I thought I would mention this to anyone with 35's. my buddy and I went out with his truck and the Jeep last night to check the the speedo. 0-45 we were the same, when he was going fifty, and I showed fifty I seem to be catching me him, then we ran out of road so we could not go much further. But up to 45it seems ok.

 

Are you sure the truck is accurate? My truck is off by about 5mph at that speed.

Bryan

 

You can see what the new speed actually is, after getting larger tires, by using the equation below.

actual speed = speedometer reading *(new tire diameter / old tire diameter)

The faster you go, the bigger the difference is between indicated speed, and actual speed.

All of this assumes that the speedometer was correct before the tires were switched.

Andrew

 

from what i remember in the academy speedo's can be 5-7 mph off either way.

tis the reason cops generally give 10 mph over the posted limit

 

I was wondering if that's what your screen name meant...

 

I still think that a GPS is the best way to check your speedometer error. My Garmin has been extremely accurate. I'm running 265/75-16 tires and I've had my computer flashed for the 255/75-17 which are 1.3% larger than mine. The GPS reflects this difference. It's less than a mile per hour at 60mph.

 

man i have had plenty of cops pull me over for less than 5mph over. of 3 tickets one was 2 over and the other 4. the middle was 10 over i admit i didn't know the limit and was flowing along w/ the rest.

 

Right now I'm running 35x12.5's. When my speedo is reading 65 mph my Garmin Map 76s says that I'm running 73 mph. I have checked it more than once with the same results. Not sure if this helps anyone or not, but just what I have experienced.

 

if you go to discount tire and put your info in it will show you the change in your speedometer. where its says "what size now" use the stock size from the dealer heres the link:

http://www.discounttire.com/dtcs/infoTireMath.dos

 

it all depends on where your from, or where your at.

each department is different on traffic enforcement.


I've seen Autolite has a GPS speedo you can buy.


it cost about $400.00