tire size choice advise

[BCFAST]

My Michelins are nearly done; I may get another 7k out of them, but I need to start planning for a new set. I am still running the stock chrome steel wheels, and as you can see in my sig. , the Michelins are a little taller than stock. I would like to go taller! I wanna drop my revs down some more at cruise... . currently, I show 67mph @ 70. I thought a 255/85 would really be trick, because it's tall without being super-wide... . but all I can find in this size are muds and I dont go off-road. The 285/70's arent as tall as this, and are barely taller than what Ive got. As of today, Im considering 315/75's... therefore my question is: will the rolling resistance and wind turbulence of the wide tires overcome the lower revs-at-speed and end up giving me worse mileage?



Brian

 

[Dennis Garrett]

My 97 had Goodyear Wrangler 245's since day one, 2 sets. Last month I moved up a size & went to Firestone Steeltex 265's. My speedo has never been very accurate, but now it was worse. Here's what I did. I found out my odometer was regestering low per mile, so I ordered a smaller gear (30 tooth instead of 31) that sticks into the side of the transmission. That brought my odometer to almost perfect, but the speedo was about 7 mph fast. I took the trim bezel off, removed the instrument lense (8 screws, about 3 min. ) & carefully pulled the speedo needle off it's shaft. Next I drove the turnpike at 2000 rmp with a stopwatch, I figured my exact MPH, and while still locked in at that speed with cruise on, I gently pressed the needle back on the little shaft at the correct speed. For the first time in 155k, my odometer AND speedometer are both correct, & working perfectly.

 

[Dennis Garrett]

Almost forgot, with the above setup, I'm travelling a true 56 mph in locked up O. D. at 1500 RPM. & 75. 5 at 2000 rpm. I'm guessing top speed would be 112 mph at 3,000 rpm, based on doubling the 1500 figures.

 

[vc]

BCFAST

I thought you were doing some towing with your truck - a race car hauler if I remember correct. Anyways, if you are, consider that the bigger the tires you put on, the more your going to loose pulling power. I just got a bigger , heavier boat and I think I'll be going back to stock size on next tire change.



vc



ps, what's the story on your rough engine and the timing adjustment?