Autocross tires, pressure, breaks need help

[FiestaPack]

I autocrossed my st for the first time yesterday and it was a blast but I was understeering a lot and the back was slipping a bit. I had about 35psi in front and about 33psi in back
in my Toyo proxes R1R's on 16x9. As for breaking I have the Tarox BBK up front with their street pads on which are great but im thinking about buying their race pads cause there is definitely room for improvement.

Does anyone know what tire pressure I should be running for autocross?

Why am I losing so much traction?

Do the rear breaks on our cars even have any stopping power and are they worth putting better rotors/pads onto?

I feel like with the amount of money in my car it should be handling and keeping up better with a lot of the other cars there. I know a lot if it is the driver and it was my first time but with the amount of sliding my car was doing I just don't see how I could've gone much faster. I mean a lot of the Miatas were beating my time by 3+ seconds and there was another fiesta st their in a lower class than me who beat me by 2 seconds. he had a whole set of track wheels he brought and I didn't see his car sliding around like mine.

 

[Erick_V]

What are your alignment specs? Suspension, chassis bracing, sway bars? Chalk the sidewalls next time to see if they're rolling over. If you're running on the sidewall, add more pressure. When I was running my Federal RSR's I believe I ran 39psi fronts and like 36psi rear. Unless I upset the chassis the car hardly under-steered. You should be fine with the street pads, I don't think you'll get enough heat in them at an autocross event to fully utilize them.

One thing that will help lower your times more than anything is having someone ride with you. It's easy to see who has been doing this for a while and ask them to go for a lap with you. They will help you with your line and technique. At least at my events there are always people standing on grid with a helmet in hand that will ask novices if they want a ride along.

 

[FiestaPack]

I have no idea about my alignment specs or how to find that out. No chassis bracing or sway bars, I have a mountune rear motor mount and thats about it. I do plan on getting all the mounts at some point but it won't be for a while. Next month is going to be my last autocross for about 6 months cause im going to school and I want to be able to keep up a little bit more for that. Thanks for the response!

 

[kevinatfms]

Focus on the driver and not the car too deep. For tire pressures chalk the tires and see if the tires are rolling over onto the sidewall during cornering. If it does roll over and scrub the chalk then add pressure.

As for the rear pressure a lot of guys want it a little loose in the rear. It helps the car rotate around the cone. You can try 36psi to start and adjust up or down to find what you like best.

Once you figure the pressures out just focus on driving. Get people to ride with you, ride with others and see the line they take, braking zones and how they apply power. Just ask the fast front wheel drive car drivers and get all the knowledge you can.


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[eric tee]

dont throw parts in the car right away, if you are under steering a lot, you might be over driving the car. Like kevinatfms said, get some old timers to ride with you and get some pointers. be smooth with the steering wheel and don't yank it. since it was your first time out, do not worry about the times, just have fun and get a lot of seat time.

were you running with ESC off or sport mode? for me, i find the car too lose with ESC off. i autox in sport mode and this is what works for me.

 

[CaptinFord]

I have 225/45r16 Dunlop Direzzas on my white car and I run 47 psi in the front and 50 psi in the rear. I am also running in H Street with this car and I feel this is the best set up for the car. It seems crazy to be running such high tire pressures but it really helps you get around the corners.

 

[Erick_V]

I agree with all that’s been said above. Go out there, have fun, learn the car and be open for critique. Don’t worry about times. It took me 6-8 events before I had one good day and won novice class. I probably had someone in my passenger seat for about 80% of those runs. To this day I’m still not perfect and I have to push my own limits just to get a podium in SMF (Very open, very deep pockets). Don’t change the car. Work with what you have and learn to drive it

 

[felopr]

If you have something to take tire temps, is hard to tell you what pressure you should use. every tire is different. is also affected by how hot it is or even what type of track.
If you don't have any tools and only a tire pressure gauge, drop all tires by 5 psi over stock and put some type of chalk on the wear marks on the tires. Do a run and when you enter the pits, check the tire wear marks, if they are over the wear marks, you need to add more air if you have space between the wear mark and the wear of the tire, decrease the air. Adjust by 1psi and do a run again

This is a bike tire but is the same on car tires. See the triangle marks on the side of the tires, that is what i am talking about

 

[kivnul]

It looks like your car is already pretty well setup parts wise. I run RE71's 215/45/r17, 42psi front, 38psi back. I keep my suspension about mid-range of the hard/soft dampening. If your course is very rough, soft can help keep the traction down. The fact that you are both understeering and the back end is rotating too much leads me to think that you may be overdriving the car a bit. A brace under the front end (like a Pierce 4 or 6 point) could help keep the front end planted.

As to brakes, does your Tarox kit upgrade the rears any? If not, you can get the focus SVT rear brackets and rotors or a custom setup to re-balance out your system a bit.

Also, it may be contentious, but I like to AutoX in sport mode. My car gets very sideways with my driving style without it. I never feel it kick in or anything, but it helps.

Results from a few weeks ago, I am top in T1 group. "Excuses" is a Mercury Cougar that can get very fast times. He just slaughters cones though

 

[Pablo Pistoffo]

What brake issues were you running into? I've always felt the stock setup is fine (if maybe a little too sensitive). I've heard race pads generally don't have great bite characteristics until they have some heat in them, and by that time, your run is over in autocross.

I'd certainly agree with what others have said, that having somebody doing ride alongs can be a great help (especially if they also drive a FiST, or you let them co-drive).

 

[green_henry]

... I run RE71's 215/45/r17, 42psi front, 38psi back....

Are those hot temps or cold temps?

 

[kivnul]

Are those hot temps or cold temps?

Every run, regardless of temperature. I bleed off air right before it is time to don the helmet and get in line. After lunch, I refill the tires back up to those pressures and begin the process over again.

Another thing to watch out for is overheating your tires. I do not know about the R1R's, but the RE71's overheat pretty easily. If after a run it is too uncomfortable to rest my hand on the tread for longer than a second or so, I spray down the tires to cool them off. If I do not, they get greasy and wear down very quickly.

 

[Reaper]

There's a difference between going faster, and being successful. The FiST is possibly the very best car to have for SCCA H-Street, but your motor mount and bigger wheels throw you out of stock and into classes where you won't be competitive without tons of money and talent.

Bridgestone RE71R 205/50-16s on 16x7 rims are all you need to be almost nationally competitive. Konis and perhaps an Eibach rear sway bar are icing on the cake. With just the tires you should be regionally competitive anywhere, skills permitting. The whole package has won Nationals.