Proper Tire Pressure Questions

[PhotoMaster]

My FR3 30DS has the often mentioned RV Drift issue and I have had the front end aligned. At the latest RV show we went to one of the seminars and spoke with the expert (Dave Solberg - Author of "the RV handbook". We were talking about tire pressure and it's effect on steering softness. We purchased his book and it talks about having each tire at a different pressure, due to different weight on each tire. It sounds like I would have to reweigh the unit every time we use it. Full or empty water/holding/propane tanks, the number of passengers, etc. Definitely sounds like major overkill. I cant even find a place less than a few hours away just to have it weighed. To buy a single wheel scale is ridiculously expensive. The least pricey one I have found was $1700.

What does the average RV user do for setting tire pressures. I always thought looking at the tire and keeping the pressure between the high and the low pressures was the answer. Apparently I am way inexperienced on this topic.
Any help would be appreciated. I did do a search of the site and found no answers.

[OldCoot]

On our 5er and also on the truck, I pump all tires to 65# which is what the ST tire max sidewall pressure. Truck tires are supposed to be at 85#, but only inflate them to 65#.

Individual pressures for different wts on each tire would be a PITA and IMO is beyond ridiculous.

[Bobb36]

The recommended air pressure for the FR3 30DS is 82psi and that's what mine are set at and will stay at

[SKnight]

I run the specs and watch the wear pattern but if you're really worried about tailoring pressure there's a very simple method we used back in the day.

Load for a typical trip, air your tires to 10 psi over their max, no it won't hurt a thing, go to a parts store and get a tire crayon. Then go find a flat, reasonably level parking lot with a straight run of a hundred yards. Draw a 2" wide stripe across the tread from sidewall to sidewall. Very smoothly drive straight for 50 feet. Get out and check the crayon marks, since you're over inflated odds are the center will wear off first. If just the very center, drop 10psi out, repair the mark and move another 50 feet. Once it gets closer to wearing off near to the sidewalls drop 5psi. Eventually it will wear off at the same rate across the tread of the tire.

At this point it will be evenly loaded across the tread face which is what you're looking for.

Easy cheesy.

[Mandoholic]

I'm with Bobb.

[ependydad]

Originally Posted by OldCoot

On our 5er and also on the truck, I pump all tires to 65# which is what the ST tire max sidewall pressure. Truck tires are supposed to be at 85#, but only inflate them to 65#.



Individual pressures for different wts on each tire would be a PITA and IMO is beyond ridiculous.

I'm essentially with OldCoot- I run max pressures on the tires and don't think twice about it.

I've never heard that you should run separate weights on each tire. I think Goodyear recommends weighing the tires individually and then using the maximum pressure for the highest loaded tire. But, for the exact reasons you mentioned - that seems like a lot of work. Given the usage of camper tires, I can't imagine you wearing a tire out prematurely with max pressure.

[PhotoMaster]

This sounds like the book is recommending overkill. I like the idea of one set pressure for every tire. I like the idea of marking the tire and looking at the road contact. Thanks for the ideas! Any other ideas/opinions would be appreciated!

[Batts-toy]

I think some 'experts' pile the cr** on just so they can say they are experts. Beside it sells books. I run max rated pressure on the TT and factory recommended pressures on the TV.

[PhotoMaster]

The expert also told me info about towing and brakes, that differs with everything I was told before. He had a chart that showed that in NJ trailer brakes are required on all trailers regardless of weight. I was told prior that if the trailer is less than 1000 lbs unladen, or under 3000 lbs laden, trailer brakes are not required. I went to the state Motor vehicle site and it shows that the 3000lb rule is correct, so the expert was mistaken on that issue.

[SKnight]

I'm guessing you're pretty serious about photography, how many experts books have you read that's so much crap it stinks?

I say as I'm getting ready for Scott Kelbys shoot like a pro seminar tomorrow.

[PhotoMaster]

I used to teach photography.

[SKnight]

There you go. Locally I'm considered an expert in photography but dislike the term because of the proliferation of "experts" that frankly don't know a thing about the subject, no matter the subject.

Is what it is I'm afraid.

[PhotoMaster]

Enjoy Scott's seminar!

[SKnight]

I'm just hoping I can keep up with him! I'm just now breaking through into the pro world and every step forward comes with two back.

[jadatis]

You can use my multilingual MotorhomeRV-tire-pressure-calculator, wich can be found in next map on my One-drive ( former skydrive) that belongs to my hotmail adress with same username as in this forum ( so combine yourselves if you want to contact me by mail, spamm machines cant)
https://onedrive.live.com/?cid=a526e...E092E6DC%21793

First download the american version ( tire instead of tyre) to your computer by RIGHTCLICKING and then choose Download from the dropdownbox.
Other means go wrong like leftclicking or choosing open in Web-app or Excell.
After download and eventual virus check ( you never know what those Dutch put in to it) open it in Excel programm on your computer. But Open Office CALC can handle it too.

