Tire Pressure On Larger Tires?

[Mr._Bill]

Wow...what the hell did I post LOL -

I never had any intention of going with 80psi...but I never had one that high...so wasn't sure where I would end up. I guessed 38 and will be doing the chalk test from this point.

Thanks Everyone...I think

You're fine. Sometimes it's better to provide too much detail. People tend to make assumptions based on the literal text, while others will read a lot into it based on their experiences, which can provide some interesting replies.

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[TennesseePA]

Relax. It's only going to affect the ride and fuel economy, not blow the truck up.

He's not running stock tires, and didn't say what he put on it. 65psi will ride better than the 80psi he reported. The MAX PSI is a starting point to go DOWN from, if you don't know what else to do. If the OP knew what to do, he wouldn't be posting here. I never said my suggestion was best, just that it's an option.

By the way, You should learn more about your target, before you start throwing insults. People pay up to $150/hr for my advice, and have been doing so for a very long time.

I’m not going to hurl any insults but if a person was to inflate the tires to 80 PSI and then drive it it would be very very dangerous. At that PSI the tires will be so rigid that they will be unable to maintain contact with the road. I am assuming that the $150/hour is for advice on subjects that you have spent years studying. My 37 inch KO2s are inflated to 27 PSI cold. They will go up to 30-31 as I drive.

 

[Mr._Bill]

I’m not going to hurl any insults but if a person was to inflate the tires to 80 PSI and then drive it it would be very very dangerous. At that PSI the tires will be so rigid that they will be unable to maintain contact with the road. I am assuming that the $150/hour is for advice on subjects that you have spent years studying. My 37 inch KO2s are inflated to 27 PSI cold. They will go up to 30-31 as I drive.

Driving at 80psi can be dangerous, but it depends on the tire, the vehicle, and the load. If the tires are rated to handle 80psi, it can be done safely, unless the vehicle is not designed to run with those tires, or is running with no load on them.

The stock tires on my Jeep are only rated for a MAX of 44psi. To try and run them at 80psi would be extremely dangerous. The wording from the OP led me to believe that he had tires rated for 80psi, and that was what he had them filled to. Going down from there, as I suggested, would be a good thing.

And, no, I don't charge for automotive advice.

 

[WildJD]

I face a double whammy... I live in the Mountains outside of Santa Fe (NM) at 8500ft. Not only do we wake up to low temps, lowering psi, but altitude also lowers psi. So, on a cold morning, I start off with 29 psi, which is fine for our dirt roads and snow (offgrid wilderness cabin) getting to a paved road. When I do hit the pavement, the speed and heat raise the psi to 32, 33... then when I go down (in altitude) to Santa Fe or Albuquerque, it rises to 34, 35... and when I hit the low country interstates, it goes up to 36, 37!
Course, when I picked it up from the dealer, psi was 45 cold and 48, 50, at hiway speeds... (just a little floaty on the pavement)! I only drove a mile or two before pulling into a Walmart and airing down! ;{

 

[bgenlvtex]

I face a double whammy... I live in the Mountains outside of Santa Fe (NM) at 8500ft. Not only do we wake up to low temps, lowering psi, but altitude also lowers psi. So, on a cold morning, I start off with 29 psi, which is fine for our dirt roads and snow (offgrid wilderness cabin) getting to a paved road. When I do hit the pavement, the speed and heat raise the psi to 32, 33... then when I go down (in altitude) to Santa Fe or Albuquerque, it rises to 34, 35... and when I hit the low country interstates, it goes up to 36, 37!
Course, when I picked it up from the dealer, psi was 45 cold and 48, 50, at hiway speeds... (just a little floaty on the pavement)! I only drove a mile or two before pulling into a Walmart and airing down! ;{

Your application is a good argument for nitrogen, which will not demonstrate the pressure gain/loss at altitude and temperature fluctuation. This and the lack of combustibility are why it is used in aircraft tires.

 

[Deleted member 24603]

Wow...what the hell did I post LOL -

I never had any intention of going with 80psi...but I never had one that high...so wasn't sure where I would end up. I guessed 38 and will be doing the chalk test from this point.

Thanks Everyone...I think

I'm replacing the stock 33's on my Gladiator with 35's this Friday and have pondered the same question as to what pressure to run them at. After some google searching I found information from Toyo Tires website on using Load Inflation Tables (see attached pdf) to replicate the stock tire load capacity when installing larger aftermarket tires. Long story short, I will probably end up between 30-35 psi for my new tires vs. 37 psi for the stock ones, and will "chalk test" as well to settle on a final psi.

