do bigger tires throw off your speedometer?
#1
#5
#6
The OP didn't give any info on his truck, so we can't answer how to fix his speedo calibration. If he has a 99 or newer F-150, he can recalibrate with one of the aftermarket computer tuners.
In theory, you could recalibrate the speedo by changing the gears in the differentials but that would depend on what gears are available. The gears he needs may not be available for his truck.
In theory, you could recalibrate the speedo by changing the gears in the differentials but that would depend on what gears are available. The gears he needs may not be available for his truck.
#7
Trending Topics
#8
#9
people that say its off by X mph are not giving accurate description.
its would be off by a percentage. If your 31" tires are factory, then the 33s would be 93% of the 31s. so if you are actually doing 20, the display would show 20x.93=18.6 If you're doing 75 the gauge would read 75x.93=69.75. So at 20 its off by 1mph, and at 75 its off by 5.
So its really inaccurate to say "its off by 2mph"
its would be off by a percentage. If your 31" tires are factory, then the 33s would be 93% of the 31s. so if you are actually doing 20, the display would show 20x.93=18.6 If you're doing 75 the gauge would read 75x.93=69.75. So at 20 its off by 1mph, and at 75 its off by 5.
So its really inaccurate to say "its off by 2mph"
#10
#13
#14
30mph cop days 47
I'm in need of some information as well. I have a 2004 f150.. I had like 265s (31s)on my truck. I now have 315s (35s) my father said it should only be a few miles off the speedometer. but yesterday I got pulled over on my road (25mph) in which i was doing 30. Cop says I was doing 47. Now going that slow isnt going to be a 17mph difference. Is the cop full of ****. Or do I need to do somthing.
#15
Divide the new tire diameter by the old size diameter and multiply this fraction by the old speedometer reading at a given speed and that will be the new speed. A GPS is good for checking real speed. Or you can time the vehicle between mile markers on the interstate. A tuner will allow you to adjust the tire diameter in the computer and correct the speedometer.
So, 35/31 = 1.129
1.129 x 30 = 33.87
So, if your speedometer was correct before, you were going about 34 mph. How did the cop clock your speed? It's impossible to accurately judge speed by just following someone unless it's done over a very long distance.
So, 35/31 = 1.129
1.129 x 30 = 33.87
So, if your speedometer was correct before, you were going about 34 mph. How did the cop clock your speed? It's impossible to accurately judge speed by just following someone unless it's done over a very long distance.