tire pressure discrepancy

[hamhorn]

I drive a 2002 Chevy Tahoe for a state agency. New Michelin LTX M/S tires (LT 245/75R16) were put on the Tahoe in October. The ride has been great.

I had the tire pressure checked this morning at the state's service department and learned that there were 80 lbs. in them, which is what is listed on the tire. However, the pressure tire pressure sticker on the left door specifies 35 lbs. as the proper pressure. I usually carry about 400 lbs. of business material in the back, not that much.

Which is correct? Thanks in advance for your advice.

 

[Colt45ws]

Check the size and load rating of tire specified on the door sticker. If it matches what is on the truck, then use the sticker.

 

[ctc]

I would think 80 lb is the max rating for the tire and not the recommended psi.

 

[cchase]

Use the number on the door unless you are running with a lot of weight or at very high speeds. In that case, check in the manual.

Don't use the number on the tire, it doesn't know what the vehicle or use is.

 

[Boomer]

If the door sticker says 35, it did NOT come with LT tires but rather P rated tires. LT tires require higher pressures to carry the same load as a P tire and running them at a P reted pressure results in enormous heat. This has been discussed at some length on thios board previously.

Your LT should probably be run around 45-50 psi with that type of load.

 

[Zaedock]

Originally Posted By: Boomer
If the door sticker says 35, it did NOT come with LT tires but rather P rated tires.


My 2003 F150 placard states LT265/70R17 35PSI cold.

 

[CapriRacer]

Originally Posted By: Zaedock
My 2003 F150 placard states LT265/70R17 35PSI cold.

Zardock,

Sorry, but you need to look at the placard again.

According to Tire Guides, some versions of 2003 F-150's came with P265/70R17, and NO versions came with LT265/70R17's. Tire Guides has been known to be wrong, but what they've published makes contextual sense to me.

But if they are indeed incorrect, take a photo and publish it. I'll forward it on to Bennet-Garfield to encourage them to make a correctuion.

 

[Zaedock]

Originally Posted By: CapriRacer
Originally Posted By: Zaedock
My 2003 F150 placard states LT265/70R17 35PSI cold.

Zardock,

Sorry, but you need to look at the placard again.

According to Tire Guides, some versions of 2003 F-150's came with P265/70R17, and NO versions came with LT265/70R17's. Tire Guides has been known to be wrong, but what they've published makes contextual sense to me.

But if they are indeed incorrect, take a photo and publish it. I'll forward it on to Bennet-Garfield to encourage them to make a correctuion.


Tire Guides is incorrect. The tires that came on my truck, match the placard, and are still the original Goodyears (although I've been shopping around for replacement LT's). There is no mention, whatsoever, of "P" anywhere on the placard.

LT265's were an option with the 4WD XLT and FX4 Off Road Equipment group.

 

[CapriRacer]

Zaedock,

Would you please take a photo of the placard so I can send it to Bennet Garfield?

Thanks

 

[Zaedock]

Originally Posted By: Boomer
If the door sticker says 35, it did NOT come with LT tires but rather P rated tires.


Originally Posted By: CapriRacer
Would you please take a photo of the placard so I can send it to Bennet Garfield?


OK guys, here you go.

 

[Kuato]

I've always used the placard and tire pressures as a guideline. Tires are correctly inflated when the most tread is on the ground, and you get even wear across the tire. Checking at least once a month is mandatory, especially when the temperature is changing from season to season.

The numbers are the numbers, but I've tried to inflate to the manufacturer's recommendation on several vehicles and found my tires wearing very quickly on the outside edges, indicating under inflation. This has been tried on everything from an 08 Nissan Versa to an 04 Dodge Ram 1500 to a Ford Crown Vic (93 and 86).

On my current vehicle, 04 Grand Cherokee, the tires say 44psi and the placard 35. At 35psi it is a very mushy ride and to me, an unsafe one, with the tires squirming under hard braking and cornering. Also at 35 the tires were wearing rapidly on the outside edges.