 

[Godfadr]

I'm replacing the stock 33's on my Gladiator with 35's this Friday and have pondered the same question as to what pressure to run them at. After some google searching I found information from Toyo Tires website on using Load Inflation Tables (see attached pdf) to replicate the stock tire load capacity when installing larger aftermarket tires. Long story short, I will probably end up between 30-35 psi for my new tires vs. 37 psi for the stock ones, and will "chalk test" as well to settle on a final psi.

Chalk Test put me at 34-37.

 

[SleepyJeep]

Chalk Test put me at 34-37.

Thank you for finally putting a recommended number range for stock tires. All this discussion and I was looking for a recommended figure without having to do this chalk test :P. I am assuming a chalk test is when you draw a line on each tire with a chalk and make sure it is all erased after driving for a few yards?

I drove to Boston for thanksgiving with 39 PSI and it was pretty comfortable but I did notice that it went all the way up to 42 after a few hours of highway driving and then it started dropping down when the weather was cooler etc. I really didn't know that so many environmental factors affect tire pressure right away including the expansion of air in the tires from long drives etc...

I was looking for an optimal tire pressure number on stock Gladiator LEs to get the best mileage. I get 16.5mph LOL. Idk how some ppl are getting 19mph+ tbh.

 

[WXman]

I usually work off percentages. My new tires are rated at 3195 lbs each @ 65 PSI. The weight of my truck will only use 40% of this capacity. So, I'll inflate the tires to 40% of their max capacity. This works out to 26-28 PSI. From prior experience, 28 PSI seems to be great for even treadwear so that's cool.

 

[Reasons]

I'm replacing the stock 33's on my Gladiator with 35's this Friday and have pondered the same question as to what pressure to run them at. After some google searching I found information from Toyo Tires website on using Load Inflation Tables (see attached pdf) to replicate the stock tire load capacity when installing larger aftermarket tires. Long story short, I will probably end up between 30-35 psi for my new tires vs. 37 psi for the stock ones, and will "chalk test" as well to settle on a final psi.

Just did the chalk test this evening in my Rubicon with stock 33" Falkens. I ended up with 32cold/34warm. Chalk showed even wear throughout the width of the treads.

Prior to chalk test I was running 34cold/36warm. 1/4" to 1/8" of tread on the outer tires were not contacting the ground at 36 psi when warm.

 

[jrf]

Just did the chalk test this evening in my Rubicon with stock 33" Falkens. I ended up with 32cold/34warm. Chalk showed even wear throughout the width of the treads.

Hmmmm... again I say...pretty sure that 37psi cold is to help increase fuel mileage....at the cost of uneven tire wear. Good to see pretty much everyone coming up with the same conclusions after actually testing or calculating the proper pressures.

 

[WXman]

Hmmmm... again I say...pretty sure that 37psi cold is to help increase fuel mileage....at the cost of uneven tire wear. Good to see pretty much everyone coming up with the same conclusions after actually testing or calculating the proper pressures.

Yep purely a fuel efficiency move on FCA's part, just like the magical switch to 0W20 oil.

 

[ShadowsPapa]

How many know that you can get really close on the weight of your Jeep just by using your tires to weigh it?
Seen it done, tried it myself a few years back. Some tires work better than others for that purpose, but still, it does work and you can get really close.

>> just like the magical switch to 0W20 oil.<< Yup.

 

[Reasons]

Hmmmm... again I say...pretty sure that 37psi cold is to help increase fuel mileage....at the cost of uneven tire wear. Good to see pretty much everyone coming up with the same conclusions after actually testing or calculating the proper pressures.

I need to do more testing for sure with regards to fuel economy. However, when I was running my tires at 36psi, my fuel avg was around 18mpg driving to and from home/work. I always reset both trip and avg fuel menus when I fill up.

Anyways, in just a few days of driving at 33/34psi to and from home/work, my fuel avg still is at 18mpg. I'll give it two fill ups until I come to a conclusion but I predict I wont see any difference. We shall see.

 

[ShadowsPapa]

I did the "chalk test" on my STOCK OVERLAND TIRES. I tried both methods - checking the concrete and checking the tires after a longer drive. At 38 psi the line seemed to go side to side, not more in the center. It was once again cold and windy and my chalk isn't the best but driving a few feet the lines disappeared off the tires all across the face. Nothing left. And after just going a very few feet, say two or three rotations, similar, the impact of the tires on the pavement was pretty much the same edge to edge. COULD be a teeny bit less on the outer .15" of the tires, but that would be about it.
I checked all 4 this way, same results.

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