Busted crankset Need new parts please help.- Mtbr.com
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  1. #1
    Single Speed Junkie
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    Busted crankset Need new parts please help.

    So I did in a few sets of Race face cranks recently, now the bike does not seem to ride as well missing a few parts. As I understand it the square taper has the bearing life, ISIS is stiff, and the new integrated setup is lighter and looks neat. But Square taper is flexy, ISIS bearings do not last, Integrated cranks do not allow for an adjustible driveline.

    I love the phil bottom bracket currently in place, and require the adjustible chain line to get every thing to line up right. So I not to quick to want to give this up. However riding without cranks takes away most of the functionality of any bike. I would love to find some old stock FSA carbon pro's to replace the RF Next that failed, but all that seems to be out there is ISIS. Anyone know where I could find some old stock FSAs? Any solution to the drive line woes.

  2. #2
    bonkin' clyde
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    interesting

    Quote Originally Posted by crux
    So I did in a few sets of Race face cranks recently, now the bike does not seem to ride as well missing a few parts. As I understand it the square taper has the bearing life, ISIS is stiff, and the new integrated setup is lighter and looks neat. But Square taper is flexy, ISIS bearings do not last, Integrated cranks do not allow for an adjustible driveline.

    I love the phil bottom bracket currently in place, and require the adjustible chain line to get every thing to line up right. So I not to quick to want to give this up. However riding without cranks takes away most of the functionality of any bike. I would love to find some old stock FSA carbon pro's to replace the RF Next that failed, but all that seems to be out there is ISIS. Anyone know where I could find some old stock FSAs? Any solution to the drive line woes.
    I had first thought it was just me who looked down at my crankset when pounding uphill to see the cranks bend and sway ever-so-little (probly 5 mm or so) which still scared me a little. Oh well, either I'm too powerful for the crankset (not likely) or its a little too light and racy...

    PS: i am running RF Forged stock cranks that came on NRS1
    My bed comforts my body. Sleep comforts my mind. The trail comforts my soul. And without a soul, what is a body anyway?

  3. #3
    theHeadlessThompsonGunner
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    Quote Originally Posted by crux
    Integrated cranks do not allow for an adjustible driveline.
    I don't think that's completely true. I think washers are available (or included) that fit between the frame and "cup" - ie, over the threads - this is exactly how the left (non-drive) is adjusted for narrower/wider shells, and I'd guess the same applies for the right (drive).

    Whatever the case, you left Shimano's spline out of your list. My XTs have been downright flawless, and I've beat the hell out of the BB for 18 months now with nary a wayward wander (in dusty conditions that have made short work of others). It's also pretty durned stiff.
    "I've courted brain damage like some courtesan of darkness."


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  4. #4
    mtbr member
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    BMX style

    I keep looking at BMX bottom brackets and cranks. Maybe that's the answer for SS - might need to go SSing on a cruiser frame.

  5. #5
    mtbr member
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    Quote Originally Posted by SDizzle
    I don't think that's completely true.
    With a 73mm BB shell, you have 2.5mm of adjustment, and with a 68mm BBshell you have 5mm of adjustment.

    dd..''

  6. #6
    all hail der Fuhrer Bush
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    theory vs reality

    But Square taper is flexy

    a fat, hollow steel tube will always be more rigid than a solid bar of steel of the same weight. so yes, compared to a well designed ISIS spindle, square taper spindles are flexy.

    but you'd need some kind of calibrated monster spindle-flexing machine to detect the difference.

    steel square taper spindles work fine for any rider, even big strong track professionals.

    the amount of flex in the bottom bracket area of any frame is so much greater than the amount you can get out of a steel square taper spindle that the discussion about the lack of flex in an ISIS vs square taper is pretty much just an academic exercise.

    of all the components that connect your feet to the rear wheel -- frame, cranks, pedals, and spindle -- the spindle is the least flex-prone part of the system.

    square taper spindle have proven themselves over many decades of cycling. Eddy Merckx rode a square taper Campy spindle. So did Indurain, LeMond, Marty Nothstein, and any other cycling god you can name from the '90s or earlier.

    If you think a square taper spindle will be too flexy for your powerful legs, you need an ego check.

    it's all about marketing, the producers of ISIS can cite evidence from the aforementioned monster spindle flexer machine that "proves" ISIS is better.

