Which way does a sprocket change affect the speedometer?

[loadedthorn]

My '97 CBR 600 was taken -1 in the front by the previous owner, and he said it wouldn't need a speedohealer. I disagree, just because of the inaccuracy of stock speedos anyway. My question is, where would the error show up? It seems to me based on the flow of traffic that the speedo shows that I'm going 8-10mph faster than I really am. Is this an understandable error given the -1 sprocket up front?

[slickwill]

Yep that's about right. -1 in the front is a 6.25% change. Your speedo will say that you are going 6.25% faster than you are actually going. However most bikes are already off by a few % anyway so you might be as much as 10% off total, could even be worse than that.

Edit: if it was me, I would get the speedo healer.

[Maholli]

10% off easily.. Speedo healer is a must when doing any sprocket change +or -... Its always important to know your speed... At least for me it is...

[randyjoy]

+1

I have a -1 front right now and my Speedohealer change is 10.5%.

[loadedthorn]

Great, thanks guys!

[juspimpin]

how simple is the speedo healer installed? where do you mount it-near speedometer or in the trunk? I am now off by 20% and need one just want to know a little more about install.