I have the -1 front sprocket and it does affect yourspeedo quite a bit. I was going to go on the interstate with a watch and see how fast I have to driveon the speedoto goa mile in 1 minute(60 mph) andthat should tell me how far off it is. TodayI was riding and opended upfor a little while and fifth down ahill. Thespeedo went to 145 but I doubt I was doing over 130.