changing sprockets makes speedometer invalid?

andy andy at
Wed Oct 6 15:48:09 PDT 2010

I've never bothered rigging up a speedo on my GSXR front end, but running 
15/45 on my SVS I can tell you that 3500rpm is 45mph, 5K is 65, 6K is 75 
and once you get used to it, you can know what the drop off in rpm per mph 
in the gears.  A lot of the other speeds, such as 9K in 2nd, you've got 
other problems than the basic speed law any way.


On Wed, 6 Oct 2010, Jo Rhett wrote:

> I have repeatedly seen comments on here about different sprockets and how the odometer is inaccurate.  I'm confused.  The sensor is on the front wheel -- how would running different sprockets change the validity of the odometer?  Or am I confusing this with changing front wheels?
> Reason I'm asking is that I need to replace the sprockets & chain on my street bike.  I have a whole 520 kit with a 45 rear sprocket sitting here.  Is going from a 44 stock to a 45 rear going to affect my speedometer accuracy?  I'd rather not, as I currently live in Sunnyvale where cops are *BORED* and are known for giving tickets for 5mph over.
> Yes I know the speedometer is "optimistic" at best.  I've done a lot of testing and it appears to be consistently 10% high -- so 44mph reported is 40mph, 66mph reported is 60mph, etc.  I'm very used to that.
> -- 
> Jo Rhett /  velociRaptor Racing
> #553 WERA

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