mx5-kiwi

Hi Guys

I am trying to make a track day in two days time and in preperation wonder what is a starting point for tyre pressures in my Toyo T1r's (195 x 15).

Also, what do you look for if the pressure is too high or too low....

I have raced bikes most of my life and am well versed in tyres for them but it sounds like car tyres are a different story....

Any advice appreciated....

Cheers,
Mark.

sixshooter

iTrader: (12)

I'll take a stab at this since no one else is responding. If it is my first time ever with a tire and car I will start with a cold tire pressure just a couple of pounds short of the tire manufacturer's maximum. I will use chalk or a grease pencil to put a little mark the shoulder of the tire from the sidewall around to the tread face. After making a couple of laps check your hot tire pressure and make sure it hasn't gone over the max spec. Inspect the chalk mark and see if the ground is making contact all the way over to the edge of the corner of the shoulder. If it isn't getting far enough toward the corner let a few pounds out and try again until it does. If you are too far over the corner, add a couple of pounds of air. to keep from burning off the corner of the shoulder before the main body of the tread.

Adding negative camber to your alignment will allow you to run less air without burning off the shoulder thereby allowing you to have a slightly larger contact patch. It will keep the tread more square to the ground when cornering hard.

Seefo

iTrader: (5)

sixshooter got it pretty close. If you don't know what the tire manufacturer suggests, then call them up tomorrow and find out.

Run a bit more when cold as the tires won't heat up very much.

ScottFW

iTrader: (4)

First track event I did with the Miata was on T1Rs, 195/?? on the stock NA hollow-spoke 14" wheels. IIRC they worked okay around 38-40 psi hot. Start around 34 psi cold and see where you end up after the first session. Read the wear around the shoulder area like sixshooter mentioned. My experience was that those tires got noticeably worse when over 40 psi hot.

Seefo

iTrader: (5)

it seems that a number of street tires don't like it higher than 40. my star specs feel like **** up there and I had a buddy in an s2k who ended up at 45 psi and was crying a storm about how he didn't like them anymore (stars specs also). I told him to bring the PSI back down and then he loved it haha.

mx5-kiwi

Thanks guys, thats great info!

Man where would we be without the internet!!

sixshooter

iTrader: (12)

The recommended max psi is always embossed on the sidewall of the tire for safety (legal) reasons.

illeniummx5

..just going to add my input incase you havent tried it. After racing in NASA MA for the last 5 years. My 2100lb comp weight miata responds the absolute best about 4 laps in when starting out at:
Toyo RA1: 30f 29r
ToyoR888: 33f 30r
Hoosier R6: 29f 26r

of course depending on the track your racing will determine the .5 to 1lb side to side difference.
ex. when i race VIR i put 1lb less in DS rear and 1.5lb less in DS front. this helped me run a 2:15.1 lap time

emilio700

iTrader: (3)

This is what I set my pressures at: Emilio's Tire Pressure

billybobster

Excellent information and instructions on tire pyrometers.

My soon to be wife just got me this for my birthday (perhaps via a suggestion from me).



It's a IR pyrometer that has a probe type that plugs into it. Longacre 50620 dual function for about $200. Haven't used it at the track yet but highly looking forward to it. Been reading up on proper use and Emilio's are the best I've seen so far.

IR pyrometer is also useful around the house.

- Laser designator is an excellent cat toy

- "Honey, is the freezer cold enough?" - Why yes it is...

- "Honey, is the oven thermostat accurate?" - Why no it isn't, oven is actually 25 degrees lower.

Seefo

iTrader: (5)

- "Honey, am I still hot like an 18 year old?" -...yes you are!