I am running my first track day with my 05 mcs on Friday the 14th. The suspension is stock. My track wheels and tires are 15x7 Sendel S70 rims with 205/50-15 Azenis st-615 (at full tread depth, unfortunately).

I have never run a fwd car (let alone the mini) before. What starting tire pressures do you recommend?

Thanks!

 

Depending on the ambient temp, I'd start with 35 psi all around if it's cool... and 37 if it's warmer. If you notice understeer, add 2 psi to the rear. Oversteer and take 2 psi out of the rear.

I'd recommend marking the shoulder of the tire with chalk and checking to see if the sidewalls are rolling over - but it's pretty hard to make the Azenis do that.

You'll be fine at full depth. I've done it many a time!

 

Where's your track day? I have my first one friday the 14 as well.

 

 

Cooler, I ran less pressure in the Azenis - more sidewall flex so the tires warmed up quicker.

Warmer, I run more pressure in the Azenis - less sidewall flex and they seem to avoid heat soaking as badly and getting greasy.

Just my experience with the Azenis on the track. At a January track event awhile back, it was 70 degrees one day and 45 the next - running the same pressures both days, it only took one lap for them to come up to griptastic levels when it was 70 out, but it took 2-3 when it was 45 out. For the later run sessions on the 45 degree day, I took some pressure out all around and I was back down to a one-lap warm up.

I always adjusted pressures for autocrossing, depending on the outside temps - but never thought about doing it for the track until someone said, "Hey, stupid, take some pressure out and they'll warm up faster".

 

what track?


with new tires i go 35 and chalk mark em. your tires will have an arrow or some wear mark on them. after your first session check your marks. you don't ever want to go all the way to the mark, just to the edge of it. if your making right turns all day your gonna need more pressure in the left tires.

with full tread you'll get a little slop on track and your tires will make a lot of noise the next few weeks due to uneven wear of each tread block.

where are you? maybe some nice MINI driver will let you use a set of track wheels and tires.

 

If it's really warm out, I go with an even lower pressure than those above. At Buttonwillow in the summer, temps can be upwards of 100 degrees, and the track gets really hot and slippery. I start pressures closer to 30 psi, and even that can be too high sometimes.

Measure your tire pressures when you come off the track, and pay attention to the feel of the tires when you're on the track. That will give you the best indication of how the pressures are overall.

 

Well, I guess there are many thoughts on tire pressure tuning.
I couldn't be much more opposite then this suggestion. I concentrate more on what my pressure is when finishing a 30 min session. I strive for around 43 front and 41 rear hot (but thats for my particular car and setup). I also run lower in the rear to induce oversteer, not higher. If it's hotter out I start with lower pressure and colder I start with a bit higher pressure.
Maybe this is a difference in Auto-X and a 30 min track session.

 

True, I should have clarified and originally said, "This is what works with my setup". Everyone's will be a bit different.

Much of the pressure differences may have to do with suspension setup. I normally run 2 psi more in the fronts than in the rears, which dials out any oversteer in my car - the opposite of you. If I run the same pressures all the way around, I get more oversteer. If I run more pressure in the rear, I get even more oversteer. Shrug. Spring rates + rebound/dampening rates + swaybars + alignment = different requirements for pressures. Even so, pressures are only fine tuning, anyway.

I also measure hot pressures - with my Pilot Sport Cups, I shoot for 36/31 hot, measured 30/28 cold - as well as pyrometer readings. Well, I did until I dialed in the setup. Now, I just set 'em cold and forget 'em, whether it's autocross or track.

In my experiments in the Texas heat (100+) and autocrossing, I've found the Azenis really do better with more pressure in them when it's really hot out. Shrug. With less pressure, they tend to get too hot, too fast and get greasy. Interestingly enough, hot pressure readings are usually about the same either way!

On the track, I tend to run lower pressures than I would for autocrossing. Even so, I tend to run about 37/35 when it's hot out and 35/33 when it's cold, which works well on my car... Shrug.

