03 F-250 Tire pressure question w/out load.
#1
03 F-250 Tire pressure question w/out load.
Pretty simple question, 90% of the time I'm driving, I am without a load.
Without a load (stock size tires 265) what's a good recommended psi?
50 front & back?
I know that with a load you want the recommended door sticker psi of 80.
Reason I ask is the truck still has the slicker stock tires on it & would like any extra bite for the slick winter.
New tires in a few months.
Thanks in advance!
Without a load (stock size tires 265) what's a good recommended psi?
50 front & back?
I know that with a load you want the recommended door sticker psi of 80.
Reason I ask is the truck still has the slicker stock tires on it & would like any extra bite for the slick winter.
New tires in a few months.
Thanks in advance!
#4
Whoaaaaaa on the 35psi there, especially if you're running OEM sized 80psi-max E-rated tires on 17s or 18s. Eberlestock is likely saying he runs 35psi is either D-rated tires, or wider E-rated tires that have a 65-psi max on the sidewall. You don't want to under inflate a tire, a blowout is a bad deal on a 7000# truck, especially in the front.
You can find load index tables on the internet that should tell you the load capacity of a tire at a given inflation pressure based on the rating of the tire. Examples:
http://static1.1.sqspcdn.com/static/...+inflation.pdf
How to Determine Tire Load Ratings - Article - Work Truck
I read a paper that gave a minimum pressure "rule of thumb" of the ratio of load to load index times max psi:
For example, my BFG Rugged Trail 265/70R17 121 tire is rated to 3195# and 80psi max. My truck weights 8300#, 4800# in the front, 3500# on the rear, per a CAT scale ticket.
Front axle (per tire, so axle weight is cut in half):
( 2400 / 3195 ) * 80 = 60psi minimum
Rear axle:
( 1750 / 3195 ) * 80 = 43psi minimum
This would be a more conservative estimate, since the load index tables don't tend to be perfectly linear. An example given in the first link above is that a 121 Load Index "E-Rated" tire at 50% of max PSI the tire is rated for 64% of it's max load, not the 50% that the math problem above gives you. There is also the consideration that running any tire below 50% is essentially running it "flat", and that can cause damage to the carcass.
If you have 20" rims and 65psi-max E-Rated tires, 35psi might not be too low, but I'd still try to find a load index table for that type/rating of tire instead of guessing.
You can find load index tables on the internet that should tell you the load capacity of a tire at a given inflation pressure based on the rating of the tire. Examples:
http://static1.1.sqspcdn.com/static/...+inflation.pdf
How to Determine Tire Load Ratings - Article - Work Truck
I read a paper that gave a minimum pressure "rule of thumb" of the ratio of load to load index times max psi:
(Weight Carried by Tire / Load Index of Tire) * Max Sidewall PSI
Front axle (per tire, so axle weight is cut in half):
( 2400 / 3195 ) * 80 = 60psi minimum
Rear axle:
( 1750 / 3195 ) * 80 = 43psi minimum
This would be a more conservative estimate, since the load index tables don't tend to be perfectly linear. An example given in the first link above is that a 121 Load Index "E-Rated" tire at 50% of max PSI the tire is rated for 64% of it's max load, not the 50% that the math problem above gives you. There is also the consideration that running any tire below 50% is essentially running it "flat", and that can cause damage to the carcass.
If you have 20" rims and 65psi-max E-Rated tires, 35psi might not be too low, but I'd still try to find a load index table for that type/rating of tire instead of guessing.
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