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swapping to sram red compact crank

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swapping to sram red compact crank

Old 05-02-12, 11:48 AM
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aramis
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swapping to sram red compact crank

I have a Dura Ace 7800 standard crank on my bike now (53/39) and want to swap to a compact crank because I do a lot of hill climbing and some of the really tough stuff is killing me in the lowest gear (25/11 rear sprocket).

I bought a new take off SRAM red crankset with no BB.

I'm guessing I can't re-use my hollowtech bottom bracket? Any suggestions on what bottom bracket is good and reasonably priced?

Anything I would need to worry about? Chain/Cassette/derailleurs/etc are all dura ace 7800 right now. I figure the chain will have to be shortened but that's about it.

I was going to look into a chain catcher too, any recommendations?
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Old 05-02-12, 03:22 PM
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You will need to drop the FD to within about 1 mm from the top of the large chianring -- or to match the current clearance with the 53 tooth chainring. Assuming you have the DA 7800 FD, your shouldn't have any front shifing problems. But keep in mind that this will increase the ring size difference from 14 teeth on the 53/39 to 16 on the 50/34 (the normal compact combination). Thus, the FD has to lift the chain higher when upshifting. If you should have shifting problems, I think the latest DA FD works for both standard and compact -- I don't think they make one specifically for compact.
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Old 05-02-12, 05:03 PM
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aramis
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Originally Posted by bikepro View Post
You will need to drop the FD to within about 1 mm from the top of the large chianring -- or to match the current clearance with the 53 tooth chainring. Assuming you have the DA 7800 FD, your shouldn't have any front shifing problems. But keep in mind that this will increase the ring size difference from 14 teeth on the 53/39 to 16 on the 50/34 (the normal compact combination). Thus, the FD has to lift the chain higher when upshifting. If you should have shifting problems, I think the latest DA FD works for both standard and compact -- I don't think they make one specifically for compact.
Thanks for the advice. I actually forgot that I had an ultegra 6700 front derailleur on there because I switched this groupset from a frame with a clamp on FD and the Ultegra was about half the price of the DA one (and the current frame takes a braze on FD).

I think that one should be ok with a compact.

Will this Bottom Bracket work, and would it be a bad choice for any reason?

http://www.amazon.com/gp/product/B00...=ATVPDKIKX0DER
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Old 05-02-12, 05:28 PM
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Originally Posted by aramis View Post
Thanks for the advice. I actually forgot that I had an ultegra 6700 front derailleur on there because I switched this groupset from a frame with a clamp on FD and the Ultegra was about half the price of the DA one (and the current frame takes a braze on FD).

I think that one should be ok with a compact.

Will this Bottom Bracket work, and would it be a bad choice for any reason?

http://www.amazon.com/gp/product/B00...=ATVPDKIKX0DER
I'm not familiar with SRAM cranksets; however, as long as the BB fits you frame and the crankset, there should be no problems.

The braze on FD might be a problem, depending on the amount of vertical adjustment it has. There might be adjustment in the braze on hanger on the frame, or the FD might be slotted to permit vertical adjustment.
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Old 05-02-12, 05:37 PM
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aramis
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Originally Posted by bikepro View Post
I'm not familiar with SRAM cranksets; however, as long as the BB fits you frame and the crankset, there should be no problems.

The braze on FD might be a problem, depending on the amount of vertical adjustment it has. There might be adjustment in the braze on hanger on the frame, or the FD might be slotted to permit vertical adjustment.
It's an 09 frame and has a lot of vertical adjustment (I think it could come spec'd with a compact crank) so I think it should be fine. I'm going to order that bottom bracket and hopefully enjoy the really steep hills a little bit more.
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Old 05-02-12, 05:41 PM
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Originally Posted by aramis View Post
Thanks for the advice. I actually forgot that I had an ultegra 6700 front derailleur on there because I switched this groupset from a frame with a clamp on FD and the Ultegra was about half the price of the DA one (and the current frame takes a braze on FD).

I think that one should be ok with a compact.

Will this Bottom Bracket work, and would it be a bad choice for any reason?

http://www.amazon.com/gp/product/B00...=ATVPDKIKX0DER
That BB is fine. It's pretty much identical to the Red BB, but uses steel rather than ceramic bearings. I have had both, can't tell the difference between the two, and the cost difference is significant.
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Old 05-02-12, 06:17 PM
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Originally Posted by caloso View Post
That BB is fine. It's pretty much identical to the Red BB, but uses steel rather than ceramic bearings. I have had both, can't tell the difference between the two, and the cost difference is significant.
Ahh good to hear. I looked up the ceramic one and saw it was around $170-200 and that seems a little steep for a bottom bracket!

I'll just go for the $30 one.

Any recommendations for a chain catcher? I was just going to order the kind that bolted to the braze on FD mount.
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Old 05-02-12, 08:52 PM
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Originally Posted by aramis View Post
Ahh good to hear. I looked up the ceramic one and saw it was around $170-200 and that seems a little steep for a bottom bracket!

I'll just go for the $30 one.

Any recommendations for a chain catcher? I was just going to order the kind that bolted to the braze on FD mount.
Assuming you have a round seat tube: http://www.competitivecyclist.com/pr...4180.23.1.html
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Old 05-02-12, 10:52 PM
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Any GXP compatable bottom bracket (sram, truvativ or other) will work fine. I have a regular, cheap Sram or Truvativ BB w/ my Red crankset and it is smooth and I have no reason to think I won't get $30 worth of durability with it.

Oh, and make sure you get whichever thread version (English or Italian) that your frame has.
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Old 05-02-12, 11:15 PM
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aramis
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Cool thanks for all the help!

I'm ordering that $30 BB tonight and I'll go order a chain catcher asap.

It looks like my hollowtech wrench will work with this too.. that's good news at least.

Last edited by aramis; 05-02-12 at 11:27 PM.
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