I adjusted my Bama Tuner revs per mile to 655 (per http://www.tirerack.com/tires/Spec.j...D215R5ATAKORWL) however I am now starting to seriously doubt the accuracy of my speedometer. I have passed numerous speed radar stations that post your speed, and without fail I'm always off. Everytime I'm cruising with the speedo at 55 MPH they show 50 MPH.

Anyone know how to verify that my speedometer readings are correct?

 

gps

 

bfgs site show 656 revs per mile.

not that is matters 1 rev

are you sure it downloaded correctly?

 

I also think something is screwed up. I went from my stock tire size (30'' or so) to 33''s and now my speed-o is dead on without a tuner. Do they low ball the speed-o from the factory?

 

drive 60 mph on the freeway and check it w/ the mile markers

 

Mine is perfect.

BTW, I wouldn't check it with that kind of "radar". That is not what police usually use to catch you speeding (or rather that isn't what you should use for an accurate speedo).

You would want to use a "regular" or "laser" radar. They are most accurate and can pinpoint an actual moving object. The radar you are explaining is a "wide range" radar and it could actually be pointing at the car next to you (if there is one next to you). I don't trust those actually at all.

 

There are only certain types of radar that police are legally allowed to use. The type inside the roadside stands are what the police use. Some of those roadside stands may have a camera in them. Some of the bands used by police are wider bands. I believe X band is 14 feet wide whereas a laser is less than 4 inches.

 

We (FL) are transitioning into ONLY using laser. We still do have a bit of x band radar, but it doesn't work worth a crap IMO!!! I love laser, so accurate. The only thing is, down here people that speed...REALLY speed. It doesn't take a high dollar piece of equipment to figure out someone is literally FLYING through the intersection. They usually go 20mph above the speed limit.

 

Is there a way to take my gear ratio, tire size, RPMS, and figure out my speed? If so, what would my speed be at 3,000 RPMs?

That's what I experienced, when I went to 32s without adjusting the revs per mile the radar stations were reading me speed identical to my speedometer. However I really really really hope this isnt the case... when I calculated my gas
mileage before correcting for the tire size my MPG is 13 MPG.

How did you verify it? maybe I can do the same thing

Nah I'm a late night driver, I've driven by the stations many times without another car in sight.