Aftermarket wheels and Speedo operation?.....

[LunchBox04V]

Ok, I have a real mystery for you folks. I switched tover to my snow tires yesterday. They are 195/60/15 (stock size for L Wagon). I have been using 215/50/17 all summer and part of spring.
Here is where the problem is..... Once I went to the aftermarket wheels, I started to get intermitent operation of the speedo. It would drop to zero, while I was doing any speed (1-70mph mad no difference). Now that I switched back to the stock sized tires, the problem has gone. The speedo has worked grreat, zero problems!?......
What do you guys think? Am I just nuts, or should I just stop complaining? Have you heard of this happening before?

[99SUS SFD]

That does seem strange, but you're running a pretty good difference in tire size (overall). When running the 17s, you're speedo is reading 5.2% too slow. I wonder if that's enough to make it act weird.

Here's a good calculator.
http://www.miata.net/garage/tirecalc.html

[LunchBox04V]

Sorry gave you the wrong size......they are 215/45/17's. It is something like 2.1% difference. (Car travelling 2.1% faster than indicated). It is not a issue between actual speed and indicated speed. The speedo just goes to 0. It also had a +45mm offset. We will see how she does when I get home. I am currently stuck in TRI, and have to overnight in MKG tonight and then I am off on personal travel........I will report any changes once I drive again.......haha