I fill the tires to 44psi F&R and refill when they bleed down to 42psi. Handling is what I'd consider normal, with no squirm on braking and very even wear. IMO there's some trial and error involved for each vehicle.

 

[Zaedock]

Originally Posted By: fredjacksonsan
The numbers are the numbers...


Not here on BITOG. Numbers mean nothing. If you don't have pictures, no one believes you.

 

[CapriRacer]

Originally Posted By: Zaedock
Originally Posted By: CapriRacer
Would you please take a photo of the placard so I can send it to Bennet Garfield?


OK guys, here you go.

(Photo omitted!)

Zaedock,

Thanks, again.

Looking more closely at Tire Guides, I see they have an entry:

2003 Ford F-150
Lariat FX4 4X4 H.D.
Super Cab

tire size LT265/70R17 Load Range C
inflation 40 / 60

- which I know is wrong because Load Range C stops at 50 psi.

Does the vehicle description match what you have?

(I'm assuming tha H. D. means "Harley Davidson")

If not, is there a description in a similar format that would apply?

When I send the photo to Bennett Garfield, it always helps to put it in the format they have chosen to use. On the plus side, would be if I can point out that the pressure listed is merely incorrect and they don't need to make a new entry.

BTW, this is important because many folks use this publication to program their computers to automatically give them inflation pressure. If the publication is wrong, their computer is wrong.

 

[Zaedock]

IIRC, all Harley Davidson models were 2WD. I could be mistaken though.

My truck is an XLT Ex.cab, 4x4 with the FX4 Off Road package and towing group (w/ oil& tranny coolers). If memory serves, the LT265's were an available $300.00 option (from the build sheet) with the FX4 package.

I'm leaving on a trail run with my Jeep club in an hour or so. I'll dig through my glove box for the window sticker tonight.

Happy Trails.

 

[Boomer]

There is NO WAY I would run an LT tire at 35 psi.

 

[George Bynum]

Originally Posted By: Boomer
There is NO WAY I would run an LT tire at 35 psi.
No disagreement, but just to SORTA quantify it, per Bridgestone who publishes ratings on the web,

LT265/70-17 @ 35psi, 1890; @50psi, 2470
P265/70-17 @35+psi, 2535 less 10%, 2305
267/70-17 @36+psi, 2679 less 10%, 2435

The LT at 35 has much lower capacity than a P-metric or Euro-metric at 35.

 

[Zaedock]

Originally Posted By: Boomer
There is NO WAY I would run an LT tire at 35 psi.


Why not? If each tire holds 1890 at 35psi, that's 7560 lbs of capacity.

 

[ewetho]

If you are only used to thinking an LT tire is E rated than sure it makes sense not to use 35 PSI. However in a C load rating where 50 is max that is not that big a deal Extra load generally max out at 42 PSI for load even though some go higher.

Standard Load max weight is normally at 35 PSI
Extra Load max Weight is normally at 41 PSI
C rated LT tires is 50 PSI
E is at 80 PSI

We run E rated at 50/70, 55/65, and other splits so it depends on my tire.

 

[Audioshot]

You absolutely can run an LT tire at 35psi. It all comes down to the amount of weight the axle is rated for. If your placard says 35 psi at a certain size, then that is based on the amount of cubic inches (volume) of air inside the container (tire and wheel). All those cubic inches add up to the total carrying capacity of the tire and wheel. If you run a higher pressure to increase you load capacity, then your rim may fail because it may not be rated for that pressure.

If you alter your tire/wheel/suspension that exceeds the capacity of that axle, then the vehicle needs to be re-placarded. Otherwise if you get in a (tire related)accident, and the tires and air pressures don't meet that placard, then the lawyers will eat you up. Always go off the placard. The tire sidewall is MAX pressure only. I field inspect tire failures for certain plants so I see this all day long.