Tire PSI

[kbenfield]

For a 34 FDDS with a max inflation of 100 PSI, what PSI should I run my tires at?

Dwayne and Kristi
34 FDDS ALPINE SELECT
2012 Mini Cooper

[Alpine06]

Kbenfield,
Your max tire pressure is raising a couple questions for me.
The short answers is run 100 psi.
But have a look what weight rating your tires are. It is on the outside of the tire. Preferably you want a 16 ply tire and that is a “H” weight rating.
Now if you weigh your coach you find out that you can get away by using 14 ply I.e. on the front however by the rating of the Axel you can not.
So find out what exact tire you have. Now look into the inflation table of the manufacturer and inflate accordantly.
If you are at a large gas station drive on the scale fully loaded and go from there.
Hope that helps
Joerg
PS: what I like about the 34 is That you will find it is nearly impossible to overpack your coach unless you have a lot of gold to carry ... or lead ... or ...

[DrDaveMA]

For the correct answer to this question get the coach weighed, once you know the weigh at each corner you can go to the tire manufacturer’s web site and pull up a chart that shows the correct psi. You can even add 5 psi for a safety factor.

[Skilletface]

Originally Posted by kbenfield

For a 34 FDDS with a max inflation of 100 PSI, what PSI should I run my tires at?

Dwayne and Kristi
34 FDDS ALPINE SELECT
2012 Mini Cooper

This is one of those subjects I am pasionate about because over 4 million miles of being able to count on one hand how many tire failures I’ve had, have proven at least to me this works. This was passed on to me by an uncle that back in the day truckers had to fix there own flats.
As stated above get your unit axled out and adjust cargo inside if necessary, inflate your tires to mfg. max cold inflation, take a short trip preferably on a non asphalt surface, observe how the tread face of the tire is contacting the ground it should appear lighter than the sidewall and make 2-5 psi adjustments down until a nice even wear appears on the tread face.
Running max inflation is not a bad thing but tires build pressure as they heat up.

[richard5933]

Running at max inflation will not likely result in any harm to the tires themselves, and it certainly beats under inflation. But, it's not without negatives.

Running with over inflated tires can have negative impacts on handling and cause the coach to wander on the road, making steering control more difficult. It also results in a harsh ride which can get really tiring on a long trip. The other safety issue is that over inflated tires will have reduced braking since the full width of the tread is not making even contact with the pavement. This obviously reduced traction when stopping and when turning.

The advice given above to weigh your coach is a really good first step. Then you can set the pressure according to the tire manufacturer's Load & Inflation Table, as long as you don't go below the coach manufacturer's recommendations for minimum inflation.

[wolfe10]

Rather than coming up with your own method of determining the correct PSI, my STRONG suggestion is to follow the advice of the tire engineers who designed your tires.



There is a reason they went to the time and trouble to develop and publish tire inflation tables.


BEST: With the coach loaded as you travel, weigh each wheel position and use the heavier position to go to the inflation table to determine the correct MINIMUM PSI and use that PSI for all tires on that axle. Yes, that is the minimum PSI for that weight. Most of us add 5-10 PSI to that minimum so we aren't over-thinking it every time we add groceries, aren't able to dump tanks before driving, etc.


Next best: Weigh axles and add 10% to account for left/right imbalance and do the rest the same as above.

[Old Scout]

I love this question--one of my favorite. First, where does the idea come from that max tire pressure on the OP's rig is 100 PSI? My understanding is that max cold rim pressure is 120 PSI [at least on my 2003]; and as stated, the particular tire manufacture provides recommended pressures based on tire load rating and size, and vehicle weights.
So while we are here--should tires be adjusted daily, or as appropriate, based on changes in ambient temps and altitude???? Inquiring minds want to know....

[richard5933]

Originally Posted by Old Scout

I love this question--one of my favorite. First, where does the idea come from that max tire pressure on the OP's rig is 100 PSI? My understanding is that max cold rim pressure is 120 PSI [at least on my 2003]; and as stated, the particular tire manufacture provides recommended pressures based on tire load rating and size, and vehicle weights.
So while we are here--should tires be adjusted daily, or as appropriate, based on changes in ambient temps and altitude???? Inquiring minds want to know....

At the least they should be checked at the start of every travel day. Not everyone does this, but it is best practice.

[wolfe10]

Originally Posted by richard5933

At the least they should be checked at the start of every travel day. Not everyone does this, but it is best practice.

OR


Have a TPMS-- they check tire pressure 24/7!

[Old Scout]

OK--good answers, but that is not the question--"should you adjust tire pressures based on changes in ambient air pressure and altitude?" Say I drive from south Texas to Red River NM in the summer--its 90 degrees in Texas when I leave and 50 the next morning in Red River--do I adjust tire pressure? If I do, when I return to south Texas--do I adjust again? Do long-haul truckers adjust as they drive from Wis to Florida?
PS--yes, I have a TPMS and observe that accept in severe temp conditions, cold tire pressure may vary modestly, but tire pressures at ops temps don't vary that much, regardless of where my cold temps were that morning?

[richard5933]

Originally Posted by Old Scout

OK--good answers, but that is not the question--"should you adjust tire pressures based on changes in ambient air pressure and altitude?" Say I drive from south Texas to Red River NM in the summer--its 90 degrees in Texas when I leave and 50 the next morning in Red River--do I adjust tire pressure? If I do, when I return to south Texas--do I adjust again? Do long-haul truckers adjust as they drive from Wis to Florida?
PS--yes, I have a TPMS and observe that accept in severe temp conditions, cold tire pressure may vary modestly, but tire pressures at ops temps don't vary that much, regardless of where my cold temps were that morning?

Not sure what others do, but I have included a few PSI 'buffer' in the pressure I normally run in my tires. The buffer is enough to accommodate this type of daily temperature fluctuation. It's not necessary to have the pressure set spot on to the exact chart value, and leaving a few PSI buffer makes life much easier.

[PitMan51]

At an FMCA rally a few years ago, we had the coach (09 40 MDTS) weighed (4corners). They recommend 95 rears and 90 for the fronts and suggested 95 all around. We are full timers, so fairly loaded.

Bill & Sonia
09 40MDTS

[Brianna]

I am new to RVing.
I haven't done the 4-corner weigh yet.
I am set at 100psi cold pressure.

Last summer, highway driving on asphalt, the sunny side of the coach went up to 134psi according to the tpms. The alarm went off.

Is this normal and/or Safe?

The shaded side of the coach was at about 120.

[ArtJoyce]

When you do look up the tire to load psi chart. If you have dual rear tires it's not just double or half the load capability or psi of the tires. There should be a chart for dual tires.