bavarian06

Like the title says, is there a difference? I would assume yes but to what degree?

My car was setup for big tracks (PO raced it on Putnam Park, Road America, Mid-Ohio, even Daytona). Since I owned it, I took it to Willow Springs Int'l and it handled beautifully. However, I was having a hard time getting it turned in and hooked up at this past weekends AX event (or I may just suck at AX).

Just curious what I can do differently to the car if I were to ever attend another AX event (soften/stiffen the bound/rebound, camber, sways? increase/decrease tire pressure?).

Jim Michaels

Yes, the optimum AX and track set-ups are somewhat different, but you need to hear from someone whose car is better prepared for AX than mine is. My Cayman S does AX (in A Stock), track (DE only), and road, so it has a very compromised suspension set-up.

While noticeable oversteer might be a bit scary on track, it's usually desirable on an AX course. That usually means a bit of front toe-out (or at least zero toe), a lot of negative front camber, and a soft front end relative to the rear. If you have adjustable shocks and sway bars, you might soften the front shocks and bar. Some even disconnect the front sway bar. More tire pressure in the fronts might help as well.

Brake pads and sticky tires that work effectively from the start (cold) are helpful. Track pads work fine after they have some heat, but that could be several hard slows into the course. Some R-comps (Michelin Cups) are a bit too cold natured for AX, while others (Hoosier A6) are good from the start. Even street tires need a few corners to heat up on the first run.

Tire pressures don't increase as much at AX as they do on the track, so set them a bit higher cold than you would before going on track. I usually start at about 35 psi at both ends whether I'm on R-comps (R888s) or street tires (RE-11s). You'll have time to adjust tire pressures between runs, so keep a gauge in the door pocket or glove compartment.

Tires: In AX they say the more sticky rubber (contact patch), the better. Thus, serious drivers tend to fit some impressively wide rubber, even on OEM sized wheels. At the last AX I attended, I saw an H Stock Mini Cooper on 15X5.5" rims shod with 225/45/15 Hoosier A6s.

If you're just starting out at AX, you probably do suck, at least compared to those that have years of AX experience. Those coming from track to AX for the first time often try to go too fast too soon, thus over-driving the course. Car positioning and balance (smoothness) is important, so locking up the brakes and scrubbing off speed (and rubber) through corners costs time. Another aspect of autocrossing that takes some getting used to is figuring out the tight course (a sea of cones). Walking the course (several times) is important, but I usually learn more about what I should try to do from my first run, when the car tries to tell me where to be, what to do, and when to do it.

Fortunately, the AX learning curve is steep, so most drivers don't suck for long. Seat time is a great cure.

levtron

nothing beats seat time.

racer

I tend to prefer my AX cars "looser", ie, easier to rotate with more oversteering bias. This can be achieved with sway bar settings, sure, but alignment (esp toe) will really bring this into focus.

Most folks at the track prefer understeer, at least upon corner entry, if not throughout a corner.

how much adjustability your car has, or you want it to have, is up to you. Learning to live with a compromise is what I did.. then seat time really comes into play.

Auto-X-er

So on a very related note. What kind of alignments does everyone run as the compromise setup for autox, track, and street? Obviously at least on the standard 911s getting the most camber up front possible is probably good. Does anyone actually go toe out up front. Thats pretty common for autox on other cars, but seems like it could be too extreme on a 911.

The rear setup is a lot more unknown for me. The stock appear to run a decent amount of camber and toe in. I guess messing with the rear too much could make it too unstable for track.

racer

What do you mean by "standard 911" - there are 40 years worth of 911s.

iirc, and its going back about 7 years since my 911SC, 1/16 toe out. Helps turn in responsiveness. "max" neg camber, but without camber plates it couldn't have been more than -2.0 up front and maybe -2.0 rear. 7/8 x 16s with 225/245 tires. Lowered, stiffer torsion bars and shocks.

Similar camber specs on my Boxster.. that car too was camber limited. -.8 front and -1.5 rear iirc (maybe -1.8?) 225/275-18s, RA1s, stock springs and shocks.

Jim Michaels

Auto-X-er: Another question is whether one is running in stock or non-stock (allowing camber plates) classes. My compromise alignments on 911s have been compromised more toward road driving than racer's non-stock 911SC above. I ran about -1.5 front camber on an A Stock (at the time) '88 911, and a '93 911 RS America (ASP at the time). I didn't notice excessive inside edge wear from road driving at -1.5. I consider any toe-in a compromise, but try to get just enough toe-in to keep from having to work the steering wheel so much on the road. Rear settings were a little more negative camber, and about double the minimum toe-in in front.

