What pressure for towing?

Nick1994

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Tomorrow my brother and I are picking up a Jeep Cherokee and towing it on a Uhaul car hauler trailer behind a 2002 Chevy Trailblazer LTZ. Trailer weighs a little over 2,200 pounds and the Jeep weighs 3,500 pounds with at least probably 200 pounds of extra parts and wheels and tires in it. Trailblazer is rated to tow 5,900 pounds according to the owners manual whistle Tires are 245/65-17 Michelin Cross Terrains. I believe it says 35 psi max on the tires but what I've always done is pump them up to 40 psi and refill them once a year, they ride extremely smooth and quiet and handle great at this psi. So what do you guys recommend for psi on these tires? I can always pump them up for the tow then lower back down for regular driving. Even 40 psi with just the Trailblazer makes them "look real low" Thanks
 
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What does GM recommend for PSI? If the tire says 35 PSI max..duno why you would exceed that...thats also a very low max inflation pressure...if you have them at 40 now..and they work well..keep pressure the same.
 
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Alberta, Canada
If the vehicle is rated to tow 5,900lbs, then it's rated to tow that on the stock tire PSI listed in the door jamb. No need to over think this and try to re-engineer the vehicle. Double check your fluids, trailer connections and lights, and cargo is tied down safely. Good luck with the new jeep
 
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South Florida
I've never seen a tire with a max inflation pressure of just 35 pounds. They are usually at least 44 pounds max. When I was in the police academy, they had us drive two different patrol cars through the driving obstacle course. Once car had 20 psi in the tires and one car had 45 psi in the tires. The one with 20 psi was flat out dangerous to drive, non responsive, etc. It was a big eye opener on the impact of tire pressure on the handling of a car. I would rather go slightly over pressure, especially while towing, then under pressure. Much better margin of safety and better handling. As far as door jamb pressure vs pressure listed on the side of the tire, if the car calls for 32 PSI, that is with the factory tires ONLY. If you change the tires, you will have to adjust up or down for the new tires.
 
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The XJ with the extra stuff inside will weigh about 4K. Just be careful as you'll be a tad over - and X2 on checking the rental trailer tires.
 
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Washington St.
The tow ratings seem to be set my the marketing department, not the engineering department. Be careful. Test the trailer's brakes as soon as you load it. Get rolling, then apply the SUVs brakes moderately hard. You should feel the trailer pulling back on you as its hydraulic surge brakes work. If you don't feel it, exchange it for trailer with working brakes. Air up your tires to the sidewall max. The extra pressure over the sticker pressure often gives more stability when towing. Also watch the U-Haul guy check the pressure in the trailer tires--sidewall max as well.
 
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Trailer tires should be set to the number on the sidewall. I'd bump the tow vehicle pressure, but I like higher pressure unloaded in the first place. I'd probably like it more while towing.
 
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i read somewhere that tongue pressure=10-15% of towed weight. So if you're towing 4000lbs, that's like the equivalent of say ~500lbs. Do you also have a load or backseat passengers in in the cherokee's rear as well? shift that to the trailer if you can. I think a few psi over the "base" door recommendation will be a fine compromise, and your owner's manual might say so too. Doublecheck the sidewall. if the tire says 35 though, the only prudent advice would be to obey that and only run 35 in the rear. Michelin probably had a good reason to put 35max and lower it from a more typical 40+ number; With the front, maybe you can set that to the door specs, so what does that get you? 32front, 35rear. If you're going to ignore specs, just do do whatever you want; Take a good look and see if you're just fishing for validation for what you want to do; and not really requesting unbiased advice.
 
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Originally Posted By: bubbatime
As far as door jamb pressure vs pressure listed on the side of the tire, if the car calls for 32 PSI, that is with the factory tires ONLY. If you change the tires, you will have to adjust up or down for the new tires.
Are you serious? spank
 
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Originally Posted By: bubbatime
......As far as door jamb pressure vs pressure listed on the side of the tire, if the car calls for 32 PSI, that is with the factory tires ONLY. If you change the tires, you will have to adjust up or down for the new tires.
Sorry, but that is an old wives tale. While different tires give different ride and handling characteristics, the inflation pressure listed on the vehicle tire placard is about load carrying capacity - and the pressure listed there is applicable for ALL tires of the same size listed. Side note to bubbatime: One reason the 20 psi tires did so badly was that they were "saturated" - that is, they were operating at the limit of their load carrying capacity, and tires don't perform well under that condition. Had the tires been inflated according to the vehicle tire placard, they would have felt a lot better. Sure, adding MORE inflation pressure does make them FEEL even better (crisper turn in, more responsive), but the difference would not have been as dramatic (which, I assume is why they did it the way they did it.)
 
