dit

I have recently aquired a Centurion Ironman with 6 speed 105 sis indexed shifting which I would like to retain since I have never owned an index shifting bike. I would like to install a long cage rear derailluer along with a wide range freewheel. What derailluers are compatable with the sis dt shifters? I am just busting to take it for a spin but I need some lower gears.

Zaphod Beeblebrox 

I use Deore XT front and rear derailleurs with 7-speed 105 shifters. Got em on eBay as a pair for like 30 bux. It works very well when its dialed in....put lots of barrell adjusters in line. I find that the Deore RD shifts very easily under load.

I'm not particularly fond of how the 105's shift in index mode however.



Basically you can use any of the more modern shimano derailleurs (Deore, Ultegra...Sora if you're a sucker for punshiment) except Dura-Ace.

miamijim

More or less anything but Dura Ace.

T-Mar

If you're replacing the freewheel, go with a Shimano HyperGlide. It will make a world of difference, especially with the larger jumps of a wider range freewheel.

mkeller234

+1 on the Hyperglide, I have one with my 20 year old 105 group and love it. I have a deore DX rear derailleur instead of the 105 and it works really great. I would bet that you can get them pretty cheap on ebay.

prof2k

Same as people have said above for derailleurs. Some freewheels have spacing that is not compatible with shimano indexing (such as some suntour models), so make sure you get a compatible freewheel.

bluenote157

depending on how big a freewheel you are going with, you might even be able to continue using that same rear derailleur. I think that 105 rear can probably go 27t max??

Like others have said, pretty much any shimano derailleur will work sans pre-97 dura-ace.

Old Fat Guy

There's a good chance that you have a freehub, not a freewheel. Is the rear hub bulbous on the drive side? If so, freehub.

dit

It seems that new 6 speed freewheels are not very plentiful. I did find a 14-34 that dropped from a 34 to 24 so the top 5 cogs are pretty close and just a big jump to the 34 to get me up the steep hills when I run out of gas. I just tried a 28 cog and it works fine but the b screw needs to be adjusted to the max. I could probably make a 30 work but I am sure the 34 is out of the question.

Thanks to all for the advise on the useable derailluers. I think I have a mtb shimano takeoff in my parts collection somewhere. I think I will give it try when I get the freewheel.

top506

I've used them with 30t with no problems.
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RobbieTunes

I swear he said he had an Ironman......I must be sleeping.
Good job..

dit

Hey Robbie

It is an Ironman. I probably paid too much but it seems original and the sprocket teeth have no dicernable wear. Everything is 105 except the seat post, stem, and rims which are Wolber. I believe it is lighter than my other 2 bikes but it doesn't have the big freewheel or triple crank. Wheels need a little trueing and I don't have a spoke wrench to fit it yet.

WAZZUBIKER

Post some pics if ya get a chance. Centurions are cool bikes.

dit

I just added some pics to the Centurion ser# thread.

miamijim

Keep in mind that 6-speed levers can be over shifted to 7-speed and 7-speed levers can be over shifted to 8-speed.

miamijim

They will index through all gears except low in 'SIS' mode. There's no 'index' shifting into low but its really not needed because your limit screw prevents over-shifting.

top506

I've heard that the 7-speed shifters can be made to work with 8, but I've never, in half a dozen attempts, gotten a 6 to work with 7, and that's trying the overshift at both the top and bottom of the range.
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dit

That is interesting that a 6 speed shifter will work with the 7 speed freewheel. I have a 7 speed fw to try it with. I would not have tried it without the suggestion. I don't think the fw is a Shimano though. I will still give it a try.

miamijim

8-speed center to center is touch narrower than 7-speed but its been done before. Some 8-speed cassetttes and freewheels have the same C2C as a 7 speed.

miamijim

I wanted to make sure I wasn't spreading bad information so I headed out ot the garage and played around.

My test subject was a 1988 Peugeot Triathlon with a full Shimano 105 SIS group. Its a 6-speed bike with 1050 series 105 components including 6-speed SIS levers, Uniglide chain and Uniglide cassette.

For the test I used the following parts:

Shimano 105SC 1055 7-speed SIS shiftlevers
Sachs 8-speed freewheel mounted to a 126mm 105 freewheel hub'd wheel.
Shimano Dura-Ace 8-speed cassette hub
Stock Triathlon wheel w/ 6-speed Uniglide cassette

Test 1: Installed 1055 105SC 7-speed levers on the otherwise stock Peugeot with a 6-speed Uniglide casstte. Verdict: Indexed fine after properly adjusting the derailleur and indexing.

Test 2: Installed 1055 7-speed levers and 8-speed Sachs freewheel equipted wheel. Verdict: Indexed fine after properly adjusting derailleur and indexing. As a side note the wheel only needed a thin spacer on the gear side for the 8-speed freewheel to clear the dropout and this was with a Uniglide chain. Based on this test I'd say a 126mm 8-speed setup is somewhat feasible. When its not so hot out I'll do another test with a narrower HG chain.

Test 3: Installed 1055 7-speed levers and Dura-Ace equipted 8-speed cassette wheel. Verdict: Indexd fine after properly adjusting derailleur and indexing.

dit

Jim

I installled a 7 speed Shimano **********? freewheel and the system still indexed fine for me too. The 105 rd just did not like the 32 cog at all. Thanks to all for your help. Now I need a long cage rd.

miamijim

More than happy to help. 32t is pushing it!! While you waiting to acquire a long cage derailleur try turning the 'd' screw in all the way. Its the screw that makes contact with the derailleur hanger.

Zaphod Beeblebrox 

This is why C&V rocks. Very cool Jim, good work.

dit

I tried turning the b screw in and even put it in from the bottom to give it some extra length to no no avail. This paticular freewheel has a big jump from the 32 cog to the next cog which is a 24. When it gets onto the 24 cog it jams up against the 34 cog and will not get up and over it. It also will not run on the 24 cog because the cage is rubbing against the side of the 32 cog. I also tried an old mtb rd that I had in the part bin but it would not go up and over the 32 either. ............While writing this I realized that if I clamp the old mtb cage back a little farther than I did on the original attempt it may work. I think I will go out and give it a go if Di doesn't give me too much grief.

dit

A Deore came up on CL yesterday afternoon for $10 so I jumped on it. I am ready to get out the wrenches again. Thank to all for thier help.