5-speed versus 6-speed

[JabeSmith]

I've got a Raleigh road bike, 531 main tubes and forks, and love it - had it for 30 years, and done many happy miles on it. Unfortunately, I had a severe mechanical failure on it the other weekend when the rear mech snapped in two and mangled the chain, buckled the wheel, and bent the boss that the rear mech screws into.

I don't really want to be bending the stays to make it wide enough to fit modern 8/9/10-speed wheels, nor have the agro of finding long enough rim brakes, etc. to take 700c wheels.

My current gearing is a Shimano SIS 5-speed block, and I have Sachs Huret Rival Aris 6 indexed shifter. I'm struggling to find a 5-speed block, but have found a Shimano 6-speed block (14-24). What I want to know is whether the indexing for the 5-speed block and the 6-speed block is the same. Visually, the 6-speed just looks like the 5-speed with an additional sprocket next to the wheel. That is, if one click of the shifter moves the chain a certain distance for the 5-speed block to move one gear, will that distance be the same for a 6-speed block.

As for how I bend the brased-on boss for the rear mech, that's tomorrow's problem.

Hoping someone can help.

 

[Tim Hall]

You could be in luck. The Sainted Sheldon says:

6 Speeds

In the 1970s, there was a move toward 6-speed freewheels. These were of two types:

• "Standard" spaced 6 speeds had sprocket-to-sprocket spacing the same as the existing 5 speeds, around 5.5 mm
  Standard spaced 6-speeds required increasing the frame spacing to 126 mm, aggravating the problems introduced with the move to 5-speed, but still providing satisfactory service in most cases.
• "Ultra Six ®" spaced 6 speeds used a closer spacing, around 5 mm. This permitted an Ultra Six ® freewheel to directly replace a standard 5-speed unit on a 120 mm hub. The key to making this work was the use of a narrower chain. The interior width of the chain was the same as always, but the new narrower chains used shorter rivets, so the ends of the rivets didn't protrude past the outer chain plates, as the rivets in traditional chains did.

More here.

 

[lpretro1]

I have a 5 speed freewheel which I can sell you!

 

[Pat "5mph"]

I bought a new 5 speed freewheel recently from my lbs. On my question "is their production going to be phased out soon?" he said no, there is still a demand for them for children's bikes.

 

[TheDoctor]

^^This. 5 speed blocks are still out there. Linky.

 

[mrandmrspoves]

Take care bending the brazed boss. There is a derailleur allignment tool that is perfect for this - and almost a necessity for modern indexed gears as a slight misalignment will badly affect the indexing. If you can, get a large adjustable spanner onto it for leverage and try to bend it just once - because repeated bending will weaken the metal severely. If it does snap, it is still possible to get the old bolt on hangers that some bikes used to have.....

 

[mrandmrspoves]

Just type in Gear Hanger on eBay

 

[Smurfy]

I'm struggling to find a 5-speed block

Interlock Racing Designs (IRD) are the best bet for older freewheels. They're rather expensive, however, they do include modern innovations such as shift gates, ramps and profiled teeth to make them perform similarly to today's cassettes.

If you can't stretch to the expense of an IRD freewheel, there are plenty of other 5-speed freewheels available.