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Topic: Tire “cold” temperature (Read 1095 times) previous topic - next topic

Re: Tire “cold” temperature

Reply #25 –
I had a test long ago that worked then and have no idea if it still works but I have posted this before.

I found a piece of white concrete and dropped a large area of water on it. 

Or drove through a puddle

Driving through it at an arc the tires as the  dried out the foot print seems to show the actual contact area of the tire.

Adjusting the tire pressures a few pounds then repeating the test would show a different contact pattern.

Surely seemed to work on the older coaches and the first Unihomes.

I and a lot of owners back then drove in rain and snow and ice.

Having a correct contact patch made hydroplaning less of an issue.

Plus on ice traction issues are magnified

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Tire “cold” temperature

Reply #26 –
Are you saying that Firestone, my fire department and our Mercedes tire pressure sticker are putting the public at risk maxing the tire pressure?

When meeting customers in different parts of the country, I usually spent a least a couple of hours on the Autobahn every day with the speedo pointing straight down indicating about 155 mph (actually 143 mph true) With the normally poor weather, we still were over 160Ks or 100 MPH if traffic allowed in the rain. Everyone was. Driving that fast, checking tire pressures with a close adherence to the glove box/gas filler door sticker was done all the time. All the gas stations had mini pressure tanks to lift off the air filler and take to the vehicle to fill the tires. This is how important they considered the pressures.

After the wall fell, the Autobahn was filled with the tiny Trabants and the normal 2CVs. They would pull out to pass a truck while maxed at about 60 mph and when approaching them at 150 MPH, it was close to ABS activation for quite a few seconds before matching speeds. Scary feeling when you can't apply any more brakes but the vehicle keeps getting closer and closer in slow motion. Keeping the recommended pressures meant the shortest possible stops and best handling in all weather conditions.

While the MBs that the factory came to the states with Michelin XAS, in Germany we used the twice as heavy XWX V rated tires as they were mandatory for the speeds involved.

Now I'm using V rated Atturo tires from China. How the world changes.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Tire “cold” temperature

Reply #27 –
Well now, this appears to debunk what I was told about 70°F being the industry standard "cold" tire pressure.

Maybe it is, but just for testing purposes.

My take is adjusting so that the pressure will be correct plus 5 psi at 70° is still a good plan. If the morning air temperature is 90°, let the tire pressure be 2-4 psi over. That's still good. Las Vegas on a 110° summer morning, let it be 4-8 psi over. No problem. On my coach the placard and weight tables call for 115 psi in front. Adding 5 for safety and 4-8 for Las Vegas puts it at 124-128 psi. It's a darn good thing the maximum cold inflation pressure on the sidewall is not a "do not exceed" maximum.  I use my PressurePro FX to check pressures every morning, and don't ever take air out.

On the other end of the spectrum, I've seen cold mornings in Quartzsite ( not Montana winter cold, but plenty cold for me ) were temps are in the 20's.
Here my front tires might read 5-10 psi low. I use my 5 psi safety margin to good advantage.

I need to go back and see how much pressure drops with a 50° temp drop. The industry says 5 psi. I seem to recall it being a bit more. But again, I'm not worried too much. For sure the weight tables have a safety factor built in, and both air and tire temperatures rise as the sun also rises and the tires roll.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Tire “cold” temperature

Reply #28 –
 If you are 20# over the tire chart pressure , there is a 98% chance that you  have compromised the stopping distance . More pressure = less grip, less than optimal footprint, more dynamic load pressure.  all bad.

Re: Tire “cold” temperature

Reply #29 –
I don't want to upset anyone but why do people overthink this?  Wait for a couple of hours after driving coach then put in recommended pressures for the load on the axle.  Tire company will supply this info if you ask nicely.  Use wheel that has highest load as reference. I add a few pounds pressure to this.  Make sure that tires are same temperature IE one side not in sun.  The thing to avoid is under pressure.  Truckers do not change pressures for the load and it seems OK, road alligators are mostly caused by running low or flat.  When I was in the fleet business our vehicles would experience everything from empty weight to the occasional gross overloading (bad operators).  We had very few tire failures, mostly on garbage trucks caused by constant curbing and damage at the landfill.  Pressure will increase as the tire heats up when driving.  Don't worry about altitude you can't get the coach high enough up to make a real difference in the US.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Tire “cold” temperature

Reply #30 –
Quote from: Protech Racing –
If you are 20# over the tire chart pressure , there is a 98% chance that you  have compromised the stopping distance . More pressure = less grip, less than optimal footprint, more dynamic load pressure.  all bad.
Contact patch is ONLY and I repeat the ONLY connection to the road surface from the coach, Technology or anything else can't overcome this fact. Overinflated tires for any reason are if fact overinflated with a reduced contact patch, our coach weights probably don't fluctuate much more than 5% on a day to day or yearly basis. Just call me crazy, but I like to be at least 20 feet from the scene of an accident. Do what makes you responsible!
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake