Changing crankset from 53/39 to compact

jack264
jack264 Posts: 39
edited May 2014 in Workshop
On this bike...

az1FMgC.jpg

Would any 50/34 Ultegra set go in nicely? Or do I need anything specific. The bike is from either 2006 or 07. And specs are here - http://www.bianchiusa.com/archives/2007 ... 85-ultegra .

I'm watching a few used ones on ebay, but the numbers just putting me off throwing bids on right now. 6750, 6700 etc etc. Does it even have to be ultegra?

Just enquiring for a friend really, as the bike used to be mine, but on a group ride he was the only one not on compact. Cheers for any help.

Comments

  • dj58
    dj58 Posts: 2,223
    If you want to swop to compact Ultegra you will probably need these, I'm assuming the BB is threaded.

    http://techdocs.shimano.com/media/techd ... 671289.pdf

    http://techdocs.shimano.com/media/techd ... 753779.pdf

    http://techdocs.shimano.com/media/techd ... 750016.pdf
  • krankers
    krankers Posts: 283
    Any HT2 (hollowtech) shimano chainset will work with the current bottom bracket that is fitted. You will need to move the front derailleur down as the chain rings are smaller and set up the front shifting, also will probably have to remove a couple of links from the chain. All straightforward stuff though.
  • jack264
    jack264 Posts: 39
    Someone I know has suggested simply changing chainrings with another bike.....however that bike is on Compag, does that matter with chainrings?

    Could someone link me to pair of 34/50 rings that would be compatible with the bike if not.
  • StillGoing
    StillGoing Posts: 5,211
    jack264 wrote:
    Someone I know has suggested simply changing chainrings with another bike.....however that bike is on Compag, does that matter with chainrings?

    Could someone link me to pair of 34/50 rings that would be compatible with the bike if not.

    No it won't work. A compact is 110BCD and a 53/39 double is 130BCD which in short means the spider in the centre will be too big to take compact chainrings.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • angry_bird
    angry_bird Posts: 3,787
    You can probably get down to 50/38 with 130mm BCD chainset, I know at the moment I'm running 50/39 which I quite like.
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  • rolf_f
    rolf_f Posts: 16,015
    The cassette seems pretty small - your friend might be able to stay on happily just buy buying a lower range cassette. There's nothing wrong with being the only one not on a compact as long as you are able to keep up OK!
    Faster than a tent.......
  • arlowood
    arlowood Posts: 2,561
    Rolf F wrote:
    The cassette seems pretty small - your friend might be able to stay on happily just buy buying a lower range cassette. There's nothing wrong with being the only one not on a compact as long as you are able to keep up OK!

    As Rolf F says the 12-25 cassette could be swapped out for an 11-28 or 12-30 to provide some easier gearing while keeping the 53/39. However you could also consider one of the new Shimano 105 5800 cranksets which are 52/36

    http://www.chainreactioncycles.com/shim ... prod116491

    Bit pricey at £90 but could fit the bill. They are part of the new 105 11-speed package but will work OK with other 10-speed components
  • markhewitt1978
    markhewitt1978 Posts: 7,614
    In general if changing the gearing the cassette is the first thing to tackle as it's much easier and cheaper to swap out
  • jack264
    jack264 Posts: 39
    OK. I think I've got a general understanding now.

    Looking a the Sheldon Brown Calculator, changing the cassette to a 12-30T would give him better leeway than changing the crankset.

    At 60RPM as an example.
    34x25t - 6.6mph
    39x30t - 6.3mph
    39x27t - 7mph

    So looking at this - http://www.chainreactioncycles.com/shim ... -prod39014

    Would there be any problems with that on the current derailleur? Any chance you get the 6800 11sp in there, because having the option of (12t-)32t would obviously be a lot better for him. If not the 12-30 would be fine, as we could just change to compact in future anyway with a medium RD in there if he doesn't get a new bike.

    I believe the short derailleur should be fine give it's 39/53 rather than compact....or at least that's what I was told when when I was building my own current build as I was looking into a compact and higher tooth, but settled on compact 13-26t.
  • andrewc3142
    andrewc3142 Posts: 906
    I used a 53/39 with a 12/27 until recently. Going up White Hill at 54 years old I decided to give myself the luxury of a compact and switched to a 50/34, keeping the same cassette.

    Other than perhaps Hardknott Pass and the like I can't imagine you'd need anything lower than that.

    Don't know whether that bike's Shimano, but if it is and unless you're a serious racer or like to pose, 105 is absolutely fine and fairly bomb-proof. Wiggle and Chain Reaction both have cranksets for £86.

    Swapping them is about 10 mins plus a bit longer to reset the FD (easiest in the end is just to do it as if it's a new mech rather than moving it down a bit). Only tools needed are whatever to get the crank off (if Hollowtech the plastic thing for about £1.50), an allan key (5mm from memory), possibly a plastic/rubber hammer and some grease. Only thing that can really go wrong is over-tightening the pre-load (almost impossible with Hollowtech unless you're daft enough to use a wrench on the plastic thing) or not tightening it enough so that there's play on the cranks - both fairly hard to mess up in reality.

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