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Originally Posted By: The Critic
Originally Posted By: bubbatime
As far as door jamb pressure vs pressure listed on the side of the tire, if the car calls for 32 PSI, that is with the factory tires ONLY. If you change the tires, you will have to adjust up or down for the new tires.
Are you serious? spank
100% serious. Just because you car calls for 28 psi on FACTORY TIRES, does not mean that the car will be safe to drive at 28 PSI with new replacement tires. There are too many variables in replacement tires. You might as well spank yourself for chastising me, because I am 1000% correct on this. I know my stuff. I'm usually one to recommend factory door jamb pressures for most cars with factory tires, but I have seen with my own eyes and driven a few cars myself that were unsafe to drive with factory door jamb pressures. Some aftermarket tires have soft squirrelly sidewalls. The engineers do a good job of recommending a good PSI, but they only test ONE OEM tire combination. They don't bother testing every type and brand of tire out there.
 
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When i tow, i run 2 pounds under the max cold pressure on the tire sidewall. This keeps the back of my truck feeling tigher when i turn. i run an equalizer wd hitch.
 
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Originally Posted By: bubbatime
.......The engineers do a good job of recommending a good PSI, but they only test ONE OEM tire combination......
Sorry, but there are multiple tire manufacturers competing for the business, so the ride engineers at the OEM's ride all the candidates. From that ride and handling evaluation and a few other things, the particular tire (and therefore the manufacturer, make, and model) is decided. Sometimes the selection has more to do with availability than the actual engineering evaluation.
Originally Posted By: bubbatime
...... They don't bother testing every type and brand of tire out there.
That, of course, is impossible. But having said that, they do test more than one and the fundamental difference is in the way the tires ride and handle. So while you felt uncomfortable with the handling of several particular tires, that had to do with the particular characteristics of that tire. That, of course, is your personal preference. Others would disagree. My personal preference is for a more crisp steering feel, and I'm willing to sacrifice ride harshness to get it. Usually that means more inflation pressure, but it could also mean selecting a tire with a stiffer sidewall. But that doesn't mean the OEM inflation pressure specification is faulty in some way. But the one thing that is true about the OEM tire inflation pressure specification is that it is adequate for handling the load the vehicle was designed to carry. THAT is THEE most important thing about that specification. You could say the same thing about the springs or the shocks. Those could always be tailored towards better handling and away from a soft ride - but that doesn't mean the OEM specification is faulty.
 

OVERKILL

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Originally Posted By: bubbatime
Originally Posted By: The Critic
Originally Posted By: bubbatime
As far as door jamb pressure vs pressure listed on the side of the tire, if the car calls for 32 PSI, that is with the factory tires ONLY. If you change the tires, you will have to adjust up or down for the new tires.
Are you serious? spank
100% serious. Just because you car calls for 28 psi on FACTORY TIRES, does not mean that the car will be safe to drive at 28 PSI with new replacement tires. There are too many variables in replacement tires. You might as well spank yourself for chastising me, because I am 1000% correct on this. I know my stuff. I'm usually one to recommend factory door jamb pressures for most cars with factory tires, but I have seen with my own eyes and driven a few cars myself that were unsafe to drive with factory door jamb pressures. Some aftermarket tires have soft squirrelly sidewalls. The engineers do a good job of recommending a good PSI, but they only test ONE OEM tire combination. They don't bother testing every type and brand of tire out there.
I'll defer to CapriRacer's expertise on this issue (he replied in the post above yours) as he designs tires for a living.
 

OVERKILL

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Originally Posted By: Miller88
I'm sure a 90s Explorer, towing it's rated 5000 pound will be completely safe with 26PSi in the rear tires ...
I believe this applied primarily to the 1st gen Explorer SUV (not to be confused with the Explorer version of the F-150), which replaced the Bronco II, as the 2nd gen, (96+) although first carrying the same spec, was revised. My '97 spec'd 30/30 according to the placard, though I know Barry's site shows a '98 placard that has the 26 on it so perhaps there was some overlap? shrug The Explorer Sport was the one involved in most of the roll-over incidents IIRC. It indeed had a towing capacity of 5,000lbs, whilst its V8 4-door sibling had a capacity of 6,700lbs. Both in 2WD configurations of course. Capacities taken from this manual (1996): http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/96expog1e.pdf The Explorer sport with its short wheelbase was somewhat like a Tracker or Jimmy; it was a lot sketchier than its 4-door siblings. I towed right up to the max capacity with my '97 (think 22' antique boat on a tandem) with no issues. But as I said, it spec'd the higher pressures.
 
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If you had an Explorer with an OEM recommendation of 26 psi, that was revised under recall to 30 psi and the tire pressure recommendation placard was replaced with a new one. Had a '97 Explorer that was the case on. So, no, I wouldn't feel comfortable towing at 26 psi, but I would at the OEM recommended 30 psi, which I did.
 
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