Where do you get a bike in Pokemon FireRed?
In Vermillion City there is a Pokemon Fan Club if you listen to the Chairman of the Fanclub talk about his Rapidash, he will apologise to you and give you the Bicycle Voucher which you can redeem for a bike in Cerulean City.
Get to Vermilion City and find the Pokemon fan club you can't miss it its a green building with a sign next to it there is a chairman of the club talk to him and listen to his story about his rapidash once he is done he will give you a bike voucher show this to the bike shop in cerulean city to get a free bike.
Go to vermilion city and find the Pokemon fan club its a green roofed building has a sign near it. Go inside and talk to the chairman listen to his story about his rapidash then after he's done he gives you a bike voucher go back to cerulean city and go into the bike shop give the voucher to the cashier to get a free Bike!