autocrossing the 318ti

[tastade]

I just went to my third autocross with the 318ti club sport. It was a blast, I actually got two wheels off the ground today. Didn't even notice until I reviewed the tape (I just thought the steering felt a little light); when I was making a tight right hand corner I hit the rumble strip and it lifted my right side off the ground. There was a left turn coming up so it never got more then a few inches off the ground, but kind of suprised me to see it on the tape. This was on a go-kart track, was a nice change for an autocross, it felt like a mini road race course.

I have heard several people complain about the 318ti's handling, and that it has a tendancy to oversteer suddenly since it has the E30's rear suspension. Has anyone had this happen? My car has felt like it has a little understeer when street driving, and when pushed hard it is almost totally neutral with a very tad amount of oversteer. I made a nice 4 wheel drift on the track today, flooring the throttle going around a banked turn, gave me a scare because of how well it went.

I was just curious about this because I haven't experienced this oversteering handling quirk. At the track I was running 30 front, 38 rear, with my Eagle F1 D3's, which is a combination that should induce oversteer, and I get none. It feels almost like my Prelude, but without the understeer, it just goes where I turn the steering wheel.

Another question, what air pressure do you run? I have been thinking about going even lower, maybe 28 front 36 rear, because my tires are hardly rolling, At 30 for the fronts, there was still a half inch of tread that wasn't making contact (by checking with shoe polish and seeing where it rubs off).

If you aren't all ready, get out and go autocross your car. It is a blast. I took the video camera today, but next time I will take my normal camera and get some photos so I can post them.

[1996 328ti]

All cars understeer. It is something that is built in.

I suck at autocrossing but I would not use pressures like that on the track. When I was running street tires on the track it was closer to 38 front, 36 rear. I think the differential between front and rear are too high. At 30 pounds you are not rolling over the sidewalls? I'd be pushing like a pig. Are they street tires or R compound?

[tastade]

They are street compound treadwear of like 280, goodyear Eagle F1 GS-D3's, http://www.tirerack.com/tires/tires.jsp?tireMake=Goodyear&tireModel=Eagle+F1+GS-D3

Like I said, there was next to zero roll in the sidewall of either the front or the back tires. And the car gripped like everything. Even when I was running 24 front 30 back there wasn't much sidewall roll. I am also checking this with an accurate tire pressure gauge which I know is dead on.

The only reason I upped the rear pressure so much was to make the car more neutral with less understeer.

As for what you said "All cars understeer. It is something that is built in.", that is true for factory cars, but their were a few cars that could suddenly oversteer without much provocation. Like the 91-92 MR2s, and many porsche's suffered from drop throttle oversteer.

[KIRASIR]

Believe it or not but your tire pressure setup will actually induce UNDERSTEER.

To create more oversteer:
Reduce the rear tire width
Stiffen rear springs
Increase rear sway bar diameter
Lower front sway bar diameter
Lower rear tire pressure/Raise front tire pressure
etc.

Try 38PSI front / 35PSI rear combination. With 30/38 you are rubbing off the side walls at the front for sure. You really need to have at least 35PSI in all 4 tires during autocrossing, otherwise you are losing time.

SL

[tastade]

The thing is I am not scrubbing the front sidewalls at all with those pressures, at least it isn't showing on the tread, it is only making contact about 1/4 - 1/2 inch above where the tread starts. The rears are obviously only making contact with the top of the tread with 38 psi.

It still feels pretty neutral with those pressures, but that may explain why I am not getting any oversteer. With my race compound tires I had before, I had to up the rear pressure to reduce understeer, but that was also on a front wheel drive.

I will give 35 front, 30 rear this weekend and 38 front 35 rear next weekend and let you know how it goes. But I was still making good times with the tire pressures how I had them, but maybe this will give me a little more time. Thanks!

[tzdevill]

what class are you running and what have you done to your ti. i have one and there is some killer body roll. we ran 35 front and 38 rear this past weekend.

[tastade]

Sorry, I am resurrecting dead threads. It is a stock club sport which puts me in GS class (I think all the compacts run in GS when stock). I don't notice any significant body roll. I am going autocrossing this weekend after taking a couple years off. I am going to try 38 front 35 rear, what do you think? I will try the shoe polish as well to see if I scrub any off. My tires are still the same Goodyear Eagle F1 - D3s, they are a little past their prime but still have a little tread left after 3 years and 20,000 miles. They are just hitting the wear bars.

