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Author Topic: Tire pressure - rain tires
ChrisMH
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So let's assume that I've figured out on a given day at a given track what tire pressure to use in my dry weather tires (shaved Toyo RA1s). And it begins to rain so I switch to rains just before the start.

Is there a rule of thumb re tire pressure to use in the rains (full tread Toyos) in this situation? My gut tells me that I need to put in more air as the tire will be running slower - and also cooled by the rain.

kevin 22 Verified Driver
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I was told to set the rain tires at 38 psi cold.

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Kevin Anderson

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Be careful about putting in more pressure than you would in the dry. If the rain stops and you start to get drying on the racing line your tires will heat and pressure will go through the roof quickly. Over about 42 hot is getting too high. When it dries the pressures can go up 8 or 10 psi. So if you start with 38 and it goes to 48 that sounds dangerous to me.

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Geoff
SM 80

Kim Ouye Verified Driver Made Donation to Website
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I was told to add 3-4 lbs and it worked out well...it also dried out, and they worked decent for full tread.

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Kim

91 BRG SMT RIP
06 MX-5 Cup

"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting 'Holy sh*t...what a ride!'" - Unknown

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quote:
Originally posted by ChrisMH:
My gut tells me that I need to put in more air as the tire will be running slower - and also cooled by the rain.

Also, more air is necessary in order for the tire to be firm enough for the tread to do its job of evacuating the water.

speedjohnson Verified Driver
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I got advise to start them at 28 psi cold. It was a rain race, about 60 degrees ambient. It worked very well.

In the first rain session I had tried a higher pressure and felt that the Toyos were slippery. After letting some air pressure out, they seemed to heat up faster and provided more grip.

Yep, lower pressure in the rain is better in my book.

Pat Newton Verified Driver Made Donation to Website
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I'm another "lower pressure works better for me" person. In downpour conditions at Portland last month, I ran 29.5f/27.5r cold, and it worked great. The car was very neutral. Grip was good enough that I was able to stay on the track during the race while many others spun off- that alone was enough to return one of my best finishes ever.

I've tried higher pressures in the rain, and the car never felt as good.

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Crew Chief, 3D Racing #64, aka Team Scrappy 2.0
3rd place E2, 2009 25 Hours of Thunderhill

Crew Chief, EGR/Miller Motorsports #64, aka Team Scrappy
E2 Champions, 2008 25 Hours of Thunderhill

Qik Nip Verified Driver Made Donation to Website Series Champ
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This thread is obstensibly about full tread Toyo's but the pressure discussions seem to bear on running shaved RA1's in the rain.
My question is at what pressures are folks running full tread Toyo's?
Rick

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Fortune Cookie Racing SM 60
Directions for use: Race, Rumple, Repair ... Repeat!

   

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