Tire Pressure

[dale farley]

I am trying to determine the best average tire pressure to run in my tires on my 40' Marathon. I see different recommendations everywhere. My tires say run a max of 120 psi. I don't think I am maxed out with my weight, so I am currently running 105 in front, 110 on drive axles and 105 on tag. I see that some run 75 in tags. Is there an average setting for each of my axles that I can use that will cover most situations? Thanks.

[Jon Wehrenberg]

Dale,

Ignore any tire pressure recommendations from any source that does not base that recommendation on the axle or wheel loading.

That is not an opinion but is based on what tire manufacturers have on their web sites.

If you go to this site you can scroll through and find the tire pressure requirements based on your specific weights.

http://www.michelintruck.com/michelintruck/tireSelector.do?veh_type=13&position=Z&size=315%2F80R22.5

Further, if you really want to do more research do a search and find the Michelin Truck Tire Service Manual. You might be able to link to it via the above site. That is a PDF file that is very informative about all factors relating to your tires.

Your tires are critical to your safety and will contribute to all of the handling characteristics of your coach. It is important that you treat them as required to get the most from them.

You don't say what size tires you are now running, but one very good reason to treat your tires well is that a 315R80 22.5 Michelin is now $600+ dollars.

[dale farley]

Jon,

The tires I now have were installed by the previous owner a few months ago. They are Hankook, 12R 22.5, Load Range H with Max load capacity of 7390 each. He was a trucker and said he ran these tires for years. I realize they are probably not the best suited for the bus but so far have noticed no problems, and I hate to change new tires unless there is a compelling reason. I see on the Michelin chart that the specs are the same on my tires as the XZ2 Michelin. I realize that doesn't mean all the ride and drive characteristics are the same. Thanks. Dale

[Jon Wehrenberg]

Welcome to the club. Roger and I just installed some Shanghai produced tires on our coaches and I am using the Michelin tables for tire pressures.

Just look up your size and inflate to the load they are carrying. I went to a scale as soon as we had our bus fully loaded with fuel, water, clothers, food and other goodies.

[dale farley]

That sounds like a plan. Thanks.

[lewpopp]

Where are you boyfriends going?

[dale farley]

I've seen a post where at least one person is using a laser thermometer to check their tire pressures; not literally check the pressure, but compare one tire to another. I am wondering if this is a feasible and reliable way to ensure that all tires are relatively the same from one side to the other or does it turn out to be excessively confusing? I assume you just walk around the bus and compare the readings of the tires on one side to the same tires on the other side.

The best price I see on a dual, laser and contact probe, thermometer (Mastercool 52225-A) is $75 plus shipping, and I don't want to spend the money if its not worth the cost. Of course $75 is now about the same as a small bat to whack the tire with. So far, my hammer is the cheapest tire tool I have. Anyone actually using the laser thermometer method?

[garyde]

Dale. I have been lectured by the group to check all tires every morning before leaving with a a tire guage. Gary

[dale farley]

Gary,

I've seen those posts also, and that is part of my confusion. I've seen some (including Jon) who have said every time you check your tires with an air gauge you are subject to causing leaks in or around the valve stems, and I understand the validity of that statement. I am trying to determine if there is a better way to get a relative check without using a gauge.

I currently use a hammer most of the time and use a gauge only occassionally. I also purchased some of the valve caps ($5 each) that are supposed to alert you when the air pressure drops. I haven't installed them yet because I am waiting to fully load the bus and find a set of scales to do the job. Once the caps are installed they adjust to the current pressure cannot be changed from that setting. Thanks. Dale

[Ray Davis]

Dale,

There was an earlier thread about those $5 valve caps which monitored tire pressure. Jon installed them, and evidently they caused leaks. Search back in the threads and I'll bet you'll find it.

Jon's recommendation was to NOT use those caps.

[dale farley]

Well, at least I haven't installed the LED valves yet, so I know they are not causing me any problems in my garage. I would think it they leak, the lights would immediately come on and stay on.

Obviously, there are no simple answers to many of these problems. I see that Roger is using the laser thermometer, so I might get one of those to use when on the road for a quick check and comparison of the tire pressure. Maybe if I have the laser thermometer, a bat, hammer, and good tire gauge, I can keep up with the air pressure.

[Ray Davis]

Dale,

Assuming you are talking about the same caps, or similar, here's the previous thread for your perusal.

http://www.prevostownersgroup.com/forum/showthread.php?t=313

[MangoMike]

Dale,

I have one of those laser thermometers from Harbor Freight Tools (about $50) and used it on my 7k trip in '05. I always checked the pressure in the tires before departing for the day and used the laser to check the tires at rest and fuel stops just for giggles and grins. I was hoping that a tire that was lower on air would register a higher temperature. I never had an air problem so don't know if it the system worked. I do know that the tires on the sun side of the bus were always higher.

I use the thermometer frequently to check output for the cruise airs. And we used it all the time in the restaurants.

For $50 it's a good tool/toy.

Mike

[Joe Cannarozzi]

I didn't realize you could get one of those for that price, I'm gonna have to get one of those:cool:

[MangoMike]

Joe,

On sale now for a measly $39.95.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91778

Mango