The original Stearman brakes were hydraulic but the wheels were 24 inch. When most of them were converted to sprayers they got 27 inch wheels (handled the higher weight better, better on rough fields, plus the BT-13 type brake is just a better design). To put the bigger wheels and brakes on required changing the axles. Duster's and Sprayer's Supply in Chickisha OK have most everything you'll need when the time comes but alot of guys today are switching to Redline disc brakes (available from Air Repair (
www.airrepairinc.com) who also stock just about everything you might need for your airplane.) The original Stearman brakes and the BT brakes are kinda finicky - you're forever adjusting and playing with them, but the Redlines have a really good reputation. I'm just about to order the Redline kit for my airplane.
By the way - there is an automotive type lining that will fit the BT brake shoes but NEVER use one. They'll heat, swell, seize the wheel, and you're upside down in the dirt faster than it took to read this sentence.
Dan