Bicycle Mechanics - Converting Compact Dura Ace Crank to Triple
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01-19-08, 09:17 AM
I am trying to buy the parts to convert my double chainring dura ace into a triple chainring, in prep for the cross-Great Britain ride this summer - Lands End John O Groats. I have seen a few varying postings re what parts I need to replace: obviously the crank, the FD, the RD (which I cant see why I'd need to change that) and the BB. Then I read somewhere that if you want to use the Dura Ace Triple chainring and you had the 7800 Double Compact Crank you didnt need to change the BB........so I am a bit confused! Any help would be great! I got the bike with the 2005 model of the compact crank set.
01-19-08, 10:32 AM
All of the 7800-series (10-speed) cranks have the spindle integral with the crank and use external bottom bracket cups. These cups are universal since the crank spacing is built into the crank itself.
You shouldn't need a new fd since Shimano claims their road 10-speed fd's are both standard and compact compatible. You will need a longer cage rd only if you insist on using the small chainrings with the small cogs and exceed the short cage rear derailleur's wrap-up capacity.
01-19-08, 08:24 PM
You dont need the bb because the same bb is used on both the double and tripe dura ace cranks. Front der you will need a triple der. The durace double frt der will work on a reg double or the compact but it is a different frt der for triple. The rear der you will need a long cage der. and a new chain most likely as your old one may be abit short by a link or two unless you have spare links.
PM me if you dont mind a slighlty used crank and der's as i have a set at the shop we just took off a bike that was ridden for a few months untill the customer decided he wanted to go to a double.
01-19-08, 08:54 PM
Front der you will need a triple der. The durace double frt der will work on a reg double or the compact but it is a different frt der for triple.
Yes, I missed that.
The rear der you will need a long cage der.
Only if he insists on using all of the small/small combinations. As I mentioned, the short cage rd will work if he avoids them and stays within it's wrap capacity.
The biggest expense and most work will be the shifters. Your 7800 D-A shifters won't work with a triple crankset.
The same BB will work but I believe there's a spacer or two you have to add or remove (I forget which). Look at the Shimano exploded drawings.
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