Classic & Vintage - Shimano Light Action derailleur question

I'm working on a bike with light Action 6 speed indexed RD. I'm having to let up on the pedals a little to shift, the same way I would with a friction Derailleur. Is this normal with older index shifting, or is it time for a new freewheel.


Thanks

Light Action RD's have a spring loaded arm on them; could be that you're mashing hard enough that the spring is compensating for the additional force otherwise required to move the RD.

-Kurt

Letting up is fairly normal and a good technique. At least you have something that shifts better than NR.

I have the same experience with my 6-speed light action setup, which isn't a bad thing at all :)

Is this upshifting or down shifting? I didn't really notice what you're talking about on the Prelude I just traded. (Then again, maybe I was just happy to get it working in indexed mode.)

It happens down shifting, up shifting is pretty crisp. After going for another spin around the block, it seems more prevalent shifting to the 4th ,3rd , and 2nd sprockets.

It's always a good practice to let up a little prior to a shift. Having said that, Light Action 6 speed should have Uniglide cogs, which means it won't shift shift under load like HyperGlide but should shift better under load than a standard cogs. It's hard say where or if there is a problem. However, HyperGlide freewheels are inexpensive and perform far better than Uniglide. It's worth the $20 investment for a new HyperGlide freewheel and chain, even if this doesn't turn out ot be the source of the problem.

Edit: The OP posted more info just as I was composing my response. Since the problem is occurring in the middle cogs and not the extermes, it is unlikely that the spring or cable tensions are at fault. It is most likely wear on the chain and/or cogs.

Another cheap/easy fix is to replace the section of cable housing that runs from the chain stay to the derailleur with SIS housing. As I recall, my Prelude just had normal housing and when I replaced it with SIS it started working much better. Some of the early SIS bikes did not have the SIS cable housing. It's stiffer and does make a difference.

it might also be worth making sure the chain is the correct length and that the derailleur cage isn't trying to wrap too much chain. is the problem the same when using either front chainring?

I'm reasonable sure the chain and freewheel are original to the bike. This is a $150 flip that i have about $50 invested. I obviously want make as much as possible, but I like to sell things that are right. Would you spend the money to replace the parts.

A short section of SIS housing is pretty cheap. Just try replacing the section going into the derailleur and see how things work.

I paid $50 for my Prelude, $5 for the SIS levers at a swap meet, and maybe a buck or two on the SIS housing, and I got the SIS working pretty good.

I'm reasonable sure the chain and freewheel are original to the bike. This is a $150 flip that i have about $50 invested. I obviously want make as much as possible, but I like to sell things that are right. Would you spend the money to replace the parts.

If I'm going to sell it, it needs to work properly. If it needs parts to work properly, I get the parts. Nothing goes out of my garage that malfunctions or fails to work properly. Unless I sell it as such, and clearly advise the buyer.

Off topic: BBM, nice avatar. :)

I'll try the cable housing first. If that doesn't do it, then a freewheel and chain.

Thank you all for the help!

Off topic: BBM, nice avatar. :)

+1. Funny.

Another cheap/easy fix is to replace the section of cable housing that runs from the chain stay to the derailleur with SIS housing. As I recall, my Prelude just had normal housing and when I replaced it with SIS it started working much better. Some of the early SIS bikes did not have the SIS cable housing. It's stiffer and does make a difference.



Good point. It could also be slight corrosion of the cable and/or housing. A good lube may solve the problem but both are inexpensive to replace.

Finally replaced the shifter cable housing today. Best $2 I ever spent, it made a huge difference. Thanks Doohickie:thumb:,