Tire pressure recommendations??

[GoingPostal]

I'm running LT285/70R17 on my '21 RHD (Sport S with the steering wheel on the wrong side for anyone unfamiliar), and I can't seem to keep my rubber from cupping. I've dutifully kept my last set at 32-34 PSI cold, and while I feel like they may be wearing *slightly* more evenly across, my MPG has tanked and they're still wearing faster in the middle of the tire than on the shoulders. I went from a comfortable 19-20mpg on my mail route to 16-17mpg on a good day. Some other folks on different forums have recommended a higher PSI - even as high as 50 - but that just feels like it's too high? Especially considering the base 245/75R17 is supposed to be run at 38 PSI...

Can anyone who is running a similar setup recommend a good PSI to encourage even treadwear? 2/3 of my miles are on some pretty awful gravel roads, and I'm currently sitting on BFG T/A Ko2s, if that helps to influence your advice at all. Sorry if this is a super newbie question; just getting tired of throwing out $1200 on new tires every 6 months when the obvious issue is tire pressure... just not sure which direction my numbers need to be going at this point.

TIA!

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[autotragic]

I'm running LT285/70R17 on my '21 RHD (Sport S with the steering wheel on the wrong side for anyone unfamiliar), and I can't seem to keep my rubber from cupping. I've dutifully kept my last set at 32-34 PSI cold, and while I feel like they may be wearing *slightly* more evenly across, my MPG has tanked and they're still wearing faster in the middle of the tire than on the shoulders. I went from a comfortable 19-20mpg on my mail route to 16-17mpg on a good day. Some other folks on different forums have recommended a higher PSI - even as high as 50 - but that just feels like it's too high? Especially considering the base 245/75R17 is supposed to be run at 38 PSI...

Can anyone who is running a similar setup recommend a good PSI to encourage even treadwear? 2/3 of my miles are on some pretty awful gravel roads, and I'm currently sitting on BFG T/A Ko2s, if that helps to influence your advice at all. Sorry if this is a super newbie question; just getting tired of throwing out $1200 on new tires every 6 months when the obvious issue is tire pressure... just not sure which direction my numbers need to be going at this point.

TIA!

Sounds like your pressure is still too high.

 

[Nokones]

If you are cupping, it is not an air pressure problem, could be a wheel balance issue. But, I wouldn't overlook your suspension components, Bushings, alignment, and/or shock.

Cupping is a result of the wheel/tire oscillating and the shock(s) is/are not controlling it.

 

[GoingPostal]

Sounds like your pressure is still too high.

So, I'll have to sacrifice even more MPG just to have a bit of poke, and have something nicer to look at than the factory '21 wheels? Ffs.

 

[GoingPostal]

If you are cupping, it is not an air pressure problem, could be a wheel balance issue. But, I wouldn't overlook your suspension components, Bushings, alignment, and/or shock.

Cupping is a result of the wheel/tire oscillating and the shock(s) is/are not controlling it.

Suspension was in decent shape when I mounted my first set of oversized tires (~62,000 miles), and they still cupped like hell - but I was also running those tires at 38psi like the door sill sticker recommends, because I didn't know any better.

That being said, I'm still willing to concede that my shocks need replacing, and I'm currently waiting on a quote to replace my drag link, since it's got some slop in the ball joint at the spindle and pitman arm. Not fully willing to rule out suspension issues, but I think it goes deeper than just shit shocks.

ETA: I also don't fully trust the shop that did my last mount/balance. My wheel weights are double stacked, and look rather hastily slapped on.. but this issue was also an issue before this shop ever laid their hands on my Mailcrawler.

 

[autotragic]

Suspension was in decent shape when I mounted my first set of oversized tires (~62,000 miles), and they still cupped like hell - but I was also running those tires at 38psi like the door sill sticker recommends, because I didn't know any better.

That being said, I'm still willing to concede that my shocks need replacing, and I'm currently waiting on a quote to replace my drag link, since it's got some slop in the ball joint at the spindle and pitman arm. Not fully willing to rule out suspension issues, but I think it goes deeper than just shit shocks.

He also said he's wearing out the middle of the tread and has uneven tire wear...

I think he'd be better off with different tires and his Jeep could probably use some suspension TLC.

 

[azwjowner]

So, I'll have to sacrifice even more MPG just to have a bit of poke, and have something nicer to look at than the factory '21 wheels? Ffs.

Yeah. Here's the thing: I'm pretty sure the reason Jeep specifies 37 PSI for the tires is because LT tires aren't officially rated below 35 PSI (because they're for heavy trucks). So Jeep can't officially have them below 35 PSI (plus some margin for TPMS).

But if you actually look at the weights that the tires can support, per manufacturer load charts, LT285/70/17 is rated at 2,105 pounds per tire at 35 PSI. Your Jeep doesn't weigh 8400 pounds. You can go lower.

Flotation size tires (the ones measured in inches) have charts down to 25 PSI, and those charts + extrapolation to similar metric tire sizes, plus decades of people's experiences with various tire pressures would suggest around 28-30 PSI for 285/70/17 tires.

I run smaller tires than you - 255/75/17 and I have them at 32 PSI cold on my 2 door, for reference, and they're great. The larger the tire, the greater the volume of air, the lower the pressure needs to be to support the same weight.

