Another example of learning correct tire inflation

Quote:

Originally Posted by Ron Tireman9 and others....I just ran my coach over to the local Cat Scales at a truck stop nearby. As I stated earlier they do not make things easy and a 6" curb on each side of the scales prevented me from putting each side on separately so that I could get a close four corner figure. I settled on the two axle approach. All tanks were full, (water tank was actually just over 2/3, it fills very slowly and I got bored). Front axle came in at 11,400 lbs, rear axle was 16,560 lbs. My front axle is rated at 13,300 lbs and the rear is 21,000 lbs with a GVW of 34,300 lbs. 295-75R-22.5 tires. I have looked at the tables but would like to see what you folks come up with for approx. front/rear inflation? Thanks, Ron

Ron, you didn't say the brand tires. To my knowledge all major brands except Michelin have the same info for load & inflation and Michelin is same on maybe 95% and those that differ may only differ by 5 psi or so.

Since you only have total for an axle and do not know the heavy side we estimate one side at 53% -- So Front would be 6,042 and rear 8777 (4,389 per tire).

Most 295/75R22.5 LR-G need 110 to support 6,175 F (single) and 80 psi to support 4,540 in Dual.

Since I recommend a +10% of air for a good margin, that would suggest 121 psi front and 88 for the rear. BUT a LR-G is only rated for 110 psi so you need LR-H on the front. Also need to confirm the front wheels are rated for 120 psi and since even H are only rated for 120 that makes the recommended Front inflation 120 psi.

Clearly the estimate of 53% is causing the problem so it increases the need for you to learn the actual side to side load on the tires by going somewhere other than CAT truck stop scale.

It is CAT policy to not do one side weights and that is why they are making it harder to only get one side on the scale.

I suggest RVSEF

EDIT AND UPDATE   8/16/20

Locations with scales
https://www.dieselboss.com/service.htm
https://www.allstays.com/c/weigh-scales-locations.htm
https://www.publicscaleslocator.com/
SmartWeigh is another option

I checked around home and found a local building supply that had a scale that would give me 4 weights for $10. Only about 3 mi off I76 just East of Akron OH.

##RVT799

How to weigh your RV for free

If you live in or travel through Oregon you can check the load on each axle and even get an approximation on your individual corner weights. I did this myself last week.

There are many truck scales across the state that are open and the electronic scale are left on after hours. You simply drive onto the pad and read the total load for that axle on the display panel located on a post about 40' ahead of you.

Now if there are no trucks using the scale you may be able to simply swing around or back up and get just the right side tire loads for each axle. With those figures its easy to subtract and get the approximate load on the left side positions.

See it in this picture where I am getting the weight on my Right Rear duals.

I say "approximate" as unlike the scale set-up used by RVSEF there will be a slight tilt away from the scale pad but I would think you should be within a couple percent of the actual side-to-side load distribution. I am pretty confident that most of you will have figures that are closer to the actual side-to-side weight distribution than just assuming you have a 50/50 side-to-side split on each axle.

With the individual corner loading you can then use the published Load/Inflation tables from your tire manufacturer company to learn the MINIMUM inflation you need based on the heavy side loads. Then simply add 10% to that inflation number for your "inflation margin" and you should be good to go. At least till you get on real, properly set-up individual RV corner weight scales.

Now I admit I do not know which other states provide this safety service to motorists, truck and RV owners, but for folks on the far west coast this is a great deal, at least till you are able to get the actual corner weights of your RV, or individual tire loads for trailers, confirmed by RVSEF.

If you know of another state that has scales available to the public as Oregon does, please post in the comments below as this information will help your fellow RVers


EDIT AND UPDATE   8/16/20

Locations with scales
https://www.dieselboss.com/service.htm
https://www.allstays.com/c/weigh-scales-locations.htm
https://www.publicscaleslocator.com/
This post relates to Motorized RVs NOT Towables. Trailers have SPECIAL considerations for setting the inflation that I cover in THIS post.


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