Alignment and tire pressure question

[Silver Square]

I've been doing some research with ChatGPT as well as on some FB groups, trying to determine the best tire pressure to run in my 35x12.50-15 Boggers. Truck is a 77 K15 with a 6" lift. Seems that around 20-25 is ideal. Can anybody confirm? Also wondering if the factory alignment specs change to something different with that level of lift. I have a suspicion that lots of the folks with serious complaints about Boggers on the street are doing 3 things wrong... stick on weights instead of beads, too high of tire pressure, and not compensating the alignment for the lift. Am I onto something? It seems split 50/50 on folks saying they ride fine and others saying it's the end of the world.

 

[Turbo4whl]

Generally higher pressure on the highway, lower pressure off road. That is why many off roaders keep a 12V tire pump with them.

AI Overview

For a 35x12.50R15 Interco Super Swamper Bogger, recommended tire pressure varies significantly based on driving conditions and vehicle weight, typically running lower than traditional radial tires due to their stiff bias-ply construction.
Recommended Tire Pressure Chart (35x12.50R15 Bogger)

• Highway/Street Driving: 25–35 PSI (30 PSI is often listed as the maximum recommended pressure, though some users run slightly higher or lower based on comfort/wear).
• General Off-Road/Trail: 15–20 PSI.
• Mud/Deep Mud: 10–15 PSI (can go lower with beadlocks).
• Sand: 8–10 PSI.
• Rock Crawling:8–12 PSI.
  
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Key Considerations for Boggers

• Maximum Pressure: The 35x12.50/15LT Bogger has a max load at 30 PSI.
• Vehicle Weight: Lighter vehicles like Jeeps often run lower pressures (e.g., 22-26 PSI on the street) to prevent premature center tread wear.
• Rim Width: If using a 15x8 rim, 8-10 PSI is generally safe off-road; 10-inch wide wheels might require slightly higher pressure to hold the bead.
• Handling:Because Boggers are bias-ply, they tend to ride stiffly, leading many users to prefer lower street pressures for comfort.
  
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Disclaimer: Tire pressures should be monitored closely for heat, especially at higher speeds.

 

[Ricko1966]

Learn to chalk your tires. I've done beads and weights. I personally think weights are better. And I think most of the discrepancy on ride quality is how the lift was achieved and who's springs you are running.

 

[idahovette]

If I remember right the factory alignment settings were around 1 and a half degrees positive for the camber and if you run that it will eat the outer edge of the tires. My go to was/is 0 degrees plus or minus quarter and as much caster as you can get......4,5,6 degrees or more?? I usually set the toe at 1/8 inch in......YMMV

 

[Grit dog]

If I remember right the factory alignment settings were around 1 and a half degrees positive for the camber and if you run that it will eat the outer edge of the tires. My go to was/is 0 degrees plus or minus quarter and as much caster as you can get......4,5,6 degrees or more?? I usually set the toe at 1/8 inch in......YMMV

I know you’ve said this before and I still struggle with the understanding. That’s 1/2” “out of plumb” on a 33” tire. Could see it across the parking lot.
And yes I’m pretty sure it would chew the tires up quickly.
Maybe my memory ain’t good but was around alot of 4x4 squares when they were current models and now recently again. Never seen one with severely positive camber.

 

[Grit dog]

20-25 sounds aboot right. More in front, less in rear.
Look at a load/pressure chart for that size tire and use your approx axle curb weights. 3klb front, 2klb rear is a solid approximation for a 1/2 ton 4x4.
Stiff heavy wall 35s on the K20 I’m at 30F 25R iirc.

 

[idahovette]

Most of the 4wd pickups that came into the Chev/Cad dealership when I started aligning rigs(1969) were before our squares, but they had about the same front axle, closed then went to the open knuckle. The specs GM sent out at first was either 1 or 1 1/12 degrees POSITIVE camber.........way too much!!! It was quite awhile before they sent out a bulletin that said that may be too much camber...........YA THINK!!!!! Didn't give us a new spec, just that we may have to decrease it, some. That's about the time the aftermarket came out with the shim for between the spindle and the knuckle and then the offset bushing for the upper ball joint. I much prefer the shim method, that lets you clean, inspect, and pack/replace the wheel bearings while you have it apart. If you can get the camber to around the 0 degree mark you usually have the wear problem solved........as long as everything is tight and the air pressure is right and ALL the stars are aligned ......YMMV

 

[Radiohead]

Zero is best. ¼ positive is about all I would go.
I remember the shims too, the bushings were a pita compared. I still have the socket for the bushing style floating around somewhere out there.

 

[idahovette]

Yep, I have a lot of one off tools that I will NEVER use again. The one you mentioned, a strut compressor, a few different spanner wrenches, just to mention a few. Probably some nobody would even know what they are for?? The price of doing business in my own shop for 20 years plus being in the trade 30 before that.......Wouldn't trade it for the world

 

[nvrenuf]

Tire pressure will obviously affect how flat the tread sits on the ground and wheel width is also a big factor.

I run 22 psi in my 40” Boggers on 11” wide wheels. The tread is pretty flat but the low pressure makes the tires squishy/soft which translates to a boat-ish feel on the road.

Being bias ply tires they will wear fast, running lower pressure will exaggerate that. I’ve got about 600 miles on my tires and they are beginning to show wear.

 

[Silver Square]

Tire pressure will obviously affect how flat the tread sits on the ground and wheel width is also a big factor.

I run 22 psi in my 40” Boggers on 11” wide wheels. The tread is pretty flat but the low pressure makes the tires squishy/soft which translates to a boat-ish feel on the road.

Being bias ply tires they will wear fast, running lower pressure will exaggerate that. I’ve got about 600 miles on my tires and they are beginning to show wear.

I know I'll be lucky to get 5,000 miles out of the set on the street. When they wear out I'll get radials. Hopefully Interco will have the Ground Hawgs in 35x12.50 by then. I reached out to them a few months back and they said that they would eventually be releasing that size. The Boggers do look sweet though lol.