Community Forums

allynne · 05-28-2011, 03:37 PM

Wayne,

I hate to dispute a retired Marine being retired AF, but the chart I have has the XZA3 and the XZE load range G and load range H. There is a difference, for example LRG 100psi single tire the weight is 5780 same psi for the LRH the weight is 6190.

The load range is important for a reasonable tire pressure to be calculated.

Al Sawyer
'05 MADP

RickO · 05-28-2011, 05:19 PM

Thanks Al. I'll check out the load range when I get back to the coach in a couple of days but the corner weights from Henderson's are too stale to be of much value. I do plan to get fresh axle weights before hitting the road however and that, along with clarifying the LR question, should get me in the ballpark.

rick

ImagineIF · 05-28-2011, 06:10 PM

The placard should reflect the pressure at the axle weight stated on the placard. The stated axle weight, except tag axle, should be the maximum axle weight ratings. The tag axle weight should be the recommended weight. So, the placard shpuld state the maxmum tire pressure for the tites originally supplied.

As others have said, actual tire weights can/should be used. FWIW, it's common practice to accept the maximum tire weiht on a given axle and use the same tire pressu for the lighter tire on the same axle. The tire pressu on all tires on a given axle should be the same.

Wayne M · 05-28-2011, 08:19 PM

Al,
No dispute intended. I have only put on this forum those values that I just got from the Michelin web site. I hope that site is up-to-date.

Having just attended the Freightliner seminar on the Freightliner line of chassis on May 19, and 20th of this year I received a Michelin tire chart (along with a Goodyear) and the date on the back cover is (04/09). I personally will only use the current values, but that will be based on the year of my tires. Some were manufactured in 07 and 2 were manufactured in 2010.

What to do, what to do.

As I stated, you will not be wrong to air up the tires to the tire manufacturer's max pressure. Climate will have an effect if traveling at max pressure, but you will not be wrong to travel with the max PSI. Just a heck of a bumpy ride.

If in doubt I'll call Michelin and ask specific questions regarding my tires. I suggest that if anyone has any doubt, they should do the same.

CJ7ole · 05-29-2011, 03:44 PM

I don't understand why you would run a tire pressure less than what is neeed for a fully loaded axle unless you KNOW you ALWAYS run at a lower weight. In other words when you weigh the rig, you will NEVER have more water, fuel, propane, black water, grey water, food, clothes, people, junk, etc. than when you are on the scale. I agree that you do need to weigh when you are fully loaded to be sure you aren't overloaded. How many people weigh their rigs at all, let alone more than once? Everyone is trashing the placards, but you must know that they are required by the Feds and Federal regs have guidelines as to how they are calculated. Unless the mfr is violating federal regs, those numbers aren't just made up. They relate to the maximum gross vehicle weight.

Elkhartjim · 05-29-2011, 03:55 PM

Quote:

Originally Posted by CJ7ole

I don't understand why you would run a tire pressure less than what is neeed for a fully loaded axle unless you KNOW you ALWAYS run at a lower weight. In other words when you weigh the rig, you will NEVER have more water, fuel, propane, black water, grey water, food, clothes, people, junk, etc. than when you are on the scale. I agree that you do need to weigh when you are fully loaded to be sure you aren't overloaded. How many people weigh their rigs at all, let alone more than once? Everyone is trashing the placards, but you must know that they are required by the Feds and Federal regs have guidelines as to how they are calculated. Unless the mfr is violating federal regs, those numbers aren't just made up. They relate to the maximum gross vehicle weight.

If this is where your comfort zone is then by all means you should run at the placard pressures.

RickO · 05-29-2011, 04:23 PM

Quote:

Originally Posted by CJ7ole

I don't understand why you would run a tire pressure less than what is neeed for a fully loaded axle unless you KNOW you ALWAYS run at a lower weight. In other words when you weigh the rig, you will NEVER have more water, fuel, propane, black water, grey water, food, clothes, people, junk, etc. than when you are on the scale. I agree that you do need to weigh when you are fully loaded to be sure you aren't overloaded. How many people weigh their rigs at all, let alone more than once? Everyone is trashing the placards, but you must know that they are required by the Feds and Federal regs have guidelines as to how they are calculated. Unless the mfr is violating federal regs, those numbers aren't just made up. They relate to the maximum gross vehicle weight.

