I have been rowing through McCalley's "Model T Ford, the Car that Changed the World" looking for the dimentions of the small drum. My '23 Runabout is supposed to have small drums but the ones on it look like the large drums and measure more than 11" OD. What should the small drum measure?
The Rock Mountain outside brakes for a small drum car uses an 11 3/4" drum that fits over the original small drum. Some folks leave the little drum off when adding outside brakes.
I think the small drum is 7 inches.
1. The original 1906 (same size on the NRS Fords) to 1925 rear brake drum was approximately 8 inches on the inside and 8 1/4 when I measured outside to outside with the plastic 12 inch ruler.
2. It looks like you have one of the many accessory external brakes installed on the rear axle. If working properly that is normally a good thing. Most of those included an additional drum that was larger and more substantial than the original 1906-1925 brake drum. However, some external brakes when fitted to the 1926-27 rear axle just used the larger 1926-27 rear axle brake drum that came standard on the 1926-27 cars rather than providing a larger brake drum.
3. An easy way to check which axle you have is to look on the inside of the rear wheel at the backing plate. Take a look on the inside of the rear wheel at the backing plate. If it looks like the one below it is the late 1915-1925 style backing plate and is just under 8 inches across so the 8 inch drum will not drag as bad. (for additional pictures see page 587 of Bruce’s book) The picture below is from the page 38 of the Sep Oct 1989 Vintage Ford.
If it looks like the picture below from page 27 of the Nov- Dec 1980 Vintage Ford it is the 1926-27 style rear axle (ok 1926-27 rear axle backing plates – they could have been installed on an earlier axle – but probably not). For an additional photo see page 589 of Bruce’s book.
4. I hope that helps. My guess – you don’t have a problem. Even if it is the 1926-27 style rear axle – it will work great and you will also have a better emergency brake. And nice looking roadster on your profile page.
Hap Tucker 1915 Model T Ford touring cut off and made into a pickup truck and 1907 Model S Runabout. Sumter SC.
Thanks guys, with you help I figured it out. I DO have a small drum rear end but it has Rockies and they have a large drum added over the top. It sure LOOKS like a large drum setup.
No wonder the parking brake is so feeble . . .