How to determine stock size tire, will the vin help?

[Jorge6.5]

Sorry if this is posted in the wrong area, not sure where else to post it.

I want to put Oem size tires on my truck, 1990 k1500 short bed standard cab with 5speed and 305 v8. Reason being, I want best fuel economy and to accurately determine fuel mileage. I currently have 265s but they are doggy with the 3.42 gears. I always thought 245s were stock size but after some recent searching, I have found that 225s were a possible size. So I'm not sure on what tires to buy.

Will my vin number be able to tell me what the truck came with from factory?

Thanks

 

[95C1500]

check the door jamb

 

[michael hurd]

As mentioned check the door jamb, in the case the sticker has been removed / painted over etc, a call to your dealer may help with the VIN.

Out of many GMT-400's in the family, only 2 originally had 225/75/16's on them, however most are 3/4 ton's with 235/85/16's and only 4 half tons.

As far as getting the best fuel economy, that depends on a lot of factors, including the temperature, speed, starts and stops, distance, alignment, pressures, general tune up, and so on. In town, low gearing can be somewhat beneficial, as less power is needed to get up to speed.

Too high a gear / too large a tire can hurt performance as well as having too low a gear / too small a tire for the intended operating RPM / speed.

 

[Jorge6.5]

Oh yeah the sticker on the door has that info! Too bad mine is gone so no help there.

 

[Ruger_556]

What size is your spare? Just a shot in the dark there but... 2wds got full size spares. I don't if 4wd's did or not but worth looking.

 

[cjman250]

i wanna say its 245/75/16 but im not sure

 

[Jorge6.5]

No spare came with the truck and the PO put on 15" wheels with 30x9.50 tire. I got stock 16" wheel and bought 265s before knowing the gear ratio. I should have just bought 245s. Been considering going with 215/85r16 tires, same height as 245s but not as wide. I figure those would further help my MPGs.

This is just a commuter vehicle, come spring time I will be traveling back and forth to work just over 100 miles a day. Looking to get better gas mileage and an accurate way of figuring out miles to the gallon.

Thanks guys

 

[Ruger_556]

No spare came with the truck and the PO put on 15" wheels with 30x9.50 tire. I got stock 16" wheel and bought 265s before knowing the gear ratio. I should have just bought 245s. Been considering going with 215/85r16 tires, same height as 245s but not as wide. I figure those would further help my MPGs.

This is just a commuter vehicle, come spring time I will be traveling back and forth to work just over 100 miles a day. Looking to get better gas mileage and an accurate way of figuring out miles to the gallon.

Thanks guys

I'd probably just go with 245's myself... To figure your fuel economy check your odometer against the mile markers. Once you have a percentage you can just multiply it by your miles driven and you get an accurate mpg figure.

 

[19trax95]

My rclb 4.3 came with 225/75r16. I currently have 215/85r16. For the short time I had the 225 on there I didn't notice any significant mpg changes. I sort of wish I stuck with 225 or went wider because the skinny tires look a little goofy and they sink into soft ground really easy.

I know that skinny tires can do better in mud and snow but when they are h/t they certainly don't.

 

[cjman250]

I think that the rpo codes have the tire size in them too

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