Tire pressure

[Mario944]

Anybody have an idea what to set the cold air pressure at on a set of Hankook Ventus C51 tires for my 94 Miata? The C51 is a racing slick like Hoosier.
I'm used to Hoosiers on a heavier car so these will probably run with less air pressure. ??
Thanks for any help.
Mario B.

[StephanAlfa]

Hi Mario:
I ran those when I had my Alfa and used same pressures that would END the session with NOT MORE THAN 40 psi and ideally around 38 psi. After that it gets very slippery.
Depending totally on weather conditions etc. but typically started at 32 Front/ 34 Rear.
If you are using it only for the TT laps then I'd bump it to 34/36.
Again there are a lot of factors involved for starting pressure but hope the info above helps you get to the ideal running pressure.

[SEISAN]

Try going onto Tire Rack or the manufactures website. You can print a sheet at what the pressures should be set at cold. I have the sheet for Hoosiers but it seems to be a lot less that it should be. You will have to find the right pressure that works for you. I run around 36 to 37 hot. At times they only get up to about 33 / 34 so I check them when I immedialty get off the track and add set accordingly. Other time I get off the track and they are over 40 so I take out some and they run fine. My vehicle weight about 3200 lbs.

You can also keep a log book at what pressure you run with on a specific day ( sunny, temp, rain, cold.. ect) this will give you a starting point for each event.

Hope this helps.

BB

[962porsche]

the general rule of thumb when it comes to setting cold tire pressures is 10 LBS for every 1000 LBS of your cars weight . this is for R-DOT and SPORT type tires when it comes to a full slick this rule does not apply .
so if your cars running weight is say 2600 LBS then you set your cold tire pressure at 26 LBS for a starting point .

[StephanAlfa]

the general rule of thumb when it comes to setting cold tire pressures is 10 LBS for every 1000 LBS of your cars weight . this is for R-DOT and SPORT type tires when it comes to a full slick this rule does not apply .
so if your cars running weight is say 2600 LBS then you set your cold tire pressure at 26 LBS for a starting point .

Not trying to confuse Mario with my response here please, but I graciously beg to differ Dave. There is no way a car weighting 2,600 lbs will start at 26 psi and reach an optional tire temperature under TT conditions. Not even on a hot day with 20 min session you'd reach optimal psi of "not more than 38-40 psi" at tend of session in most cases. You'd be riding on the tire walls for most of the start of the sessions at the pressure ...

If he is coming to the NHMS event in Oct-12/13 chances are it will be "cloudy with a chance of meatballs" and at the start psi the car would never reach optimal conditions.
Consider starting at higher psi as the psi rise is not progressive.
My 2cts fwiw.

[962porsche]

what i stated comes from 3 different tire CO's .
hoosier , kumho , and good year . i have also set up god knows how many race car some for pretty famous racers and teams .
that is the GENERAL rule for a starting point .
that is not to say a tire temp of a 3 lap time attact event is the same as the set up would use for the 20 to 30 minute run sessions . as if you bumpped up the pressures to what you would need to do a 3 hot lap time attack you would in fact over heat your tires and could even cord them in a 20 to 30 minute run session .
most people use the same tire as they do for the time attack as they do in the run sessions and they are for the most part a road racing R DOT or a sport tire . if you were to run say a auto cross type tire for the 3 hot laps then with them too you would use the same general rule of 10 to 1000 lbs as they would just over heat in no time if you went to use them in a 20 to 30 minute session .
the true fact is you should only setup your car by it's tire temps and that is some thing very few people will do .
it the last LRP's event we took a mid pack car and by taking it's temp and seting the suspension to the tire temps turn it into a front runner finishing 3rd . i also did that to a car in the historics event there except that car started as a back marker .

[dradernh]

the true fact is you should only setup your car by it's tire temps

Professionals use tire temperatures and driver feedback to determine how effectively cars like ours are set up. That information is used to arrive at the optimal pressures for the tire being run, as well as the toe and camber called for by that car/tire/driver combo.

