• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

TR2/3/3A Speedometer

Share this page

GeorgetheTR3

GeorgetheTR3

Freshman Member
Country flag
Offline
Is it common for the Speedometer to be off, mine is showing 70 when my gps speed shows 55?

Is there a way to correct the difference? not that it really makes too much difference.I am just wondering.

George the TR#
 
Yes, it can be calibrated easily by an instrument shop, or yourself if you are handy. Before getting into it too deeply, is there a chance your car used to have 4:10 differential gearing, and switched to 3:70’s? If your odometer reads faster than it should, then you likely have a 4:10 speedo. That would make it better to swap out the unit for a 3:70 speedo.
 
That’s a big gap in accuracy
You could use this table at assess your gearing and tyre size to give you an indication of what it should be to the RPM in any gear
Most of our gearboxes run 1:1 in 4th with the differences on tyres and diff.


they can be rebuilt with accuracy typically with wheel rotation counts etc

Speedos

J D O Instruments...Classic car instrument repairs for most British & European post war classic cars (est 1963)
www.jdo1.com

This is the info method for calibration

Speedo calibration 1

J D O Instruments...Classic car instrument repairs for most British & European post war classic cars (est 1963)
www.jdo1.com

As a uk base enthusiast it appears to me to be a USA speedo if it reads the “double nickel “
 
Attached are a couple of pages showing various speedos and other instruments, along with a speedo "readings" chart. I hope they help.
 

Attachments

  • TR Gauge Listing.pdf
    31.5 KB · Views: 143
  • TR-Speedo-v-RPM.pdf
    126 KB · Views: 136
Mine read 70 at 55. I sent it to West Valley Instruments and it’s right on the dot now at 60 - 70, where it matters to me. Turn around was about a week, but that was during good driving weather. They also repaired my tachometer that had slowly lost all touch with reality over the last year and a half. Both are steady as rocks, and look great though I did not request that they be made pretty.

Steve
TR2
 
Back
Top