To answer your gripe, yes, this is one of the reasons why I run the narrowest tires possible -- I want to maintain MPG. Wide heavy tires give bad MPG.

Do lots of people run your size at 35 PSI or higher? Yes. But they have accelerated center wear, loss of traction for emergency maneuvers (because less tread is making contact), and twitchier steering. I'm always of the opinion that running giant tires (some people really overinflate their 35s and 37s) on the middle of the tread is just silly. If you don't like the MPG hit, don't run bigger tires, but don't overinflate a large tire to try to improve MPG. But that's just my personal opinion.

You will have less MPG at lower pressure, but the wear should be more even, so your tires will last longer.

It sounds like you drive a lot for your postal duties. I wouldn't use 285/70/17 tires -- 255/75/17 (32.1") will give you better mileage. Alternatively, if you just want longer tread life given all your gravel roads, try the BFG HD Terrain A/T KT in 285/70/17 -- it's an E rated tire, might have a touch less MPG and comfort, but they are a harder rubber compound for oil-field trucks and the like and will last you much longer. However, they aren't 3 peak rated like the KO2/KO3 so it would not be a good choice if you face snow conditions.

Also, worn shocks will definitely cause cupping, so get those checked.

 

[NPC 20883467]

Two words: Chalk Test

The factory recommendation of 36-40 psi is absurd, and is probably the cause of a lot of premature suspension wear.

That said, I have 285/65/R17s, load range 'E' Cooper AT3 LT tires on stock wheels. All stock suspension. Close to 80% of my driving is on gravel or fire/logging roads. The chalk test indicated to me that I need to be in the 20-25 PSI range. The 20psi is what I normally air down to on the gravel, and only go to 25 if I'm planning a long stretch on the highway (20 psi is a little squishy in the turns). 20K miles later and I have no abnormal wear patterns, and I expect another 10K miles before I need to replace.

 

[2nd 392]

Two words: Chalk Test

The factory recommendation of 36-40 psi is absurd, and is probably the cause of a lot of premature suspension wear.

That said, I have 285/65/R17s, load range 'E' Cooper AT3 LT tires on stock wheels. All stock suspension. Close to 80% of my driving is on gravel or fire/logging roads. The chalk test indicated to me that I need to be in the 20-25 PSI range. The 20psi is what I normally air down to on the gravel, and only go to 25 if I'm planning a long stretch on the highway (20 psi is a little squishy in the turns). 20K miles later and I have no abnormal wear patterns, and I expect another 10K miles before I need to replace.

Yep- for the OP

 

[Nokones]

I am running Mickey Bajas LT315-70-17 Load Range E on Method 106 Beadlocks at 37 PSI and I have 6,000 miles on the tires and I have a little more rubber in the center treadblock than the outsides. I may increase to 39 PSI square.

For the trail, I air down to 10 PSI. It only takes no more than 8-10 minutes to air up all four tires back to 37 pounds.

 

[au176]

I'm running LT285/70R17 on my '21 RHD (Sport S with the steering wheel on the wrong side for anyone unfamiliar), and I can't seem to keep my rubber from cupping. I've dutifully kept my last set at 32-34 PSI cold, and while I feel like they may be wearing *slightly* more evenly across, my MPG has tanked and they're still wearing faster in the middle of the tire than on the shoulders. I went from a comfortable 19-20mpg on my mail route to 16-17mpg on a good day. Some other folks on different forums have recommended a higher PSI - even as high as 50 - but that just feels like it's too high? Especially considering the base 245/75R17 is supposed to be run at 38 PSI...

Can anyone who is running a similar setup recommend a good PSI to encourage even treadwear? 2/3 of my miles are on some pretty awful gravel roads, and I'm currently sitting on BFG T/A Ko2s, if that helps to influence your advice at all. Sorry if this is a super newbie question; just getting tired of throwing out $1200 on new tires every 6 months when the obvious issue is tire pressure... just not sure which direction my numbers need to be going at this point.

TIA!

There's a lot of good tire info in these responses. Start there.

Curbside delivery is tough on vehicles. More so if you do actual Rural out in the sticks. With your mileage, I'd definitely have someone go over the suspension.

And it won't help with your tires, but have you seen these?

 

[WranglerMan]

No running that size I have my BFG KO2 35’s at 28-30#

I initially was running 35# but after doing some chalk tests I down to 28 cold and 30-31 heated up and get super even wear but my MPG’s are at 17 on a good day

 

[Vinman]

2/3’s of your driving is “awful gravel roads”? You are going to chew through tires, there’s no getting around that.

 

[DogsRule]

Chalked mine by rolling over baking soda. Used my silicone water wiper and laid out a molecule layer. Very telling.

My 285's 4 ply P-rated tire on flat concrete run best at 29psi outside cold temp. Always lined up to run true. Never had anything but rail-like tracking. Not bragging cause its weekly maintenance.

 

[virkdoc]

Resurrecting this thread. New jeep to me 2022 Rubicon. Original owner upgraded it to 285/70/17 Yokohama Geolander AT.
In India the Rubi came with 255 BFGOODRICH MT.
So I filled in 37psi and damn the ride is hard and unsettling. It was running at 32-33 when I picked it up and was very planted. Now its kind of bouncy. What would be a good tire pressure be?

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