Joined: Feb 2012
Posts: 19,362
Likes: 5,502
From: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
If the exercise bike uses a 1 piece crank, like many kids and older American bikes do, it's likely a 1/2" pedal threading. If the crank is a three piece (two arms and one spindle) then more likely to be the 9/16". But there's no assuming with a direct measurement. Remove the RH pedal and measure the thread diameter. Or take it to your LBS. Andy