i have 27" tires and 2.94 rear gears, chart says i need a 29 tooth gear, but only a 28 seems to readily available. how far off will speedometer be with a 28 tooth gear?

I had a similar situation with my set up. All you can do is buy it, install it and check it. But be prepared to try the next closest gear if you don't think it registers close enough. I got lucky and my was close enough. I'd rather show 1 or 2 mph over than under. The gears in my opinion are not that expensive.

The actual math calls for 28.55 which rounds up to 29 but when it's near .50 I like to round down so that the speedo reads a little high. In this case you're talking less than 2%.