The calculator calculates the needed pressure with my own formula wich is better then the American used formula and even better then the European one wich I once got hold of and my tire pressure story began with.
It also takes a reserve for overloading and unequall loading, and shows what is used and the reserves , but you can chanche it to your own ideas.
So if real seperate wheel weights are known , use part 3 for it . if only GAWR's are known it uses that in part 2 .
Also usefull information about loads and reserves, so you dont have to calculate that yourselfes.

It calculates same pressure R/L because car- and tire-makers advice that.
But using different R/L per axle is not that bad to my opinion.
Reasons for same pressure could be , that the mass on an axle gives same sideward forces on Right and left wheel so sideward stifnes of tire should be the same.
Mayby something in the middle would be best.

If you cant work with my calculator , give the weighs ( weighed or GAWR's) and the exact tire data ( maximum load or loadindex, Loadkind ( C to H -load) or AT-pressure ( reference-pressure, wich is not the maximum pressure) and the maximum speed of tire( mostly N speedrated is max speed of tire 140km/87m/h) )

[bubbles]

Originally Posted by jadatis

You can use my multilingual MotorhomeRV-tire-pressure-calculator, wich can be found in next map on my One-drive ( former skydrive) that belongs to my hotmail adress with same username as in this forum ( so combine yourselves if you want to contact me by mail, spamm machines cant)
https://onedrive.live.com/?cid=a526e...E092E6DC%21793

First download the american version ( tire instead of tyre) to your computer by RIGHTCLICKING and then choose Download from the dropdownbox.
Other means go wrong like leftclicking or choosing open in Web-app or Excell.
After download and eventual virus check ( you never know what those Dutch put in to it) open it in Excel programm on your computer. But Open Office CALC can handle it too.

The calculator calculates the needed pressure with my own formula wich is better then the American used formula and even better then the European one wich I once got hold of and my tire pressure story began with.
It also takes a reserve for overloading and unequall loading, and shows what is used and the reserves , but you can chanche it to your own ideas.
So if real seperate wheel weights are known , use part 3 for it . if only GAWR's are known it uses that in part 2 .
Also usefull information about loads and reserves, so you dont have to calculate that yourselfes.

It calculates same pressure R/L because car- and tire-makers advice that.
But using different R/L per axle is not that bad to my opinion.
Reasons for same pressure could be , that the mass on an axle gives same sideward forces on Right and left wheel so sideward stifnes of tire should be the same.
Mayby something in the middle would be best.

If you cant work with my calculator , give the weighs ( weighed or GAWR's) and the exact tire data ( maximum load or loadindex, Loadkind ( C to H -load) or AT-pressure ( reference-pressure, wich is not the maximum pressure) and the maximum speed of tire( mostly N speedrated is max speed of tire 140km/87m/h) )

ummm, what!

[cucamelsmd15]

Originally Posted by OldCoot

On our 5er and also on the truck, I pump all tires to 65# which is what the ST tire max sidewall pressure. Truck tires are supposed to be at 85#, but only inflate them to 65#.

Individual pressures for different wts on each tire would be a PITA and IMO is beyond ridiculous.

That might be fine for ST and truck tires, its NOT fine for RV and big rig tires. Those pressures are load based, unlike most common light truck tires which only list max pressures, i.e. load range E tires.

Max pressure for the Goodyear's FR supplies is 110psi IIRC. The PROPER pressure for the FR3 is between 80-85 psi depending on how its loaded from what I remember. FR supplies load range G tires, which at max pressures will best the axle rating in front by almost 2000 pounds, and by over 4000 pounds in the rear. Running over pressure in tires like these is just as bad as being underinflated.

The real solution is a four corner weight. Axle weight (like a CAT) scale is close enough for government work. But my guess is that you'll find the magic number between 80-84 psi.

As far as the drift, is it actual drift? What were your alignment specs? Could it just be that you're not used to the type of steering box on a heavy duty chassis?

[PhotoMaster]

I used to drive full sized dump and jetter trucks, but this has a real drift. I am getting used to it and compensating. For my wife it's a whole new experience.

I never saw the alignment numbers. The RV dealer sent it out to the company they use.

Finding scales around here is a problem. The nearest ones I have found are well over an hour from home.

[Brother Les]

Originally Posted by PhotoMaster

My FR3 30DS has the often mentioned RV Drift issue and I have had the front end aligned. At the latest RV show we went to one of the seminars and spoke with the expert (Dave Solberg - Author of "the RV handbook". We were talking about tire pressure and it's effect on steering softness. We purchased his book and it talks about having each tire at a different pressure, due to different weight on each tire.

What does the average RV user do for setting tire pressures. I always thought looking at the tire and keeping the pressure between the high and the low pressures was the answer. Apparently I am way inexperienced on this topic.
Any help would be appreciated. I did do a search of the site and found no answers.

Ask for your money back on the book.

[OL Creeker]

Ditto Old Coot! I run mine at max psi while towing - 5er also, since that too is so close to GVWR.