    They don't say much about the bearings. For every rider troubled by a "flexy" square taper spindle, there are 10,000 riders who have issues with tiny little wimpy bearings trying in vain to endure the stress of their pedaling, and weight.

  7. #7
    hot like a box of fire
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    go middleburn if you want to keep your PW bb. I ride Profiles myself. unmatched for stiffness/simplicity/adjustment.

  8. #8
    Single Speed Junkie
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    Quote Originally Posted by bulC
    But Square taper is flexy

    a fat, hollow steel tube will always be more rigid than a solid bar of steel of the same weight. so yes, compared to a well designed ISIS spindle, square taper spindles are flexy.

    but you'd need some kind of calibrated monster spindle-flexing machine to detect the difference.

    steel square taper spindles work fine for any rider, even big strong track professionals.

    the amount of flex in the bottom bracket area of any frame is so much greater than the amount you can get out of a steel square taper spindle that the discussion about the lack of flex in an ISIS vs square taper is pretty much just an academic exercise.

    of all the components that connect your feet to the rear wheel -- frame, cranks, pedals, and spindle -- the spindle is the least flex-prone part of the system.

    square taper spindle have proven themselves over many decades of cycling. Eddy Merckx rode a square taper Campy spindle. So did Indurain, LeMond, Marty Nothstein, and any other cycling god you can name from the '90s or earlier.

    If you think a square taper spindle will be too flexy for your powerful legs, you need an ego check.

    it's all about marketing, the producers of ISIS can cite evidence from the aforementioned monster spindle flexer machine that "proves" ISIS is better.

    They don't say much about the bearings. For every rider troubled by a "flexy" square taper spindle, there are 10,000 riders who have issues with tiny little wimpy bearings trying in vain to endure the stress of their pedaling, and weight.
    Please note that I'm more than please with the bottom bracket and want to keep the square taper, just need to find some old stock parts to replace them with. My ego is definatly in check, I know that I'm slow.

    Found a few at cambria, but they are asking over $300 for a set of standard LPs. I bought the set of failed next from them for $189. Why are they attempting to charge a premium for "old" technology.

  9. #9
    mtbr member
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    Real Numbers.

    ISIS-Drive vs. Octalink

    ISIS-Drive BB's with 22mm diameter axles have superior strength and stiffness compared to Octalink BB's (also 22mm axles), which in turn were already an improvement over square-taper BB axles (17mm diameter axles). In our testing, ISIS-Drive BB's are typically at least 20 to 30 percent stronger and stiffer than Octalink, for comparable BB's (i.e., we weren't using M12 DH ISIS-Drive BB's). Strength and stiffness of ISIS-Drive set the bar high in those categories. Going to the 24mm diameter axle used in integrated BB's offers a marginal improvement, only a 9 percent diameter increase. In comparison, the 22mm axle is already 29 percent larger diameter than the old benchmark 17mm axle.

    Currently, FSA ISIS-Drive BB bearing life is acceptable, although in the past, many ISIS-Drive BB's suffered from short bearing life. The same oversize axle that is great for strength and stiffness presented engineering and manufacturing challenges to fit bearings with a high enough load capacity inside the BB shell. (High-end Octalink BB's had similar problems.) The difficulty of engineering ISIS bearings can be evidenced by the fact that one of the three members of the ISIS-Drive Committee never produced an ISIS-Drive BB, while another member was the first to follow with an external bearing BB.

    FSA has used its bearing know-how to develop long-lasting ISIS-Drive bearing BB's. Last year, CSC was on ISIS-Drive with good results (ridden to three stage wins in the Tour de France). We have taken the feedback from CSC and have continued to improve our ISIS-Drive BB's by introducing high-end quadruple bearing versions with improved sealing, under the designation "MegaQuad." Next year, we will introduce an external bearing ISIS-Drive BB for MTB cranks.

    Alternative systems - oversize integrated BB's

    That said, over two years ago we started new developments looking beyond ISIS Drive. We looked at all the novel systems that came before, such as integrated cranks like Bullseye and Sweet Parts, etc. as well as external bearing BB's such made by Magic Motorcycle. But the conclusion we came to was that the weakest point in the system was the small diameter BB shell and that the best system was to enlarge the BB shell and integrate the BB into frame. The oversize integrated BB in the frame offers the greatest absolute system (frame + BB + crank) stiffness at the lowest overall weight. Cannondale previously proved this point by switching from the Magic Motorcycle external bearing system (which they owned) to a frame-integrated BB. More recently, Pinarello is headed this way.

