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 > Front tire pressure?

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jadatis

Holland

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Posted: 06/18/19 07:14am Link  |  Quote  |  Print  |  Notify Moderator

Answer to above
What you give is lineair calculation, and is not bad .
Official European calc is
( A/B) ^ 1.25 x 80 = psi.
The ^1.25is to the power, like square is ^2, and root is ^0.5.

But you dont add 10% first . Wich is for R/L unbalance, but also for pressureloss in time or misreading or inacuracy of pressure device.
Then it would give lineair 3190/3420 x 80 = 74,61 psi , so lineair calc comes to about the same as my extra safe calc is 75 psi.

Must have missed something , where did you get the 3472 maxload from?

jadatis

Holland

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Posted: 06/18/19 07:48am Link  |  Quote  |  Print  |  Notify Moderator

Your cupping is not from low pressure, though that can make it worse.
Alignment, bad shockbrakers( already mentioned) and someting loose are the real cources. Even going to wider tires and not compensating that in the alignment, has influence. Even the weightdivision here can havevits influence. Higher pressure then gives less cupping , but your fillings come out if your teeth.

JIMNLIN

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Posted: 06/18/19 08:09am Link  |  Quote  |  Print  |  Notify Moderator

My old '01 2500 Dodge/Cummins came with LT265/75-16 E. The silly tire placard said 50 psi in the front and 80 in the rears.
As I drove the new truck home (165 miles) I noticed the front tire plowed around corners. The back of the truck rode like a hay wagon. This truck had 4080 lb on the front axle and 2780 on the rear with no load.
I ran a chalk test on the fronts and found 65 psi worked best (2280 lb pin weight in the bed) along with no more plowing around corners.

No more weight than the 6.0 weighs IMO 70 lbs in the front may be a bit much. At 3350 lb front axle load = about 1700 lbs per tire. 60 psi sounds about right.

Agree with others on tire cupping issues.


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stevenal

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Posted: 06/18/19 09:01am Link  |  Quote  |  Print  |  Notify Moderator

https://www.michelintruck.com/reference-........-warranties/load-and-inflation-tables/#/


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Ramblin' Ralph

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Posted: 06/18/19 09:04am Link  |  Quote  |  Print  |  Notify Moderator

Many thanks for input and the formulas! My shocks do have a lot of miles, so that could be causing the cupping. Tires are load range E, 80 lb max, one size up from the OEMs.

Yes, I should have used the word "opinion" vs. "consensus". [emoticon]

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Grit dog

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Posted: 06/18/19 09:27am Link  |  Quote  |  Print  |  Notify Moderator

If there is nothing wrong with the front end, simply driving highway speed on predominately curvy roads (your location is the CA coast, not too many straight roads there) will feather front and rear tires pretty quickly.
Learnt that when we lived in the mountains. Almost couldn't rotate truck tires fast enough to prevent it, when the daily drive was 60-70 mph through the mountains.
Yes cupping is different (1 tread high, next one worn lower) and can/is an indicator of shocks or other front end issues. But where you drive, type of tire and load contribute to both.
That's why heavy vehicle steer tires typically have closed shoulder treads. A heavy pickup running AT or MT tires is just trying to chew the front tires up. Just how it be.


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BradW

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Posted: 06/18/19 12:21pm Link  |  Quote  |  Print  |  Notify Moderator

towpro wrote:

C is max PSI (marked on sidewall)


I have never seen an E rated tire with the maximum psi shown on the sidewall. What is shown is the maximum load of the tire at 80 psi.

bradw


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Posted: 06/18/19 12:45pm Link  |  Quote  |  Print  |  Notify Moderator

MORSNOW wrote:

BradW wrote:

When we hauled our Lance on our SRW trucks, I had less sway when we ran the front tires at 80 psi. Tires are part of the suspension and when the rear rocks side to side, the front does also. So anything you do to stiffen the front suspension helps, even though 90% of the added load is on the rear tires.


I honestly never thought about the front tire pressure and sway before due to almost all of the weight is added to the rear. Hmmm


I could really tell the front end had a significant effect on the side to side rocking when I had Rancho 9000 adjustable shocks on all four corners of our srw trucks. I experimented quite a bit with different setting and I found that without the camper I needed run the front socks on nearly the softest setting and with the camper I needed run the front shocks on nearly the stiffest setting. The front shocks had almost as much (maybe 70% - 80%) effect as the rear shocks on reducing side to side rocking.

bradw

MORSNOW

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Posted: 06/18/19 09:02pm Link  |  Quote  |  Print  |  Notify Moderator

BradW wrote:

I could really tell the front end had a significant effect on the side to side rocking when I had Rancho 9000 adjustable shocks on all four corners of our srw trucks. I experimented quite a bit with different setting and I found that without the camper I needed run the front socks on nearly the softest setting and with the camper I needed run the front shocks on nearly the stiffest setting. The front shocks had almost as much (maybe 70% - 80%) effect as the rear shocks on reducing side to side rocking.

bradw


Thank you for the additional information, I may play with my front pressure.


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deltabravo

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Posted: 06/19/19 10:22pm Link  |  Quote  |  Print  |  Notify Moderator

Ramblin' Ralph wrote:

I'm getting ready to hit the road again for several months. What is the consensus on proper front tire pressure?

Thanks,


Do the Chalk Test. Lots of examples on YouTube of how to do it.


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