Tire Size

[Jackpine]

Originally Posted by BigSur

I wanted to use this thread to clarify TS for myself. I have 285-65 R18's. The manual calculation puts at about 2522 (w/ 3% squish). I tested it today by pacing w/ my wife in her car. Speed seemed to be fairly accurate but a little fast at times. However, Over an approximate 4.8 mile ride (according to the Camry), my odometer was .1 mile low. SO, I need to increase TS, correct. I'm thinking 2575????

You would increase TS if your truck's odometer reads lower than actual. However, if the Gryphon speed PID is reading high, then you should REDUCE your TS! As has been said before, the dash speedo will read a bit fast (about 2mph) when the odometer and Gryphon are accurate.

The Camry's odometer can be off too. Everything is fairly approximate. I personally like to use interstate mileage markers (the longer the run, the better) or a GPS. I have a Garmin hiking GPS that shows current speed as well as distance.

Your 2575 figure is correct, however, for a 0.1 mile error in 4.8 miles (About 2%). And, your initial figure of 2522 is what I would have started at too. Personally, I suspect it is VERY close to the right number, Camry or no Camry!

- Jack