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Converting from downtube shifters to STI

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Converting from downtube shifters to STI

Old 03-27-08, 08:17 PM
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Converting from downtube shifters to STI

I have an '87 Fuji Sagres that has Suntour 6 speed indexed downtube shifter and two speed friction front shifter, Suntour 6 cog 13-28 freewheel and Sugino VP crank with 52/42 rings. My project is to convert the bike to STI shifters. I already have the replacement derailleurs and Sora STI shifters/brake levers, and have my eye on a Shimano 7 cog 14-28 freewheel. My original goal was to have eight cogs and three chainrings, but would have had to buy a 36 hole 130mm freehub and relace the rear wheel, but due to cost constraints and time involved I decided to go with the 7 cog Shimano freewheel, which I can screw onto the existing hub and respace the wheel easily enough. I love to build wheels, so my long term project will be to build a set of updated wheels and hubs with eight cogs.

Issue 1: I bought the STIs before I decided on the final drive choice, so I wound up with a used set of 3 x 8 in good condition for $50. If I am going to have indexed front shifting, would it be adviseable to replace my current 52/42 chainrings with ones that are ramped and pinned? Would front index shifting work with unpined/unramped rings? My main concern was having a low enough gear for riding Southern Indiana hills, and the original setup of 42 front ring and 28 rear cog as my lowest gear was still a little too tall for my taste. I originally was going to have triple front setup by adding a 30 tooth granny ring to the Sugino crank, but decided to go compact, and can get a 50/34 set of rings and just run dual.

Issue 2: I want to confirm, but I'm pretty sure that I can use my 8 speed shifter with 7 speed cog, and three speed front shifter with 2 front rings.

I searched for quite awhile trying to find info before starting a new thread, but couldn't find anything specific. Thanks for your help and advice!

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Old 03-27-08, 08:51 PM
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I can answer one of your questions. Yes the left shifter will work with a double instead of a triple. I just completed the same change on my Bianchi and it works fine.
I'm sure you know when you change to a 7 speed freewheel, you will have to redish the wheel, but it sounds like you know what your doing there.
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Old 03-27-08, 09:45 PM
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Issue 1: I bought the STIs before I decided on the final drive choice, so I wound up with a used set of 3 x 8 in good condition for $50. If I am going to have indexed front shifting, would it be adviseable to replace my current 52/42 chainrings with ones that are ramped and pinned? Would front index shifting work with unpined/unramped rings?


The current chain rings will work fine. You will however notice a slight delay when upshifting to the larger cog. Actually, you won't notice any delay because you have been using those same chain rings, but if you are used to grooved rings, that is when you will notice the slight delay.

My main concern was having a low enough gear for riding Southern Indiana hills, and the original setup of 42 front ring and 28 rear cog as my lowest gear was still a little too tall for my taste. I originally was going to have triple front setup by adding a 30 tooth granny ring to the Sugino crank, but decided to go compact, and can get a 50/34 set of rings and just run dual.


Sounds good to me.
You probably already know that the ratio is 3:1, so the best way to achieve an "easy" gear ratio is in th rear, but the 50/34 will give you a pretend 27 cog in the back on the 50, and a pretend quasi-28 on the 34, this is if we are comparing to the 42/53.

Issue 2: I want to confirm, but I'm pretty sure that I can use my 8 speed shifter with 7 speed cog, and three speed front shifter with 2 front rings.

Yes, you can. The cable pull/throw ratios are minutely different, but you can surely get away with it. If the derailleur is tuned in right, you will not notice the discrepancy at all.
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Old 03-27-08, 11:03 PM
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Just remember to lock out one of the shift settings by adjusting the limit screw so you don't shift the RD too much by mistake.
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Old 03-28-08, 09:01 AM
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Thanks to all for the great replies! I can't wait to get all my parts together and start to work. Another reason I decided to stay with the double front crank was simplicity; the BB is the original Fuji cup and cone with 118mm spindle that still works great and spins free and smooth, and it looked like I'd have to move up to a 122 to run triple.

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