|
|
11-04-2007, 05:42 AM
|
#21
|
Rivet Master
, Minnesota
Join Date: Aug 2003
Posts: 7,721
|
Quote:
Originally Posted by CrawfordGene
. I'm not sure this proves anything except that pressure is approximate, especially depending on the quality of the pressure gauge.
Gene
|
Gene,
It proves that your pressure gauge has excellent precision. Tire pressure should change 4 psi for a 27 deg. F change in temperature.
|
|
|
11-04-2007, 08:06 AM
|
#22
|
Rivet Master
1991 34' Excella
Princeton
, New Jersey
Join Date: Aug 2003
Posts: 7,070
|
Quote:
Originally Posted by markdoane
Gene,
It proves that your pressure gauge has excellent precision. Tire pressure should change 4 psi for a 27 deg. F change in temperature.
|
A very interesting point.
No manufacture includes a temperature/pressure compinsation factor on their inflation chart but rather just suggests inflating tires while at abient. That's OK when I leave NJ in January headed for Fl. but not so good for anyone leaving Fl in Jan. and headed for NJ, not that anyone would do that.
I have long and often suggested to that individuals refer to the manufactures inflation charts when selecting a tire pressure. Now it is becoming increasingly clear that that advice may not be an all inclusive idea.
For the last 100,000 miles plus I have always set my tire pressure by an inflation chart. When I bought my 2004 Ford Excursion, a month ago, I used the same logic. This appears to have been a major mistake. Having almost lost the trailer due to sway I posted on this and other Ford Excursion sites for comments. 85% came back that one should not use the charts when dealing with an Excursion but rather increase the pressure almost to max.
If this is in fact the case with the Excursion how many other situations fall outside the manufactures recomendations? To date I have not tested this idea of higher inflation pressure because it flys in the face of all historical engineering recomendations. But it is causing me to think and look for strong supporting evidence on either side.
__________________
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles
|
|
|
11-04-2007, 08:53 AM
|
#23
|
Rivet Master
Currently Looking...
Pittsfield
, Maine
Join Date: Oct 2003
Posts: 1,108
|
Simple rule of thumb - Weigh and Inflate according to the tire manufacturer's recommendation. That said, the Airstream recommended 50 psi for my trailer's original "C" rated Marathons appears to provide more than a reasonable safety margin for potential asymetrical loading. My scale weight is 7,400 lbs, loaded, with 990 lbs on the ball. At 50 psi the tires have a capacity of 2,150 lbs/each, or a net of 8,600 lbs. I have since gone to "D" rated Marathons (---replaced due to age) - but I still use 50 psi. I tossed around the idea of increasing the pressure to the max rating for the "D" tires (65 psi) but decided that I didn't have any reason to do so. I tow at no greater than 65 mph, but usually around 60 mph on the highway and much less on my preferred secondary roads. I've never had a tire failure in over 40 years of trailering all sorts of rigs - including one 12,000 mile summer trip with the notorious small tires on a heavily-loaded large pop-up camper. I also run my dually rear tires at a much lower pressure than that shown on the door sticker - but that discussion has already been well hashed over.
__________________
Cracker
2003 GMC 3500 D/A, CC, LB, 4x4 and 2000 Airstream Excella 30. WBCCI 7074
|
|
|
11-04-2007, 09:41 PM
|
#24
|
Master of Universe
2008 25' Safari FB SE
Grand Junction
, Colorado
Join Date: Sep 2007
Posts: 12,711
|
Toyota has no information in the driver's manual or on the tire pressure sticker on the truck about tire pressure while towing or if loading the bed with a half ton of cinderblocks. Maybe other manufacturers do include that information. Toyota's only recommendations are for 30 front, 33 rear. I assume the higher pressure for the rear is to account for the load in the bed that probably isn't there on most pickups since they are used as a family car. It surely doesn't account for the weight of all the options on the truck—about 500 lbs.—or what part of the truck they are on.
If I hadn't been reading these threads, I wouldn't have even thought of increasing the pressure as obvious as it is once I read about it. Thinking about all the many variables—temperature, sun, altitude, weight, accuracy of gauge, leaks, type of tire—makes me crazy. I decided to try the max on the truck tires and see how it worked. It did. The truck front end came down and it stopped feeling too light. We could easily see the hood was lower. I have no idea why more air pressure in all the tires should do that, but why argue? I thought of maintaining Toyota's 3 lb. difference between front and rear, and maybe I'll try that later.
By the way when I check tire pressure in the spring (in Colorado, about 5 minutes long) when temps one day may be 80˚ and the next 20˚, I learned long ago there's a variation of 2 or 3 lbs.—less than Mark suggests, but I wasn't being scientific. I just set them according to temp averages for the season.
My gauge appreciates Mark's compliment. It's a cheap, old round guy that reads up to 60 lbs—I have to guess above that. It gets dropped a lot too. One step above the kind with the stick that pops out. I was thinking of getting a new fancy one, but I will now trust it.
Gene
|
|
|
|
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|