Tire pressure question

[gbpack]

Hi guys. We just put new tires on our tow vehicle (2015 Jeep Grand Cherokee 4x4) and I have a question about what tire pressure (cold) I should have in them when towing our 21BHS. The tires are Yokohama Geolander GO55 P265/50 R20 and they are rated for max load of 2,403 lbs (each) which is much better than the original tires and they have a better temperature rating as well (A). The max cold tire pressure is listed at 50 lbs but I think I should run them at 40 lbs cold. I suppose I could put a little more air in them if you feel that's prudent, but I don't want a rock hard ride when towing as even now (at 40) they already have a stiffer ride than the originals. Leaving for the Maine trip tomorrow morning. Your thoughts?

[PYG RYDR]

Hi guys. We just put new tires on our tow vehicle (2015 Jeep Grand Cherokee 4x4) and I have a question about what tire pressure (cold) I should have in them when towing our 21BHS. The tires are Yokohama Geolander GO55 P265/50 R20 and they are rated for max load of 2,403 lbs (each) which is much better than the original tires and they have a better temperature rating as well (A). The max cold tire pressure is listed at 50 lbs but I think I should run them at 40 lbs cold. I suppose I could put a little more air in them if you feel that's prudent, but I don't want a rock hard ride when towing as even now (at 40) they already have a stiffer ride than the originals. Leaving for the Maine trip tomorrow morning. Your thoughts?

I would check with the dealer who installed your tires, or Google Yokohama website for their towing tire pressure recommendations.

I read somewhere when carrying loads, one should run the maximum pressure, which run cooler than lower also. 

I understand your thinking with running 40 pounds, but I am concerned that lower pressure may cause your tires to overheat.

And if under-inflated, the sidewalls will not function properly and will negatively effect stability. 

More professional recommendation is needed.

[gbpack]

Thanks. I just increased them to 45psi to be closer to the max. They will heat up once on the road and the pressure will increase by 3-4 pounds so I'm thinking I'll be good at 45, but always interested in hearing additional thoughts!

[PYG RYDR]

And check the recommended tire pressure on your door frame, and use that as the base.

[gbpack]

And check the recommended tire pressure on your door frame, and use that as the base.

Won't that apply to just the original tires (which had a lower suggested psi)?

[Merlin]

I assume your '15 JGC Ltd came with the Goodyear Fortera in the same 265/50-R20 size and the recommended inflation on the door jamb is 36psi. The new GO55 in that size has the same (51 vs. 50 PSI) maximum pressure, so it's not an E rated heavy duty tire. It has a higher load rating at the maximum pressure (by 390 lbs), so it's a XL tire instead of a SL tire like the Fortera.    I'm in a very similar situation and decided to increase the tire pressure by about 10% to account for the stresses and loads of towing, so I'm going from 33 to 37 psi. If you did the same, you'd be about 40 psi. With that heavier construction tire anything from 36 PSI and up will be safe, but it may be an unbearably harsh ride at 50 psi and your handling, braking, and wear would likely be affected.

Here are some additional things I've learned from another person who knows tires and inflation.

First, the recommended cold pressure on the door jam is a safe operating pressure for the original equipment tires up to the load capacity of the vehicle. Increasing the tire pressure will not increase the load capacity of the vehicle.

The maximum tire pressure on the sidewall is the safe maximum for that tire and accounts for the increase in pressure when the tire heats up. Increasing the tire pressure over the number on the door jam up to the maximum is possible, but ride, handling, braking, and wear will be affected.

Don't reduce the pressure of a hot tire, even if it's over the maximum on the sidewall, assuming the tire was inflated properly when cold.

Changing tire size or construction results in a new inflation minimum and should come from the  tire manufacturer, which has tables of pressures for most vehicles.

And finally, trailer tires are different, always run them at the maximum cold inflation pressure listed on the sidewall.

