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Old 06-24-2011, 08:26 AM   #1
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Dual Tire Pressure Variation

Ok... I know that this topic has been touched before in various different ways and I apologize for bringing back up an old topic. I currently have a Berkshire on which I installed a set of Cat's Eyes (dual pressure equalization system) primarily due to the fact that it was impossible to get one of my TPMS caps on the one of the tires. Not to mention the fact that it was a lot easier to adjust the pressure. I am an engineer so I bought into the theory that having the same pressure in both tires would be a good thing. Now I have ordered a new coach that just so happens has plenty of room for a TPMS cap on each of the tires. I am struggling with the decision as to whether or not install a similar system (Cat's eye or Crossfire) on my new coach. The only reason to now would purely be for the equalization aspect.

I would like to hear from those of you that actually have monitors on each of your duals and share with me what level of variation you have actually seen between the inner an outer tires. Supposedly it is ideal that all 4 of your tires have exactly the same pressure (within maybe 5%) but does this logic flow onto your tag? What happens if I run my tag at a different pressure than the drive? Sure it is not on the same axle but it is right there directly behind the drive. One would think that it would be equally important for it to run at the same pressure as well. Those of you that have monitors AND a tag, what do you see from cold to warm pressure variations on your inner and outer duals as well as your tag?

Thanks in advance for your responses as I am sure it will be a interesting discussion - at least I hope so.

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Old 06-24-2011, 08:57 AM   #2
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The tag should have tire pressures appropriate for the load (weight) on the tag axle. It is not desirable to have them the same as the drive axle. Usually the tag is designed to carry only a modest portion of the total weight, maybe 6000-9000 lbs and the tire pressure should match. Excessive pressure in the tag actually reduces the weight carried on the drive axle, i.e. it lifts the chassis off the drive axle and thus reduces traction there.

I do not us Cat's Eye or Corssfire and have TPMS sensors on each tire. When cold, my duals are within 1 lb of each other, but there is some further variation as I drive. The inner dual gets a bit higher, probably becasue it runs hotter (less cooling air flow). And one end of the axle sometimes gets 1-2 psi hotter than the other, usually the sunny side.
Gary Brinck
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
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Old 06-24-2011, 09:51 AM   #3
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thanks for your response! How much of a variation do you see when the tires heat up after being on the road awhile? Looking to see how much higher the inner dual is as compared to the outer.
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