[962porsche]

the general rule i stated is nothing i pulled out of my ass it's for the engineers of the tire CO's them selfs and has been the general rule for years and years . i 1st fould this out when i was running the A008's inn the mid 1980's and the people in the clubs used to tell me to bump up my tire pressures . the one time i left them at what i was running for a street pressure i turned a faster lap so i called yokohama only to find out i should be dopping my pressures . the engineer for them (yokohama) told me to drop my pressure from the 32 to 34 they call for during street use to about 26 to 28 lbs for track use .
this is what happend when i was bumping my pressures up the GTI would turn a average time of 1:11 at LRP .
when i FORGOT TO AIR UP MY TIRES i turned a average for the day of high 1:09 .
when i dropped the pressures to the 10 lbs of AIR pressure to the 1000 lbs rule the car started turning low 1:08 average times .
i then shaved the tires and started taking temps after every run session and and with proper chassis set up got the car into the mid 1:07 .

part of what my business is and how i make a living from is setting up race cars .
the 1st thing you do is take your temps tire and brake temps .
most people over cool there brakes with to much ducting and over heat there tires from to much air pressure .

the average R-dot and sport tire should be up to temp in about 2 miles of pushing the car on the track .
at NHMS that would be a lap or two leaving only one lap left in the time attack to put in a good fast lap .
there for it would be ok to bump up your pressure for that but only for that .
for the rest of the event and days run sessions you should START with the 10 to 1000 rule and go from there .

[TroyV]

I set C51's high (for a Miata) when I ran them. I found them to be very good right around 33 hot, or maybe just a little less depending on which end of the car needed more bite. Kooks seem to flat spot when left overnight at low pressure, and will thump around for a few miles when you get back to it in the morning, so I would set them up to 40 psi at the end of the day prior to parking the car for the night....then bleed them back down in the morning so that the first practice session of day two wouldn't be wasted.

[962porsche]

old posting but worth bring up again .
at the may's NHMS event ballers instructor told baller to set his tire pressures at 30 or 31 LBS .
I told steve aka baller before the event to set the fronts at 24 and the rears at 26 LBS cold . but like a good student he did what the instructor told him to do . looking at the in car video he had from the event I could see the car was squarely and under steering like mad . his lap times also showing a bad set up at if I remember right 1:31 average .
for the last NHMS 3 day event I told him this time do what I tell you ! set the temps as I stated !
he did and the in car video shows a much more drivable car more settled with no under steer .
the lap time also show a better handling car as his average lap time was a high 1:27 low 1:28 .
I still have to do some suspension setting and I think I could get the car into the 1:26 with that .
with his tire pressures set as he was told from the instructor in the may event there would be no way in hell he could have gotten a 1st place trophy for the most consistent laps .

this comes back to again you want about 1 lb of cold tire pressure for every 80 to 100 lbs of the cars weight with a track surface temp of about 100 degrees .

[Shawn624]

I ran my Hankook Ventus C51 tires for my 97 Miata cold at 36 and monitored them to run hot at 40 psi. Other people who drove it said it felt loose, but it responded just the way I like it.

[djsteviec]

Dave is right. It was recom. that i run 35F and 32R cold, or something close. I did and the car did grip with my NT01's, but did have a lot of understeer.
Running them this time at 24F and 26R, HUGE difference. It stuck like glue with very little understeer. (only in turn 3 uphill)
Track temp was about 105.

[Shawn624]

How did it effect your lap times?

[djsteviec]

The times decreased. I went from 1:31s and 1:32 to 1:29,1:28, and a 1:27.

Definitely felt a lot better. Haydyn was in my car the 2nd day and can attest to the grip. Nate drove it a couple laps in light rain and still really grippy on Monday.

[Shawn624]

Wow! 5 seconds per lap from tire pressure is certainly an impressive change.