DogBoy

I want to do the following but I'm afraid I'll mess something up. Can anyone let me know the dangers of doing this?

1. I currently have a triple crank, and DA Triple brifter, (9sp rear). (I'm unsure about the bb width)
2. I want to put a double crank on the bike, and keep the same brifter/derailleur, but use the limit screws to prevent shifting off the inner chainring.

My questions: Is there anything preventing the use of the longer triple BB with a double crank or do I need to replace the BB? All the triple to double threads say you need a new BB. Is that really a NEED or a "will be better with." Will I be okay with the triple shifter or do I need to get a double shifter?

I only want to do this on a temporary basis to give the double the old college try. If I really like the double setup I may spring for the other stuff, but just to give it a go I'd prefer not to. Also, changing cranks is one thing, I'm not sure I'm ready to mess with the bottom bracket, so I don't really want to change it unless I risk damage to the bike by not doing so. Thanks for the advice.

sydney

Why don't you just remove the granny ring off the triple instead of buying a double crank? If you don't also use a shorter spindle BB the chainline will be off. That ain't a killer,but it ain't the ideal situation for extended use. The triple shifter will shift a double.

SteveE

Are the chainrings on your double going to be different than the outer chainrings on your triple? If not, an even easier test is to leave the inner chainring on and just adjust the limit screws on the front derailleur. If the double setup doesn't suit you, just go back to the way it was before.

mooncricket

My TCR came with 04Dura Ace Triple shifters/drifter but with a double crank 53-39. And a 9sp cassette in the rear. I find that on the lower gears of the large ring, I have to click into the middle "non-existent" second ring or the chain would rub on the drifter. In the granny ring, no problem. So just something to remmeber when the chain rub a bit. No problem otherwise. What's the tooth count on your smallest ring?

Wanna sell your triple crank?

khuon

Are you sure you have a 2004 Dura-Ace triple brifter (ST-7803)? I didn't think those were available in 2004. Also, how are you indexing a 9-speed cassette? The spacing is different. Do you have 7700-series Dura-Ace? Also remember that a 7700-series Dura-Ace double-chainring brifter does have a trim position. This is not the same as a middle-ring position.

mooncricket

Not sure if it's 2004. I bought the bike in Bangkok, Thailand. The lbs stripped the shifters from a new TCR and strapped them on the bike I bought, so it could be 2005 (in which case, I'm extra thrilled). They explained that the shifters were for a triple front, and for the new shimano 10 cassette for the rear (English not too clear). The brifter, derailuer, cassette and so on were already on the bike (new TCR 2003 frame).

By the way, should it say 7700 Dura-Ace somewhere?

khuon

It's actually pretty easy to tell.

This is a 2005 Shimano ST-7803 triple-compatible Dura-Ace left brifter. The right brifter of this set is 10-speed compatible.



Here is a pre-2003 Shimano ST-7703 triple-compatible Dura-Ace left brifter. The right brifter of this set is 9-speed compatible.

sydney

Dollars to donuts,you are using the trim function regardless of whether the shifter is a double or triple model. The 'middle ring click' would give you a complete shift to the smaller ring.

sydney

To my knowledge,a 10 speed DA triple is not even available yet.

DogBoy

The middle on the triple is a 42 and I want to use a 39, hence the different cranks. I guess I could also just buy a 39 inner and put it on the current triple and play with the limit screws.

Thanks for the advice.

sydney

A generic 39 ring is alot cheaper than a new crankset. I assumed when you said you had DA triple shifters you also had the DA triple crank with the 39 middle ring.

khuon

I was at least announced. Are they not shipping it yet? Even as OEM?