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Compact crank on a Dura Ace 7700 BB?

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Compact crank on a Dura Ace 7700 BB?

Old 03-25-12, 07:30 AM
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Compact crank on a Dura Ace 7700 BB?

I have a 2001 bike with 9 spd DA7700, crank is the usual 130mm bolt 53/39.

The bike came with a 11-23 cassette, fine for many of my rides but not local club rides which include moderately long and steep climbs.

I went with a 12-26 cassette, which helped but still isn't low enough for me.

I could get a 38t chainring for this crank, and there are 12-27 DA cassettes available - which i find odd since the spec sheet for RD 7700 says 26t max cog size (a guy at a bike shop told me you can get a 28t low on there no problem).

a 38x27 or 38x28 would get me down to around a 36" gear which I think would be okay on most of the hills that don't hit 10%+ grades for any length of time (I've been doing the rides with a 32" low on my old slightly heavier bike), but people keep advising me to get a compact - I can't argue with the logic that it would let me use a closer-spaced cassette.

I can't afford a new bike right now, so my question is, are there any compact cranks which will fit on this DA BB? If it starts getting into buying a new crank and BB, I am wondering if maybe I should just sell the bike and get something else newer...
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Old 03-25-12, 09:05 AM
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There were some Octalink compact cranks but they were never very popular, and Octalink wasn't even around that long. Don't limit your crank selection based on the BB, lots of used Hollowtech compact cranks are around and the BBs for them are pretty cheap.

I'm trying to sell my own DA7900 crank on eBay right now though, and there doesn't seem to be much demand for them.
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Old 03-25-12, 09:10 AM
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A new BB costs $25+/- not a major factor.
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Old 03-25-12, 01:52 PM
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Design of the crank-arm determines the BB length, even in square taper,
super low profile come in to meet a short spindle. older TA and Campag have a need
for a much longer BB...
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Old 03-25-12, 02:18 PM
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I just don't know how much work it is to swap out BBs on this frame - seems like every 3-4 yrs the standard sizes change; since this bike has a gruppo towards the end of its lifespan, would a newer BB fit the frame?
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Old 03-25-12, 03:00 PM
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Originally Posted by pgoat View Post
I just don't know how much work it is to swap out BBs on this frame - seems like every 3-4 yrs the standard sizes change; since this bike has a gruppo towards the end of its lifespan, would a newer BB fit the frame?
Yeah, if it'll take Octalink it'll take other standards too. If you're going with a Shimano compact crank, I recommend the Tiagra BB for $20-$25 since there's no meaningful difference among the different "levels" of Shimano outboard-bearing BBs.

Oh, and to go with that, Tiagra 4500 or 4600 cranks would be a good value if weight's not a priority. If weight's an issue, watch Ebay for Ultegra SL or Ultegra 6650. You may want to switch to narrower 10-speed chains to reduce chain rub on the big ring when using the small ring.

You've probably thought this through already, but the large jump in chainring sizes on compacts can be annoying. Punching down from the big ring and having to counter-shift the rear three gears for your next ratio is not a trait I personally like. But your alternate poison is a wide-range cassette with bigger cog-to-cog jumps that demand a wider "powerband" from your legs.

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Old 03-25-12, 03:43 PM
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excellent point Mechbgon. I use a touring bike with 53/39 up front on my club rides now, with a 11-32 SRAM mtb cassette. It gets me around but I hate the wide skips in the middle on the cassette. I usually use the 53 with the whole cassette on those rides and just go to the 39 for climbs.

Event though the Orbea is a lighter stiffer bike I have problems with a 26t low on hills - I'm just too fat and out of shape at present. (Spent a year off the bike in '11 due to injury).
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Old 03-25-12, 04:26 PM
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Another option would be a triple, of course. I mean hey, it's only money You can get used Dura-Ace triple left levers, I think we even have a couple new left ones for like $100 at the LBS. Pair that up with the aforementioned Tiagra BB and your choice of Shimano road triple cranks, get a triple front derailleur designed for the ring setup on your chosen crank, and there you go... you can run something like a 12-26 SRAM PG950 cassette and still have a great bailout gear on tap.
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Old 03-25-12, 06:21 PM
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Solution: Truvativ square taper compact, 50/34. Have it on a couple bikes, flawless shifting with 7700 brifters. Generally less than $75 including the BB.
Alternative: Velo Orange Sugino square taper compact (example below). Have it on two bikes, both with 7700, works beautifully. More expensive at $135 for the crankset and $35 for the BB, but if you like the bike...

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