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Have some questions about Shimano RSX levers

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Have some questions about Shimano RSX levers

Old 06-01-16, 08:12 PM
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jbohan6
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Have some questions about Shimano RSX levers

Hey BF mechanics, I have come across a set of Shimano RSX levers, and would like to install them on my '88 Schwinn Prelude. Currently the bike has Suntour Accushift components. The freewheel on the back is a 6 speed. So, what i gather i will need to do is acquire a rear derailleur that is compatible with the RSX levers, and change my freewheel to a 7 speed cassette. I would then need to change the length of my chain to accomodate the larger cassette. Now here is what I don't know- What derailleur would be compatible with these RSX levers? Would a Shimano Tiagra derailleur work? I have installed the FD lever, and it seems to work fine with the Suntour Accushift FD. Second, how will I know how much I should lengthen my chain by?

I am slowly learning how to work on my bike myself, so I'm looking forward to learning about this. Thanks!
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Old 06-01-16, 08:37 PM
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Raiden
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You don't just change your freewheel to a cassette- a freewheel is a ratcheting mechanism that threads on to your hub; a cassette slides on to a hub with a ratcheting mechanism built into it. You're looking at replacing your rear wheel. You can buy 7 speed freewheels, but you might run into needing to respace your rear axle (the 7 speed freewheel will be wider than your 6 speed freewheel, and might contact your frame, especially with a chain on the high gear) and re-dish your rear wheel.

Yes the Tiagra RD will work (I'd get an old 8/9 speed model, not a new generation 10 speed model), but make sure to use a modern 7/8/9 speed chain- if you use some old 7 speed model or re-use your 6-speed chain it may be too wide for the derailer's cage/jockey wheels and cause damage.

As for chain sizing, check youtube or park tool's webpage, you should be able to find detailed instruction on a few methods. Don't add new links to an old chain- toss the old chain and use a new one. It's not good to mix old and new links, and it may not play right with narrower 7+ speed parts.

Be careful with that old front derailer- yes it should have no problem pushing the chain up and down the crank, but it's likely wide enough between the two plates to let the chain escape off the outside of the high gear or inside the low gear. Also, with a narrower 7+speed chain you might need to worry about jamming your chain between the chainrings.

Last edited by Raiden; 06-01-16 at 08:42 PM.
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Old 06-01-16, 10:57 PM
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SkyDog75
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Originally Posted by jbohan6 View Post
The freewheel on the back is a 6 speed. So, what i gather i will need to do is acquire a rear derailleur that is compatible with the RSX levers, and change my freewheel to a 7 speed cassette.
Change your 6-speed SunTour Accushift freewheel to a 7-speed Shimano-spaced freewheel. Like Raiden mentioned, a cassette is a different animal. You'd need a different rear wheel, or at least a different hub.

Originally Posted by jbohan6 View Post
I would then need to change the length of my chain to accomodate the larger cassette.
You'd only need to increase the length of the chain if the largest cog on your new freewheel is bigger than the largest cog on your old freewheel. The number of cogs is irrelevant to chain length; it just needs to be long enough to make it around the combination of your biggest chainring and biggest cog on your freewheel.

Originally Posted by jbohan6 View Post
Now here is what I don't know- What derailleur would be compatible with these RSX levers? Would a Shimano Tiagra derailleur work?
With a few exceptions, most Shimano SIS (indexing) rear derailleurs would work. Stay at 9 speeds or less and you avoid most of those exceptions. Shimano road front derailleurs will work, but not mountain bike derailleurs because they're designed for a different cable pull ratio.

Originally Posted by jbohan6 View Post
I have installed the FD lever, and it seems to work fine with the Suntour Accushift FD.
Indexed shifting requires both the derailleur and shifter to be designed to use a precise amount of cable pull per shift. If you can get a Shimano shifter and SunTour derailleur to work well together, it's sheer dumb luck that they share a similar cable actuation ratio because they certainly weren't designed to work together.

Originally Posted by jbohan6 View Post
Second, how will I know how much I should lengthen my chain by?
If you're just starting to work on bikes, you'll find lots of good info on Sheldon Brown's web site. Here's his method for sizing chains:
Derailer Adjustment
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