XR Xtreme Recon and High Tide -- tire pressure lesson learned

[Old Jeeper]

Maybe Ill drop mine a bit more to get closer to full contact. Even at 33, I am not hitting about an inch or so on both sides of the stock tires. I think the most I have seen mine heat to is 35 when its in the 70s.

Splash some water on a flat hard surface and read the pattern, edge to edge but no more...

Sponsored

 

[Byrds8]

Splash some water on a flat hard surface and read the pattern, edge to edge but no more...

The outside edges are dry/not dusty. They do need to be lowered. I have done the chalk/water tests and just havent moved them lower.

 

[Viking Jeeper]

You are welcome.

It reads in half psi increments. so to get them all EXACTLY the same, and I realize its ridiculous to do, but I kind of just wanted to see if I could do it.

I have one that was cheaper but reads in tenths of a pound. The chuck is worthless though.

 

[Old Jeeper]

The outside edges are dry/not dusty. They do need to be lowered. I have done the chalk/water tests and just havent moved them lower.

I adjst 2 lbs at a time, then when I get close start to dial in the +/- .5 lb

 

[azwjowner]

Remember, 35x12.5R17 tires are rated by tire manufacturers to safely carry 1,875 pounds per tire at 25 PSI: https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

So you can safely run 25 PSI without worrying about blowouts, anything above that is to satisfy other concerns such as tread wear, MPG, feel, etc.

 

[6.2Blazer]

The OEM recommended tire pressure is based on the vehicle running at max GVW and the max towing load. They do this to be on the safe side to ensure there is sufficient pressure in the worse case scenario....unfortunately most people aren't smart enough to handle having light load versus heavy load tire pressures and would turn around and sue people if they wreck their vehicle because of this.

With that said, I'm kinda' surprised that somebody is reporting that much of a difference between 37 and 32 psi. You could see that much difference in a day if it's cold out in the morning and warms up quite a bit while you cruise down the freeway. In cases like that you don't expect people to adjust their air pressure in the tires throughtout the day by a few pounds.

 

[Old Jeeper]

Remember, 35x12.5R17 tires are rated by tire manufacturers to safely carry 1,875 pounds per tire at 25 PSI: https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

So you can safely run 25 PSI without worrying about blowouts, anything above that is to satisfy other concerns such as tread wear, MPG, feel, etc.

35 x 12:50 x 17 Tires are rated by each mfg, they are all different, my GY Duratrac is rated at "Max Load 3195 lbs". Not all tire sizes are built the same.

Tire size and how its built across mfg are not all alike or equal.

 

[azwjowner]

35 x 12:50 x 17 Tires are rated by each mfg, they are all different, my GY Duratrac is rated at "Max Load 3195 lbs". Not all tire sizes are built the same.

Tire size and how its built across mfg are not all alike or equal.

Not as far as size and load capacity go. Those are standardized by the Tire & Rim Association which publishes the load charts for U.S. flotation size tires: http://www.us-tra.org/publications.html

All tires sold with a particular size are rated to carry the loads at the pressures specified in the load charts.

Actually, this is also law: FMVSS No. 119, codified at 49 CFR § 571.119, requires light truck tires to conform to the published load standards of certain organizations, including the TRA and ETRTO (which governs passenger metric tires).

So other characteristics can vary, but if the tire is sold with a "35x12.5R17" marking, that is a TRA flotation size, and it is required to meet the minimum (could be capable of more, of course) load standards that the TRA publishes, which includes carrying 1,875 pounds per tire at 25 PSI (and more at higher pressures).

 

[Byrds8]

Not as far as size and load capacity go. Those are standardized by the Tire & Rim Association which publishes the load charts for U.S. flotation size tires: http://www.us-tra.org/publications.html

All tires sold with a particular size are rated to carry the loads at the pressures specified in the load charts.

Actually, this is also law: FMVSS No. 119, codified at 49 CFR § 571.119, requires light truck tires to conform to the published load standards of certain organizations, including the TRA and ETRTO (which governs passenger metric tires).

So other characteristics can vary, but if the tire is sold with a "35x12.5R17" marking, that is a TRA flotation size, and it is required to meet the minimum (could be capable of more, of course) load standards that the TRA publishes, which includes carrying 1,875 pounds per tire at 25 PSI (and more at higher pressures).

From what I am understanding here, you are saying that every tire is the same load rating as long as its size remains the same. This is not accurate. BFG 315/70R17 KO2s come in the same size with different load ratings. Unless I misunderstood what you stated.

 

[azwjowner]

From what I am understanding here, you are saying that every tire is the same load rating as long as its size remains the same. This is not accurate. BFG 315/70R17 KO2s come in the same size with different load ratings. Unless I misunderstood what you stated.

That's not what I'm saying at all. I'm saying that tire sizes are standardized in terms of load capacity at particular pressures. The size marking 35x12.5R17 means that the tire meets the specs, which require it to support a given weight at a given pressure.

