Tire Pressure

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
Barryn514

Barryn514

Well-known member
Joined
Jul 9, 2011
Posts
380
Location
San Diego
Am still new to RVing and sure this question has been asked before, so here we go.

Was wondering what others that have tire size of 245/70R19.5 run their tire pressure at?  I know that the weight will have to be considered. I have not weighed my new to us RV since we only got it a few weeks ago.

2002 National Sea Breeze Scout. 30'

Specs:

WEIGHTS (POUNDS) SB300
Gross Vehicle Weight Rating 22,000
Gross Combined Weight Rating 26,000
Front Gross Axle Weight Rating 7,000
Rear Gross Axle Weight Rating 15,000
Unloaded Vehicle Weight 14,890
Maximum Carrying Capacity 5,859

Keep in mind that we do not carry a lot of water other than what is in the black tank and possible 15 gal of fresh water when traveling. Other than that, just the usual stuff for camping.

THANKS in advance!


 
Barry,

Get your RV weighed then look up the proper inflation on the tire manufacturer's web site.

Tire inflation is determined by the weight the tire is actually carrying not what it is rated at.
 
Hi,
Until you get it weighed, use the pressure placarded somewhere close to the drivers door (required by law). This pressure will be for a loaded unit and should ensure safe operation until you can do as suggested above.
Ernie
 
Not trying to get into a tire war here but looking at the tire guild, the pressure does not change that much with my spec.

      75      80      85    90    95  (PSI)
      3390  3570  3750 3925 4100  (single)
      6420  6760  7100 7430 7760  ( Dual)

So with this chart and with my Spec. I should be in the 80 - 85 psi (on my side wall it says Max psi is 120 lbs)

Just trying to get a rough idea where I should be. I know that 18 wheelers carry different weights, sometime their weights can change a lot within a day and I don't think they change PSI every time they change a load. As we also do the same thing such as carrying water for example. I could get my coach weighed today with almost dry tanks and in a week I could go on a long trip and have a full tank of gas (75 gal) and have more fresh water them the norm.





 
If you err on the maximum side and run the tires higher ...you have a harsher ride..
You'll probably not wear out the tires due to tread wear..age seems to be the deciding factor..
When checking your tires if you have a slow leak-er than you might catch that before disaster rears it's ugly head..
Personally that's the route I have decided to take...at least for now..I might change that opinion after I have installed a tire monitoring system...
 
For that reason we suggest getting an actual weight when loaded for normal travel, and then moving up one notch in the inflation tables to give you some extra capacity for those days when you travel heavier than usual.
 
The pressures shown on the sidewall are the pressures that will support the  maximum the tire can handle. The maximum weight the tire can support on a given vehicle is defined by the total suspension system (GVWR) of which the tires are one component. That is usually less than the sidewall pressure.

A truck trailer doesn't have any passengers so ride and handling are not a concern. Truckers will usually air up the trailer tires to the GVWR maximum so the pressures needn't be changed daily with changes in load.

On a coach, ride and handling are a concern, but the load doesn't change much so pressures can almost be a set and forget other than checking that the set value hasn't changed. That's why we always say, weigh the coach. That will permit reducing the pressure to a level that will provide a comfortable ride and good handling without concern of overloading.
 
I did check the weight sticker in the coach and it says the GVWR is 18,000, front 7,000 and rear 11,000. Listed the size of the tire, 245/70R195, 85psi cold.
 
Disregard the weight information posted at the beginning of this post. That's what it says on the spec sheet for the MH.  I sticker in the coach by the driver door stay, " GVWR 18000' GAWR front 7000 and GAWR rear 11000, weight with 245/R70/19R PSI 85"

Had it weighted at Mayflower and they are certified sales. Loaded less FULL load of holding tanks. Front 5'740 rear 9'860 and total weight of coach, 15'600. 

Am not able to find tire manufacture (dynatrac S990)weight chart, other than what it says on the side of the tire," max at 5675 single and 5510 duel, 125psi.

I know when I picked the coach up at the dealing, they had 110 psi and driving home, it was like steering a bull with a thread. LOL. I have since lowered the PSI down to 100 and seems better.

