Speed Indicator Reading

[alwaysme]

If I have 35 Inch Tires, and the Speed indicator reads 200 KM/H, does this mean i am actually driving faster because of the larger diameter? Any Mathmatecians can do a quick calculation of stock LC at 200 KM vs a 200 KM/H reading on 35 Inch tyes? how fast is it really traveling?


is there a way to get an accurate measurement?

 

[BigDouggieDoug]

I don't know of any formula. But I've used a GPS to check against my speedometer readings after having changed to 35s on another truck. I've ended up installing a speedometer calibration module (Hypertech) to correct the readings.

 

[sptsdn]

There are numerous tire calculators online. Most are for metric-only conversions so you'll have to play around with the 'tire 2' spec to get the overall diameter to as close to 35" as you can get.

Discount Tire calculator

 

[JBHorne]

You can use the online figures to determine the difference, however note that even from the factory the speedometer can be of by as much as 3%. In fact, with my first set of replacement tires, the speedometer was actually more accurate than stock.

The GPS method is the best. There are numerous speedometer applications for iPhone, Android, and BlackBerry for free. I'd know what percentage it's off by (note that it's not always going to be off by the same amount -- it will be more off at 100mph than at 60mph than at 25mph). If you really care to fix it (and I would with a 35" tire increase), you should use a recalibrator like mentioned previously.

Does anyone know if this recalibration could actually be done by a Toyota dealer using TechStream?

 

[alwaysme]

Thanks JBhorn, i came accross an online calc, had issues figuring out the metric wheel sizes vs standard. Anyhow 200km/h reading with 35 is approx 212 km/h on the speedo.