Factory wheel/tire size 85 crew long box 3/4 ton?

[Wincks2]

Is a 16 x 6.5 L wheel and LT235/85R16 load range E tire the original from the factory basic combination for this truck? I'm using LT265/75R tires now but one blew and I'm thinking of going back to original style.

I went with LT265/75R tires last year figuring the 265 would put more tire on the road during our icy winters. Only now have I seen that the 265 and 235 are section widths measured in the middle of the tire rather than where the tire tread hits the road. So would there be no safety advantage on ice and snow with the 265 rather than the 235?

Here is how I've reached the conclusion about the above original specs:

The GMC shop manual has a 1985 Truck Wheel Chart with a column headed "Usage" under which are S100, El Camino, Axle, T100, C100, many others including "CKP 200, 300" and "CK 2-300, P300"

Would the last two, "CKP 200, 300" and "CK 2-300, P300" be my truck? Nothing else in the list has a "C" combined with a "200". I'm guessing the "C" and "200" cover my C2500 truck.

Elsewhere in the manual looks like the factory tires were LT235/85R16 with load range E since load range D doesn't go up to 2740 max weight.


Some vin info is:

1 us built
G GENERAL MOTORS
T GMC TRUCK
G GVWR RANGE 8001-9000 HYDRAULIC BRAKE SYSTEM
C LINE AND CHASIS TYPE LINE CONVENTIONAL CAB, CHASIS TYPE 4 - 2, (I THINK THIS MEANS IT IS A C NOT A K)
2 3/4 TON
3 FOUR DOOR CAB
M ENGINE TYPE AND MAKE PRODUCER CHEVROLET, TYPE 5.7L V8 4BBL, MODEL USAGE C-K-G-P, RPO LT9

[Dooley]

I'm sorry I don't have a 1985 sheet but, hope the 1986 would be the same.
The 1986 C20 crewcab is listed as having 235/85R-16's.
My 1988 V30 came with the 235/85-16's also.

[Keith Seymore]

Wincks -

Here is the factory data packet from the GM Heritage Center archive for 1985. This should tell you (almost) everything you could want to know about your truck.

Take a look and see if you find what you need here; let me know if you need some help interpreting the info and I will walk you through it.

K

http://www.gmheritagecenter.com/gm-h...olet-Truck.pdf

Tire/wheel info on page 4 (page 4 as labeled in the original document; page 7 of the pdf file).

Your interpretation of the CKP200-300 reference is correct; it is shorthand for the model types covered:
C20 (same as a C2500) - 2wd 3/4 ton
K20 - 4wd 3/4 ton
P20 (P truck chassis is the "bread truck" chassis)
C30 - 2wd one ton
K30 - 4wd one ton
P30

[Keith Seymore]

It looks like the answer to your question is "yes" - except D range on the fronts and E range on the rear.

K

[Wincks2]

Thanks guys.*

Interesting they had D on front and E on back.

Kieth, based on pages 6 and 7 it looks like I should check to see if these changes have been made with the conversion to diesel:

Axel ratio 4.1 to 3.73*

Brake booster dual diaphragm to hydraulic power

Battery to batteries

Delcotron generator from 36 amps to 66 amps

Add an engine block heater

Steering gear type manual recirculating ball gear to integral power

No steering linkage.

**

*
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[Wincks2]

And some other things listed on page 31 too. Looks like I should keep reading before post in.
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