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archived.

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71dsp

I used to know, but now I have forgotten. Something really soft like 180 lb/in front, and 150 lb/in rear progressive. I am not 100% sure. All I know is that my setup is A LOT stiffer and rougher than stock!

71dsp

Probably the best advice that I was given was to leave the car ALONE!! My problem was that I was changing it between every event, so I never learned exactly how my car behaved with certain settings. This season (if I get my car back together this season!), I plan to just leave it alone, and if I make changes it will be a single change at a time.

floundericiousFL

What? LOL were they trying to set it up for, say, world rallying?

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2000 Ficus Green Prelude (SOLD)
2002 F150 SuperCab XLT
2001 Ford Focus ZX3

Jape Ownz You!
Rest In Peace, John!

Darth Luder

Right now I am burning off my stock tires for when I finally get my quaife and have to move to DSP out of STS. The sidewalls are so flimbsy that I have to make sure more is up front than the rear. At my last event I had more in the rear than the front in the first three runs. Then I switched to higher up front than the rear. I was at 35f/39r then went to 40f/35r and I lost 1.8 sec right on the first run of the second heat. Then I finally got to talk to one of the experienced guys there and we figured it out that the reason was that I needed to stiffen those sidewalls up. When you roll over, you lose tons of traction. You want to stay on the tread, that is where your grip is. Deflating to the point where your contact patch is on some sidewalls is very bad. This is why you can get some more oversteer if you deflate the rear tires some.

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If you only knew the power of the Lude...
'94 Porsche 968 - National PCA HPDE Instructor
'98 Red Base Prelude - 02 & 03 DSP Champion - Sold
"Straights are for fast cars. Turns are for fast drivers." - SCCA Solo2

BluePowder7

Huh..? I thought that having softer rears keeps the back end planted more, thereby preventing it from snapping out and going INTO oversteer.....

Pork Chop

There's an optimal tire pressure at which you've maximized the contact patch (typically with lower pressures), yet you don't roll over on the sidewalls (typically with higher pressures). Hypothetically, let's say 44 psi is the magic number for your rear tires. If you increase the pressure, your contact patch gets smaller, which means less grip on that end, and more oversteer. On the other hand, if you start to decrease the pressure, the tire starts to roll over onto the sidewall, which is less grippy than if it were using the full contact patch. Same principle here, where you end up getting less overall grip and more oversteer.

If you take a car that understeers terribly (like an Accord wagon), the car will be setup at 40+ psi in the front (keeps the fronts from rolling over) with something in the low 30's or even high 20's in the rear to negate all that understeer and help the tail end rotate. I suppose it's possible to get the same effect by increasing pressure, but you'd probably have to go into the really high 40's/low 50's, which is way over the recommended pressures of the tire itself.

Pork Chop

Another example:

On my Kumho V700's I run 44 psi front and 48 psi rear (on the stock 16x6.5" rim, so they have to be that high, otherwise they feel mushy). With this setup, the car is fairly neutral on concrete, but on asphalt, it will probably be too loose (too much oversteer). To counteract this, I'll lower the pressure in the rear to 46 or 44, until it's neutral again.

The optimal pressure for my rears at which they have the maximum contact patch yet they don't roll over is probably around 40 psi. However, at that pressure, the car will probably understeer quite a bit, so I need to decrease grip at that end by either lowering pressures (um, probably not a good idea, since the 225 is pushing the limit for such a skinny rim) or increasing pressure (better idea). So, I keep raising the pressure until it feels neutral again.

BTW, a lot of this increasing/decreasing the rear is a matter of driver preference. Try both and see which one you prefer.

BluePowder7

Well, I just got into this whole autocross / Solo II thing this spring, so I guess I have a lot to learn. I'm learning all of this on a set of my stock RE92's so I can afford to wear them down. I'll be putting on a pair of Toyo RA-1's (205/55-16, to match the size of my rears which are also 205/55-16 but regular street GoodYears).

Pork Chop

I'd strongly suggest running the same tire all around. The RA-1, while not the stickiest R-tire around, will still be far grippier than your street tires in the rear.

BluePowder7

So should I be in the mid-30's or low-40's for pressures..? Oh, I'm also going to be putting on a set of H&R race springs and KYB AGX shocks. Any advice on how to set it up, at least as a starting point..?

Pork Chop

Try 44psi F and 42 psi R at first. As for the shocks, set them halfway front and rear, and then adjust the rear until it's neutral (or maybe a little bit of understeer).

If you haven't done a lot of events, it's really best if you leave the car alone for a while. It's hard enough figuring out tire pressures when the car is stock, let alone trying to figure out shock settings at the same time. Once you've figured out how each little setting affects the way the car feels and understand why it behaves that way, then you can go ahead and start messing around with the car.