in my reasoning about tire size and speedo error when I said that 165s would be just about right with the black gear. If I had a 10% optimistic error with 185/65/15 tires, that error would have been even greater with 165/70/15s. So, you're right, the 22 tooth gear would go well with your 225/50/15s, which have a 75" circumference, vs 76.9" for my 185/65/15s. The fact that my 142E with the 195/60/15s on it has a pessimistic speedometer comes from its being about 8% optimistic after I swapped its BW35 for an M41 and my then trying to recalibrate the speedometer and not having gotten it quite right yet. But rather than doing more fiddling on it and screwing it up even more, Ill just shave a little lead off my foot. ;-)

If you decide to order from OD Spares, it might help with the dimensions if you tell them you want the same gear they sent to R.C. Silvius on Jan.11,2006 under their invoice #501.
Bob S.