I got Kuhmo 205/60 R-15 on the 7 and I'm wondering what a good tire pressure is for autocross. I tried searching but its not working for me. Can I get some feedback from anyone with this same tire size/brand?

Gracias

 

I kept searching and found some results.

 

Tire pressures really depend on a number of things. I would start at 40psi and go down from there....some people I know prefer to start at 44-45psi....but when the tires heat up, pressure goes up.

 

Every car is different, every day is different. if you are serious about tire pressures you need to learn the signs to look for on how to adjust your pressure. A good indicator is to look at your tire and see where the wear is coming to. Really you need to be shown this by someone experienced in person though. My recommendation is read up what conditions to look for and what changes to make to the tire pressure will do and have someone experienced in real life show you the conditions to look for as well.

 

What Kuhmo's????

 

How wide are your rims? Any suspension mods?

You need to provide more information in order to get a good recommendation.

 

Stock GXL suspension (has the auto adjust buttons on the center console) stock meat cutter rims 15"

The tires say Kuhmo Touring ST if I remember correctly. I'm not sure about the ST part because I'm at work and I didn't drive the car today. I'm looking at getting some Tein S-tech springs which will lower the car some, but right now everything is stock.

The reason why I was asking about tire pressure is that I keep getting understeer when going through sloloms. It might just be my inexperience though. This past weekend was my second attempt at it. I consistantly suck at it, though I am having fun and I am learning. I tried to get a friend of mine to video tape my runs so I could see what I am doing on different parts of the course vs other people on the course, but it didn't work out. I think that will be a big help when I can step back and see myself and my car go through the course.

 

Suspension is key when it comes to auto-x... as far as tire pressure is concerned, I'd run between 35 and 40 PSI depending on how hot it is.

I'd honestly get some decent suspension other than stock, then some wider tires all around....

As far as the understeer is concerned, get some camber plates...they'll help your cornering by a LOT...

 

Thanks for the input. A friend of mine came out to run his car and I noticed that his tires were like 235 or 245. I took note of that right away. I'm definately going to focus on the suspension and try to learn as much as I can about how each part affects the handling of the car. The springs will be new vs stock, and the amount they lower the car will help lower center of gravity a bit. I saw some camber plates somewhere, so I'll get those and get the car on an alignment rack.

 

[QUOTE=Project84]The reason why I was asking about tire pressure is that I keep getting understeer when going through sloloms. QUOTE]

Try higher front pressures. I don't autocross much anymore and am more familiar with race tire pressures. On my FD with SO3's I would run like 40 in the front 38 rear. I was never much good at autocross either.

BTW-Icemaster had some good advice.

 

I'm taking in all the info and starting to see a bigger picture. I did some searching and the only thing I found that is conflicting is how some people say to run higher pressure, while others say run lower pressure. I'll definately keep searching that topic to find out all I can and to see what works best on my vehicle.

I found some camber adjustment kits and I know a guy who works in a dealer's service department who will put my car on the alignment rack for free. Wider tires, better and newer suspension parts, and research the tire pressures. Seems like I'm well on my way. Thanks guys. I have another question but its a totally different topic so I'll start a new thread if I can't find it by searching first.

Thanks for all the help guys!

 

If you're really serious about suspension tuning (as most good racers should be), look into buying a pyrometer to measure tire temperatures.

In the meantime, you could try the 'chalk trick,' which involves making a few chalk stripes on your tire to see how far it's rolling over. If the chalk on the sidewalls is getting worn out, increase pressure. If the chalk on the tread isn't getting worn out, decrease pressure.





If you're looking to become a better driver, I'd recommend driving the car with very few mods and focus on technique as the way towards faster lap times. If you modify your suspension so that your car handles better, it will usually increase the limits of the car, yielding faster times without forcing you to improve your driving skills. A good driver in a 'bad' car will be faster than a bad driver in a 'good' car 99% of the time. The saying goes "fix the nut behind the wheel first."

-s-

 

The more reading I've been doing, the more I see that it just takes time and practice to get some skill. I have run across the phrase you used about the nut behind the wheel. Thanks for the chalk tip. I read something about it yesterday, but what I read didn't clearly describe what the chalk was supposed to indicate. The next event is on June 12 so I'm looking forward to going out, having fun and getting some seat time.

 

As for adjusting tire pressures up or down, they're both right.. potentially. If you figure there is one tire pressure that gives you optimum cornering grip, then either increasing or decreasing your pressures away from that optimum pressure (assuming you can find it- it's tire/car/course/weather dependent) is going to result in less than optimum cornering grip. Generally, though, if you're rolling over onto the sidewalls (as shown by the chalk trick), you want more air (in my experience).

One more thing, if you are running on the stock shocks, they are very likely nigh worthless.. it made a huge difference going from stock to Koni Sports on my 86 GXL. My car would need to "take a set" before it would really start to turn with the original worn-out shocks. With the new shocks, it responded much more quickly and stabily. Since a slalom is all about constant transition, bad shocks can destroy your ability to navigate that element of the course effectively.

Of course it's good to learn to drive the car before worrying about upgrading the car, but the condition of the shocks after 15-20 years is well below original stock condition (at least in my case). You are not so much "upgrading" the car by replacing the shocks as you are "fixing" something that's gone bad.

Good luck..

