How were you checking that your speedo was reading correctly?

The 2.3" increase in diameter means that your new tires are approximately 8% taller than your stock tires. Since you did not adjust your tune for the new tire size it means that you were actually going 8% faster than your speedometer was indicating. So at an indicated 60 mph you were actually going about 64.5 mph. If Jesse adjusted your new tune for the 285/75/16 tires then your speedo should be correct and your rpms should be 8% lower than before the W4M tune.

 

ok let me try....


Before the tune i paced other cars and then those little speed poster cops post off to read your limit always was right with my speedo..

So i infact never got the tune for the 285's

 

I'm not sure what you're missing here, it's pretty simple.

If your tire size was not changed with the tune, then:
1) You were running incorrectly before the tune, and are running correctly now, or
2) You were running correctly before the tune, and are running incorrectly now.

 

Or i guess ive never ran correctly.

 

My speedo has never been changed for the gears and it was not tuned also..

But my speedo has never seemed off.

 

so what if i was going 112.

 

The difference is about 8% so 112 X 1.08 = 120 mph actual speed at an indicated speed of 112 mph. It is possible that you speedo was reading low before you put the larger tires on. The point is if Jesse adjusted your tune for the tires you have on now then your rpms will drop about 8% because of it.

 

the correct way to do this would be to have your tuner enter the value of your rear gears and the physical measurement you took of your tire while your truck was parked on a level surface.

I used a 3ft level, positioned it until the middle bubble was centered, then ran a tape from the deck to the level. My tire is spec'd at 32" tall but only measured 31.5".
holla

 

I never told jesse to adjust for tires since ill be switching back to stock setup for winter.

 

sounds like you did the right thing then