The size of the wheels has a direct affect on gear ratio.
Imagine if you left all things the same and put on a set of 10 inch wheels. Your top speed would be way lower, but you would have tonnes of torque.

Now imagine swapping those out for 30 inch tall wheels (like the old skool 1800 bicycles).
Your top speed would be huge, but you would have no torque or acceleration.

Changing the size of your tires has the same affect as changing the size of your sprockets.

Now, having said that, I realized something wrong that my statement above... I changed out both the front AND rear tire for D606.
Both tires got taller (probably by some ratio that is fairly equivalent to one another).
Meaning whatever gearing ration change happened on the rear, also happened on the front (where the speedo measurement is taken).
So that's why my speedo accuracy didn't change so much when I went to a taller tire.

 

Gear ratios and rear tire sizes have nothing to do with speedo accuracy. You finally got to the point of confusion when you said you changed the front tire. THAT of course makes sense.

 

larger rear tire=less power and slower handling, that's a fact. it's not a 450.

 

It's not just the size of the tyre, the weight plays a major role in the performance.

 

How come nobody is running the Pirelli Scorpions?
They're a really popular off-road tyre for 4X4 down here in AUS.
When I set the list they were on special too.
120/90-18 $62.99 at Motorcycle superstore.
Are they too expensive compared to the Kenda tyres?

"Rated best DOT tire by Dirt Bike Magazine!
Front and rear tires are competition-designed with FIM homologation in mind
Used by MX World Champions Mickael Pichon and Stefan Everts
Durable new tread compound increases structural stability, provides higher mileage and better traction
New and improved version of the MT 83
DOT approved front and rear"

 

well, most generally when something is larger, it weighs more.

 

Are you trying to tell me that with 10 inch tires on this bike, the speedo is not going to be affected? Think again...
Tire size DOES affect speedo accuracy.

The calibration of the speedometer is based on a specific wheel circumfrence.
That's how it measures distance... [&:]

 

kawi- he said rear tires won't affect it. go ahead and put on a 10 inch rear, it won't matter because your speedo pickup is on the front tire so the rear will have no bearing on how fast the speedo pickup reads.
you answered your owncomment in a way when you said that "calibration of the speedometer is based on a specific wheel circumference". you're right, the front one. the rear has no effect on how fast the front speedo delivers info to the gauge. unless your KLX has a speedo pickup on the rear tire somewhere and I doubt that.

 

I run that tire on my bike. I love them. I have a 90/90-21 on front 120/90-18 on the rear. BEST tire I have ever purchased for this bike! I wouldnt trade it for any kenda. I had on and the tire flew apart. It sucked. never buy a kenda. save the lil bit of money and buy either pirelli scorpion or the mt-90 are v rated! HIGH SPEED enduro tires are the way to go for less than 90 bucks us. lol

 

I just ordered the pirelli mt21. They arrived today and I'm geeting ready to put them on. (klr 250) They look a little more agressive than I thought, I hope they are ok on the road. I ride some single track that is sandy in places. I'll give a report when I get them on.