Pedal thread sizes
 

I own an older Schwinn exercise bike that has pedals with wide straps across the top to help keep your feet on the pedals. They work well but I am wanting to replace them with a spare set of Shimano road pedals that I have laying around. The problem that I have run into is that the diameter of the Shimano pedals (9/16" x 20 tpi) is larger than hole in the crank arm.

The way I see it, to swap out the pedals I have 4 options.
Drill and retap the holes (1 CW and 1 CCW).
Replace the crank assembly.
Find a pedal with the smaller diameter shaft.
Live with it the way that it is.

I need to learn to search better. The older is 1/2"x20tpi

http://www.bikeforums.net/archive/in...p/t-28349.html

I think they use 1/2 inch pedal size. Most exercise bikes are that size. You can find simple 1/2 inch pedals at Walmart. Nashbar and others also sell 1/2 inch pedals. Or you can find standard exercise bike pedals on ebay.

I personally would not be drilling and taping the crank arms. #1: Its a lot of work. #2 It weakens the crank arms. #3. Its a lot of work.....

I have seen references to higher-quality 1/2" pedals.

http://www.bikeforums.net/showthread...ght=pedals+1/2

I'd also recommend getting some kind of 1/2" pedals and putting toeclips on them and using the bike as-is.

If you're okay with the pedals sitting a bit further away from the crankarms (q-factor) you can get 9/16 to 1/2 adapters
http://sheldonbrown.com/harris/pedals.html

Nope- it won't work. The old Schwinn one-piece cranks don't have enough material to allow them to be drilled & tapped for 9/16" thread pedals.

It's possible to replace the cranks with a conversion bottom bracket and 3-piece cranks, but the chainring on the old Schwinn Exercisers was huge- something like 60 teeth. These are available for recumbents and downhill bikes, but it's a pricey proposition.

Or you can get a set of these <http://www.bikemania.biz/Bicycle_Pedals_s/50.htm> pedal adapters. They are about half way down the page. It allows you to use 9/16 pedals on 1/2 crank arms. I used them on my schwinn. They do move the pedals out a little but not bad.