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PastorCharlie
NC
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Joined: 03/28/2004
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High mileage tires have a harder rubber compound than low mileage tires. That is why tires have 40,000 miles or 80,000 miles ratings.
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CapriRacer
Somewhere in the US
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Joined: 01/27/2012
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mkirsch wrote:valhalla360 wrote:The ABCD... is an old system based on how many nylon plies the tire is made from...
I'd have to go back and look to verify, but I don't think that the OEM 245/75R16 tires off Dad's 1989 Chevy C2500 Scottsdale have an LT designation or an ABCDE load range rating. They just say "10 ply rating."
So ply rating was how it started. Then at some point in the 80's or 90's they must have adopted the LT-ABCDE system. Later on they started this load index/speed rating deal. Now pickup truck tires have ALL THREE which makes it confusing. IF you're not up on the legacy nomenclature you and the customer are talking two different languages.
Here's a copy of a page from the 1970 Tire and Rim Association Yearbook that has Load Range and Not Ply Rating: Barry's Tire Tech: 1970 TRA, page 2-04
The TRA yearbook from 1960 still uses PR, so somewhere in the 1960's is when they started using Load Ranges.
And according to Tire Guides, your 1989 C2500 will show an LT245/75R16 Load Range C or D and it had Load Range on the placard and the tire. Nowadays, you can only get Load Range E's in an LT245/75R16, but that's OK because the load carrying capacity of a Load Range E at the same pressure as a LR C or D is the same.
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CapriRacer
Visit my web site: www.BarrysTireTech.com
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Cummins12V98
on the road
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Joined: 06/03/2012
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My 14" tires on my boat trailer OE were "C" full inflation 50psi and I went to same size in "D" and I run them at 50psi. Weight/inflation chart dictated 45psi based on load. I always add 5psi (per GY Tech) when up sizing load range so 50 is the perfect number as I have towed at least 25k at that pressure with perfect tread wear.
Bonus of having extra capacity if needed was when I recently had a total hub bearing failure and aired up the one tire to 70psi and towed home on back roads for 60 miles with the single tire only getting to less than 120 degrees.
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2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"
"HeavyWeight" B&W RVK3600
2016 MobileSuites 39TKSB3 highly "Elited" In the stable
2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD
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Grit dog
Black Diamond, WA
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Joined: 05/06/2013
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Cummins12V98 wrote:My 14" tires on my boat trailer OE were "C" full inflation 50psi and I went to same size in "D" and I run them at 50psi. Weight/inflation chart dictated 45psi based on load. I always add 5psi (per GY Tech) when up sizing load range so 50 is the perfect number as I have towed at least 25k at that pressure with perfect tread wear.
Bonus of having extra capacity if needed was when I recently had a total hub bearing failure and aired up the one tire to 70psi and towed home on back roads for 60 miles with the single tire only getting to less than 120 degrees.
God bless torsion axles. Didn't even need to chain up the dead wheel!
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold
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Cummins12V98
on the road
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Joined: 06/03/2012
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Grit dog wrote:Cummins12V98 wrote:My 14" tires on my boat trailer OE were "C" full inflation 50psi and I went to same size in "D" and I run them at 50psi. Weight/inflation chart dictated 45psi based on load. I always add 5psi (per GY Tech) when up sizing load range so 50 is the perfect number as I have towed at least 25k at that pressure with perfect tread wear.
Bonus of having extra capacity if needed was when I recently had a total hub bearing failure and aired up the one tire to 70psi and towed home on back roads for 60 miles with the single tire only getting to less than 120 degrees.
God bless torsion axles. Didn't even need to chain up the dead wheel!
I actually put the "C" spare on and it was 1/2 flat and I knew that would not have worked!
I have an extra complete hub assembly on a spindle now and the tools to change if needed in about 15 minutes. That stays on the Boat.
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