View Single Post
Old 05-23-18, 03:30 PM
  #3  
Ghrumpy
Senior Member
 
Join Date: Jul 2009
Posts: 800
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 379 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Originally Posted by unclejemima View Post
My sons bike has a crappy old 5 speed falcon rear derailleur and grip shift. The bike has 20Ē wheels.

The derailleur is a pos from day one and has never worked good, and Iíve adjust it for hours and itís just a poor quality part. (And old)

A 6-speed setup is not necessarily better quality than a 5-speed. It just goes to 6. Quality is a matter entirely unrelated to how many cogs it has.

Originally Posted by unclejemima View Post
My other son has a 6 speed shimano unit on his bike and it works great. I want to get something like that to replace the 5 speed on my other sons bike so his shifts and works nice as well.
The shift quality may have as much to do with the shifter as the derailleur. It has nothing directly to do with how many clicks it has.

See where I'm going with this?

Originally Posted by unclejemima View Post
my question is how and what do I order for a derailleur, cog set, shifter and chain? Iíve heard a 5-6 speed cog set are identical width and should interchange just fine, but can I use a shimano derailleur with say a sram grip shift?
Certain SRAM shifters work with standard spacing and Shimano derailleurs. The gaps between the cogs are the same for 5s and 6s standard freewheels. But some shifters have more clicks.
A 6s freewheel is wider than a 5s of course, so you will probably have to respace the rear axle to accommodate the wider freewheel. Then you will have to re-center the rim.
Originally Posted by unclejemima View Post
at what point do the cog sets get to wide to work on a smaller kids bike? (Example can I use 7 speed cog set?). Looks like there is approx 130mm between the dropouts. Is this standard? Itís a steel frame so I could bend it out a bit if needed.
Not needed. 130mm will certainly accept a 7s freewheel. But you would have to respace the rear axle even more because the 7s freewheel is wider still than the 6s.

So, yes, 130mm will accept anything from 7s to 11s rear hubs, but they would be kind of a silly indulgence on such a bike.
Originally Posted by unclejemima View Post
5 speed chain ok with 6 speed?
Depends on the cogset. Flat cogs, no problem. Cogs that have Hyperglide-style ramps will not work with a standard 5s chain if the chain pins protrude from the side of the plates.

Allow me to suggest you replace the derailleur first, before attempting to change to a 6-speed setup. Might save you a lot of unnecessary work.
Ghrumpy is offline