 

MechE00 is right a good driver in a bad handling car can still drive but it mgiht not be pretty. As a beginning driver I do recommend getting your car in prime condition for racing with your stock components. Worn out parts or an incorrect alignment can really make the car a handful to race. It is better to learn on a car with correct alignment settings, and no worn out components than one that is unpredictable. Start with decent tires, get your bushings checked and see if any are worn out and replace them, and get a good alignment with what some other forum members are recommending. Then do the chalk trick to see where your tires are wearing and adjust the pressures at the track as needed. Have someone experienced co-drive your car and they can tell you problems they see in the handling of the car and how to fix them. You will be surprised how big of changes replacing stock components or setting the alignment will make to your times without going adjustable shocks, springs, full out suspension etc.

 

Before putting on ANY aftermarket parts, you should decide what class you want to race in, in the long term. The least expensive class will be stock. Your car is already there. It sounds like you just need to fix what you have to become more competitive.

Installing ONE aftermarket part, like wider wheels, will put you into a street prepared class. In order to be competitive there, you will have to spend lots of money.

Stay stock!! I suggest that you buy an SCCA rule book. It will tell you what modifications are legal, and which are not.

 

If you're rolling onto the sidewalls you can also not have enough negative camber........... Look @ my REPU below, lots of sidewall wear on the front tires from that run.

 

For the slolom, what is the best technique for getting through it as quickly as possible? (should this question be a different thread?) When I walk the course, I look to see if I want to enter on the left or the right based on what side I'll be exiting on in relation to the next turn/obstacle. But actually driving the slolom, where do I want to pass between the cones? Should I pass right before a cone, right after a cone, or half way between the cones? I have been trying to pass through at the half way point. Also, I realize that some sloloms are set up with the distance between the cones constantly decreasing. I don't try to brake in the turn if I have to slow down toward the end, I wait until I'm straight, then brake and turn to go through again. I see other people at the track do it different ways, but they have different types of cars. Everything from SRTs to Mini Coopers to Corvettes so I know each cars has stregnths and weaknesses as far as acceleration, braking and handling. There aren't many RX-7s out there, just me and a friend. He has a lowered TII with wider tires so I don't think his car is a good comparison to mine at this point.

As far as the camber and alignment issues, I'm taking the car in Saturday to get it put on the rack and to inspect all the bushings under the car so I can make a list of what needs to be replaced. I'm sure it all needs to be replaced, but working with a budget has its limits.

Thanks again for all the great advice.

 

A top level national competitor that I have co-driven with told me, it doesn't matter what the car is or how fast it is the line is the line. If you go from a 120whp Maita to a 400rwhp RX-7 drive the same line just faster. In a slalom the fastest way is to be turned before the cone and be as close to the cone as possible. This minimizes the direction in and out from the cone that your car has to turn and allows you to be setup straight before the next cone. If you want to get good fast, have a national level driver co-drive with you in your car whether it be at an event or a practice then copy their line.

 

I don't live in an area where autocross is at the national level. We follow the SCCA rulebook, but its a local event, nothing national. But thanks for the advice with the slolom.

 

Another auto-x driving technique is to turn in earlier and turning the wheel less. Which creates a wider arc of travel. Instead of turning in late and really cranking the wheel. Which generally speaking creates big slip angels on the front tires and understeer.

Also dial in a little more oversteer, helps turn the car into the tight corner. More rear spring, rear swaybar, or rear shock.

Also zero toe out lets it turn in faster and reduce understeer.

 

Hey DriveFast7, what is the airdam you've got on your car? I live the functional no nonsense look to it, seems like it could take a beating.
I've only drive AutoX for a single season but I must say your best bet is to follow the rules for stock class, although the car might not be very quick on the street it can be fast on the track. I took the other extreme because where I race there really isn't much worry with classes and I wanted to car to be entertaining to drive on the street so I'm now in C-mod this year with just a few engine-swapped Civics. If you really must prep the car then look into the ST2 class or whatever the new sport-compact streetcar based class is (I forget what is called).
Cheers,
Grant

 

If he has an early GXL (clutch-type LSD) then he can't do ST2. :/
edit: noticed the link to the car in the sig.. Project84 is already far from stock class..

Regarding slalom technique, it's difficult for me to express in just words and feel confident that I'm not just confusing the issue, but I'll throw my hat in on this..

In a slalom, being "early" is good, getting "late" or "falling behind" is bad, and usually leads to blowing the slalom or spinning out. Early means that the car is crossing the line between two cones as close as feasible to the cone just past and as far as possible from the next one coming up. Note: this means that the car has already turned at this point, the steering wheel should already be back straight and about to turn back the other way..

Another way I've heard this expressed is that you want to think about trying to hit the cone with your inside rear wheel (without hitting it with your front...).

Another trick mentioned to me is that you want to try to focus on the last cone of the slalom even from the beginning of the slalom. This is just an extension of looking ahead. This bit of just looking at the last cone of the slalom can be difficult (along with looking well ahead of the car in general) depending on how familiar you are with autocrossing your car. If it doesn't work out for you at first, don't worry.. just give it a try every now and then over time, and one day you might find it clicking and suddenly making things easier...

Lots of people in this thread and elsewhere have already pointed this stuff out. I'm just trying to repackage it in the ways that were the easiest for me to grok.

It wouldn't hurt for this to be a separate thread.. but it's done now, so...

 

Great info, I'm looking forward to the next event so I can try it out. The car is not stock. Its something that I've had and have been working on for a while before I got into autocross. L'm not really worried about what class I fall in, I want to get better as a driver so I figured I'd start looking into some things that affect all autocross cars, and thats tires and suspension. I'm learning a lot by reading and from you guys on here about camber and caster and different techniques to use on the track too.

You can copy and paste what you posted into a new thread in the Race Techniques section found above this Race Car Tech section. Thats good stuff.