Bigger tires?

[Jackpine]

Nice reply, Longshot!

I would not be surprised to see a fuel economy increase in the 50 mph range with slightly bigger tires. I hardly ever drive at that speed in Arizona with our 75 mph interstates and 65 mph country roads (everyone runs about 80 mph and 70 mph on each of those).

About the only time I'm at 50 is in the city, where the speed limit is 45. (I'm keeping up with traffic).

- Jack

[Longshot270]

My programmer makes an electrical average of 15-17ish when I'm either going to or coming back from Cabela's. That includes jumps from 70 to 95 and maintaining that speed. I'm usually anxious when I go there and pissed off when I leave so I dont have any "normal" driving numbers.

[ticopowell]

Great posts all! I just have a little to add, I put some bigger tires on my truck, 315/70R17's and I did notice a difference in mileage, I expected mileage to go down overall, but I drive a lot between 45 and 75mph and while there wasnt a large bump, it was noticable . I also enjoy the look, I put a 3" block in the front so my truck is a little "over leveled"(2" would make it level), but I love the look and the tires seem to fill the void quite nicely. I have some pics posted on my profile here but if you want to see any specific areas I can go take a pic for ya .
I did notice a large difference in off the line performance, and I use more gas to go, but once I am up to speed I didnt notice any difference. I have 3.73 gears btw, and if anyone wants to donate to me to put 4.10's or 4.56's in feel free!

[jmwilso2]

Thanks for the great replys everyone. Its really given me a lot to think about. I'll see about getting some time at the local track come spring and then do some math. The vac gauge sounds a lot like a manifold pressure gauge from an airplane. I'm a commercial pilot by trade, and on many light aircraft you use a combination of manifold pressure(actually manifold suction), engine rpm, and fuel air mixture controls to set power. I have an aircraft mechanic friend that may have an old manifold pressure guage around that cant be used in an aircraft anymore. It would be pretty simple to plumb it in. As for trips to cabelas, I'm sorry to say we dont have one around here yet, but we do have a bass pro shop a couple hours away. I've found my fuel economy is usually better on the way there than it is coming home. I have attributed this to an increase in vehicle weight on the return trip as a result of exchaning light portable money for heavier items like guns and fishing gear.

Thanks again guys

Joe

[Longshot270]

That sounds like the exact same guage so it should work. The guage I use measures manifold "pressure". You'll need one that only reads to about 25-35 inches of Hg. Regular driving I see 20" on idle, 25" if there is a bit of engine braking. Probably will be the same exact guage and your already trained to use one.

[Jackpine]

Ah, the joys of recips. Throttle, mixture, prop - and all for just ONE engine! (Too damned many levers in my opinion.)

As for your mileage to and from the shop, I suspect it is "downhill" from you. You could confirm this with a GPS that shows elevation.

- Jack

[jmwilso2]

Are you a pilot too Jack?