Advice on Optimal Tire Pressure (LR4 with 265/65R18 BFG A/T KOs)

[Finlayforprez]

Hello Everyone,

I know this may have been discussed elsewhere, but I can't seem to find specifics. I contacted the folks at BFG and they just state that I should use the manufacturer's recommended numbers. For the US LR4 those numbers are 36 front / 42 rear (this is for the 19" standard wheel option). I put 18" Compomotive wheels on my LR4 with BF Goodrich A/T KOs in size 265/65R18. I'm not looking for tire advice, but more so some thoughts on the optimal pressure. The max PSI is 80, and I have heard of guys running 40-50 psi with luck, and it makes sense to have something around in the middle, but it depends on the vehicle's weight and other factors.

My LR4 is a bit heavier than stock as I have the following added weight:

- Full-size Urban Offroad rack with the spare tire on the roof and a permanent Pelican box with about 30 pounds of supplies
- Tactical 4x4 rock sliders, gas tank skid plate, and transfer case skid plate
- ARB front bumper with WARN winch (metal line)

A lot of the weight is distributed evenly with the rock sliders and skid plates, but all of these modifications add a fair amount of weight. With that in mind, and what I have heard from others running BFG A/T KOs, I am doing 44 front / 48 rear. My tire wear seems to great, no issues with handling, but I am always curious if I should be doing something different.

Thanks in advance for your comments.

Regards, David

Here is a pic of it that someone took - it's actually clean:

 

[roverandom]

With a 80psi limit you must have an LT and not a P rated tyre? That's a very good thing as they are made to handle higher loads.......and these things need it. A stock 19" P rated tyre on a 6,000lb SUV rated to tow an additional 7,000lbs is a joke.

My LR3 is set up similar to yours. The 50 psi sounds reasonable but to make sure why not just do the chalk test?

Get some chalk. Cover a 6-8" area of the tyre tread with chalk. Drive 20 yards and take a look at the chalked area.

If it has only rubbed off in the centre the you have too much pressure.

If it has only rubbed off at the sides then you have too little pressure.

If it is evenly rubbed off the entire width of the tyre then you are in the ball park for optimal PSI.




Sent from my iPhone using Tapatalk

 

[zelatore]

David, I suspect you're pretty close on the pressures. The trick I use is from my old road racing days - I use a cheap infra-red thermometer to measure tire temp across the tread. Hot in the middle and you've got too much; hot on the edges and too little. You can pick up a cheap laser thermometer like this from Harbor Freight or Amazon for less than $35 (don't forget your 20% off coupon!)
http://www.harborfreight.com/catalogsearch/result?q=thermometer

Or you could borrow mine if you want.

Be warned; you'll play with the thing for hours and annoy the wife with it as you walk around the house measuring the temperature of everything in sight, including her. She will not see the humor in this; they never do.

<edit>
I see I was beat to the punch. I'm doing basically the same thing as the chalk test, just with a fancier gadget. Plus I can tell how cool my beverage is.

 

[Red90]

Another good starting point. Find a scale and weigh each axle. Find the load rating for each tire and the pressure and adjust proportional to that. The tires are rated at 3000 lbs at 80 psi, so if the actual weight on the tire is 1500 pounds, then 40 psi is a good place to start.

 

[perkj]

I've found the sweet spot with my cooper zeon ltz 285/60-18s to be 44 front and 47 rear when the car if fully loaded with gear and fuel....max stated on the tire is 50. I drop it down to 40 front 42 rear when not fully loaded. Key is to to the chalk test with the rig fully loaded (including passengers) & fully fueled and then fully fueled & unloaded with just yourself in it. This way you'll get your range and can know what you have to play with depending on the load.

 

[Finlayforprez]

Thanks, Everyone!

roverandom: Yes, they are LT tires. With the truck being so heavy and adding a considerable amount of extra weight, I definitely wanted an LT tire with a high load rating. I really like the Duratrecs like Don (zelatore) has, but at this point I don't want to have to do a permanent lift or cutting/trimming. I really like the BFGs and they get me where I would ever be willing to go (at this point).

Red90 and perkj: Thanks for the input. I am actually going to weigh the truck in various scenarios so I have a range of tire pressures.

zelatore (Don): The laser thermometer sounds way too fun! I think between using that and the chalk method I can get my optimal PSI at various load scenarios. With that said, I would likely do it primarily at my normal load and then change it up when I am packed up only for longer trips.

I appreciate all the input!!!

Regards, David

 

[mteilers]

David,

I know this has been talked about on other threads but I really like your set up. Just bought another LR4 and want to change out the wheels and tires. Did you just buy compomotive wheels and the BFG 265/65 R18 AT's and have them mounted our did you do other modification to the suspension?
Mark

 

[newhue]

I've used the 4psi rule for a while now. Works well in my view.

http://www.aawen4x4.com.au