Help me out with my trackday sessions:

If I notice the car is pushing a little through the corners, what action can I take with tire pressures to help out a bit? A little less pressure up front? And at a place like LRP, I should take even more out of the front left tire, right?

Thanks!

 

Go to Tire Rack web site. Go Products/Tires/Tire Tech. Scroll to Bottom of the list to competition tire info.

 

Raise the rear pressure. When auto crossing I typically raise the rear 10-15 psi. It gives the rear tires less grip. You can also try "slow in fast out" when cornering. Get your breaking done in a straight line prior to corner entry and accelerate out of the corner. If you go in too fast you will push like crazy.

For track days increase the rear pressures gradually until you get your desired handling.

 

I've always tried getting the hot pressures to be equal all around as a first step. I take a guess in the morning, and after the first session drop all the hot pressures down to 40-ish psi. That will probably make the cold pressures different from side to side, but I haven't checked that.

From there, I'll adjust pressures as I (or more often, my instructor) feel like it. Usually, to remove understeer I'd lower the front pressures. I'm sure someone will come along any minute now and tell me I'm doing it all wrong. :D

 

Thanks for the help guys!

mb

 

I guess we should know what kind of tires your running on the track.

 

azenis 205/50/15

 

I don't know enought about those to even venture a guess. Alot of people use them so you should get alot of advise on pressures. Have you tried Vulcan Tire who sells those.

 

The key to setting tire pressures is finding the ideal pressure window. You can get pretty darn close by putting white shoe polish marks on your sidewalls. Then after you make a run, check the sidewalls to see how much is worn off, and how far into the sidewall. You don't ever want run onto the sidewalls, you want to always stay on the tread, about 1/8" from the edge depending on the tread design of the tire. I think the Azenis actually has little arrows that point to where the "edge" is. (I don't have RT-615's, I only have experience with the Rt-215's) Usually you can find about a 3-5 psi window that works for most tracks. If it's a cold day, start with 2-3 psi less than your window and they will heat up faster and the pressure will end up being right wear you want it after 2-3 turns. Don't be fooled by running low front tire pressures because they "feel" better. Softer tires (low pressure) are more forgiving and its easy to fall into that trap. You'll be giving up some grip if you do this.

Once you find the correct front tire pressures, you know you're getting maximum grip out of the front which is ALWAYS what you want. Now you can choose to either over or under shoot the window with the rear tires to reduce grip (reduce understeer). Most people choose to over shoot (higher pressure) the rear tires as it doesn't wear the shoulders. That way you can rotate the fronts to the rear when the shoulders start to get worn, or just to keep the wear equal.

 

Does anyone have pictures of chalked tires and how far onto the sidewall is too far? If there were a clear line between the tread and the shoulder, I'd be able to figure out how far is too far. But the tire usually is sorta rounded on the shoulders, and I have no idea what is "right" when looking at marks on tires.

 

I'll take a photo.....give me an hour. (I'm promised my wife I'd do some house work for her)

 

Of course everyone's tread is going to be different, you have to look at yours and decide what exactly is "tread" and what isn't. Also consider this....

If the tread is flat to the asphalt and the sidewall is 90-degrees to the asphalt, you shouldn't wear rubber much farther than 30-40 degrees. You'll be surprised at how many people you'll see with FWD cars and wear marks clear into the Dunlop logo. No kidding!

Also consider that you can cause the tire roll over more than normal and give you some false readings. You need to get some experience with how much tire squeel you can get away with mid-turn. The tires shouldn't be SCREAMING, they should just be talking to you. I've seen someone wear out a set of Hoosier A6 autocross tires in 10 runs because they weren't listening to their tires.

You do autocross with your windows down....right?

 

While I do agree with most of what you say above, it is damn near impossible to have a track day (HPDE) with anygroup and achieve the wear you speak of without camber plates. On stock suspension and properly inflated tires most people are farther down then your picture illustrates.

 

i've run w/ lgenf: we have both burned out too many sets of "street" tires. add camber.....track only tires is the better solution...if you aren' t ready for this, be prepared to buy many sets of "street" tires. greg

 

I'll admit, I have 20 years of autocross experience but NO track day experience.....so you may be right.