[bullmand]

Last year on 6 inch rims I was running 40 front and rear. This year on 7 inch rims (and different tires) I'm only running 38. The only times I've ever had oversteer issues are in the rain or when it's too cold to get the tires hot. I think I may actually drop the rear pressure a little next time to try and dial out a little of my understeer. I'm also planning on doing the M coupe rear swaybar thing at some point.

EDIT: BTW, my suspension is not stock, so YMMV.

[tastade]

I forgot to air them up before I went to the track, so I ended up running 26f/32r. Not ideal for autocrossing. Sidewall rollover wasn't pronounced, but it was also raining. So in 3 weeks when I go again I will make sure to air up my tires :) I will say that the Eagle F1s ran wonderfully in the rain, it almost felt like a dry track. Only hydroplaned once when I hit a water puddle about 2 or 3" deep at about 50 mph.

[mohaughn]

Shouldn't you actually be running 6PSI less than what you want the tires to run at hot when the tires are cold? Meaning if you want the tires to be at 40PSI warmed up, you would want them to be 34PSI cold? Or do you guys want to run your tires at 46PSI warm?

I have the kumho mx's and they are running 40PSI front and 42PSI rear warmed up. It was raining yesterday, and I spent to much time at the beach on Saturday, so I didn't make my first autocross with these tires yesterday.

[AlaskaBlue]

I have found that my hankooks like about 45 front and 43-42 rear hot. Otherwise the lack of camber upfront causes the car to understeer and the tires to roll over. This may only vaugely apply to your case though since it is 17 x 8.5 et 40 with a 12mm spacer front and rear with a 235/40/17 Hankook R-S2.

EDIT: to answer mohaugn's question. You just check your PSI right after a run and adjust from there. You can always take air out on the grid easily, but putting it back in is more challenging.

[PeteN95]

I went for the second time Sunday, since getting my ti. First time with decent tires, but still not the hot setup, 18x7.5 wheels with 225 40-18 Khumo 711 tires (cheapest I could find, but not bad grip). I ran STS and finished last, but not by much and I was the only car with stock suspension.

I ran STS because I have an exhaust, the wheels, and a "not very" CAI that was on the car when I got it. I ran 34f/30r cold and never checked while hot, but there was not evidence of rolling off the tread. I'm still getting used to the car, but I really like it. I got beat by a newer 330 with springs, shocks, and bigger, stickier tires by less than a second.

[IndianaTravis]

those 18" wheels aren't helping you. The car doesn't have a lot of power to spin those things (even though they probably look great).

Pick up a set of 15" wheels from someone, and put some falken Azenis on them. I'd bet you'd pick up over a second.

[S10mafia50]

I went for the second time Sunday, since getting my ti. First time with decent tires, but still not the hot setup, 18x7.5 wheels with 225 40-18 Khumo 711 tires (cheapest I could find, but not bad grip). I ran STS and finished last, but not by much and I was the only car with stock suspension.

I ran STS because I have an exhaust, the wheels, and a "not very" CAI that was on the car when I got it. I ran 34f/30r cold and never checked while hot, but there was not evidence of rolling off the tread. I'm still getting used to the car, but I really like it. I got beat by a newer 330 with springs, shocks, and bigger, stickier tires by less than a second.

Travis is right, ditch the 18's due to the rotating mass, I'd find a factory intake box(if possible) then you could run G-stock(if you find some 15" rims)

I am a bit confused as to how a 330 was in sts though.....lol, I thought sts limited the engine size to something like 2.0L. I only wonder that since a guy I know can't run sts due to having a 2.2L n/a mr2, and no back seats.....lol. Also do yourself a favor and instead of lowering springs just buy the koni red's(yes they are adjustable) or the koni adjustables. I recommend these and the other things to keep you in G-stock for some driving experience. Lowering springs will leave you in sts and may actually hurt your times. Alaskablue's ti is just always at the limit and if I remember straight, his car likes eating cones sideways.... :evil_lau:
Andrew

[andy]

Travis is right, ditch the 18's due to the rotating mass, I'd find a factory intake box(if possible) then you could run G-stock(if you find some 15" rims)

I am a bit confused as to how a 330 was in sts though.....lol, I thought sts limited the engine size to something like 2.0L.

Sts = 3.0l naturally aspirated, and pretty skinny tires. A LSD is illegal, though, you can bet the 330 was annhilating his inside rear tire coming out of every tight turn.

I'd second the recommendation to do less mods and more driving at this point.