I currently run approximately 32/36 on my 225/265 18" StarSpecs for both street and autocross. Having RE-71Rs on my other car and being able to compare on different cars, i suspect that I'd run about the same pressures for RE-71Rs on a 993. I find that less than about 4 psi difference front to rear in this range, and the car doesn't want to turn. I'm curious why you like yours to be that much closer front to rear? What's the f/r width and what springs/bars?

Sorry, I will not comment on all-season tires.

 

+1 .. to nile13 -

The belly laugh of the day. SNL's "I Hate When That Happens" skit. circa 1983 or '84
None better ... Christopher Guest and Billy Crystal

 

Is that cold or hot temp?

I'm running 235/265 and have no problem with turning in, if anything its my rear end that's a little loose. I can get the back to shake free under too much acceleration or with a nice dose of throttleoff or a touch of the brake. I messed with my pss10 settings for a while to get the chassis balance I wanted and then tire pressure is the final tune. Maybe its just my imagination but I felt with 4psi difference i actually understeer more. Doesn't adding pressure to a side increase traction (up to a point). I do notice that if I allow my hot pressures in the rear to get above 36 the back starts to feel 'tippy' and doesn't hook up like I want it to.

Sorry for hijacking this thread, I could talk about this stuff for hours...

In terms of the A/S tires, they are surprisingly capable. They have lower limits than the RE71r, as to be expected, but they turn in nicely and the lower grip means you can have a lot of fun with them on the street without having to go too fast. They are great for suspension tuning, in my opinion, because you can feel understeer/oversteer on them at so much lower speeds. And they hold their handling characteristics in cold weather, which is very nice.

 

We, non-track types, don't really deal with "hot pressure" concept. At autocross, they are kind of all hot pressure. You check and adjust between the runs, so you get a chance to see pretty much in real time what you are running.

On the tire pressure giving more or less traction... it's interesting, non-linear and pretty frustrating. From what I've learned, and you already know, there seems to be a happy "range". In that range, slight adjustments are more or less predictable. For something like an 18" RE-71R on the back of a 993, all other things being balanced, I think that range is 34-38 psi or so. Go above or below that and you'll see quick traction loss in either direction (which is the non-linear part). Within that range, however, I feel I want more pressure as I can always apply more throttle to step the rear out, so I want more stick. As I end to drive the 993 with my right foot, rather than the steering wheel, I want both an ability to slide the tail out with throttle and catch it with traction, if that makes sense? And more pressure give me that. OTOH, if I go high on the front, I don;t like what the front end does and I have smaller tire there.

You seem to have the tire setup similar to Bill.V and Martin.S and they are both track guys. So, if you are more concerned with track, I'd pick their brains much more than mine, there's more there to begin with

PS One thing I've learned, though have hard time applying, is this. Go wit big changes. try it for a bit, see what the car does. Once you find teh limits of 'acceptable, you slowly bring the variable to something that makes you happy. So, I'd live the front RE-71Rs at 32 and start playing with rear, going to, say, 40 on one end and 32 on the other end and than converging to where I liked it. What I've also learned is that.., car setup really heavily depends on driving style. I'm notoriously numb on car setup and I've done 18 seasons of this crap. I don't set up the car, I let the car set me up. I just learn to drive what I have and complain regardless

 

Thanks for your thoughts Mike. I hear you on the big changes. That's how I got to where I am now. At higher rear pressures I could feel the rear-end start to get greasy and 'tippy' like it was rolling over a bit. I noticed it over 40 psi on the A/S and over 36 psi on the RE71r. So I started moving downward and found my sweet spot. If I move even a few pounds up or down from here, the car doesn't feel as solid and planted. I could probably play with the fronts a bit more, they may have additional room to go lower but I'm happy with how the car handles and the chassis balance. I couldn't really ask for more.

BTW - I know most people think in terms of cold for the street but I found the car handles better and is more consistent if I measure and adjust hot. And by hot I mean right after an intense winding road, not just driving in a straight line for a while. For instance I discovered that the right side of the car is hotter than the left (due to oil coolers, etc) and an even cold pressure does not result in an even hot pressure. My car is happiest when I set pressures hot and then let it cool to whatever it needs in order to get the same hot pressures again on the next drive.

 

One thing I'll mention is this. I've been thinking for some years now that it would be nice to use blind method on car setup sometimes. In other words, when I adjust my shocks or pressure, I think about it and analyze it. Too much. Have somebody else do adjustments and not tell me what they did would give a single blind approach.

I just bought double adjustable Penskes. They will be a nightmare to set up.

 

Yeah that would be cool. The best thing I've done is just run the same stretch of road over and over while adjusting as few variables as possible.

I'm not looking for fastest lap (or autoX) times, so that makes my job easier. I'm purely looking for what makes my car the most fun and enjoyable to drive. So for that measurement, my butt, brain (and other senses) are ideal.

I thought about using double-adjustable shocks but I knew I'd drive myself quite insane trying to dial them in. I have the same problem with my mountain bike shocks, which have lots of adjustments: compression, rebound, high speed, low speed, spring pressure. It takes me months to get them set they way I want and then I'm very reluctant to change shocks, or bike for fear of having to go through the process again.