I have a question about speedometer calibrators. How far can your speedo be off initially, to where a calibrator will bring it back to accurate?

Let me explain this; let say at 70 mph on the speedo with 33s and 3.21s your actual speed is 79 mph, will the calibrators on the market bring the speedo back to spec? (I arrived at this by using the formula; speed X trans gear X diff gear / stock tire diameter X 336 = rpm. If you work this backwards with your new tire diameter you get actual speed.) It has been my experience that calibrators have limitations as to how far off you can be initially.

Also, recommendations as to which calibrator is best and has the widest range would be helpful.

Thanks in advance.

 

Get a Procal. It will get you calibrated. No limitation, unless you are running under a 24" tire, or something insanely large.

 

ProCal is the way to go and will handle 24" - 54" tires

http://www.aev-conversions.com/pdf/i..._Reference.pdf