    We introduced in 2002 the "MegaTech" integrated BB standard, open to all frame and BB manufacturers. The large-diameter BB shell offered frame designers a larger foundation to work around with lots of space inside for BB manufacturers to engineer better axles and bearings. However, bicycle manufacturers have been reluctant to embrace the MegaTech standard (which is surprising because they sure drive the experiments with headset standards), despite the great advantages of integrated BB's.

    Alternative systems - oversize threaded BB's

    A season after we introduced MegaTech, the ISIS-Drive Committee proposed another standard for an internal oversize BB, called OverDrive. The difference is that OverDrive is not integrated, but uses oversize threaded cups. OverDrive's advantages compared to MegaTech are that frame builders do not have to hold as tight tolerances (a thread can have sloppier dimensions than the ream required for a press-fit bearing) and it is more "familiar" to dealers and consumers than a press-fit. It is significantly heavier than other BB systems, which is probably OK for the mid-end and heavy-duty bikes it is targeted toward.

    Alternative systems - external bearings and integrated cranks

    External bearing BB's combined with integrated cranks offer some modest weight and stiffness improvement over ISIS Drive. For a given crankarm technology, the main weight savings is the elimination of BB bolts and thinner axle, but the larger bearings, external cups, and longer axle do limit the weight reduction compared to frame-integrated BB's.

    There are advantages to external bearings, which are different from the advantages of integrated cranks.

    The advantages to the BB manufacturer of the Magic-type external bearing are that the bearings are both larger (last longer) and are common off-the-shelf cartridge bearings (cheaper), which are easier to produce and procure than custom bearings for Octalink or ISIS BB's.

    The advantages to the crank manufacturer of integrated Bullseye-type cranks are that they are guaranteed that the customer will always use the intended BB with the crank (and it doesn't hurt that they will always sell a BB with a crank). The advantage to the bike company and dealers is that there are fewer worries about mismatched BB's, faster assembly and compatibility with current threaded frame designs. For a bike company assembling tens of thousands of bikes a year, reduced assembly time is important.

    When bike manufacturers and consumers are free to mix and match cranks and BB's, there is the small chance that a crank will be installed on a BB it was not intended for, which can in turn cause problems for chainline (shifting performance), crank-arm clearance and q-factor.

    There are two major problems with square taper BB's in that (i) there is no standard axle length for cranks and (ii) their taper dimensions can be made to either Japanese dimension (which follow JIS) or European dimension (which follow ISO), so even if you get the right axle length then you may have the wrong taper size.

    ISIS-Drive cleverly addressed this problem by assigning standard lengths (i.e., 108mm for road double, 113mm for MTB, 118mm for road triple, etc.), so you almost always know which length of axle you need for your cranks, and by using chainline control shoulders, so your chainline would always be as intended.

    The great power of ISIS-Drive's open standard is also its weakness - the tapered spline requires great care to produce and the ISIS standard leaves manufacturing open to interpretation in some respects. In some instances early on, manufacturers found that their in-spec products would not work with another's in-spec product - exactly what was not supposed to happen with ISIS-Drive. Fortunately, many ISIS-Drive competitors have cooperated together to hammer out the manufacturing kinks.

    So, external bearing BB's offer some simplified manufacturing and some performance benefit compared to ISIS-Drive BB's. They are compatible with most current bikes and frames. Integrated cranks reduce the possibility of mismatched BB axles and allow faster assembly.

    Summary

    FSA will introduce an external oversize bearing integrated-BB crank for next year. The code name is "MegaExo," to reflect the trickle-down over-size bearing technology from our MegaTech effort.

    The main reason is a need to keep our price and performance stable for our customers. Worldwide, the cost of raw materials is rising and we need to reduce costs somewhere - by saving cost on the bearing, we can continue to offer our famous carbon technology and performance.

    We will continue to support ISIS-Drive well into the future.

    As long as that answer is, it really simplifies and glosses over many points and details about the advantages and disadvantages about crank interfaces. It is not intended to be a definitive treatise, but just matter-of-fact for the interest of your readers.

    Dave Anthony
    Design, Research and Development, Full Speed Ahead





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