 
I have the same size and (H rated - 120psi) tires on my Bounder and my total weight is about 2000 pounds over what yours is. My weight chart says I'm good with 85 pounds, but I run the front ones at 90 and the rears at 95. I think you still might be a little high at 100, and by dropping 10 pounds you might see a handling improvement. Goodyear has a load chart for this size on page 11 here and while I would suggest using load ratings from your manufacturer if they are available, from what I've seen of load tables they are either the same or very close for the particular load ratings throughout the brands.
Edit: Fixed link.
 
Barryn514 said:
Disregard the weight information posted at the beginning of this post. That's what it says on the spec sheet for the MH.  I sticker in the coach by the driver door stay, " GVWR 18000' GAWR front 7000 and GAWR rear 11000, weight with 245/R70/19R PSI 85"

Had it weighted at Mayflower and they are certified sales. Loaded less FULL load of holding tanks. Front 5'740 rear 9'860 and total weight of coach, 15'600. 

Am not able to find tire manufacture (dynatrac S990)weight chart, other than what it says on the side of the tire," max at 5675 single and 5510 duel, 125psi.

I know when I picked the coach up at the dealing, they had 110 psi and driving home, it was like steering a bull with a thread. LOL. I have since lowered the PSI down to 100 and seems better.
Click to expand...

Attached is a spreadsheet that I think was first posted by Gary Brinck. On it you can input your numbers and get the recommended tire pressures. The results are not exact from the tire charts but is very close and is a good guide for people that can't get a chart from their tire manufacturer. Most people add 5 to 10 pounds for safety.

I've put your numbers in the spreadsheet that I attached.
 

Attachments

  • Tire Pressure 1.xls
    21.5 KB · Views: 27
Alaskansnowbirds said:
Attached is a spreadsheet that I think was first posted by Gary Brinck. On it you can input your numbers and get the recommended tire pressures. The results are not exact from the tire charts but is very close and is a good guide for people that can't get a chart from their tire manufacturer. Most people add 5 to 10 pounds for safety.

I've put your numbers in the spreadsheet that I attached.
Click to expand...

I'm wondering if there's a minimum on "H" rated tires Don? 56 psi seems very low. I know on mine when I decreased down to a little less than 85, when by the chart 80 would have been enough, the sidewalls were bulging a little and I just flat out didn't like the looks of it. I ran into the same thing on my Jeep Wrangler...it has tires rated for up to 45 pounds, but according to the weight tables they should be about 20. I've found if I keep about 30-35 in them they handle nice and wear evenly.
 
Don, couldn't see sheet 2 or 3, only 1.  I see you used my weights and showed the psi which to me seem extremely low. Was that just an illustration?  With that being said, the last posted a link and after reading that is show the rear tire having the most psi rating. I believe someone else also showed the rear to have less tire pressure than the front. Am I not reading these correctly?
 
According to the attached inflation chart (for Goodyear but should be comparable) you have way more tire than needed for your axle weights.  In any case, never run the tire pressure below the lowest value shown in the chart.
 

Attachments

  • GoodyearTire.PNG
    GoodyearTire.PNG
    68.3 KB · Views: 25
Yes there is a minimum inflation for any tire. Below that the sidewall flex will be excessive and cause overheating, which shortens tire life dramatically and can cause sudden blow outs. Few H rated tires will go below 70 psi and many will have a minimum of 80-90 psi.
 
I don't recall posting that spreadsheet and it 's not something I keep in my files for reference use.  It certainly appears that it can generate pressures that are below the minimums for a specific model of tire, so that should be a caveat in its use.
 
The spreadsheet works fairly well if the tires are well matched to the actual loads.  In this case, they aren't, so the results are not valid.  With the posted GAWR it would seem 225/70R19.5 tires would be a better match.
 
You must log in or register to reply here.

Latest posts

Members online

Total: 1,089 (members: 32, guests: 1,057)

Forum statistics

Threads
133,776
Posts
1,416,192
Members
139,361
Latest member
BLard
Back
Top Bottom