The best advice as previously mentioned it pick a starting point, mark the shoulder of the tire, make notes to yourself as you track... as soon as you get off, measure hot pressures and temps (if you're interested). Make an adjustment the next time you go out, if necessary. Repeat.

 

Tomorrow's day will be at Streets of Willow. I am anticipating weather in the mid-80's. My car's suspension is stock as is the alignment.

There will be two drivers tomorrow... me, who has a fair amount of experience, and a first timer. I think I will set the car to be safe and primarily to understeer for him. Since it is not a timed day, I will just have to deal with being a touch slower but still driving the car home.

If I understand everybody correctly, increasing pressure in front will increase understeer and vice versa... So I think I will start out at 36 all around for the first session, and hopefully the first runs will be with me driving. At the end of my run I will take the temps and adjust as needed. I anticipate ending-up at 32 front and 36 rear (cold).

On a different note... it is amazing how much more grip these azenis have then the OE runflats...they are also so much more comfortable and don't track the rain grooves as much.

Thanks again for the advice!

 

If a front driver is understeering and you want to correct this with tire pressure, you must ADD pressure to the front tires. If you want to correct oversteer with a front driver using air pressure, ADD air pressure to the rear tires.

Air pressure affects many things, but most importantly, it gives strength to the sidewall and therefore stabilizes the tread area and reduces heat. This should be true no matter the set-up as the modification is isolated to the tires.

 

 

Between work and house I've had zero time for cars.

How are you Onasled?

In a month I'll report on my fist track experience with Michelin's Pilot Exalto and my tire psi recommendations.

 

Does anybody know the target pressure for the azenis 615's?

 

What size, and with what vehicle (MC or MCS)?

 

doesn't is say on the side of the tire?

 

It will tell the max PSI on the side of the tire, but not necessarily where I would put the tires.

I would do it like this:

Say the max load capacity of the tire was 1100lbs. (4400 for 4), and the max pressure was 50 psi. If your MINI weighed 2750, then:

2750/4400=0.625

0.625*50=~32 psi

I'm guessing that you have an MCS (from the name), and figuring you might be using the 215/40-17, which have a load rating of 87. This means 1201 lbs/tire. I'm guessing the car, with driver, weighs around 2850 lbs. Also, I figure your tires have a max pressure rating of 51 psi - pretty common for these tires.

Thus:

2850/4804=0.5933

0.5933*51=~31 psi

Now, remember, this is probably what will give your tire even wear on the street, with normal driving. For track driving, I would put a few more pounds in there so that the sidewalls have more rigidity to them. Start out with something like 35 - maybe 36 front 34 rear as the MINI is very front-heavy. You can see how that feels after a few laps and then change accordingly.

 

Here is some more interesting reading on tire pressures. By the way, on the track, I would recommend having slightly more pressure in the front than the rear tires - see the article:

http://www.sportcompactcarweb.com/tech/0208scc_tires/

 

Depending on ambient temp, and using street tires, I usually start about 35 cold, and immediately take pressures post session, with a goal of being about 42 at front and 40 rear HOT off track...

I must adjust throughout the day to stay in this range... Also, I'll state the obvious, to remain equal pressures post HOT session, there is different presures on tires on the same axle when the tires cool.

Dont forget to equalize pressures as best you can when leaving the track, and readjust the following morning when everything has cooled to make it functional for street..

 

 

This does NOT work for my car, against my initial thoughts when I started motorsports with the MINI... Shrug. I've run 3 full autocross seasons now using 2 psi less in the rear and the car is neutral. If they're equal, I get slight oversteer. If I run 2 psi more in the rear than in the front, it's way tail happy. Equal pressures resulted in the car rotating too much, and adding more made it less and less predictable. Same thing occurs on the track for me.

On other cars I have owned, it's always been as you said - more pressure in the rear = more understeer, less pressure in the rear = more oversteer, less in the front = more understeer, more in the front = more oversteer.

All I know is that I have had to run 2 psi less in the rear for all the tires I've had on the track or autocross circuit (ES100's, RT-215 Azenis, RT-615 Azenis, Michelin Pilot Sport Cups). It works for me, even though I don't get it and it flies in the face of reason!