maybe that will help...

</STRONG>

Definitely do that. I'm a big fan of running sequential on the street since I don't like putting up with the lag of a single without getting the top end of one (yes that was directed at Mr. "double lag" Baritchi) , but it just doesn't work well on a racetrack. Lifting at high rpms/boost and getting back on the throttle seems to confuse it.

<STRONG>
If it doesn't, I guess I need stiffer springs in the front...</STRONG>

If your alignment is adequate, that's what I'd recommend. The TRDs also created corner exit oversteer on my car that wasn't there before I put them on. Increasing spring rates up front fixed the problem, and made the car a lot faster since I didn't have to worry about a world of outlaws corner exit if I pushed it.

 

[wizard_of_oz]

I'll have to skidpad to be sure, but I could power oversteer at 3/4 throttle at 3000 rpm when exiting any tight (70 deg) corner. I'm only BPU at this point, so I thought I could get away with 275 rear tires.

In the carosel it felt very loose, like it was about to let go. It was certainly right on the edge, and if it was more balanced towards understeer I would have been comfortable pushing it harder in the carosel. I personally can feel understeer in the steering wheel a lot sooner than I can feel oversteer in the pit of my stomach, maybe that's just inexperience.

I also have Lance's alignment: 4 deg front caster (each), -1.1 deg front camber (each), 0 front toe, -1.5 deg rear camber (each), 1.3 mm total rear toe in.

Incidentally, I understeered with stock suspension and street tires (the last time I was on the track).

Thanks!

 

[wizard_of_oz]

Oh, and when it oversteered it was always most of the way towards the track out point, not near the apex. It was very consistent, so I learned to apex really late and leave an extra foot of pavement to catch the oversteer. Not the fast way around the track.

I still kept up with everyone in my run group (and passed a lot of M3's and such).

 

[Eric]

Originally posted by Grant:
<STRONG>
Eric what camber do you run in the back for good tire temps? 1.5? Best I could get out of my stock ride height was -1.8 in the front, and with little caster.</STRONG>

I run -1.5 in back. I get tire temps that are hotter than optimal on the inside edge, but I think that's a function of the car squatting on acceleration and gaining negative camber at corner exit. I'm going to spend some time on the skidpad on my next trip to Buttonwillow to see what tire temps look like with steady state cornering.

 

[jkbrauch]

Just had my 2nd autox day yesterday. I realigned my car the night before and seemed to max out the adjustment at -1.75 front camber with the eibach springs ride height. I set the caster at 3.5 since one side was also maxed out at that setting. Are you guys able to get any more camber/caster than this when lowered?? The car was much more balanced with the increased camber. I had also added the rear strut tower brace and TRD rear bar only. I'm about 2 seconds off the pace of the fast guys in my class (ESP). Tire temps were about 10 hotter on the outside of the front tires than the mid and inside. The rears were even with my camber at -1.5. I'm going to set the Konis up stiffer and am now expecting to find I'll need a stiffer spring rate to keep body roll where I want it. Guess you can't have your cake and eat it, too. Jeff