Tire Pressure on Proxes RA-1

#1

hey all,

i’m getting ready for next year’s season and i just got a set of Proxes RA-1 opposed to the Kumho Victoracers which i ran last three years… i’m in ITS so the car is a bit different but i am using virtually the same suspension setup on my car as the spec e30 and i wanted to know what cold tire pressure (range) are you guys running on very hot days (it’s always hot here in PR for a race) and what s the expected temp i should get once its warmed up?

thx,

Mike

P.S. sorry to post it here but i didn’t think this would fit under the suspension forum

#2

I think most would agree that you want your hot tire pressure to be about 40psi. Its hard to say what to start out since the track and ambient temperature will vary. From my experience you can expect about 7-9 psi increase from cold to hot tires.

#3

thx for the info… i guess 40 is the range to be… victoracers i ran at 38-40 depending on the day… and whether i was getting understeer

thx again

Mike

#4
#5

I usually start mine between 28-31 cold, with a target temp of 36-38 hot. My fronts tend to heat up more than the rears so I usually start of the fronts about 1psi lower than the rear and they end up even when hot. I’ve tried running all the way up to 40 hot, but the laptimes seem to start falling off above 38 for me. Also, some tracks like 38 and others like 36 so you’ll need to keep a log of all this stuff.

#6

One other thing you’ll want to keep in mind…

By the time you get to the paddock and check your tire pressures, you lost a pound or 2 from when you were running "hot"

#7

thx for the info…

Cheers

Mike

#8

I’m with Traqrat - I aim for 36-38 lbs also, depending on the track.

One thing to add is that in addition to starting fronts & rears at different pressures I also vary left & right starting pressures at some tracks (ie Willow Springs, which is 80% right-hand turns). At Willow I’ll start, for example, at LF 28, RF 29, LR 29, RR 30 and end up at 37 all around once up to temp.

#9

I might need to experiment with a little less pressure than 40 psi. It doesn’t help that my tires have over 40 heat cycles on them. I started out on them in March with 6/32 of tread and they are down to about 1-2/32". I figure I’ll start out next year at VIR with a set shaved to 4/32".

#10

I’ve run with Toyo’s before on my J Stock car and I think 38-40 hot is a pretty good range. I’ll have a better idea once I start running them all the time but based on my experiences there are few things to consider.

  1. Not all pressure gauges are the same. I have seen a difference of 7psi between gauges, so one man’s recommendation may be different from another just based on the guages. Use one gauge all the time, and if you get a new gauge compare it to your old to see where it is.

  2. Be consistent about where you take the pressure reading. Directly off the track is best. You can lose as much as 3 psi by the time you have driven back to the pits got out of your car and taken the reading. For example on my JS car running Hoosiers 04/05’s I like to run around 46 psi hot off the track but since I’m a one man shop I take the reading back in the paddock and I set them to 43 hot.

  3. Keep a log book. Keep a log book of pressures you use at different tracks.
    I keep starting cold pressures, the tire (RA1 obviously), the temp, weather conditions and the hot pressures. Depending on the track different tires will be used more. Lime Rock is an extreme example since it only has 1 left hander and the rest are rights. The starting cold pressures for my tires at that track might have a difference as high as 4 psi.

So considering all this it is best that you figure out what works best for you since you might not always be comparing apples to apples when you talk to other drivers. Driving style might also dictate how high the tire pressure gets so 2 different drivers with the same starting pressure might end up at different ending pressures. I’m probably going to get my tires shaved to 3/32 and will start my pressures at around 27-28 cold and see where I’m at from there. I’ve never used a pyrometer since I couldn’t adjust camber on my old car but that might be another good reference point to use to see if you close to the right pressure.