I think there is a difference in the OD of the drums for the Rocky Mountain brakes, if so :
- What is the OD of the new drums for the 1909- 1925 brakes
- What is the OD of the original 1926-1927 drums
Thank you in advance Toon
The 1909-25 set includes new drums with 11 3/4"" diameter while the 1926/27 set uses the std drums with 11-1/4" outside diameter.
There are two different diameters of Rocky Mountain brake drums, the original, and the reproduction. You need to know which one you have. The 26 uses a stock drum.
Thanks for the information !!! But can some one tell me why they make two different sizes ??
The Rocky Mountain drum size for the "Small Drum" are larger compared to the later original 26/27 rear drums. The emergency brakes for the 26/27 were made to fit that size drum with larger backing plates. The original Rocky Mountain brakes were designed for the small drum/small backing plate rear ends. The RM replacement large drum was originally cast iron with a small drum to retain the original emergency brakes. Back then, you discarded the original small drum when installing the RM brakes.
I happen to have the original style RM brakes on out 13 touring. I prefer the earlier style because they stop better when backing up compared to the later style that is offered now. Also, prefer having cast iron drums vice pressed steel.
I asked Bud (Who Makes RM Brakes) why he no-longer supplies them with cast iron drums....his answer...."Cost".
Don Skille had some cast up a few years back for himself and me. They are messy to machine, but work better in the long run. The original drums were riveted to the Rocky Mountain drum, but are not as effective as the cast iron.
There was also various accessory outside brake systems that used a supplied 10 inch drum as well. It can be a challenge locating that size replacement drum nowadays. Maybe early Chevy drums are 10 inch.
With the lack of effective braking in reverse with the presently available RM brakes, I am puzzled why they are not made like the originals, which are known to be quite effective in both directions.
Anybody know? Is it also a cost issue?
The new ones stop much better going forward. The transmission brake and parking brake should be kept in operation for stopping while going backward. This is important if you stop going uphill, or if the axle should break, leaving the car in freewheeling. The parking brake will still work in reverse.