Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
Sunline RV Forum
Sunline User Photos

Go Back   Sunline Coach Owner's Club > Technical Forums > Towing and Tow Vehicles
Click Here to Login

Join Sunline Club Forums Today


Reply
 
Thread Tools Search this Thread Display Modes
Old 04-08-2008, 06:56 PM   #1
Moderator Emeritus
 
HappyCampers's Avatar
 
Join Date: Sep 2007
Posts: 473
SUN #395
HappyCampers is an unknown quantity at this point
Tow Vehicle Tire Pressure

I was just wondering what the correct pressure is. Is it the psi listed on the data plate on the door? Or is it the psi rating on the tire? My buddy suggests that I run 5 lbs less than the max psi stamped on the tire. I've always run close to the psi on the tire, but now I'm wondering. My tires have a max psi rating of 80. The truck plate says 70 psi in the rears, and 60 psi in the fronts. Right now I have them at 75 and 65 psi. I'm just wondering because the fiver puts a bunch of weight on the truck and I want to be safe. The tires are Firestone Transforce ATs and I have no complaints on these tires. I had a set of Transforce HTs on my 3/4 ton and they were great too, although a little slippy in the snow. Any suggestions, opinions appreciated.
Lowell
__________________

__________________
Lowell, Amanda, Marley, and Winnie
1996 T-2053 (First Sunline "Little One")
2001 T-295SR (Favorite Sunline)
2003 F-304SR (Last Sunline "The Big One")
1985 T-1650 (Current Sunline)
2004.5 Dodge Ram 3500 5.9 HO Cummins
HappyCampers is offline   Reply With Quote
Old 04-08-2008, 08:34 PM   #2
Moderator
 
JohnB's Avatar
 
Join Date: Nov 2006
Location: Ohio
Posts: 12,643
SUN #89
JohnB is on a distinguished road
Lowell

Here is what I have found. When towing TT’s with friction type sway controls, and friction meaning, friction sway bar, Reese DC, or Equa-I-izer type hitches, tires stiffness plays a major role in rig stability. In this TT towing setup the tires need to be inflated higher then actual load required to create a stiff side wall and not flex which can create towing instable from sway effects on the TT. A soft side wall tire even if inflated well to handle the weight can cause a true sway feeling as the TV is literally shifting on the soggy tire as the anti sway hitch try’s to hold the truck stable.

On your 5’er you have a slightly different setup. Sway effects of a TT are no where near the same. So you do not have that same anti sway need. But you do need tire capacity. The name plate pressure generally follows the TV GAWR’s. So the front psi = the front axle load rating and so does the rear. So when towing you need at least the name plate psi. I say at least as some day you need to hit the scales. If the actual scaled weight is more then the axle rating you may not have enough air in the tire. Not to mention you are over the axle rating. Your dual tires can handle more weight then the TV axle rating. But only if inflated properly.

What you do NOT want, is to run the tire at a pressure under the actual rated psi for the weight it is holding up. Then heat comes and soon tire failure. Tire manufactures do have psi charts per load ratings. Some are even on line on the tire brands web site. You can then look up the min psi for the load. But again you need to know the load and that is only done by a truck scale.

On the front end, the same load ratings apply. Need enough psi for the load. You can go above that PSI all the way to max side wall but you probably do not want to do that on the front. I have found on GM and Ford suspension that when approaching that max side wall in the front, to much bound and wander comes from it.

If you do go to max side wall, front or rear, make sure it is done cold. I personally doubt you will really need max side wall on the front.

Hope this helps

John

As a point of reference, on my 2500 Suburban, I ran 80psi (max side wall) in rear and 65 psi front. Name palte was 80psi rear/50 psi front. LT 75R16’s

On the F350, I run name plate in my case. 75psi rear, 65 psi front. That will take me to a full 11,000 GVW create enough tire stiffness for anti sway and not bounce the front end. But again now I have LT’s and 18” tires. You can’t just go by psi, it needs to line up with the weight rating and the anti-sway requirements. And in my case I’m using the extra load rating for tire stiffness not load rating. I do no come close yet to the 11,000# GVWR
__________________

__________________
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

Google Custom Search For Sunline Owners Club
JohnB is offline   Reply With Quote
Old 04-08-2008, 09:17 PM   #3
Moderator
 
Sunline Fan's Avatar
 
Join Date: Dec 2006
Location: Michigan
Posts: 6,155
SUN #123
Sunline Fan is an unknown quantity at this point
John,

Do you run 75 in the rear all the time? I run all four at 65. I'm thinking I should up the rears to 75.

On a side note, always check the tires and compare them to the sticker. My Ex originally came with D range tires, so they had a max pressure of 65. The sticker says 45 front, 55 rear, which was fine for those. But, since it was upgraded to E range, with a max pressure of 80, 45/55 is really flat and you get horrible mileage that way. The previous owner of mine ran the sticker pressures because he claimed they were "big tires and need to be left aired down" ( ).

Jon
__________________
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9473.8 (as of 6/18/21)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR
Sunline Fan is offline   Reply With Quote
Old 04-09-2008, 08:24 PM   #4
Moderator
 
JohnB's Avatar
 
Join Date: Nov 2006
Location: Ohio
Posts: 12,643
SUN #89
JohnB is on a distinguished road
Quote:
Originally Posted by Sunline Fan
John,

Do you run 75 in the rear all the time? I run all four at 65. I'm thinking I should up the rears to 75.

Jon
Jon

On the F350, NO I do not run my 18" tires. (LT275/70R1 at 75 when non towing. I drop them down to 65. And if not the bounce on that 1 ton suspension is pretty bad. But towing not an issue. Again I can load 3000# cargo on my rear axle and still not hit the tire ratings. They are 3,630#/tire rated at 80 psi. I have larger capacity tires, so pressure is relevant to the tire.

On my 2500 Suburban, LT75R16 I went 80 psi towing and down to 65 psi non towing on the rear. The SUV would bounce hard on the back at 80 with no load in it. These are 3,042# / tire at 80 psi

Driving around empty on a harder tire will help with gas mileage. But there is a point where the bounce just is not worth it. So I find the middle ground. It comes out to be a tire pressure experiment. Just what ever one does, do not go below the tire pressure rating for the weight it is loaded to. Again the need to have scaled weights hitched and unhitched.

Hope this helps

John
__________________
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

Google Custom Search For Sunline Owners Club
JohnB is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tire Pressure Ron & Alice Sunline Slide Room Travel Trailers 5 12-24-2009 10:41 AM
Tire pressure on Tahoe / tow vehicle luvrque Towing and Tow Vehicles 2 03-31-2009 05:41 PM
tire pressure fiveaday Sunline Travel Trailers 6 03-26-2009 06:43 AM
tire pressure increase Hematite Sunline Community 2 06-25-2008 04:51 AM
Tire Pressure Both2Retired Sunline Community 5 05-26-2008 07:01 PM


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Sunline RV or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 03:20 AM.


×