The typical "compromise" alignments for stock classes seem somewhat similar for the rear-wheel drivers I've owned, including a BMW M3. My current A Stock Cayman S is more front camber challenged, however, as I can only get -1.0 in front.

The H Stock Mini Cooper (a front driver) front set-up is similar, but rear camber is minimized, with rear tire pressures set in the 40+ psi range.

Preferred alignment settings also vary by tires used and driving style, so expect to see some range of preferences for both compromised and dedicated AX applications.

oldporman

He is talking about my Porsche, 2004 911 40th which I just got CPO from Porsche of Colorado Springs. I'm planning on taking it the Porsche dealer next week to set the alignment. Right now the front is neutral toe and camber and the rear I would assume whatever is standard for it. After the two AX events, we noticed that the right front tire was cupped and feathered on the outside tread. They were supposedly new Michelin PS2 N3's. I have just PDX's for the first time and it seem to be OK out there, other than small vibration at speeds above 100. So, I'm thinking I need to do something to keep from making it worse when I AX.

Jim Michaels

Ah, the dad finally chimes in. Congratulations on your recent purchase, and welcome to Porsche and rennlist, oldporman.

An alignment check for your purchase is a good idea even without unusual tire wear. Feathering could be due to a toe misalignment, and cupping sometimes indicates worn shocks. If so, a proper alignment and new shocks should help at the next AX.

utkinpol

for AX overall you may befefit from softer shocks on both compression/rebound and bit stiffer sways than on track - your goal is to ensure all 4 contact patches are in contact with road at all times and as speeds are way lower than on track it dictates certain changes to suspension setup.
overall you can also notice many AX folks like overstaggered tires with very wide tires in front which will make car bite in better. say, good track tires would be stretched on wide rims, like 245/305 on 9/12 rims and for AX you may want way more rubber, like 275/315 or 275/335 if you prefer rear end to be planted more.
most different thing at AX is car control - with much more used forced rotation than on track, differently timed inputs but still you need to see an optimal line same as on track and make car go smooth but be way more agressive with inputs for positioning car from one element to another.

oldporman

That's why I'm taking it in to Porsche, to get a proper alignment. I'm just trying to determine what the best setup would be for AX. I am concerned about the cupping from 1 AX. Seems a little much for that unless the alignment was way off, but it does not appear to be. It drove fine in PDX and on the highway.

balefire

to the OP:
the answer depends on what suspension components you have that are adjustable.

scca national autox winning 996 gt3 alignment
https://rennlist.com/forums/autocros...ml#post4625046

unfortunately, you can't get that camber.
if ur running street tire, and you run anything like that setup, you will be very "rotate" happy.
tried that and scared my wife.
now, i basically ran the same toe, but kept a bigger differential between my maxed front camber and rear camber for my own skills.
i would be leery of running toe out for a DD. i have no highway wander with ian and peter toe setup from above.

also, i noticed a big improvement in replacing shocks even though my 40th only had 33k miles.

congrats again on your 996 40th.

bavarian06

thanks for the input everyone. it seems that a softer suspension is key w/ lots of camber. i'll know better for the next AX event as i try to dial it in. my setup is extremely stiff, 950/1150ft-lbs spring rate and 8/15 clicks on the rebound/compression setting. what's the ideal tire pressure when the tires are hot (on street tires)? i run 35/37 psi.

my camber is -1.75 front and -2.0 rear, 0 toe front, 0.125 toe rear

Jim Michaels

That is stiff. I don't think you'll ever come close to full spring compression at AX. Short of going to the trouble of having two different set-ups, you might just do what you can to soften the front a bit relative to the rear; maybe by softening the front sway bar, or even disconnecting it. From what little I know, your alignment looks okay for AX. Even less rear toe may unsettle the rear some, making it easier to rotate in sharp turns.

bavarian06

figures, i dont think my car was meant to pivot around a cone =). i loose most of the time trying to get the car turned in and rotated around, waiting for the steering wheel to unwind itself. the car has TRG sways and its on the softest setting front and rear.

oh well, unlikely i'll attend any future AX events, too much waiting for your turn. 6mins of fun then wait 1-3hrs before its your turn again.