Perfect tire pressure may help with steering.

[Greenlane Overland Co]

Are you trying to decide what the best PSI is for the tires on your grenadier?

Whether you’ve outfitted it with rooftop tent and the kitchen sink, or you’re just picking up coffee at Starbucks.

Take your vehicle to a certified CAT scale and they will give you the axle weight for front and rear axle. ($13.50)

You can then divide the axle weight by two tires to see how much weight is on your tires. Then using the formula below, or the chart attached, you can determine the correct psi.

Running the correct PSI will make your vehicle smoother and more enjoyable to drive in a lot of cases. 

Tire Weight / Tire Pressure = Load Capacity Pounds per PSI

Tire Inflation Chart

www.yournexttire.com

 

[trobex]

I found after 3,000km that my steering just naturally become very smooth, and far less wandering than as new.

 

[bigleonski]

I’ve always worked roughly on the 4psi rule.
If your pressure (edited) after running on the highway is 4psi higher than it was cold, you’re on the money.

Unladen I’ve settled on 37psi cold all around and so far it feels good and stable. A little lower than I used to run in the 200, but it feels about right.

 

[[ Adam ]]

 

[bigleonski]

View attachment 7857628

Yeah I saw that, and I know it’s only 1 psi lower, but it just doesn’t feel right. Perhaps psychological, who knows.

 

[ecohen2]

So I have been trying to figure this out and actually sent Grenadier and email about it. The manual says 36 but the door jam says something considerably higher. I think it might make a difference on whether you have the KO or the less aggressive tires. I have the less aggressive and found with my limited mileage that 41 PSI gets good wear across the entire tire and it doesn't heat up on the highway. When they were pumped up to the door jam level and I was on the highway it felt like the tires were greasy and I could wag the back of the Grenadier without trying very hard. I got a high of 22 mpg on the highway and am getting high teens in town.

I agree with @bigleonski and that is what I see as far as temp gains. I am doing highway, in town and rough trails, nothing extreme..

 

[[ Adam ]]

So I have been trying to figure this out and actually sent Grenadier and email about it. The manual says 36 but the door jam says something considerably higher. I think it might make a difference on whether you have the KO or the less aggressive tires. I have the less aggressive and found with my limited mileage that 41 PSI gets good wear across the entire tire and it doesn't heat up on the highway. When they were pumped up to the door jam level and I was on the highway it felt like the tires were greasy and I could wag the back of the Grenadier without trying very hard. I got a high of 22 mpg on the highway and am getting high teens in town.

I agree with @bigleonski and that is what I see as far as temp gains. I am doing highway, in town and rough trails, nothing extreme..

Door jam is mandated by NHTSA, manual is the recommended tire pressure from Ineos based on load.

https://www.motortrend.com/features/the-inadequate-tire-pressure-sticker/

 

[ecohen2]

Door jam is mandated by NHTSA, manual is the recommended tire pressure from Ineos based on load.

https://www.motortrend.com/features/the-inadequate-tire-pressure-sticker/

Wow! I never knew that!

 

[DenisM]

I’ve always worked roughly on the 4psi rule.
If your temp after running on the highway is 4psi higher than it was cold, you’re on the money.

Unladen I’ve settled on 37psi cold all around and so far it feels good and stable. A little lower than I used to run in the 200, but it feels about right.

Are we talking temp +4 centigrade degrees or +4 psi?.... or both a temp and pressure increase?

 

[bigleonski]

Are we talking temp +4 centigrade degrees or +4 psi?.... or both a temp and pressure increase?

Now you’re just poking the bear!

 

[Clark Kent]

Are we talking temp +4 centigrade degrees or +4 psi?.... or both a temp and pressure increase?

I see your confusion @DenisM.

The rule is looking for a predicted 4psi rise because the tyre cavity temperature increases during operation. A 4psi pressure rise after 20-30 mins running on bitumen means the starting cold pressure is correct for the current load. More than 4psi rise means the starting cold pressure was too low. Less than 4psi rise means the starting cold pressure was too high. 4psi is the Goldilocks reading.

The Cooper Tyres 4WD Guide covers it well. For light truck (LT) construction and off-road tyres they suggest a 6psi rule for on bitumen use.

https://www.coopertires.com.au/wp-content/uploads/2022/10/4WD-Drivers-Guide_LR.pdf

 

[DenisM]

Now you’re just poking the bear!

sorry.. it wasn't a dig.... actually it is a serious question...I'd seen reference previously on the AULRO forum to something I vaguely recall as a 4+4 rule whereby after 20km at highway speed, a LR driver duly alights and measures tyre pressure and temp. of his tyres (with a then new-fangled expensive remote laser temp "gun" ...now $20 when on sale at Aldi!). If there was an increase of 4psi and 4 Cent. degrees then that was the sweet spot inflation pressure for a particular load. ..supposedly.
Last time I ventured north from Melb to Brisbane, the east facing f/r tyres were a couple of degrees warmer than those on the western side in the shade. In the afternoon the reverse occurred with the western facing tyres warmer than the other side!

 

[Clark Kent]

...Last time I ventured north from Melb to Brisbane, the east facing f/r tyres were a couple of degrees warmer than those on the western side in the shade. In the afternoon the reverse occurred with the western facing tyres warmer than the other side!

It's surprisingly sensitive. My car faces south in my work car park. When I go home in the afternoons the RHS tyres (west facing) are usually a couple of psi higher due to sun warming.

 

[bigleonski]

sorry.. it wasn't a dig.... actually it is a serious question...I'd seen reference previously on the AULRO forum to something I vaguely recall as a 4+4 rule whereby after 20km at highway speed, a LR driver duly alights and measures tyre pressure and temp. of his tyres (with a then new-fangled expensive remote laser temp "gun" ...now $20 when on sale at Aldi!). If there was an increase of 4psi and 4 Cent. degrees then that was the sweet spot inflation pressure for a particular load. ..supposedly.
Last time I ventured north from Melb to Brisbane, the east facing f/r tyres were a couple of degrees warmer than those on the western side in the shade. In the afternoon the reverse occurred with the western facing tyres warmer than the other side!

Sorry mate, I’ve edited my post.

I’ve never had the capability to measure temps before so only used the 4psi test.

 

[Lars]

The Cooper Tyres 4WD Guide covers it well. For light truck (LT) construction and off-road tyres they suggest a 6psi rule for on bitumen use.

https://www.coopertires.com.au/wp-content/uploads/2022/10/4WD-Drivers-Guide_LR.pdf

Now this is what is good about the Grenadier forum...information we can use. I've found some real gems amongst all the smoke.

 

[shiv.nandak]

View attachment 7857628

I find it very odd that all recommended pressures listed in the manual are for LT tires. No mention of the ideal psi for the Bridgestones. From my understanding, the pressures for LT tires are different than P rated tires.

 

[anand]

I find it very odd that all recommended pressures listed in the manual are for LT tires. No mention of the ideal psi for the Bridgestones. From my understanding, the pressures for LT tires are different than P rated tires.

The LT tires effectively gain their extra weight capacity from being able to be inflated to a higher extent than P-metric tires; thus at lower pressures, their weight capacity is inline with P-metric.

While these aren't BFG or Bridgestone specific, they are a very good guideline on pressure vs. weight capacity

LT265/70R17 vs. 265/70R17

In the chart above, the non LT tire actually can carry more weight at the same pressures. You'll see in the LT chart, the pressure (and subsequently weight carrying) increases and is denoted by tire load rating (C, D, or E)