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 > Lowering TV tire pressures

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Me Again

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Posted: 10/09/19 04:32pm Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

wilber1 wrote:

Cummins12V98 wrote:

Wilber buddy do what you want, call it what you want I explained what works and how. Oh and let's not forget I get by far better mileage and perfect tread wear than most by using the charts.


Your opinion only. The charts claim no such thing, they only give maximum loads for different pressures.


I guess GY Tech Support knows nothing!


Or Michelin who I talked to several times about pressure in LLT235/85R16E XPS RIBs on a 12,400 lb 5th wheel with 10K on the axles. Placard called for 65 PSI in the Kenda china bombs the size, and I up that to 71 with the RIBs for even wear. Ran R250's at same inflation after 6.5 years and 40K+ miles on the RIBs, which is sold for 200 bucks on CL, with about 60-65 percent tread left.


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Posted: 10/09/19 06:32pm Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

wilber1 wrote:

Cummins12V98 wrote:

Wilber buddy do what you want, call it what you want I explained what works and how. Oh and let's not forget I get by far better mileage and perfect tread wear than most by using the charts.


Your opinion only. The charts claim no such thing, they only give maximum loads for different pressures.


I guess GY Tech Support knows nothing!


They know how much weight their tires can support at different pressures and that is all those charts are telling you, nothing more. It says so right at the top of the chart.


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Cummins12V98

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Posted: 10/09/19 06:47pm Link  |  Quote  |  Print  |  Notify Moderator

They recommend using those charts unless you want to blindly run what the manufacturer says that is a CYA for them.


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wilber1

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Posted: 10/09/19 11:26pm Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

They recommend using those charts unless you want to blindly run what the manufacturer says that is a CYA for them.

Do you seriously think vehicle manufactures don’t know about those charts and don’t use them as one of the criteria when selecting a tire and determining what pressures are optimum for that particular vehicle?

demiles

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Posted: 10/10/19 03:26am Link  |  Quote  |  Print  |  Notify Moderator

wilber1 wrote:

Cummins12V98 wrote:

They recommend using those charts unless you want to blindly run what the manufacturer says that is a CYA for them.

Do you seriously think vehicle manufactures don’t know about those charts and don’t use them as one of the criteria when selecting a tire and determining what pressures are optimum for that particular vehicle?


Wilber1 is absolutely correct on this one. Using the chart alone for the TV tire pressure is being blind to the big picture here. My old 06 Silverado had a 25 psi differential 55 front 80 rear which stayed that way for ten years on the same tires without a wear issue. They don’t design them to ride like a luxury car. If you must reduce tire pressure always maintain at least 5-8 psi higher in the rear tires, never go lower then the front. Running in sand or loose dirt is quite different then pavement.


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Posted: 10/10/19 06:59am Link  |  Quote  |  Print  |  Notify Moderator

Just an FYI:

I spent 5 years as the technical liason from a major tire manufacturer to Ford - calling on the light truck folks.

They test their vans, pickups, and SUV's both fully loaded and empty at the specified pressures (the ones on the door placard) for both ride quality and handling. They adjust the springs, shocks, and sway bars to get the vehicle to behave benignly at both conditions - that way the consumer gets a vehicle they don't have to adjust the tire pressures to be confident the vehicle won't misbehave in emergency manuvers and has a reasonable ride quality.

They also tested their trucks pulling trailers at the rated towing capacity.

I assume that other vehicle manufacturers do the same.

So I am confident that using the pressure specified on the vehicle tire placard is what they had in mind for both fully loaded and empty vehicles - unless they specify otherwise in the owners manual.


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Posted: 10/10/19 07:23am Link  |  Quote  |  Print  |  Notify Moderator

wilber1 wrote:

Cummins12V98 wrote:

They recommend using those charts unless you want to blindly run what the manufacturer says that is a CYA for them.

Do you seriously think vehicle manufactures don’t know about those charts and don’t use them as one of the criteria when selecting a tire and determining what pressures are optimum for that particular vehicle?




