Bigger Tires, Speedo Wacked

[Simon]

I increased tire size from a 245 tire to a 265. This thru the speedometer off, can anybody tell me how to get it right? I know this has been posted before in the forum but I can't find it.

 

[Dreher]

The speedo sensor is driven off a gear in the transmission. You can change the pinion to correct your speedo. The dealer should be able to look up the correct pinion for your application.



Bob

 

[Dieselnerd]

Interesting! When I went to the 265's my speedometer became more accurate. From time to time they set up radar speed indicator signs around construction areas. I've always tried to hold an exact speed when approaching those signs to see how accurate my reading was. My speedometer always read 2 MPH fast so when it said 45 I was only going 43. Same with a stopwatch and milemarkers. Now it reads right on with 265's. My odometer, when compared to milemarkers, always gained 1/10th of a mile every 10 miles. Now it loses more than 1/10th of a mile every 10 miles. I can live with that. A friend of mine went to 265's on his '98 and said his speedometer was now right on also. If I were you I would make sure of the accuracy before changing the gear. As your tires wear it will slowly increase your speedometer reading as well. The 265's are really not much larger in diameter than the 245's. Around 2-3% larger if I recall correctly.