Running in the Rain - Tire Pressures

[Grafanton]

It looks like I'm going to be running in the rain this Sunday at Waterford Hills. Not the most exciting of prospects but, any track time is a good time.

Should I be running generally lower pressures in the rain than in the dry?

Last time I ran in the rain, I had zero pressure build over my run. With the Pilot Super Sports on a warm/dry run I get as much as 10 psi increase. Usually start at 40-45psi cold. I know it seems kind of high given what I've read here, but its what my instructor suggested and it does seem to help with tire wear.

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[Mountain376]

You're still on MPSS?

Those cold pressures seem very high. I think back when I ran MPSS I ran those pressures hot. Maybe like 42F36R hot. Something like that. Been a few years.

Do you know the wet line?

Be mindful of Big Bend and Swamp Turn in the rain. They like to form "rivers" across them. If they do, adjust your line - plan to take the corner a bit tighter than you think, don't try to put too much power down through that kind of water. If you hydroplane, you don't want the car to get pushed out and off into wet grass.

Id suggest setting cold pressure to around 40psi. Adjust from there. If it's very wet, the 40 may be fine. If it's just a wetted surface try dropping a few psi, like 38 or so. I don't agree with your starting temps for dry, but it's what you know, so (50-55psi hot?).

 

[BlkGT3]

You're still on MPSS?

Those cold pressures seem very high. I think back when I ran MPSS I ran those pressures hot. Maybe like 42F36R hot. Something like that. Been a few years.

Do you know the wet line?

Be mindful of Big Bend and Swamp Turn in the rain. They like to form "rivers" across them. If they do, adjust your line - plan to take the corner a bit tighter than you think, don't try to put too much power down through that kind of water. If you hydroplane, you don't want the car to get pushed out and off into wet grass.

Id suggest setting cold pressure to around 40psi. Adjust from there. If it's very wet, the 40 may be fine. If it's just a wetted surface try dropping a few psi, like 38 or so. I don't agree with your starting temps for dry, but it's what you know, so (50-55psi hot?).

Good advice on pressures.

Peter

 

[Grafanton]

As it turn out it was a torrential downpour for most of the morning. My first session was only 3 laps as they red flagged us after someone clouted the wall coming out of the Esses. I could have been running balloon tires with 3 psi in them and it wouldn't have made any difference. Pretty much had to run the 'wet line' as there were small lakes at the apex of turn 1, turn 3, Big Bend, Turn 6 (looked like the surf crashing at Big Sur every time a car went through) and of course Swamp.

It had stopped raining for my second run but it there was still a lot of standing water. A few laps in I started asking myself what the heck I was gaining by risking my daily driver in this mess. But a few laps later a sort of dry line started to peek it's way out and it became sort of fascinating. How close could I get to that puddle at the apex? How much concrete can I take? How much throttle before it all gets squirrely? Very, very educational.

Then it dried out in the afternoon and I set my fastest laps ever. I did a couple of 1:25.XX and slipped in a 1:25.000. Majorly chuffed.

In the dry, I did back the pressures down a bit from previous track days.

 

[Mountain376]

As it turn out it was a torrential downpour for most of the morning. My first session was only 3 laps as they red flagged us after someone clouted the wall coming out of the Esses. I could have been running balloon tires with 3 psi in them and it wouldn't have made any difference. Pretty much had to run the 'wet line' as there were small lakes at the apex of turn 1, turn 3, Big Bend, Turn 6 (looked like the surf crashing at Big Sur every time a car went through) and of course Swamp.

It had stopped raining for my second run but it there was still a lot of standing water. A few laps in I started asking myself what the heck I was gaining by risking my daily driver in this mess. But a few laps later a sort of dry line started to peek it's way out and it became sort of fascinating. How close could I get to that puddle at the apex? How much concrete can I take? How much throttle before it all gets squirrely? Very, very educational.

Then it dried out in the afternoon and I set my fastest laps ever. I did a couple of 1:25.XX and slipped in a 1:25.000. Majorly chuffed.

In the dry, I did back the pressures down a bit from previous track days.

Nice! Sounds like my experience running there in the wet last year, lol.

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