Well, looking at what nightmanx1 said, I'd have to say 1.25" or less. I had to go to 8 tooth drivers to put a 1.5". It hit my front heat exchanger with the 9 tooth drive. My kid has a 1.00" and 9 tooth drivers on his. No problems.
MAKE sure you know the drive shaft diamiter. If I end up swaping out my track this year I am going to drop down to a 7 tooth and change the axle out, I will use a Phazer axle since it is 1" and is bigger than the Exciter one that is in my sled now. 8 tooth will gain you 7/16" more clearence and the 7 tooth will give you 7/8". My new track is 136x15x2.25, I am going to have to shave the track 1/4" and I am going to drill the 1.25 holes in it, but that gives me a reason to drink beer and fire up the smoker. Also might take out the fwd heat exchanger, tunell and the rear one and put a big U heat exchanger in place of them all. Then I can stick with the 8 tooth.
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