Tire Pressure and Wet Traction

[CapriRacer]

Unfortunately, no one has done a good study of the relationship between wet traction and inflation pressure for elevated tire pressures. So the exact nature of this relationship is unknown.

However, there are plenty of anecdotal reports of issues, so caution would be advisable.

[F8L]

Originally Posted by CapriRacer

Unfortunately, no one has done a good study of the relationship between wet traction and inflation pressure for elevated tire pressures. So the exact nature of this relationship is unknown.

However, there are plenty of anecdotal reports of issues, so caution would be advisable.

I read an old study from the 80's? that tested braking in dry vs. wet and with different tire pressures and the results were mixed. Braking distance was measured on asphalt and on concrete surfaces and higher pressure favored one surface while it was negatively affected by the other surface. It was kind of confusing in that you could not simply say higher pressure is better overall or worse overall. I'll see if I can find the study again. I bet you have read it already.

[CapriRacer]

Originally Posted by F8L

I read an old study from the 80's? ...... I'll see if I can find the study again. I bet you have read it already.

I wish I did because it would have figured prominently in my earliest postings on this web site. If you find it, I'm sure evryone would appreciate a link. If you have it in hard copy form, scan it, and I'll post it on my web site.

[CRT1]

One thing to be wary of is that I seem to get more tire hop on really rough surfaces with my tires at 50psi compared to the 33 psi placarded on the car. The tire is a spring that is factored into the damper tuning my car was clearly tuned for running lower tire pressure.

This could cause skittish behavior on really choppy turns in the wet. I am almost never "at the limit" or even close and I am very familiar with the roads I drive so it has not yet been a problem. I am also comfortable managing a car that is sliding a bit through a turn so I don't sweat it and I'll take the MPGs even if it means a little teeth rattling.

[PaleMelanesian]

This is true, especially with a front-heavy weight distribution. You can back off the rear pressure to compensate, add weight to the back end*, or just know how it handles and drive accordingly.

My back end is less jittery with 150 lb of feed sacks in the trunk, like I had yesterday.

[phoebeisis]

ksstathead
Big Aside- what car calls for 26 psi??
"at 26 psi placard"
26 psi or 28psi was common in the 50's-60's 70's-bias tires I guess.
But other than the Ford Explorers (unfortunately) can't remember a mid 80's "car" that called for that little?

Just curious
Charlie

[ksstathead]

2000 Honda CR-V, iirc. Max sidewall on the tires i've had on it has always been 35. I have run 35-40 for years now. Much better wear. At 26, it has a lot of slop to it.

I biked to work today, but will confirm placard tonight.

[RedylC94]

Originally Posted by phoebeisis

... what car calls for 26 psi??
"at 26 psi placard"
26 psi or 28psi was common in the 50's-60's 70's-bias tires I guess.

24 psi was most commonly specified in the 60s. My father (and many others) thought 30 was the magic number.
My car: 26 psi, front and rear. I never used that low in front.

[XtremeRevolution]

Thanks for the info guys. Good stuff to keep in mind. I'll let you know if I come across anything definitive.

[F8L]

Barry,

Here is one of the papers I was referring to and they make mention of the older paper (Collier et al., 1980) as well but you already have that one. I'll see if I can find the third one.

http://www.nhtsa.gov/DOT/NHTSA/NRD/M...onpressure.pdf

Here is the Goodyear test. The numbers get really mixed up here.
http://www.nhtsa.gov/cars/rules/ruli...ure/LTPW3.html