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What is the thinking regarding increasing rear wheel tire pressure when towing ? In my case the trailer is about 3000# with a tongue wt of about 400#. Thanks.
 

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What is the thinking regarding increasing rear wheel tire pressure when towing ? In my case the trailer is about 3000# with a tongue wt of about 400#. Thanks.
I tow a similar weight Jayco travel trailer and run 35 pounds (18 inch wheels) all around, regardless whether I'm towing or not. 35 pounds is Subaru's recommended pressure for 18 inch wheels.
 

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When towing #4800 and over on max payload by maybe 100# I used about 50 pounds in the rear and about 40 in the front and monitored the tire temps with a thermo gun. This was on a trip over 1,300 miles.
I was looking for the best MPG and least amount of strain on the CVT.
 

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It appears to me that Subaru does not provide tire pressure recommendation based on different loading conditions. So why is it necessary to increase the tire pressure? Or why 33psi (cold), suggested by the sticker at the door jamb, is not sufficient for 500lbs tongue load? In a different case scenario, when the car payload is maxed out (e.g. no towing; load it w/ 8 adults and bunch of traveling stuff on roof and cargo), should we change the tire pressure, too?
 

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The door jamb psi reading will definitely meet the load needs of the tire for the max load the car can carry (including tongue weight). Obviously do not go below it, but you can go above it a bit for some cushion or to increase mpg. Go too far and you'll make your ride more skittish and wear the center of your tire too quickly.

I'm personally running 35psi.
 

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I've found the handling to be wobbly with the pressure at 35 and towing at max levels. I felt like i could make a better evasive maneuvers with higher tire pressure as it was more sure footed when making fast lane changes and taking off ramps at higher speeds....although i'm not if the tires would lose traction easier, but that could also help avoid traction rolling the whole rig...who knows.

My biggest concern was tire temp as that is where most catastrophe tire failures come from and found the tire ran slightly cooler with higher pressure. I've had several trailer tires blow out and one front car tire blow out at highway speed and it's made me a bit OCD on tires and pressures.
 

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All my vehicles when towing I bump the rears only!

When you put heavy trailer weight on the rear of any vehicle you can get light front end steering and in some cases impact front tire grip.

Upping the front tire pressure will increase the lightening effect thus be a negative performance change.

Bump the rears by 5-8lbs max with any heavy packed situation so that your rear tires continue to wear evenly. If you pack heavy or tow and are under inflated the outside shoulders of the tire will see heavy wear especially on hot pavement summer trips.
 

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When we tow our travel trailer I set the rears at 40psi sometimes 42-44. What I noticed at 33 psi is they heat up much more and the pressure goes up on it's own 4-5 psi, so starting at 40 psi I usually only see an increase of 1-2 psi if any. I dont mess with the fronts.
 

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FOR OEM TIRES:
Tire pressures for OEM tires on OEM rims should be the same as what you use for normal driving. Please refer to the sticker on the B-Pillar driver's side. It will be:
  • 20": 32psi or 33psi
  • 18": 35psi
If you drive with an upwards adjusted tire pressure of 1-2psi, you can leave it like that. If you drive underinflated to make your ride softer, then please properly inflate your tires to the specs on the door pillar. There is no need to overinflate or underinflate your OEM tires to tow. All tires have load carrying capabilities at certain inflation, and, the Falkens on the Ascent are designed to carry the full tongue weight and full cargo capacity of the Ascent (that's a combined figure, btw, as tongue weight is part of cargo capacity) at the inflation numbers on the door pillar.

FOR AFTERMARKET TIRES:
You may wish to consult with the manufacturer. They will have a load carrying chart.

The figure to use will be the Ascent's maximum GAWR, which is GAWR-R. Remember, the Ascent is supposed to be rear loaded (and not load distributed with a weight distributing hitch), so, even though the Ascent is normally near perfectly balanced front to back, when towing, the weight is designed to sit on the rear. Thus, the rear axle has the higher max weight rating. It is 3,296 pounds. That means each tire must be able to carry 1,698 at whatever tire inflation (plus I like a safety margin).

SUMMARY:
For the stock tires, you do not need to over-inflate the tires, and should be running at OEM designated pressures. And, for non-OEM tires, if you picked a properly load rated tires for the Ascent (which in my opinion includes a decent safety margin, meaning 102 rated or better), then, in general, you probably don't need to over-inflate your Ascent's non-OEM tires either, but you should check with the tire manufacturer.
 
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