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1993 D/A 7 speed to Triple crank, retain 7 speed and index(3 posts)

1993 D/A 7 speed to Triple crank, retain 7 speed and indexLizardman
Apr 17, 2002 8:06 PM
I have a bike with a dura ace group and a set of mavic hubs from about 1992-93. The hubs are 7 speed and the downtube shifters index really well with the rear derailleur.

I would like to upgrade the double crank to a triple crank while retaining: the down tube shifters, the 7 speed freewheel, and the indexing on the shifters.

In understand that to convert to a triple I will need at least the following: new crank, new bottom bracket, new front derailleur and new rear derailleur.

I dont care if the triple is 105/ultegra or what... I am only planning on using it for one event (Deathride). Does anyone know if I can have my cake and eat it too? Any advice in this will be VERY MUCH apprecited.

Lizardman
re: 1993 D/A 7 speed to Triple crank, retain 7 speed and indexRusty Coggs
Apr 18, 2002 5:16 AM
Pre 9 speed DA shifters and rear derailers had unique cable pull,derailer throw ratios and have to be used together.Easy way to do this and keep your down tube shifters is with a triple crank and BB and triple front derailer.Keep the short cage DA rear dealier.When using the short cage derailer. the limitation will be that when in the granny ring, some of the smallest cogs will not be usable due to inadequate chain wrap capacity.You DA rear was speced for a max large cog in the rear of 26 teeth but will shift a slightly larger one if necessary.It may also be cheaper if you can scare up an older triple crank and square taper BB, and older triple front deralier.Plenty of good used stuff around.
re: 1993 D/A 7 speed to Triple crank, retain 7 speed and indextanman
Apr 18, 2002 5:19 AM
Old (pre 1997?) New Dura Ace shifters only works with old New Dura Ace derailleurs and are/were not compatible with the rest of the Shimano derailleurs.

That would mean that you'd also need to get a new rear shifter if you got a long cage (triple) derailleur. That caveat out of the way, you may not need a new rear long cage (triple) derailleur and shifters, and instead keep the DA shifters and rear derailleur on the bike--if you make sure to run the granny front ring with only the 2 or 3 biggest cogs. You will also have to play with the chain length to take up enough slack but have enough for a granny/small cog combo.

Mountain bikers used to run this setup (triple front and short cage XT rear derailleur) to shave weight and speed shifting back in the early 90's. A shining example of this was the Bridgestone MB-0 and MB-1's with Pineapple Bob.
You will still need a new BB and front derailleur, but MAY NOT need a new crank either. You can get a triple-izer chainring (made by Willow or TA) from www.rivendellbicycles.com to add a small/granny chainring to the small ring. Good luck. JT