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Weight saving - road spec front mech and external b/b?

EarlofBarnetEarlofBarnet Posts: 673
edited January 2011 in XC and Enduro
I've started building up a (budget-spec) light weight cross-country bike, which I want to do a few races on next year. My budget is fairly limited, and I'll be swopping a lot of parts across from my Enduro to the hardtail frame I've just bought.

I just wondered if it'd be worth buying a road spec front mech and external bottom bracket to help save a bit of weight?

They wouldn't be used as much as the Enduro, so the bottom bracket not lasting too long isn't too much of an issue (if the sealing isn't as good as the mtb spec b/b's?).

Any thoughts on this, or any other advise on how best to keep the weight down on the bike?

Thanks in advance :)

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    the front mech will cause issues and may not be lighter.

    and an external BB set up can only be used with an external bearing crankset.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • RevellRiderRevellRider Posts: 1,794
    Nick, the OP is asking can he use an external bearing bottom bracket designed for road bikes instead of an external bearing bottom bracket for a mountain bike to save weight as it is shorter (no 73mm shells or e-type front mechs on road bikes)

    As far as I'm aware, it's ok to use on your MTB as people have been using them on their cross bikes. Though the weight saving is going to be tiny.

    As for the front mech, you'd probably make a bigger saving in weight terms if you changed various bolts to ti and made sure your cable routing was perfect
  • Spot on, thanks for the thoughts :)

    I'm running an XT external b/b and chainset on my Enduro, and will be swopping the chainset between bikes. Just wondered if the road b/b may be lighter. If the difference is neglegable then I'll probably just get another XT b/b.

    I'll look in to the ti-bolt route too.

    Thanks again, Matt
  • njee20njee20 Posts: 9,613
    There's so little weight saving on the BB it's not worth it, and it could cause problems with cup width.

    What's your current front mech? Deore's are pretty light, alu bolts make more sense in a front mech, far cheaper, perfectly tough, and half the weight of ti.
  • nicklousenicklouse Posts: 50,675 Lives Here
    the only difference between the shimano MTB and the Road HT2 BBs is the RH cup has less threads.

    aftermarket versions dont have this difference.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • UchigaUchiga Posts: 230
    Biggest Weight Saving Is In The Wheels, Tyres And The Frame. End Of. Finishing Kit Go Aluminium Groupset Go Deore - SLX If Your Looking For Lightweight Reliable Shimano Components. Sorted.
  • LukeBLukeB Posts: 78
    nicklouse wrote:
    the only difference between the shimano MTB and the Road HT2 BBs is the RH cup has less threads.

    aftermarket versions dont have this difference.

    This is not the case- road cups are 1mm narrower than MTB ones. You can fit spacers to counteract this but you will save next to no weight.
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