Changing to a Compact

Discussion in 'Cycling Equipment' started by Scott2468, Feb 7, 2012.

  1. Scott2468

    Scott2468 Member

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    Hi.

    I have a 2003 Giant TCR with 6500 Ultegra all over. This has the old octalink bb, 9 speed with 53 /39.

    I want to put a compact (50/34) chainset on this.
    Other than the recalled (dangerous) Ritchey chainsets on ebay, I could not find any compact chainsets with octalink.

    Are there any octalink compact chainsets on the market?

    Because of the lack of these, I am looking at changing the bb.
    Both bb6500 & bb6700 state they have 1.37" x 24T threads for a 68mm shell width.

    Is there anything else to consider, regarding compatability? Can I put a BB6700 straight on my bike which will then take a FC-6750?

    Is this the best approach?

    $38 + $293 is expensive for an old bike. Is there a cheaper approach?


    Thanks for your consideration.

    Scott
     
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  2. vspa

    vspa Active Member

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    68mm is the British thread, yeah you will pay circa 300 usd. for the compact crank + BB cups, but it is worth the money, you will be updated with the new standards and have a very helpful compact crank, you can tackle the hills better with it, you can also use the big chainring more often, for installation purposes you might need to take a few links off your chain and adjust the front derrailleur,
     
  3. alfeng

    alfeng Well-Known Member

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    First, think about getting the crankset & BB from eBay ...

    FSA's MegaExo cranks & BBs are directly interchangeable with Shimano Hollowtech II cranks & BBs ...

    FSA cranks will typically cost a fraction of what a Shimano crank will cost ... not that it necessarily matters, but 'I' like FSA components.

    • Depending on how wise a shopper you are, then your cost on eBay should be near-or-under $100 for an FSA MegaExo crankset + MegaExo BB (or, Shimano Hollowtech II) + shipping costs.

    ALSO, if you can break away from buying an Ultegra-grade-or-better Shimano crankset, then you can buy a Shimano Hollowtech II crankset which has traditional forged crankarms instead of "hollowtech" crankarms for a lot less ... at least, a lot less on eBay.
     
  4. Scott2468

    Scott2468 Member

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    Thanks you have given me a different, cheaper approach.



    I am still unsure / worried in regard to my other questions.

    Shimano states the 6750 goes with 10 speed chains. My TCR is a nine speed, obviously using 9 speed chains. (I noticed the FSA MegaExo compacts are 10 speed also.)

    Does this totally rule out these options?
     
  5. Eichers

    Eichers New Member

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    Hi Scott2468, you can ...
    • get a 38T front chainring and use a 9spd 11/28 rear cassette with your existing RD, which will give a 38/28T gearing ... 38/28T standard is > 34/28T compact
    • change your rear cassette to a shimano or sram 9spd 11/32 or 11/34 but you will need to change the RD to M772 XT 9spd GS or SGS, respectively (I would suggest an SGS for flexibility), and you will need a longer 9spd chain. Lots of low gearing in this combination and no need to change the FD system and the cassette and M772 SGS RD will work perfectly with your 6500 shifter/lever(brifter) ... EG. a 39/32T standard is = 34/28T compact, a 39/34T standard is lower, and a 38/34T standard is even lower (for those >15% or 20% climbs)
     
  6. oldbobcat

    oldbobcat Well-Known Member

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    I've never compared the spacing between 9- and 10-speed chainrings, but if they're identical, running 9-speeds on 10-speed rings should be no trouble. I'd favor FSA, as alf recommended, or an older Shimano crank (5600, 6600, 7800, or R600) over 6700, to keep the price down and reduce the risk of fussy performance. The R600 is a good choice because it was designed for conversions and operation with standard double front derailleurs.

    Here's an eBay link to a page of R600 cranksets.http://www.ebay.com/sch/i.html?_nkw=shimano+r600
     
  7. alfeng

    alfeng Well-Known Member

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    FWIW. Based on 'my' observation, you/(everyone) should MATCH the chain to the front derailleur when using an indexed Shimano or SRAM front shifter ... the exception is when you are using a Shimano TRIPLE-capable shifter with an otherwise non-compatible front derailleur on a DOUBLE crankset ...

    So, with your 6500-series of shifters & 6500 front derailleur, you want to use a 9-speed Shimano chain UNLESS you have a caliper and can ensure that the substitute chain has exactly the same width as the Shimano chain.

    Regardless, you are not precluded from using this-or-that crankset, per se.

    FYI. This may be stating the obvious -- Shimano 105-and-below chainrings typically have less sophisticated ramping-and-pinning than the Ultegra & Dura Ace chainrings of the same vintage ...

    MOST people find 105 chainrings to be fine ...

    • I reckon that the ramping-and-pinning on the FSA (+ Token, to name another brand) chainrings is comparable to that on your 9-speed Ultegra chainrings; but, maybe it isn't because that statement is based more on a visual observation than an on-the-road observation & so it should not be considered to be a definitive comparison (I finally stopped using Shimano shifters about a 10+ years ago, but the rest of the drivetrains on my bikes continue to be Shimano).
     
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