Hi All,

It is my first year of autocross. I have a 2010 JCW stock all the way right down to the run flat tires. What tire pressure would you suggest I run in them?

 

Well, since the sidewalls are so stiff, it won't matter much. Wear them out and get a good set of non-run flats. I speak from experience.

 

Grab some white shoe polish and draw line radially out from the center of the wheel around the shoulder. This will give you an idea of how much the sidewalls are rolling, but as previously stated, it shouldn't be much. If they are rolling, bump the pressures up.



Also, get yourself a decent tire pressure gauge and check your pressures between runs to keep the drive more consistent and predictable. The pressures will increase as temperature increases.

 

And also as said previously, get yourself some Dunlop Direzza Z1 Star Specs when the Run Flats are hosed. Probably won't take too long. Also, rotate front to back after every other event or so.

 

Might be a silly question but between runs when the tires are hot how do you know what to set the tire pressures to? For instance, if you set them at 38 when cold before you leave for the event... then check again when you get there.. lets say heated up to 40. Then do a run and see that they stay around 40? Always wondered with the heat how you would know what to set.

 

I keep them the same through the event. Pump them up for run 1 and bleed back down as they heat up to keep them predictable.

 

So you would set them (e.g. 40). Do a run. Then as they heat up (e.g. 42) you would drop them back down to 40?

 

Yep.

 

great information ! I am switching from 17 inch runflats to 16" RE11. the runflats i ran on the street at 35 all around on 17s, what should the 16s be for street, and what for autos?

 

I run 36-38 on the street, and bump it up for autocross. Definitely use the shoe polish technique shown above, but I'd start out with 45-50 psi in the fronts and around 40 in the rears.

After a run, check the shoe polish. It should be worn to the shoulder wear markers. If it's not quite there, let some air out. If it's beyond that, add some air.

Additionally, if you're experiencing oversteer, removing some air from the rears can dial it out. On the flip side, if you'd like more oversteer (for pivoting around cones), you can bump up the rears. I've heard of people running 50 psi in the rear to really make the car rotate. Depends on your preference. Note that these cars can spin out on you.

High pressures in the front will lead to understeer, and lowering pressures can dial that out. But decreasing front pressure too far can lead to premature shoulder wear and kill your tires.

Picking pressures isn't a one-size-fits-all thing.

Good luck!

 

The 16s which i put on are RE11 205 45 16, do you feel these should be 36-38 ? on my RF for the street I ran 35 all around. Do you feel with these tires 45 front and 40 back would be the place to start on autox ? i will get some white shoe polish and try it. I am driving to the autox on my 16s, they will arrive hot, should i use this psi as the new standard or should i figure the psi when my tires were cold before i left ? on the 30th i am doing my second autox and am quite excited. i was more scared than anything on the first one.

 

Yes, start with 45/40 (hot) and shoe polish. Watch the polish and see how it feels from there. Adjust as necessary. I typically will inflate my tires cold the night before, drive to the event on them, and bleed them back down hot.

36 is the factory recommended setting for the tires on 16s. 38 for speeds exceeding 100 mph.

 

Thank you Joe

 

when i am in the autox should i shut off the little anti slip button ?

 

I do. It saps your power. But be prepared for oversteer

 

great, my next race is sunday i think my biggest problem is getting lost on the course with all of the cones. does it get easier as time goes on?

 

Yeah. But some courses are better than others.

 

I'll second the advice Joe is providing on setting and adjusting tire pressure. Setting the initial pressure cold and bleeding down between runs helps give consistent performance. Finding the ideal pressure is the tricky part, but looking at the amount the sidewall is rolling over is the method I typically use if camber can't be adjusted. You can usually tell without the white shoe polish, but that helps. I've also seen sidewalk chalk used for the same purpose.

Another thing to note on tire pressure is that ideal pressure will change with course conditions. Generally, lower grip surfaces/conditions (cold, wet, asphalt vs concrete, etc) will require less tire pressure. The balance of the car (oversteer vs. understeer) will probably also change as grip level changes. I typically adjust rear tire pressure to account for this. If you are running high rear pressures to reduce/eliminate understeer in dry, grippy conditions, you may benefit from significantly reducing rear tire pressure in low grip situations to achieve desirable balance.

For you S guys that actually have power, lowering front pressure will typically help reduce wheelspin while accelerating. So depending on the course, it may help to drop the front pressures lower than ideal for pure cornering in order to help acceleration. It's a tradeoff for sure, but something to keep in mind if you are struggling to put down power coming out of corners.

My $0.02, YMMV, etc

 

It does get easier, but it will take practice and good habits.

Some tips to help with getting lost:

Walk the course 3+ times. I've been autocrossing for 7+ years and still find it helpful to walk the course more than 3 times. Walk the line you intend to drive and practice looking ahead while you walk. Don't fixate on the cone that's 10ft in front of you during your walks, look ahead to the next turn - that is what you want to be doing while you are driving as well. Some people like to take a notepad and draw a sketch of the course so they can review it later. I like to talk myself through the course with my eyes closed, mentally picturing the key cones while sitting in grid before my runs. I've found that helps me think about what's coming next before I get to it on course.

During your walks, you also want to identify the key cones that really define the course. Most turns only have a couple cones that define the line you will be driving. Focus on remembering where those cones are and look for them during your run. Ignore all the non-key cones. Keep looking ahead during your run and picking out the next key cone as it comes into your sight. Be careful not to fixate on the closest key cone as you approach it. Once you've got your car in the right place to get close to it, move your eyes to the next key cone. Looking far enough ahead is something that I still have to remind myself to do, but when you do it, you'll feel like time is slowing down and the cones aren't flying at you quite as fast.

You should also find that looking farther ahead will also help smooth out your inputs...and as they say "smooth is fast!"

 

Another good idea is to volunteer to help setup the course. This way you get to see the course early, plus you meet people that run the show, make some friends, get some exercise, etc. Nobody is getting paid at an autocross, people always appreciate the help!

 

Thank you all for your great advise and input. I ran my second AutoX and felt, it was getting smoother and better. I will keep at it and hopefully continue to improve. thanks again, your help was great !

 

I ordered a Tourque Wrench today and a 17mm socket so that i can check my wheels before the races. What setting should the wrench be for torque ?

 

103 ft-lbs

 

Just want to confirm should i be using a 17mm socket for the torque wrench ? I put it on the lug it seems a little loose. i did not yet receve my tourque bar.

 

Its a 17.