Shimano XT chainset....

type_grim
type_grim Posts: 54
edited May 2009 in MTB workshop & tech
Evening chaps.

I was out on a ride with the o/h today, we started a climb and the chain jumped right off the inner most sprocket on the crank. On closer inspection, a bolt was missing, and another was just about to fall out. I tried to wind it back in, but it was cross-threaded. The chain ring was pissed and not running true.

I have recently been upgrading my running gear to Shimano XT. I had a chain ring replaced a few weeks ago, as it was worn, and the shop did warn me that the other two chain rings will go too, as running gear wears together.

I wish to upgrade my chainset to XT.

After shopping around, i see they offer different lengths, and, they strongly advise that a shop fit the bottom bracket.

My father is a pretty practical chap, and can solve most problems with the bike; is it really necessary to get the bike shop to fit the BB?

I ride a 2007 21" Specialized Rockhopper and I'm about 6' 2".

Why do they offer different lengths of crank arm?

I'm sorry to be so long winded!

Any advice most appreciated!

Many thanks,

Graham

Comments

  • supersonic
    supersonic Posts: 82,708
    The frame needs the faces of the BB shell facing - requires a specialized tool.

    Different crank lengths for different leg lengths. However no set rule, most people use 170 or 175mm.
  • stumpyjon
    stumpyjon Posts: 3,983
    Facing a bottom bracket only takes a few minutes but does need a £ 300 tool. If you buy the crankset from your LBS you should be able to get them to do it for free while you wait.

    Might also be worth getting one of the slotted chainring bolt spanner thingies so you can makes sure the bolts are tight in future.
    It's easier to ask for forgiveness than for permission.

    I've bought a new bike....ouch - result
    Can I buy a new bike?...No - no result
  • AndyBike
    AndyBike Posts: 126
    supersonic wrote:
    The frame needs the faces of the BB shell facing - requires a specialized tool.

    Why??? if the BB shell face was OK before why does it need the faces facing.

    Surely its better to get the faces checked first.
  • nicklouse
    nicklouse Posts: 50,673
    AndyBike wrote:
    supersonic wrote:
    The frame needs the faces of the BB shell facing - requires a specialized tool.

    Why??? if the BB shell face was OK before why does it need the faces facing.

    Surely its better to get the faces checked first.

    how do you check if it has been done?

    with the tool.

    and i think the 2007 rockhopper did not come with external bearings? it came octalink.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • elPedro666
    elPedro666 Posts: 1,060
    It doesn't need doing, but it will help the bottom bracket last a lot longer - especially if you're changing to an external BB, as they're much more fussy about being aligned perfectly.
    WTD:
    Green Halo TwinRail
    25.0mm-26.2mm seatpost shim
    Red X-Lite bling
    Specialized ladies BG saddle (white?) 155mm
    RH thumbie
    700x28c CX tyres&tubs
    Flatbars 620mm 25,4mm & swept, ti in an ideal world
  • elPedro666
    elPedro666 Posts: 1,060
    And like StumpyJon said - the shop will probably do it for nowt if you're buying the crankset off them!
    WTD:
    Green Halo TwinRail
    25.0mm-26.2mm seatpost shim
    Red X-Lite bling
    Specialized ladies BG saddle (white?) 155mm
    RH thumbie
    700x28c CX tyres&tubs
    Flatbars 620mm 25,4mm & swept, ti in an ideal world
  • nicklouse
    nicklouse Posts: 50,673
    elPedro666 wrote:
    It doesn't need doing, but it will help the bottom bracket last a lot longer - especially if you're changing to an external BB, as they're much more fussy about being aligned perfectly.

    read the shimano fitting instructions.

    any bb shell that has a flange pressed on it needs facing.

    which is why the facing tools have been around for about as long as the bike.

    even the "old" square taper bb got the drive side face of the bb shell faced as there was a flange pressed on it.

    either do it right or expect problems.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • elPedro666
    elPedro666 Posts: 1,060
    nicklouse wrote:
    elPedro666 wrote:
    It doesn't need doing, but it will help the bottom bracket last a lot longer - especially if you're changing to an external BB, as they're much more fussy about being aligned perfectly.

    read the shimano fitting instructions.

    any bb shell that has a flange pressed on it needs facing.

    which is why the facing tools have been around for about as long as the bike.

    even the "old" square taper bb got the drive side face of the bb shell faced as there was a flange pressed on it.

    either do it right or expect problems.

    You are totally right, of course, but I have fitted plenty of BBs without facing and without any problems or noticeably shortened lifespans. That said I tend to have nicely made frames cuz that's my 'thing' :wink:

    Same for the diabolical headset/hammer/block of wood technique :twisted:

    BUT none of this is meant as advice - don't listen to me, listen to Nick :lol::lol::lol:
    WTD:
    Green Halo TwinRail
    25.0mm-26.2mm seatpost shim
    Red X-Lite bling
    Specialized ladies BG saddle (white?) 155mm
    RH thumbie
    700x28c CX tyres&tubs
    Flatbars 620mm 25,4mm & swept, ti in an ideal world
  • AndyBike
    AndyBike Posts: 126
    nicklouse wrote:
    AndyBike wrote:
    supersonic wrote:
    The frame needs the faces of the BB shell facing - requires a specialized tool.

    Why??? if the BB shell face was OK before why does it need the faces facing.

    Surely its better to get the faces checked first.

    how do you check if it has been done?

    with the tool.

    and i think the 2007 rockhopper did not come with external bearings? it came octalink.

    Ah ha, thanks Nick. I did not think of bike w/o external bearings and a BB+flange that needs facing that makes sense to me.

    But surely you not suggesting the BB is faced everytime new bearings are fitted?
  • scotto
    scotto Posts: 381
    would this be the case with the slx as well?
  • type_grim
    type_grim Posts: 54
    I spoke to my local bike shop (Cycle Surgery) and they said they will price match the crank (£139.99) plus around £20-25 to fit the BB.

    It is booked in for Saturday morning.

    Does this price sound reasonable?

    Graham
  • elPedro666
    elPedro666 Posts: 1,060
    If fitting includes facing then I'd say that's pretty fair. Price-matching Merlin, by any chance? They must hate that place :lol:
    WTD:
    Green Halo TwinRail
    25.0mm-26.2mm seatpost shim
    Red X-Lite bling
    Specialized ladies BG saddle (white?) 155mm
    RH thumbie
    700x28c CX tyres&tubs
    Flatbars 620mm 25,4mm & swept, ti in an ideal world
  • type_grim
    type_grim Posts: 54
    Yes, you are right, i buy a fair bit from Merlin!

    They do seem very cheap, and most places i have been to, won't price match them.

    I tried Cycle Surgery and they were happy to match. I think its only £10 difference! I will probably do that in petrol! :roll: