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      06-26-2015, 04:01 AM   #1
CarJunkie
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Bridgestone RE-11 hot pressures

I was at the track today and they had an On Edge tire station set up to check tires coming off the track. They have an algorithm that assesses inner, middle, outer temps and pressure for each tire and recommends a pressure adjustment for each tire based on the measurements.

I had previously settled on 39psi front and 38psi rear for HOT pressure targets based on the feel of the car and wear pattern, but never used a pyrometer. Based on information on this forum, I decided to target 37 front and 36 rear to see how the car would like that. I assumed I would see a 7-8 PSI increase during a session, so I started at 30 front and 29 rear COLD.

Set-up: BMW 1M, stock suspension and alignment, Bridgestone RE-11 on stock wheels in stock sizes front and rear.

Track: PIR, 1.9 miles, 12 turns, clockwise.

Conditions: Sunny, 70 degrees in AM, 93 degrees at end of final session

After my first session, readings were as follows:
LEFT FRONT
outer 143 middle 136 inner 144 psi 36.2 recommend +1.5 (36.2 + 1.5 = 38.3)
RIGHT FRONT
outer 146 middle 131 inner 129 psi 34.8 recommend +2.0 (34.8 + 2 = 36.8)
LEFT REAR
outer 133 middle 129 inner 143 psi 34.5 recommend +2.0 (34.5 + 2.0 = 36.5)
RIGHT REAR
outer 139 middle 128 inner 123 psi 33.3 recommend +2.5 (33.3 = 2.5 = 35.3)

I was clearly underinflated, but also did not see the 7-8 PSI rise I had expected. It was also a short session with 6-7 hot laps in about 10-12 minutes, and my first time at this track, so I didn't really get everything heated up. I added the amount of air recommended at each corner.

My second session was longer and faster, definitely got everything heated up. There was a long line at the tire station, so I checked pressures on my own. The left side tires were both just over 40 PSI, right side tires at 39 front and 38 rear. I let air out on the left to match the right, so now 39 front and 38 rear all around, where I usually target before today.

Third session the car felt great. I stopped at the tire station on track exit and got the following:

LEFT FRONT
outer 165 middle 167 inner 167 psi 39.7 recommend no change
RIGHT FRONT
outer 166 middle 159 inner 147 psi 39.3 recommend no change
LEFT REAR
outer 159 middle 162 inner 164 psi 38.4 recommend no change
RIGHT REAR
outer 158 middle 148 inner 143 psi 38.0 recommend no change

I maintained those pressures for the rest of the day, bleeding off pressure as the day got hotter, and had my best lap time in the last session. I will stay with 39 front 38 rear on these tires.

Interesting note: I drove home without adding air, 210 mile drive. I took the wheels off the car to inspect brakes and washed the wheels. Once dry and cooled off the pressures were down to 30 front and 29 rear when cold, which was exactly where I had started!
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      07-03-2015, 09:36 PM   #2
blackmist222777
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I love those tires... the new 71Rs are even better
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      07-05-2015, 12:36 AM   #3
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Quote:
Originally Posted by blackmist222777 View Post
I love those tires... the new 71Rs are even better
I am thinking they are my ticket for autocross, but have heard they will overheat at the track . . . waiting to hear from someone who has actually done track days with them. Will need to buy tires next spring.
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      07-05-2015, 12:39 AM   #4
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Quote:
Originally Posted by CarJunkie View Post
I am thinking they are my ticket for autocross, but have heard they will overheat at the track . . . waiting to hear from someone who has actually done track days with them. Will need to buy tires next spring.
if i were going to auto cross id rather use a R888 or NT01.
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      07-05-2015, 04:57 PM   #5
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Quote:
Originally Posted by blackmist222777 View Post
if i were going to auto cross id rather use a R888 or NT01.
Planning to stay in "street tire" class, treadwear 200.
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