[gbpack]

Thanks Merlin. That is very helpful. We are on the road now and the ride (at 45psi cold) is not too bad. We are loaded up a bit heavier than usual for this trip and the tongue weight on the back end of the Jeep is up higher than what it usually is, so I'm glad that I've got a little extra pressure in the Jeep tires. Thanks again for your help and we look forward to seeing you soon in Maine!

[PYG RYDR]

Merlin,

Thanks for the information regarding tow vehicle tire pressures. 

My door jam indicates 32 for front and rear tires.  I set the front tires for 32 and 35 for rear-10% increase.  My experience while towing was there was less sway and seamed a little more stable.  And when not towing, the extra air pressure is readily noticed with a harder/harsher ride.

And I always set the camper tires at maximum number on the tire.

Regards,

Galen

[Capt J-rod]

I keep mine just under max cold. This is 45 psi on my Michelins. The door jamb says 35. It puts a large belly in the side of the tire. The tire shop always gets mad and says they're over-inflated, but the wear pattern doesn't indicate a problem. I got 65000 out of my first set. I plan to change the trailer tires next spring. I just can't feel good about china's cheapest tire on my rig. The new goodyears are looking promising.

[charliem]

.......The door jamb says 35. It puts a large belly in the side of the tire. The tire shop always gets mad and says they're over-inflated, but the wear pattern doesn't indicate a problem.

In my experience tire shops know nothing about tire inflation other than to read the door jamb sticker. That sticker is for the EXACT size tire (diameter, width, height), construction (radial/bias) and category (p-metric/LT). They do not understand that an LT tire must be inflated more than a p-metric passenger tire to properly carry the load. I've argued with them 'till I realized my waste of time and elevated BP. There are several good articles on the web that deal with this. In the end, if the wear pattern is good and the tire life is good I'd say you're good  .

[PYG RYDR]

Nosing around the internet and found this article: http://www.rvtiresafety.net/2017/02/tow-vehicle-tire-question.html

Of note is this author agrees with Merlin in using the 10% increase.

And a lot more info:  http://www.rvtiresafety.net/search/label/Cold%20Inflation

[Merlin]

I keep mine just under max cold. This is 45 psi on my Michelins. The door jamb says 35. It puts a large belly in the side of the tire. The tire shop always gets mad and says they're over-inflated, but the wear pattern doesn't indicate a problem. I got 65000 out of my first set. I plan to change the trailer tires next spring. I just can't feel good about china's cheapest tire on my rig. The new goodyears are looking promising.

45 psi all the time instead of 35 psi on stock size/type tires? I wonder about the braking and handling at that pressure? The 4X4 crowd airs down (to 15-20 psi) to aid traction off road. Airing up (about 25% over in your case) would have the opposite effect and reduce traction from a smaller contact patch. Ever have any skidding or frequent ABS activation? The sidewalls of radial tire are designed to flex, so I would not inflate to get rid of the "bulge". If it works ok on your Sequoia, cool, but I would not routinely recommend everyone use 25% over-inflation as the base tire pressure.

[Capt J-rod]

I've never seen any change in wet, snow, or dry performance. I do run Michelin LT2 tires. They are expensive. A set costs just shy of $1200. I my experience there is no better tire. I tried coopers on my tacoma. They are OK but I like the Michelins better. I know you are supposed to run the door jamb specs, and if I'm not towing it is fine, but with the tongue weight you can see a big difference between front and rear bulge at 35psi. The ride does suffer, but it's not really that noticeable. These are very large 18" tires with a large road surface. On a narrower smaller tire I think you are very correct. We are worried about 10Lbs of air when every day I see people pass me doing 75mph on bald flat tires that are barely keeping the rim off the road LOL. I think the most important thing is to check the air before we travel. Aluminum rims leak a lot more than steel in my experience, so be sure to check them especially after storage.

[Steve Sanders]

On my Quicksilver 6.0 I run about 35 PSI in the tires. Since those tires are rated to carry up to 1,750 pounds (each) at the max PSI of about 60, but the loaded camper only weighs about 1,000 pounds, the tires are only loaded to about 30% of their capacity. Inflating to max pressure with that little load tends to make the trailer quite bouncy.

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