The variety of speedometers fitted to the MGB is a common source of confusion, especially in relation to the fairly common practise of swapping O/D and fully synchronized transmissions into MGBs that didn't originally have them. This will consequently cause the speedometer and odometer to read too high or too low, not an ideal situation.
"Revs" in the table below referrs to the turns-per-mile (TPM) the speedo expects to receive from the transmission via the speedometer cable. The TPM of your speedo should be printed somewhere on the face, along with a serial number.
Any variation in tire size from original specifications will of course also have an effect on the accuracy of your speedometer. See the discussion on tires and tire sizes in the Service section of the Tech Library on this website for more information on this topic.
The NAMGBR also has a cross reference table from car numbers to speedometer serial numbers by Orin Harding. [Ed. Note- this link seems to have gone MIA, so I've duplicated the table below.]
KMR reports that if you have a setup that doesn't correlate to any existing speedometer type, Nisonger can put a new faceplate on your speedometer, and recalibrate that way. Check the Directory section of this website to find a list of companies that provide Smiths and Jaeger instrument servicing.
Tooth count (transmission):
- Overdrive - 21
- Normal - 27
Thanks to Bruce Mills for scanning and submitting in this chart - it's a lot more complete than the chart I was building!
MGB Speedometer Cross Reference Chart
by Orin Harding, NAMGBR
The information displayed here is from MGB Driver, the MG Mailing List, on the Internet, or other sources. The North American MGB Register assumes no liability for the accuracy, safety, or legality of these contributions. Any opinions expressed here are those of the contributors and do not necessarily reflect the opinions or policies of the North American MGB Register.
Car # Car #
|101 - 138400||Not Germany|
|101 - 138400||Germany|
|BHA 4574||6144/05||MPH||Tire size 560-14|
|BHA 4636||6144/15||KPH||Tire size 560-14|
|BHA 4637||6144/13||KPH||Tire size 155-14|
|BHA 4638||6144/14||KPH||Tire size 165-14|
|138401 - 153877||Canada|
|138401 - 332925||Not USA, Sweden, Germany, or V8|
|138401 - 158230||Not USA, Sweden, Germany, or V8|
|158231 - 328800||Not USA, Sweden, Germany, or V8|
|332395 - 361000||Market Unknown|
|360301 - 410350||Market Unkown|
|187211 - 258000||Sweden & Germany|
|258001 - 410000||Sweden & Germany|
|138401 - 2580000||USA, USA for Germany & Canada|
|258001 - 282419||USA, USA for Germany & Canada|
|282420 - 410000||USA, USA for Germany & Canada|
|BHA 5210||5230/11S||MPH||V8 (Except police)|
|Change point unknown, but |
after car # 410000
|AAU 3036||Z 65465||MPH||RHD Police|