This weekend was my first time with the Boxster at the track.

[mdex]

What is the reasoning for the higher pressures up front? With my car with an aggressive alignment tends to work best when all the hot pressures are even. It does depend on the track of course, but most times the cold pressures end up within around 1psi of each other.

[insite]

Originally Posted by mdex

What is the reasoning for the higher pressures up front? With my car with an aggressive alignment tends to work best when all the hot pressures are even. It does depend on the track of course, but most times the cold pressures end up within around 1psi of each other.

depends on a lot of factors. i personally prefer a car that is VERY neutral (most would think it oversteers); this is faster for me because the car is most 'neutral' when i'm fully on throttle (rather than an understeering car that is most neutral when you lift a bit).

to cure the understeer, we want a bit more grip up front. we do this IN THIS CASE by adding pressure to the front tires.

i say IN THIS CASE because people will argue that increasing the pressure will DECREASE grip & that lowering the pressure will increase the size of the contact patch & add grip. tires are funny things. above & below a certain range, lowering the pressure WILL increase grip. however, within a specific range, adding air actually increases the efficiency of the tire & adds grip.

at any rate, i know from experience with THIS tire and THIS car that 34F/30R helps to neutralize understeer. give it a shot.

[Pat]

Fantastic! Thank you VERY much for the info. It's nice to have technical resources available here in addition to the common problems/mods people discuss. I'll let you guys know how things turn out.
If anyone else has something to add I'd love to hear it.

[stephen wilson]

Would these pressures be adviseable on the street? I'd like to reduce the understeer, though some is due to the rear weight bias, which gives great rear grip. In tight turns (on the street), I tend to hit the throttle to soon, causing power-on understeer.

I also think Porsche did TOO good of a job in eliminating trailing throttle oversteer. I'd like the car to rotate more with a throttle lift, for mid-corner corrections. I've never driven a car so stable off the gas and trail-braking, even with the PSM off. (MY06) I find the PSM very intrusive if I'm trying to have fun, it kicks in way too early. But, it's great for joe blow, or if you're not paying attention, you couldn't spin the car if you tried!

Steve

[insite]

Originally Posted by stephen wilson

Would these pressures be adviseable on the street? I'd like to reduce the understeer, though some is due to the rear weight bias, which gives great rear grip. In tight turns (on the street), I tend to hit the throttle to soon, causing power-on understeer.

yes this will also work on the street. the understeer is due more to factory setup than to the rear weight bias.

Originally Posted by stephen wilson

I also think Porsche did TOO good of a job in eliminating trailing throttle oversteer. I'd like the car to rotate more with a throttle lift, for mid-corner corrections. I've never driven a car so stable off the gas and trail-braking, even with the PSM off. (MY06) I find the PSM very intrusive if I'm trying to have fun, it kicks in way too early. But, it's great for joe blow, or if you're not paying attention, you couldn't spin the car if you tried!

again, this is due to a large extent to porsche's OEM setup. understeer is SAFE for road cars because, to the untrained driver, it is a self-correcting phenomenon. the instinct is to lift off the gas & this solves the problem. oversteer, on the other hand, requires a trained response. porsche spent a long time trying to engineer turn-in on throttle lift for road cars. we can, of course, add this feature with a few mods. by FAR the most bang for the buck here is a rear sway bar upgrade. simply swapping to the BASE model's M030 sway bar makes a HUGE difference.

with the right setup, a mid-engined car will rotate like a top; all the mass from the motor/tranny is right at the center of the car. this means VERY short polar moments of inertia. this can be a blessing.....and a curse.

another reason the car is tough to rotate with power ON is because it lacks a limited slip diff. right about the time the car is putting down enough power to cause power-on OS, the inside tire will spin.

i have experimented EXTENSIVELY with various isolated & incremental mods to the 986. if anyone has questions about how different things WILL effect handling (NOT are likely to, WILL) on this car, fire away. i have tried all KINDS of stuff, street & track. i have logged data to back a lot of it up.

[mdex]

Originally Posted by insite

depends on a lot of factors. i personally prefer a car that is VERY neutral (most would think it oversteers); this is faster for me because the car is most 'neutral' when i'm fully on throttle (rather than an understeering car that is most neutral when you lift a bit).

to cure the understeer, we want a bit more grip up front. we do this IN THIS CASE by adding pressure to the front tires.

i say IN THIS CASE because people will argue that increasing the pressure will DECREASE grip & that lowering the pressure will increase the size of the contact patch & add grip. tires are funny things. above & below a certain range, lowering the pressure WILL increase grip. however, within a specific range, adding air actually increases the efficiency of the tire & adds grip.

at any rate, i know from experience with THIS tire and THIS car that 34F/30R helps to neutralize understeer. give it a shot.

I never have issues with front end grip, it is mostly about balancing it with the rear with my set up so getting more front end grip isn't normally my concern. I tried running larger tires up front (actually due to stock sizing not being available in time for the next track day) and the extra grip in the front slowed things down as I wasn't able to get on the gas as early coming out of high speed corners.

What tires / sizes are you running?

I find that a 26psi to 28psi cold temp all the way around gives a dead neutral car on most "R" tires with my setup. I guess alignment and other issues have a big part in our tire pressure balance front to rear and car to car.

[insite]

Originally Posted by mdex

I never have issues with front end grip, it is mostly about balancing it with the rear with my set up so getting more front end grip isn't normally my concern. I tried running larger tires up front (actually due to stock sizing not being available in time for the next track day) and the extra grip in the front slowed things down as I wasn't able to get on the gas as early coming out of high speed corners.

What tires / sizes are you running?

I find that a 26psi to 28psi cold temp all the way around gives a dead neutral car on most "R" tires with my setup. I guess alignment and other issues have a big part in our tire pressure balance front to rear and car to car.

mdex - keep in mind you're running r-comp & the OP is running street tires. also, his car is stock. if you're on r-comp, i'm guessing you have a few other bits installed that help neutralize the handling.

[mdex]

Originally Posted by insite

mdex - keep in mind you're running r-comp & the OP is running street tires. also, his car is stock. if you're on r-comp, i'm guessing you have a few other bits installed that help neutralize the handling.

True that... but driving stock cars as well (and even on street tires!) I still have found that most understeer can be dialed out (or at least back to the point that most people don't notice it) with alignment.... which gets us back to the original posters question as well, not that I am not enjoying our discussion on set up overall with our cars.

[Pat]

I just looked at the top of my shock towers to assess the camber situation. It looks like they dialed out as much camber as they possibly could. There is a ton of room to add more. :dance:
Looks like an alignment is in my future.

[jaykay]

Great thread! Sorry diverge a bit:

I have a great deal of trouble balancing the Box (stock S with 15/23spacers) while in power on oversteer ( I hope this is the right term). Things seem a lot different in this car. Yes I am a novice driver and as some of you may have guessed already this would be in less than dry conditions. What is the single most disruptive driver input in this case? I would think coming of the throttle too abruptly would be the worst, second: over counter steer.

The slide is great fun until I come to my senses and want to properly correct it. What is the proper technique?