My 4x4 has 3.73 differentials. 5.7 throttle body fuel injection and 5 speed manual transmission. I bought around 2001. When I purchased truck owner had BF good rich all terrain tires but I am not sure if these were stock tires. I needed better boat pulling power, so I replaced them with smaller tires to give me more boat pulling power. The door tire decal has since worn off. Truck set under tarp or garage for 5-6 years. I cannot determine stock tire size. Does anyone know the stock tire size for my truck so that the speedometer reads correctly? A BF Good Rich spare tire is still in rack and reads 265/75R 16, but I am not sure that this size was the original tire size. I want to go back to stock for this year/motor/differential/trannie. Help.

 

What I find online indicates that the wheels were all 16" for that model, but the available tires ranged from 225/75R16 to 265/75R16.

Look in your glovebox and see if your RPO code sticker is still readable. It is in my 1996 C1500, and the RPO codes that start with "X" may tell us the factory tire size. The top of the label may say "Service parts identification".

Better yet... go to the top of this webpage, where it says Tools, and click on the VIN Decoder. Punch in your VIN. For my 1996 I get a 5 tab sheet of details, including original sticker price. On the last one, Tech Specs, it shows original tire size, which for my 1996 C1500 is P235/75R15. Also shows factory wheel size for me as 15x7.

Hope that helps!

 

cant say for sure but if it still has the factory rims and theyre 16s it was either 225, 245.or 265 75/16. the best thing i can suggest checking the speed with a gps and seeing how far off it is now.
if it has the 265s on it and youre going 50 but the speedo reads 46 it means it came with the 225.
if it has the 265s on it and youre going 50 but the speedo reads 48 it means it came with the 245
and if its right on then keep that size.

i just hope its drivable to do this test.

whats messed up is after writing that, i hit me you can find the tire size by using a vin decoder lol
https://chevroletforum.com/forum/vindecoder.php

 

Vin Decoder didn't provide deferential ratio and tire sizes. RPO code= XGM X88.

Found RPO CODE DECODER . Truck came with 265/75R16 size tires. Thanks

 

Glad you figured it out. That XGM was the key to the factory tire size - which sounds like what your spare already had. Note as well that the factory tire was LT (light truck) rated, which has more plies than a normal radial. At least that is what I think the LT would mean...

Decoded by https://decoderpo.com/
XGM:
- TIRE FRONT LT265/75R16/C WOL R/PE ST OOR(9591658)