Just got a Sportsman 500 Touring, it had 25's on it but I bought a set of wheels and tires. The new tires are 27's. How much is my speedometer off now? It feels like Im going way faster than the speedo says.

 

you do loose speed on the speedo w/ bigger tires. most likely @ least 5 mph. imo

 

You can figure it out witha calculator. Just add 8%. 25 on speedo=27. 50=54.

 

I have an 08 touring with 27" ITP's on it and yes the speedo is short. Mine tops out at about 48 to 49 on the speedo but the guys I ride with say it is doing about 52-53. I have not had my gps with me yet to confirm but that will happen in a couple of weeks when we head up elk hunting.

 

it's normal to loose up to 5 mph on bigger tires like that .

 

Your speed sensor will Should a slower rotation. Kinda strange since the speedo and wheel sensor (Part# wise) on a Sportsman and Scrambler are identical ,yet one has 23" wheels and the other 25".

 

Will the speedo change if you chance tires sizes... sure. Does it mean much... nope! The speedo's on ATV's are pretty inaccurate to begin with.

I've had two quads running side by side with the same size tires (and brand) and there has been as much as 7mph difference.

What would be really nice, is to have an ACCURATE tachometer on a quad.

 

This link should help you out...

Checking Your Speedometer After Changing Tire Sizes

 

Exactly! We've had our machines with same sized tires showing different speeds staying side by side. The best way is to get the GPS out. Most accurate way in my mind.