In my experience dedicated summer tires (WIDE tread blocks with no sypes) last a longer than all-season tires (little tread blocks wiht lots of sypes). The smaller tread blocks squirm and tear under hard cornering. They actually wear out faster than the sticky summer tires.

Yes, I would agree that adding camber plates is a great idea for track days. If you have camber plates, I think the wear zone in the photo above still holds true. Adding camber plates is good insurance to protect your tires from low pressure or over driving. I'd highly recommend them for a track day.

But in my case camber plates aren't legal for the autocross class I run, so if I was to do a track day, I would try to keep the tire from rolling over by adding air pressure and watch that I'm not pushing it too hard in the turns.

 

having burned up some nice tires doing HPDE's, i will re-iterate my point about increasing (negative) camber. you will smoke the tires if driving aggresively w/ street tires and stock camber settings....i'm hoping to save you the expensive lesson that i learned...camber plates/lower control arms once vs. new tires after every track session....auto-x may be an entirely different animal.....i don't run there...

 

I think the big difference in AutoX and HPDE is speed and that is what kills the tires.

Yes AutoX can get going quickly, but it's more technical and shorter courses with not so much speed.

HPDE (at least the two tracks I have attended several times each Sebring and Homestead) you carry a bunch of speed in the turns, 17 alone at Sebring is a turn that any MCS will carry 55-75 mph (depends on your ***** boys) on a stock setting, and that is just one turn, that is what is killing your sidewalls and street tires.

AutoX has it's place and so does HPDE, but I believe you can get around an AutoX course on street tires and stock settings and get much more wear out of your tires, then the same on the HPDE courses.

 

Another difference in wear between autocross and HPDE is that in a typical autocross day you have maybe 10 minutes of wear. On a typical HPDE day, you'll have around an hour of wear.

 

that's another good point - our next HPDE with PBOC in April at Homestead will have 4 x 20 minute sessions for both Sat & Sun so that is almost 3 hours of hard running - for $325

just in case anyone was going to be in the area:

http://www.sunshineminis.org/forums/...ic.php?t=11703

so far we have 9 minis signed up and 3 or 4 more coming down to watch and cheer - yes we know it's not a race, but it feels like it to us.

 

Thanks for this conversation - it's very educational.

mb

 

If the tire is rolling over too much, it needs more air. Many street tires require over 50psi for maximum grip. A 60 or 70 series front tire may be as high as 60psi.

For the 205/50/15 Azenis, I'd guess you'd be somewhere between 40 and 45psi in front, hot. Start with 45psi hot. Rear tire pressures will vary depending on car set-up and driver preference for oversteer. I'd start about 5psi lower than the front and adjust from there.

Scott
90SM

 

Slight hijack - sorry

I have track time coming up very soon. I just found out this evening that the motor in my 914 is f***ed and it is probably too late to get a refund for the track time. So I'm thinking of taking my MCS instead. It is bone stock and has runflats. I don't have the $$ right now for new wheels and tires (just spent all of _that_ for wheels and RT615s for the Porsche ). I tried the search but am just so upset right now that maybe I didn't have the patience to sit and read through a bunch of posts so I'll ask instead -- what pressures should I start with on the runflats?

Or perhaps a better question, am I totally insane for even thinking about doing this? (I saw info on ditching the OEM front pads, and if I do this I'll take the Motul I've stocked up for the Porsche and put it in the MCS)

Any advice is much welcomed, thanks in advance

 

I ran my first two track events with stock run flats, stock pads, and stock rotors. After the first track event I had to replace the front pads (recommend Mintex 1155s or EBC Yellows). After the second track event the rear pads were done.

You'll be fine as long as the brake pads have at least 5-6 mm of friction material. I'd flush the fluid and put in the Motul.

The stock wheels and run flats aren't useless. I had the Dunlop 9000s. But good 15 inch wheels with 205/50/15 tires will save you better than 10 lbs at each corner.

Go have some fun with the MINI.

Alan

 

If you want less push you really need camber plates.

If you want to set you pressures you need a pyrometer. But understand that if you don't have plates, the outside front temps are going to be high regardless.