Originally Posted by e.myers

Can you get a 110 mm 3 piece crank?
Trying to set up a bike for a very young and short 4 year old. 140mm seems too long and I'd like to get somewhere between his current 75mm crank and the one that's on a bike I just purchased for him. Also could use some recommendations/theories on gearing based on the following New Bike specs....

16x1.75" Tires, 140mm crank, 43T(+/-) chainring (also have 36T), & 16T Freewheel

His current bike that he's very comfortable on (although he has to peddle 90mph)
12" tires, 75mm crank, 28T chainwheel, & 18T "freewheel".

Remember, my goal is to keep him comfortable with the bike, so I'd like to get him geared right between these two bikes. He can get use to the longer cranks gradually is what I'm thinking. Currently I want him to be able to sit on the bike and still peddle without nailing himself in the jaw. Again, get comfortable with the new bike then start standing.

Thanks for any help.

Eddie