Will 33x12.50 tires help or hurt gas milage?

[Big-foot]

Hey all, I see a lot of NW posters here. I got this K5 a couple months back, except for the rockers it's in pretty good shape.

The tires will need replacing this year and I was wondering if the extra drag of the 33s will offset the higher gearing, they say $5.00 gas this summer.

It has the 350, 4 speed and 3.07 gears. Even with the 3.07 gears I rarely use 1st and I can get into 4th at 35 MPH if I'm not in a hurry, just feels like it could be geared higher on the street.

I have a set of 31x10.50 mud tires on another set of wheels for off-road so the 33s would only see street use.

Thanks

[bouncytruck]

Welcome to the board. Nice looking ride!

For 33's, you'll probably want gears more in the 3.73 range. I'm running 3.07's with 31's and it is right (I get about 12MPG). The bigger tires will hurt your gas mileage. It takes more effort to get them rolling and they are heavier.

[Big-foot]

I was afraid that might be the answer it's costing me $15 in gas every time I drive into town. I gotta get a good gas mileage motor into that 2400 lb 240Z sitting out there.

Thanks Bouncytruck

[mustardjimmy71]

if your worried about gas mileage maby a full size gm isnt for you

[Big-foot]

I was asking about tires and MPG.

I'm way too old to ask for lifestyle advise, thanks though.

[BBrendal]

I think he was trying to say these trucks generally do not get good gas milage and he wasnt trying to give you "lifestyle advise." About 12 MPG is all your gonna get out of these trucks. Ive heard you could take off your front driveshaft and maybe gain 2 MPG.

[SeventyOne]

Taking off the front driveshaft won't affect anything if he is running in 2hi. Nothing spins.

Now if he is running in 4hi and just doesn't have the hubs locked that's another story. Checking alignment, tire pressure, fuel filter, etc (basic maintenance and tuneup) would be the best way to increase mileage anyways.

[Erik V]

350/350/205/3.73 on 33/12.50/15 mud tires (which tape measure out to 32 and change) I checked mileage using googlemaps to get exact miles and I seem to be pulling down a proud 9.55mpg. Not a far cry from the "about 12" my truck has ran its whole life. My 350 is out of a 79 Caprice, but a stock 350 is a stock 350 as far as I'm concerned.

I'm thinking your 4spd and my auto are similar, my friend's 69 Blazer is a 4spd, but he has 4.11 gears. He gets the same 9-10mpg as I do, also on 33" tires. If you're wanting to experiment one of these days you could meet up and throw my 33s on your truck, fill up the tank, go for a 20-30 mile drive, refill up and check mileage.

Try to not get gas on your side of the river, every time I do they seem to not quite fill it up all the way. Kinda messes with mileage testing.

Erik

[bouncytruck]

How do you check the MGP using google maps? (I've got an Android phone with GPS.)

[Erik V]

Originally Posted by bouncytruck

How do you check the MGP using google maps? (I've got an Android phone with GPS.)

I drove from a gas station by my house in Vancouver out to a car show in Hillsboro. Then to a restaurant in Beaverton, then back to Vancouver. I googled the addresses to those places, entered them as a route to get exact mileage. The truck was completely full of gas to the cap when I started, and when I finished I filled it again to the cap. Took the total number of googlemap miles and divided them by the total number of gallons used. Came to 9.55mpg. I had the top on for the first half of the drive, top off the last half, and I wasnt really nice to the loud pedal except in traffic on the freeways. So real life actual mileage is what I got-since thats how I figure I'm going to drive it everytime anyways.

Erik

[Cap'n Hook]

I run 33x12.50x15 on my Jimmy and regularly get 10-10½ mpg on the highway, stock tranny and rear. Matter of fact, took it just yesterday on a 180 mile trip yesterday, and calculated it again in the 10½ mpg range!