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Discussion Starter · #1 ·
tire pressures?

I'm going to make my first long distance run across the desert this coming weekend and wondered about tire pressure....
I have 185/70/13 tires and have been running them at 30 lbs in front and 28 in the back. Does this sound within reason?
 

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The Desert sounds HOT! Take a tyre pressure gauge with you and check that the pressures don't go above 40 psi after a lengthy run. Tyres do heat up and pressures rise when running hard and fast.
 

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My understanding is that low tire pressure is what causes a tire to heat up, due to the flexing of the sidewall. If you start with 30 to 32 psi cold (in a reasonably modern tire, which are now designed to withstand at least 35 psi cold), then even if the tire pressure gets above 40 psi hot, it won't be a problem. But if you start reducing the pressure as it gets hot, the sidewall will flex even more, it will get even hotter, and you will almost certainly cause the tire to fail. IMHO
 

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Keith, that's absolutely correct. Never let air out of the tire when it's hot to bring down the air pressure. The air pressure should checked and brought up to snuff with the tire cold. Check the sidewall of the tire for the maximum pressure you can run for a given load. For you folks that live in the rain infested areas, run the max tire pressure, it will combat hydroplaning some, but will make the ride a little harsher. HTH.

Ron
 

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Discussion Starter · #5 ·
Thanks
I am trying to find the right combination of enough air yet a somewhat smooth ride......

so Ron, are you going to be up in Fallbrook on Sunday??? That's the "cross desert" run I'm going to make from Las Vegas.

Mike
 

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Mike, I run 32 psi in all my car tires, that's been the recommended pressure ever since I've been driving, and that's a day or two. I've made many trips from the cool sunny beaches of SoCal to the deserts of CA, NV, and AZ, and never had problems with tire pressures, so I don't think you'll have a problem. I would check the pressure before you head back though. Margaret and I have forgone a dog show in LA to be at Fallbrook, but the health of our oldest dog is now suspect. So it will be dependent on how he fares during the week. The last outing we had, at the North Island Classic Car Races, I was not doing to well and only made part of the first day, due to health reasons. I sure do want to make this meeting, just so I can say hi to the folks like you I meet on this site.

Ron
 

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Tire pressure is very important for handling.
I use a digital temp gage for our racing Go-Kart tires, 1 psi is a big difference in tire temp across the tread width on a tiny Kart tire.
On my GT I have 14 x 6" wheels with Yokohama 195/60R14 tires F/R.
F/R sway bars, 1-1/2 front sport spring, poly bushings.
For normal hot weather "Florida", I run the tires at:
28-29 psi cold in the front.
26-27 psi cold in the rear.
I run the car on a fast curvy road and I get good even temps across the tread.
Use a good accurate tire gauge.
Lyle
 

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Tire Pressure Recommendations

Any suggestions on different tire pressures for the different size tires we run on our Opels.

I've had good luck on GT's running P185/70-13 tires at 35 psi frt/32 psi rr. I'm trying to decide how much pressure to run in P205/50-15 tires. The plus 2 combo seems to be really harsh riding inflated to 35 psi.

TIA,

Harold
 

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Yes the temp probe will tell you exactly what part of the tire (inner edge, center, outer edge) is working the hardest, these temps can be used to determine if the air pressure is right, and helps you adjust camber, too.
On our race cars, these readings are ALWAYS taken instantly after a run so we can make the adjustments before the next run. Ambient temp and track temp are huge considerations, so there's never a "known" setting going into a race. It's trial and error, based on experience and referring to the notebook where these things are recorded for future help.
It's probably kind of unusual to get that anal for a street car, but I could see it being used on something that will be going fast down a hot highway on a hot day!
You know, we use nitrogen in the tires instead of air, it doesn't expand as much when it gets hot. The expansion effect is huge, and is something we have to consider! When we start a race with say, 30 psi in a tire, immediately after the race it could be 35 psi. Big difference you have to account for, because that changes tire circumference which alters stagger and crossweight. Notice when watching NASCAR races on TV they are always wanting an "air pressure adjustment". Meaning the fresh tires they put on have a different pressure than the ones they put on sixty laps ago.
This is why we say racing is "all about tires" more than anything. You really have to know what you're doing. On the highway it can be a safety issue, not to mention how it can affect ride and mileage.
 
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