Hello, has anyone here ever calibrated their speedo on a volvo 940 or any other simular model? My car shows me going approx 4 mph slower than I am actually going and it has resulted in 2 tickets before I realized. The former owner of my car had small low profile tires put on and I bet had adjusted the speedo to accommodate. I recently had normal size tires out on.

 

Have you checked the manual for the o.e. tire size? I run 14, 15, 16 and 17 inch rims on the same cars with negligible speedo variance. The key is to fit tires that have the same overall diameter and thus circumference. This link is an eye opener as to what a few tire sizes off will do to the speedo...
http://www.miata.net/garage/tirecalc.html
On your 940, the speed sensor is on the rear end and, other than shimming it for clearance, there really isn't any adjustment.

 

Thanks! Yes, my car did originally have very different sized tires. I'm guessing the only way to adjust would be to change some component behind the instrument cluster or get new tires.