32 replies to this topic

[Tom n N]

Tom, It's been a long time. I believe they might have been these, which you can still get at a Toyota dealer. They are the same wheels on our Troop Carrier now. It should be easy to check backspacing. 

 

 

Thanks, that should help (also appreciated the camp table info)

Tom

[Tom n N]

Finally found some nice refurbished Toyota 16x7 steel rims (like early Tacoma and Tundra spares). Had been waiting for BFG to start making the Mud Terrains in 235-85R16 again, but apparently now are not going to, so I decided to take a chance with the new HD Terrains. Before putting them on the Toyota, I mounted them on the old 65 Chevy 4x4 for an offroad snow wheeling trip. First time that truck has ever seen snow, so not much to compare to, but truck and tires did very well in slick mud and deep wet off road snow. Have now got the new tires mounted on the Toyota. Going to put on the camper and head out for a few weeks in the desert next month, so will be able to see how they compare with the old Mud Terrains I used to run.

 

Trying to decide on ideal tire pressure both loaded and unloaded. Unfortunately my local dealer and BFG Tech support absolutely no help. Rubberlegs, where did you find that pressure chart from your earlier post? Now that you’ve put on some miles on and off road and both loaded and unloaded, what pressures are working best for you. Looks like our trucks are fairly similar in use and weight. Anybody else have opinions?

 

Thanks,

Tom

 

[rubberlegs]

It's funny you should ask. I was just out on a walk and thinking I could update my opinions on the tires, now that we've done two extended trips. So far, so good. Theoretically we have another half inch of clearance. I can't tell any difference between the old tires and new, except our gas mileage has dropped a bit. But then our new tires are 31.7" diameter, and worn tires 30.0", which is 6% difference that our odometer doesn't know about. I'll need more time to comment on gas mileage.

 

On the pressure chart: I couldn't find any guidance on pressure depending on weight, except the capacity of the tires from the Tire and Rim Association that Toyo has online.

 

 

The boxed-in numbers are from the TRA charts. Then I doubled that for axle weight (the line below).

 

Then I hemmed and hawed how to use that for the weight in our truck. The manufacturer says to use 30 psi in all four tires, and they seem to think that's ok whether the rear axle is at 2000 lb empty (I weighed it), or 2800 lb full (truck at max capacity). The front axle with two people was 2700 lb, pretty close. Perhaps Toyota wanted to keep it simple with just one pressure, I don't know. 

 

Anyway, if you draw the lines on a graph (see post #2), it's pretty linear. I calculated at 2700 lb with the stock tires at 30 psi, there was a safety factor of 152%. The method of selecting tire pressure for E rated vs. P rated seems to be based on equivalent load capacity, so using the same safety factor kinda makes sense.

 

The bottom line in the spreadsheet shows the axle weights by derating with a 152% safety factor (i.e., dividing by 1.52). This is my current best guess on what pressure to use for axle weight. So I'm using 47 psi front axle, 67 psi rear axle. (I used 45/65 psi on the previous stock size E-rated tires and had reasonable wear on all four tires of 56,000 miles, tires rotated every 5,000 miles). On our last trip we used 18 psi front, 25 psi rear on rough roads, a similar ratio front/rear as for pavement.

 

I'm not totally convinced this is a proper procedure, but it worked ok on our previous tires, and the tire bulge kinda "looks right". I never did a chalk test. I'm really not sure a chalk test makes sense. 

Edited by rubberlegs, 02 March 2024 - 02:25 AM.

[Tom n N]

Thanks for the info Rubberlegs,

The T&RA charts were especially useful, that was what I really was hoping for. Page 21 had LT235/85R16 truck tires. Fully loaded I’m at #3740 on the rear axel, which should be #1860 per tire. That’s #40 of air on the chart. Of course that’s without the all important safety factor. I like your number of 150%. If I multiply the air pressure that’s #60. If I multiply the load, that’s #2790, or #70 of air. I hesitate to extrapolate from the factory recommendations, because as you pointed out, they are based on totally different tires and don’t take load into account, which makes absolutely no sense. 
 

As usual I’m giving myself a headache obsessing and trying to overthink this, and I still need to account for driving unload and also figure the front axle. If it ever stops raining around here I think I want to do a chalk test. While dirt simple, I’m thinking it’s probably pretty relevant, as it gets you the ideal tire shape and contact patch.

 

Bottom line, I need to just install the camper and hit the road and experiment! What are others out there doing?
 

Thanks,

Tom

Edited by Tom n N, 03 March 2024 - 04:18 AM.

[JHanson]

Tom,

 

The old-fashioned chalk method still works well, although I sometimes use white paint instead. Just paint a couple of white stripes across the tread of each tire, then go drive around, preferably mostly in straight lines, and checking the paint frequently. Where it wears off first will tell you which way, if any, you need to adjust pressure. Paint wears off in the center first—too much pressure. Off the edges first—too little.

[Tom n N]

Tom,

 

The old-fashioned chalk method still works well, although I sometimes use white paint instead. Just paint a couple of white stripes across the tread of each tire, then go drive around, preferably mostly in straight lines, and checking the paint frequently. Where it wears off first will tell you which way, if any, you need to adjust pressure. Paint wears off in the center first—too much pressure. Off the edges first—too little.

 

Jon,

I really like the paint idea. I did an initial test with a white paint pen and it seemed to work pretty good. As you said, key is to check frequently. Kept going too far and wearing the whole thing off. Still fine tuning, but looks like unloaded pressures are going to be #30 or less. Still need to do it all over once the camper goes back on.

 

On a totally different subject, I just read the new article you posted on your website about vehicle access to wilderness areas. Very well written, and I agree 100%

 

Tom

[JHanson]

 

Tom,

 

The old-fashioned chalk method still works well, although I sometimes use white paint instead. Just paint a couple of white stripes across the tread of each tire, then go drive around, preferably mostly in straight lines, and checking the paint frequently. Where it wears off first will tell you which way, if any, you need to adjust pressure. Paint wears off in the center first—too much pressure. Off the edges first—too little.

 

Jon,

I really like the paint idea. I did an initial test with a white paint pen and it seemed to work pretty good. As you said, key is to check frequently. Kept going too far and wearing the whole thing off. Still fine tuning, but looks like unloaded pressures are going to be #30 or less. Still need to do it all over once the camper goes back on.

 

On a totally different subject, I just read the new article you posted on your website about vehicle access to wilderness areas. Very well written, and I agree 100%

 

Tom

 

Thank you!

[ski3pin]

 

<snip>

Jon

 

On a totally different subject, I just read the new article you posted on your website about vehicle access to wilderness areas. Very well written, and I agree 100%

 

Tom

 

JHanson, excellent thoughtful article that Tom mentions above. Well done and thank you.

[AWG_Pics]

JHanson, excellent thoughtful article that Tom mentions above. Well done and thank you.

 

I agree with Tom & Monte!

 

Link: https://www.explorin...ust-pro-habitat

[Vic Harder]

+1....