Look at the door of a newer RAM SRW they call for 80psi rear. No one in their right mind would run 80 unloaded. The dash goes crazy if you lower the air on a 2500. 3500's you can lower without the nanny screaming at you. Of course they know about the charts! They base their psi's on them. Some times!

On my DRW they are right on with 80/65psi for full axle ratings. 80 is correct loaded or unloaded. I use the charts to adjust the rears. I checked yesterday my front and rears both have 8/32" tread remaining. No rotation other than moving fronts side to side with same rotation.

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Posted: 10/10/19 07:27am Link  |  Quote  |  Print  |  Notify Moderator

CapriRacer wrote:

Just an FYI:

I spent 5 years as the technical liason from a major tire manufacturer to Ford - calling on the light truck folks.

They test their vans, pickups, and SUV's both fully loaded and empty at the specified pressures (the ones on the door placard) for both ride quality and handling. They adjust the springs, shocks, and sway bars to get the vehicle to behave benignly at both conditions - that way the consumer gets a vehicle they don't have to adjust the tire pressures to be confident the vehicle won't misbehave in emergency manuvers and has a reasonable ride quality.

They also tested their trucks pulling trailers at the rated towing capacity.

I assume that other vehicle manufacturers do the same.

So I am confident that using the pressure specified on the vehicle tire placard is what they had in mind for both fully loaded and empty vehicles - unless they specify otherwise in the owners manual.


On a RAM 2500 would you feel comfortable running 80psi rear ALL the time as the door says and the Nanny requires? If it were a 3500 SRW would YOU lower based on actual unloaded weight?

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Posted: 10/10/19 08:04am Link  |  Quote  |  Print  |  Notify Moderator

Agree with Barry and add that, that placard only applies to th ed tire size & load rating listed on it

If you have a different size & load rating...and/or...different rim width than stock, it does NOT apply

An example are those who replace P's with LT's


-Ben Picture of my rig
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1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
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Me Again

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Posted: 10/10/19 08:11am Link  |  Quote  |  Print  |  Notify Moderator

CapriRacer wrote:

Just an FYI:

I spent 5 years as the technical liason from a major tire manufacturer to Ford - calling on the light truck folks.

They test their vans, pickups, and SUV's both fully loaded and empty at the specified pressures (the ones on the door placard) for both ride quality and handling. They adjust the springs, shocks, and sway bars to get the vehicle to behave benignly at both conditions - that way the consumer gets a vehicle they don't have to adjust the tire pressures to be confident the vehicle won't misbehave in emergency manuvers and has a reasonable ride quality.

They also tested their trucks pulling trailers at the rated towing capacity.

I assume that other vehicle manufacturers do the same.

So I am confident that using the pressure specified on the vehicle tire placard is what they had in mind for both fully loaded and empty vehicles - unless they specify otherwise in the owners manual.


I can tell you that my 2001.5 RAM was a bit scary with 80 in the rear tires empty. And it came with a inflation document that had full load and partial load inflation numbers for both the LT245/75R16E and optional LT265/75R16E that I had.

And I invite you to stop by this winter while we are in Arizona and I will let you drive my 2015 RAM 3500 CC SB 4x4 with the rears at 80 PSI and the 43 PSI I set them at the other day. Then you can try to tell me the ride and handling to comparable.

From my 2015 RAM owners manual:

• Over-inflation reduces a tire’s ability to cushion
shock. Objects on the road and chuckholes can
cause damage that result in tire failure.

So if the rear axle on my truck weights around 3000 lbs empty and the tires at 80 are rate to 3640 x 2 = 7280, having them at 2x+ the actual load to me would unquestionably indicate an over-inflation issue.

So does not the owners manual have inherent conflicts in it's statements?

So my conclusion is the trucks manufacture's legal department had more input to the tire placard than the engineering department. It is call CYA.

If someone wants to bang their brains out all winter driving around with 80 lbs in their rear tires so be it, however it is not for me.

* This post was edited 10/10/19 08:48am by Me Again *

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