Video- " How To"


Speed Wizard

Correct your speedometer after changing tire size


When tire size or gear ratio is modified, the speedometer on the vehicle will read incorrectly. When a vehicle's speedometer is in error, so is the odometer reading. This situation may lead to missing scheduled maintenance and even worse, traffic violations.


  • The Speed Wizard solves this problem by conditioning the speedometer signal to the correct counts per MPH. 

  • Adjustment of the speed wizard requires very little time to correct for a change. 

  • Adjustment uses the vehicle speedometer as an indication tool.

  • All of this can be accomplished while parked.




  • Does not interfere with ABS control or other onboard electrical systems.
  • Verification of speed correction when parked, by viewing the old and new speed on the speedometer.
  • Settings may be saved numerous times.
  • Simple correction techniques, by using two push buttons.
  • No trim potentiometers (mechanical screws) to get dirty or wear out.


Check out what others are saying!


PRICE is very Competitive!!!

Less intuitive devices have sold for as much as $230

Buy a Speed Wizard Now for just $209.98, free shipping to lower 48 States.

Great Birthday or Fathers Day Gift!


Speed Wizard is shipped free UPS ground to the lower 48 states.

Alaska and Hawaii will have additional shipping costs.

You can Order by calling us @ 201-828-9822

How Speed Wizard was Born

People usually are interested to know how a product came to be.  I tried my best to explain it here, if there are specific questions just send us an email.

Download The Manual

People like to research the products before they buy them, you can download the manual here, it shows how the speed wizard is used and installed. Feel free to ask us any questions using the form below.

Download Detailed 99-04 Install Guide

99-04 Owners, here is a nice guide to use for your install.

Download Detailed Wiring Diagram 05 - 08

2005 - 2008 owners, here is the wiring diagram from Ford DVD's

Download One Page Information Sheet

If you own and like the Speed Wizard, tell your friends. This is a single page document that explains the Speed Wizard and has necessary contact information.


Ask us some questions about this product, we are ready and willing to answer any questions you may have.

Video of Adjustment

Here is a video showing just how easy it is to adjust the Merlin Controls Speed Wizard.

Comments / Feedback

Already own and use a Speed Wizard? To make our product even better please Send us some feedback on the Speed Wizard.

Comments / Feedback (DOC FILE)

This is the same feedback form as above except it is in WORD format. This is for users who would prefer to fill out the form in MS WORD then send it in.

Merlin® Controls -  FMDK Technologies, Inc.