As Jim pointed out, if using the placard pressures is where one's comfort zone is then that's what should be used.

To answer your question directly, I don't use the pressures on the placard because my weight doesn't require it and it results in a VERY rough ride and not a very enjoyable trip. I don't know how many people weigh their coaches... but I'm one of them. I don't think I've seen a lot of folks trashing the placards, just saying that there's not a very good chance that they reflect the actual weight of my coach at this time.

Rick

Crabby Mike · 05-29-2011, 04:53 PM

Quote:

Originally Posted by Wayne M

Al,
As I stated, you will not be wrong to air up the tires to the tire manufacturer's max pressure. Climate will have an effect if traveling at max pressure, but you will not be wrong to travel with the max PSI.

Now now, unless Mike Cody has changed his tune, you know that's not right.

Running at a higher pressure than appropriate for your weights does at least 3 bad things, the least of which is a rough ride. You will also tend to wear your tires more in the center of the tread due to overinflation, and more importantly, your handling and breaking will be negatively affected because you have too little rubber in contact with the road.

Yes, I'll agree that overinflation is (usually) less of a sin than underinflation, but they're both unnecessarily dangerous, when all it takes to do it right is a scale, a pressure chart, and a tire gauge.

RickO · 05-30-2011, 01:53 PM

Well, it looks like a call to Michelin is in order this week.

I just confirmed that my tires are load range LRG and their current tables don't list that tire as far as I can tell.

Rick

Wayne M · 05-30-2011, 08:17 PM

Oh my, oh my!

Ole - please look at my very earlier post on tire pressure and the cushion of comfort should you go above a weight, or below a weight. If you pressure correctly according to the chart you will have a good margin of error, or a poor margin of error, depending on your choice.

Mike - I have run 110 psi for two years and my tires are all wearing even. I had a blowout last year that was posted in another thread, so I'll not go into it here, but the tire company that inspected my tires said that they were not showing much wear at all. That was with 25,000 miles on them. However, now that I understand better the charts I am gong to cut down on some pressure and still be within specifications. I think I remember Mike stating something also about "comfort zone," and as rick said that if a persons comfort zone is max pressure as indicated on the sidewall, no problem. I believe that when over inflated come into play is when more than the max sidewall pressure is used. An example would be a tire rated at 110 PSI having a constant 115 or 120 psi. That, to me, is overinflated. Not running at max indicated pressure.

Don't make me hurt myself by having to research this further.

CJ7ole · 05-31-2011, 05:55 AM

Just to clarify, my Winnebago placard says to run 80 psi in all tires in order to carry the maximum axle weight. I run 85 psi to be safe and to account for the current Goodyear tire chart. No reason to run 110 and have a bone jarring ride (on older concrete pavement).

RickO · 06-09-2011, 03:08 PM

Quote:

Originally Posted by RickO

Well, it looks like a call to Michelin is in order this week.

I just confirmed that my tires are load range LRG and their current tables don't list that tire as far as I can tell.

Rick

Ok, closure finally! Michelin confirms that they do not have an inflation table for the 275/80R22.5 XZE in LRG but the 275/80R22.5 XZA3 LRG table should be used.

With my current weights that translates to 85 front plus 5# to account for side to side variance... 90lbs. Rear results in 90 plus 5... 95lbs. These feel much better to me.

Thanks to all. Great discussion.

Rick

Elkhartjim · 06-09-2011, 03:28 PM

All right Rick! It made all the difference in the world to how my mh handled and it sure did ride nicer.

Always-RVing · 06-09-2011, 03:49 PM

My MH does not have a built-in scale like Jumbo Jets do. You know, I don't remember what the MH weighed 6 or 8 mos ago. Have I added much since? How much? Guess I need to carry a scale around. This whole thing about tire psi is so silly. People wake up with nightmares over it. Set the psi to what the maximum is minus 5# and forget about it unless your're over the vehicle's gross weight which then, the psi no longer matters.

If something happens to a tire, I'll know it wasn't due to under pressure, and since I keep it 5-10 psi under max it will not be due to over pressure. So. I'll ride on the safe side.