SHIMANO FRONT FREEWHEEL SYSTEM
This is by no means an exhaustive or technical review of the Shimano Front Freewheel System, just an overview of another way the bicycles could freewheel.
The Shimano Front Freewheel (FFS) was a proprietary bicycle drivetrain design of the 1970s that placed a freewheel between the pedal cranks and the front chainrings instead of on the rear wheel with the gears which enabled the rider to shift gears while coasting. The FFS rear freewheel is different than a standard freewheel because it’s “stiff” with more friction than a normal rear freewheel. It will slip if necessary however, to stop the chain in the event of, for example, a clothing tangle — which could otherwise lead to injuries of the leg by the drivetrain, crashing of the bicycle, or both.
FFS marketing followed Shimano’s then-current path of beginning with lower-cost implementations of the system using low tech and usually heavier materials. The resulting system was substantially heavier than the standard freewheel and, in any event, did not penetrate the market noticeably, although Panasonic, Ross, Schwinn, and Raleigh briefly equipped bicycles with FFS.
Patricia’s Suburban has the FFS
And So Does Ray’s Schwinn World Tourist
The System was made up of three or four parts depending on if you had a one piece or three piece crankset:
These chainwheels are immediately recognizable by the large black mechanism surrounding the crank arm at the base of the chainwheel. This is the freewheel.
The Bottom Bracket with the freewheel (If you had a three piece crankset)
The Friction Freewheel
These are recognizable by the warning on the outerplate that it is for use only with the Shimano FFS System. If you open one of these freewheels up, you’ll see that each ring has its own set of pawls, so take my advice and don’t open one of these.
The Positron Rear Derailleur with the ‘Push / Pull’ Wire Cable
These derailleurs were an early version of an indexing system. Instead of the shift levers being indexed the derailleur itself was. You may be able to see the indexing marks on a triangular plate at the bottom of the derailleur where it meets the pulley cage. The plate had ‘stops’ that corresponded to the individual gears. The cable is a special solid wire instead of a coiled cable, which enabled it to both pull the derailleur and push it. A return spring would not have been powerful enough to overcome the ‘stops’ built into the derailleur. Positron derailleurs can also be found on bicycles that did not have the FFS. This particular one was on a late model Peugeot Mixte.
The system had many detractors including Sheldon Brown. Most thought it was unnecessarily complex and heavy. I do think it is heavier than a standard freewheel however, it is also quite handy especially if you are an urban commuter who has to do a lot of start and stop biking. By not having to pedal in order to shift, you can shift into and easier gear while you are coasting to a stop so that you’ll be in the appropriate gear when you’re starting off again. You can also shift into a gear while you’re at a stop and as soon as the rear wheel starts moving the chain will fall into the gear that you’ve preselected.
This video with Calvin Jones from Park Tool Company illustrates the system quite well
I hope this was interesting and informative. If there is something that is confusing or wrong please let us know!