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Ask Dave: How close should the tire pressure on duals be?

Dear Dave,
We have a motorhome with dual tires on the rear. I use a TST Tire Monitoring System to keep tabs on the pressure and try to keep them as equal as possible. How close does the pressure on each set of duals need to be to assure equal wear on each tire? 1 PSI? 2 PSI? Does something like a “Cat’s Eye Tire Pressure Equalizer” make sense to assure the pressure in the tires are the same? What are your thoughts on this? —Marvin

Dear Marvin,
I have worked with RV Safety & Education Foundation developing their comprehensive safety program. We did extensive research on tires as there was quite a failure rate at the time. It’s still a concern. All tire manufacturers of the larger tires such as those used on your motorhome recommend weighing the vehicle by individual wheel position and referring to the manufacturer’s tire chart to find the recommended pressure.

This can be done by an RVSEF team or at several rallies around the country. Once you determine the weight, visit rvsafety.com to see the list of tire charts and find the recommended pressure.

It is not uncommon for RVs to be heavier on one side than the other. Data obtained from RVSEF shows the majority of rigs they weighed had this issue. It is important to have the same pressure on tires of the same axle, therefore individual wheel position weighing is important.

Check the tire pressure every morning before leaving

After you have the recommended pressure, it is important to check the pressure every morning you are going to hit the road to verify the pressure matches that recommendation. This reading is taken when the tire is cold, which it is before traveling down the road. After that, do not adjust the pressure while driving unless the tire is losing pressure. You might find that one side of the rig develops higher pressure if it is in direct sunlight. That’s common.

I don’t have much experience with the Cat’s Eye system but have seen several on units at rallies and parking lots. Another popular product is Crossfire, which some of the larger manufacturers such as Newmar offer as an option.

I have seen nothing but great reviews from owners. However, one thing I would suggest is using a TPMS as you can only tell pressure from a Cat’s Eye from the outside, not while driving.

I recommend a tire pressure monitoring system (TPMS) such as TST Technologies, as you are using and which I have used with great success. I installed sets of them on three trailers that have logged more than 250,000 miles each in the past few years. They have been a great addition and continue to work well.

I wonder what the benefit of having the Cat’s Eye product would be if the TPMS is installed? Hopefully, other readers have used the product and can let us know what they have found in the comments below or over on my forum.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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23 Comments
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Dave
3 months ago

And the correct answer is … make them the same pressure as accurately as you possibly can. All 4 tires on your drive axle the same pressure. Mine are within .5lb of each other.

James
3 months ago

His answer was “it’s important to have the tires equal in pressure on the same axle ” in my own words. The rest is good bonus info.

DW/ND
3 months ago

I concur with the comments below. This question would be better addressed to Roger Marble. It has always been my understanding (25 yrs) – dual tires should be equal or very close to it. The different pressure ideas come from driving on crowned roads with the inside dual on a higher road surface – thus more weight on it. Today’s roads are pretty much flat. Also, how many Rv owners actually wear out a set of duals? I keep mine (19.5 – LRF) the same and with a TPMS, allowing for a sunny side difference. I start getting concerned at 5 lbs if there is a trend developing. I also physically check, with a digital gauge, every morning in addition to the TPMS.

Larry Lee
3 months ago

That is it. I am done reading Dave’s non-answers

cee
3 months ago
Reply to  Larry Lee

What are you talking about? Dave said, “It is important to have the same pressure on tires of the same axle”, sure seems like an answer to me Larry Lee.

TIM MCRAE
3 months ago
Reply to  cee

The question was ‘what is ‘as close as possible’, in a numerical way”

This answer was just a waste of my time.

He could have just said, I Don’t Know!

We all know that as close as possible is correct. The requestor was clear that he knows that. That’s why he asked!

cee
3 months ago
Reply to  TIM MCRAE

Do you do some research and come up with a numerical answer?

Seems like you prefer to whine and complain?

Bob Weinfurt
3 months ago

Of course it’s best to have dual wheels in the same spot at the same pressure but one or two pounds pressure difference when checked cold is OK. Five or more pounds difference isn’t.

Last edited 3 months ago by Bob Weinfurt
TIM MCRAE
3 months ago
Reply to  Bob Weinfurt

Thanks for that concise answer!

Thomas D
3 months ago

Question was asked about 1/2/3 pound s difference where is the answer? And chart listed is for bjgger coaches. Some motorhomes use LT tires in 17/18 inch wheels. And inside dual will usually run cooler ( less pressure) if outside dual is exposed to sun.
Another question unanswered!

Bob Palin
3 months ago

YET AGAIN, you didn’t answer the question.

Dave Telenko
3 months ago

The old saying goes: If you can’t dazzle them with delight, you then baffle them with BS!
Snoopy

Bill Richardson
3 months ago

My thought was the same as most other people….does anyone out there know the answer to the question?

Dr Doug
3 months ago

I was curious to find the answer as well. Guess we will never know…..

Gary
3 months ago

Does he really RV himself!! ???

Fred
3 months ago

Your link for tire pressures doesn’t show the Michelin 17″ tires that come on all Ford Super Duty trucks in recent years. The Michelin chart jumps from 16″ to 19 1/2″.

Jack D Fetterman
3 months ago

where did the answer go?

The Lazy Q
3 months ago

Did I read the question wrong? The answer seems to be for a different question that I don’t see…hmmm

Don
3 months ago

So, I see that you also can’t see any benefit to these things, Dave. I have yet to have anyone give me an answer to that question other than a very non-specific “improves tire wear and handling” which I’m afraid I find very unconvincing.

Primo Rudy's Roadhouse
3 months ago

Again, no answer to the question. You make a habit of telling how to build a watch but not answering the question: “what time is it”

Bob p
3 months ago

That’s called a dance around, he dances all around the question without giving a definitive answer!

Scott R. Ellis
3 months ago

This totally ignores the actual question . . .

Matt
3 months ago

And the question answer was ???