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  1. #1
    weirdo
    Reputation: rodar y rodar's Avatar
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    Cranks and BBs: am I looking at this wrong?

    Short backstory- I have a dusty old Univega Alpina behind the house that I plan to refurb this winter for fire road ramblings, and I recently happend into a listing for a good price on an XT crankset with an unusual ring combo that happens to suit me. While I wasn`t originally planning to spend real money on the project, the thought of cutting some big weight sounded intiguing, so I started weighing up cranks and BBs that I have around the house to see what kind of gram per $ savings I was looking at. What I found surprises me, but I`m not sure if there`s something I`m missing. Since I don`t know for sure what`s included in the weight listings, and I don`t know for sure exactly what`s needed for the outboard bearing setup, what do you folks think?

    On the simple side, here`s the XT set I was looking at:
    Shimano XT M771 Triple Chainset | Buy Online | ChainReactionCycles.com
    I take it the claimed 853g includes bearings and whatever is needed in lieu of cups? Weight aside, is that crankset + BB combo 100 percent complete? Nothing else needed to put it on my bike? I`ve rarely dealt with anything other than cotters and sqare tapers, never with outboard setups, so completely at a loss here.

    The not-so-simple part would be figuring what it would cost me for what weight using cranks that I already have with a lighter BB and/or some lighter bolts. The cranks that are on the Alpina are 723g complete with 28-40-48 rings. I also have an old Deore crankset with the same bolt pattern and tooth count as the old Sugino set, but with rings 21g lighter (arms are slightly heavier). So, using the Sugino arms and hardware with the Shimano rings would put me at 702g + BB. By my thinking, for about the same price as the XT set, I could get a Ti BB cartridge and alloy bolts, keeping the old school look (which I prefer) at only about 50-60g heavier. With some ring filing and aluminum ring bolts, I could probably even cut the difference even more. Can that be true?

    Some aspects of the BB situation confuse me, so maybe somebody can help here also. White Ind`s site claims 162g for their Ti BBs, but no length listed. I guess that`s for whatever the shortest spindle is? Would it include the bearing weight? Bolts? Anybody know if they list weight for specific length somewhere else on their website?
    White Industries

    Phil`s online store pages list weights for each model. Those weights and prices include bearings, but not cups or bolts, correct?
    Premium Titanium Bottom Bracket Sets

    Google keeps giving me Sinz, which look like a good buy to my uneducated eye, but a search of this subforum turns up very little. Is there some reason you guys stay away from them? What the heck is a "Euro" sqare taper? Same as Campy? These are always seem to come with bolts and cups. Would those parts be included in the weight claims, then?
    https://www.jrbicycles.com/storefron...d&productId=50

    To be honest, I still haven`t decided if I`m going to spring for a new BB anyway, but looking at them has got me lusting, so I might throw a little "stupid money" that way. I guess could always roll with a BB that I already have and keep a lighter one on my wish list. One more interresting thing I learned while I was weighing up the stuff around my house is that cup-and-cone BBs, UN26, and UN54 all weigh in at very similar weights. There was some (slight) difference in spindle lengths, but I weighed one of each and they spanned between 303 and 320 without bolts. Anyway, that`s my dilema- any related comments welcome.
    Recalculating....

  2. #2
    ups and downs
    Reputation: rockyuphill's Avatar
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    That's the weight for a complete set of H2 Shimano XT touring cranks, including the entire BB. You need the correct spline wrench for an external BB cups, but that's the only specialized thing you'd need.

    That BB is going to look like this...

    Universal Cycles -- Shimano FC-800 Saint XT Hone LX Bottom Bracket Cup

    The other thing that the Shimano XT cranks have is a fixed 50mm chainline, so you'd have to adjust your FD H/L screws as well as the older cranks were typically a 47.5mm chainline.
    I'm a member of NSMBA and IMBA Canada

  3. #3
    bike rider
    Reputation: Lelandjt's Avatar
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    For a crankset I'd argue that stiffness is a more important and noticeable paramater than weight. Yes, I like building a light bike and use crazy light cranks but they're also very stiff (and expensive, Lightning). Because they sit so low and centralized on the bike you won't notice the weight difference in handling and they're such a small circle that spins slowly so they're effectively not rotational weight. A weight loss will only manifest in total bike weight. The modern external BB cranks are MUCH stiffer than old arms with square taper BB and the rings are probably stiffer too. Besides that Ti square taper spindles were notorious for being flexy and even snapping due to their small diameter and the loads involved. A final + for the XT is the BB bearings are easily replaceable and preload is adjustable.
    Keep the Country country.

  4. #4
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    Quote Originally Posted by rodar y rodar View Post
    ... I could get a Ti BB cartridge and alloy bolts...
    Ti BB's are expensive and getting harder to find. You can get a Token BB which will weigh around 220g for $40. That will put you at around a similar weight to the new XT setup if you use your old lightest combo of components.

    As for stiffness, I've never really been able to tell the difference between my square taper cranks, XT cranks with outboard BB (24mm spindle) and now my Speci FACT S-Works cranks (30mm spindle).

    The only problems I had with the square taper cranks was the crank interface did flog out over time. But until they developed play, they felt stiff enough.

  5. #5
    weirdo
    Reputation: rodar y rodar's Avatar
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    Thanks for the tips, guys. After thinking more about the situatuion, two things have become pretty clear to me:
    A- the XT set from CRC makes most sense from a purely logical standpoint
    B- I can`t bear the thought of putting outboard bearings on my bikes (strictly an asthetic objection)

    I think I`ll go back to my original "no real money" approach, but will definitely look for those Token hollow spindle BBs when replacing mine from now on. Think I`ll take my scale down to our local bike junkyard too, and see if anything in their chainring box beats my own little stash of 74/110s. Probably wouldn`t be a bad idea to take a list of part weights for the whole bike along with me. Hmmm....
    Recalculating....

  6. #6
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    Reputation: bikerjohn64's Avatar
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    I think that the real advantage you will get from updating your crankset would be shifting performance. Any weight loss in that area would be negligible.
    Your bang for your dollar for weight would be better invested in wheels, tube and tires.
    For other weight references; you can check it out on weight weenie.com.

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