tire pressures

[Tom N]

Paz;

Do you know Dr. Terry Trees from MSA???

-Tom

[paz]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tom N:
Wow Paz, you have a lot of concerns. With all your concerns the Michelin RV Tire Guide would be just about useless to you.

Good luck.

-Tom </div></BLOCKQUOTE>
I set my pressures 3 to 5 psi higher than shown in the table based on my most recent weighing. How can you say the tables are useless?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tom N:
I have a couple accurate gauges.
I can get my gauge on the tire stem for an accurate reading. I use a couple curved extenders.
I have no slow leaks and if I did I'd have it repaired.
I follow Michelins recommendations to check and adjust tire pressure in the mornings before driving when the tires are at ambient temperature. The tables are built for a wide range of temps.
Michelin does not factor altitude into it's charts and that is reassuring enough for me.
I believe a certified scale actually means certified. Read the weigh & measure certification seal on my weigh slip below.
I check my depth wear with a tire depth gauge 2 or 3 time s a year to monitor abnormal wear.
I have never had an RV tire failure.
I believe my Cat certified weigh slip below and I'm way under my CCC.
</div></BLOCKQUOTE>
I'm glad so you are confident in all your gauges, extenders, and methods that you can set your tire pressures exactly at the levels shown in the table and not need any margin for error.

BTW, your weight slip does not show separate weights for each axle, much less for each corner. How did you arrive at your pressures without even knowing the weight on each axle?

[paz]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tom N:
Paz;

Do you know Dr. Terry Trees from MSA???

-Tom </div></BLOCKQUOTE>
No.

[Tom N]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by paz:

BTW, your weight slip does not show separate weights for each axle, much less for each corner. How did you arrive at your pressures without even knowing the weight on each axle? </div></BLOCKQUOTE>

Paz;

I had each wheel position weighed at a FMCA rally but I misplaced the paperwork. From those weights and Michelin's load tables I calculated 95#s in the front and 90#s in the rear. Winnebago says the coach is 38' 11" in length.

The weigh slip I posted was fully loaded with 100 gallons water, full propane and full fuel and my wife and I were in our seats. They could have done each axle but I would have had to unhook my Honda and I didn't want to do that. I just left the Honda hang over the rear of the scale.

In a week we're headed south for 6 months and I hope to stop at a Cat scale and get individual axle weights. Cat scales can weigh each axle but they can not weigh each tire position.

I'd like to own a set of portable load cell scales. I looked at some prices and they are more than I am willing to pay. I've even thought about a little traveling sideline doing RV weighing.

We may be at the FMCA Brooksville rally in Feb. and if we are I plan to have the wheels done again.

Interestingly I had 100#s in the front until I had the individual axles weighed. When I dropped down to #95#s I noticed an improvement in handling and front end ride.

You probably know this but MAX pressure for the W24 9000# front axle is 105#s and MAX pressure for the 15500# rear axle is 95#s. To go over these pressures one would have to have the coach overloaded. MAX tire pressure is 110#s for the 235 XRVs.

-Tom

[paz]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tom N:
You probably know this but MAX pressure for the W24 9000# front axle is 105#s and MAX pressure for the 15500# rear axle is 95#s. To go over these pressures one would have to have the coach overloaded. MAX tire pressure is 110#s for the 235 XRVs.

-Tom </div></BLOCKQUOTE>
The pressures you give are not the maximum pressures for the 235/80 x 22.5 XRV tires, but they are the pressures necessary to carry the maximum weights for the W24 axles. However, that's only IF the weight is perfectly balanced left to right. For example, if the right rear corner weighs 8,000 lb and the left rear corner weighs 7,500 lb, then you would need to inflate all your rear tires to around 100 psi to carry 8,000 lb - even though only one corner weighs 8,000 lb and the total weight on the axle is only 15,500 lb. All tires on any given axle should be inflated to the same pressure and they should be inflated to carry the weight on the heavier side on that axle. This is the reason it's best to have the individual corner weights. Basing tire pressures on the result of dividing the axle weight by 2 is risky because many motorhomes are not perfectly balanced. If the motorhome is not balanced, one or more corners could be overloaded.

[Tom N]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by paz:

The pressures you give are not the maximum pressures for the 235/80 x 22.5 XRV tires, but they are the pressures necessary to carry the maximum weights for the W24 axles. However, that's only IF the weight is perfectly balanced left to right. For example, if the right rear corner weighs 8,000 lb and the left rear corner weighs 7,500 lb, then you would need to inflate all your rear tires to around 100 psi to carry 8,000 lb - even though only one corner weighs 8,000 lb and the total weight on the axle is only 15,500 lb. All tires on any given axle should be inflated to the same pressure and they should be inflated to carry the weight on the heavier side on that axle. This is the reason it's best to have the individual corner weights. Basing tire pressures on the result of dividing the axle weight by 2 is risky because many motorhomes are not perfectly balanced. If the motorhome is not balanced, one or more corners could be overloaded. </div></BLOCKQUOTE>

I understand what you have stated and this is how I arrived at 95 front and 90 rear 3 years ago. This is also how I arrived at pressures for my old Vectra many years ago. I have no intention of adjusting pressures using axle weights only.

For those that want more RV tire info I suggest downloading the Michelin RV Tires Guide. It graphically explains how to weigh your motorhome and set the correct tire pressures.

The tire guide also states, "When a vehicle is stored, tires should be inflated to the inflation pressure indicated on the sidewall."
I haven't seen this recommendation mentioned on iRV2. This is possibly why many coaches leave the dealer at maximum tire pressures.

What wheel position weights have you seen for your W24 Allegro 37DB??

-Tom

[paz]

Tom, our corner weights were as follows:
RF 3700
LF 3800
RR 7750
LR 7450

These weights were taken at the beginning of the seminar we were attending and our fuel and fresh water tanks (which are both behind the rear axle) were both full. We rarely, if ever, travel with more than 25 or 30% fresh water or with anything in the waste tanks. We have added some cargo since these weights were taken and I have also moved a few heavy items (like my tool box and compressor) closer to the front. We are due for an update on our corner weights.

[Tom N]

If you want your bare chassis weights as shipped from Workhorse register on Workhorse's website and bring up your VIN. I think all W24's show the same weights though.

GVWR: GVWRF: GVWRR: Delayed Mileage:
24000 9000 15500 957

Total Ship Wt: 6610.12

Front Ship Wt: 3580.06010742188

Rear Ship Wt: 3030.06010742188

Note: The front is heavier than the rear until the coach is built on the chassis.

-Tom