tire change= speedo way off.
 

I switched from the stock 402's to some commanderII both being the same size. 130/90/b16. now my speedo is off by 10 mphs in 5 gear, less at lower speeds. Before the switch my speedo was right on the money.

so heres whats got me scratching my head, if I got new tires with more tread then what I had, wouldn't it cause my speedo to read lower then what it really is? so what the heck is going on? can I reset my speedo? its the first year of the lcd display. I did search but all the post are about the speedo going the other way.

thanks

I'm mean it's reading 10 mph then I'm really going.

How can you tell that your going faster than the speedo says?

What makes you think your 10 mph off. Unless you have access to a radar and someone to clock you as you go by, (or some other method of measurment) you have no idea what speed your actually going.

The difference in a few millimeters tread from worn down tires and new tires of the same size is hardley enough to make a 10 mph difference in speed in either direction. Let alone any difference you could tell by just riding the bike.

Kinda like saying that synthetic made your bike run at lower RPM's. Not gonna happen......

There is a school near me that has a radar gun for your own info that tells you your speed when you should be doing 20mph. This is how I check my speedometer.

Cause those things are always accurate. They've got some going out highway #1 east from my city. I've blown past them at 150 km/h and it says I'm only going 116

Kinda like saying that synthetic made your bike run at lower RPM's.
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Well it says I'm going faster then I really am by 10 Mphs. Checked against my gps which it's always been inline with. Have had a buddy pace me and I've checked it with mile markers.

I'm thinking that the commanders II are a smaller diameter then the 402s. The bikes carb'd so I don't have a programmer. How can I fix it?

There's a product named speedohealer that you can adjust your speedometer to a true setting using a gps...I had it on my '04 Kawi Z1000 when I changed the gearing to give an accurate reading.

I don't know if works for HDs though.