Sears twin 18

paul52446m said:

Can any body tell me how to figure out these gear ratios? I know the larger tires will make it faster so to slow it down for more power, how much smaller would the engine pulley have to be? I was running a 1050 and 1250 class. Paul

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The new tires are 24 inches tall, and the old are 23 inches tall. Take 24 and divide it by 23 which gives you 1.04xxxxxxx. We'll round it to 1.04 so you get the idea here. Now take your engine pully size and divide it by 1.04, and that will give you the same speed as before. Let's say the pulley is 3 inches. 3 divded by 1.04 equals 2.88 inches. Chances are you won't find that size, so let's go to the driven pulley. Lets say it is 6 inches. (I have no clue what these machines run for pulleys, so bare with me.) Take 6 times 1.04 equals 6.24 inches. So the closest you're going to get for this value is 6.5 which is .26 inch difference. Now the other value of 2.88 inches, you can go down to 2.5 inches. A .33 inch difference. So it depends on how bad it was bogging down, If it was just barely bogging, I use the 6.5 as a driven pulley. If it was bogging a little more, then I would go with the 2.5 engine pulley. But the best way to figure this out would be to get the tire runout. The 23's should be roughly 72.22 inches of runout. And the 24's should be roughly 75.36 inches of runout. If this is too confusing, (Which I can understand that it can be.) Give us the engine pulley size, the driven pulley size, and find out what the runouts on the 23 and 24 inch tires are. Just take a tape measure and wrap it around the tire to see how many inches around it is. I'm sure we can figure it out for you.