951Dreams

So, did a rally with my local PCA yesterday. I quickly noticed my OD was off. I downloaded a GPS app and started testing. My speedo is dead on, however my OD is reading 10% over actual milage. In other words when I travel 1 mile it reads 1.1 miles. Exactly.

When I replaced my OD gear a couple of months ago, I got the 21 tooth version. Everything I found online says 85.5+ to 91 US MPH OD should be the 21 tooth. But now I'm wondering if in fact I need the 22 tooth.

Anyone know more real world experence. Or anyone know if 21 tooth vs 22 tooth = 10%?