You are talking about something related, but different, load rating. That is a maximum load classification. It doesn't affect the load capacity at each particular pressure along the way. If you have a C tire, you have to stop at a lower PSI on the charts because the tire is rated to only 35 or 50 PSI. If you have E, you're able to go to 65 or 80. Thus, your C tire can't carry as much maximum weight overall, because you can't inflate the tire as high. But the C and E tire that are both inflated at 25 psi are rated to the same load capacity at that 25 psi.

 

[Byrds8]

That's not what I'm saying at all. I'm saying that tire sizes are standardized in terms of load capacity at particular pressures. The size marking 35x12.5R17 means that the tire meets the specs, which require it to support a given weight at a given pressure.

You are talking about something related, but different, load rating. That is a maximum load classification. It doesn't affect the load ratings at particular pressures. If you have a C tire, you have to stop at a lower PSI on the charts because the tire is rated to only 35 or 50 PSI. If you have E, you're able to go to 65 or 80. Thus, your C tire can't carry as much maximum weight. But the C and E tire that are both inflated at 25 psi are rated to the same load capacity at that 25 psi.

Copy. I figured I probably misunderstood what you were saying :D

 

[Old Jeeper]

Not as far as size and load capacity go. Those are standardized by the Tire & Rim Association which publishes the load charts for U.S. flotation size tires: http://www.us-tra.org/publications.html

All tires sold with a particular size are rated to carry the loads at the pressures specified in the load charts.

Actually, this is also law: FMVSS No. 119, codified at 49 CFR § 571.119, requires light truck tires to conform to the published load standards of certain organizations, including the TRA and ETRTO (which governs passenger metric tires).

So other characteristics can vary, but if the tire is sold with a "35x12.5R17" marking, that is a TRA flotation size, and it is required to meet the minimum (could be capable of more, of course) load standards that the TRA publishes, which includes carrying 1,875 pounds per tire at 25 PSI (and more at higher pressures).

Here are 3 tires all 35 x 12:50 x 17

They have different speed ratings and different Ply ratings, for what ever reason the Load Rating was blank on all of them. I don't think the load rating is the same across these because of different speed and plys...That said as I understand YOU, you are saying it is???

 

[azwjowner]

Here are 3 tires all 35 x 12:50 x 17

They have different speed ratings and different Ply ratings, for what ever reason the Load Rating was blank on all of them. I don't think the load rating is the same across these because of different speed and plys...That said as I understand YOU, you are saying it is???

No, that's not what I'm saying at all. I'm not talking about the load rating, which is the classification (C, D, E, etc.) based on a tire's maximum load capacity at maximum pressure.

I am talking about load capacities at particular pressures. The amount of weight any tire can carry depends on the particular size and the particular pressure. More pressure, more weight (generally). These are set by the specifications of the TRA for each size available. For 35x12.5R17, the TRA specification says the load capacities are:

1,875 lbs @ 25 PSI
2,155 lbs @ 30 PSI
2,405 lbs @ 35 PSI
2,625 lbs @ 40 PSI
2,840 lbs @ 45 PSI
3,000 lbs @ 50 PSI
3,065 lbs @ 55 PSI
3,130 lbs @ 60 PSI
3,195 lbs @ 65 PSI

Every 35x12.5R17 tire is required to meet these minimum load capacities at these pressures (assuming the pressure is within the range of the tire). So every 35x12.5R17, whether load C or E, is rated to safely carry a minimum of 1,875 pounds when inflated to 25 PSI.

Now load rating (C, D, E), which does differ between tires, depends on plies, construction, etc. The same load tables show that C load in 35x12.5R17 have a maximum of 35 PSI, D load has a maximum of 50 PSI, and E load has a maximum of 65 PSI. That's how you end up with different load rating letters -- not all tires are built the same and they max out at different pressures. When they have different max pressures, it obviously results in different max loads.

My point was simply that any 35x12.5R17 tire (load C, D, E, or otherwise) is rated to safely carry 1,875 pounds at 25 PSI. That has nothing to do with the maximum pressure and load for the tire, which corresponds with the load rating letter. So with a Jeep you know you're safe at 25 PSI. There are other reasons to increase pressure (squishy sidewalls, handling, etc.), but you don't face any blowout risk. Some people were worried about blowout risk.

 

[MayThe4x4BWU]

I'm just letting the weather/temps dictate mine. I lowered them from the crazy off the delivery truck 45psi to 37 while it was still warm out right after I got her home from the dealer. Currently, running in winter temps, they hover between 33 and 35 depending on how long I'm driving.

Really haven't noticed a big difference. But my tolerance for these types of things is a lot higher given the sport settings I used to drive in my old SRT GC lol

 

[commbubba19]

wheel width has a huge impact on contact patch given a tire's width

skinny wheels with wide tires will roll the contact patch more than a wide wheel.

xr wheels are what 8" wide with a 315mm width tire. take that same tire a the same psi on a 9.5" wide wheel and you'll see a better contact patch and less tread bulge.

my point is it's not just about air pressure.

Sponsored