why bother upgrading cranks to external BB?

Home Forum Bike Forum why bother upgrading cranks to external BB?

Viewing 40 posts - 1 through 40 (of 46 total)
  • why bother upgrading cranks to external BB?
  • TuckerUK
    Member

    Some think the axle is stiffer, but having seen someone try to bend a square taper axle I seriously doubt that, maybe it just stiffens the BB area of the frame better? Anywho, this apparently translates to more power to the drive train, less power lost in flexing.

    And you’re right, can can get some ST or Octalink setups lighter than some external BB.

    ollie151
    Member

    i assumed upgrading to newer external BB and hollowtech cranks would be big weight saver, but a bit of research tells me i may be wrong..

    am i?
    is it an upgrade?

    ndthornton
    Member

    Its just better on all fronts really

    Its lighter…
    stiffer…
    More bearings so better load spreading = longer life (as long as its a nice BB with good seals = Hope)….
    easier to install + remove (especially shimano)….
    Your crank will never fall off (iv had this with square taper)
    doesn’t creek like square taper can

    Just a better solution to the problem of cranks

    Premier Icon oldnpastit
    Subscriber

    your crank will never fall off (iv had this with square taper)

    Not entirely true. I’ve had HTII fall off.

    Premier Icon richmars
    Subscriber

    Your crank will never fall off (iv had this with square taper)

    Not true. Loose fixings are loose fixings, whether square or external.

    winch
    Member

    I prefer them for the above reasons, but only just. You can expect an increase in friction in my experience, which is the main downside.

    Premier Icon njee20
    Subscriber

    your crank will never fall off (iv had this with square taper

    )

    Although many HT2 cranks do have the little doofry to hinder ones crank coming off. Personally I’ve had it with HT2 as well.

    orangeboy
    Member

    Personaly I can’t see a great advantage apart from shimano stopped making good taper bb
    And crank choice is limited now

    Phil wood or Royce bb and some nice rs7 or rs8 arms does me just fine thanks

    mattbibbings
    Member

    Better from a simple case that there is only one ‘joint’ between cranks and axle as opposed to 2. In climbing we refer to this as the safety chain. Not so critical in MTBing but the logic is the same.

    The bb life thing though is an issue. I had some old shimano UN54 BBs that went on for donkeys regardless of how I treated them whereas some external BBs (inc simano and FSA) have been made of stiffened tissue paper and give up at the first sniff of winter.

    Hope external BBs on the other hand. Like that popular singer on the hair advert says

    ” because you’re worth it”

    TiRed
    Member

    Performance-wise I’ve not really noticed a difference.

    Not entirely true. I’ve had HTII fall off.

    This. The difference is that when your HTII crank falls off, it won’t be trashed and can be reinstalled on the octalink axle. A square taper will be rounded out and will probably be heading for the bin.

    Installation and removal are the real advantages for me. I have a Stages Power crank and swapping between bikes is a five minute job.

    ndthornton
    Member

    Not true. Loose fixings are loose fixings, whether square or external.

    Not sure about this – mine were pretty damn tight to start with – and if I’m supposed to periodically re-tighten them – then that’s another disadvantage.

    I’ve had HTII fall off.

    No experience of these – Shimano hollowtech is never coming off though – unless you tell it to

    pdw
    Member

    The main advantage is that you’ll never have to deal with a BB seized in your frame again, as the BB will fail long before this has a chance to happen.

    IHN
    Member

    Is it an upgrade?

    No.

    I’ve upgraded back to a UN54 square taper BB and Middleburn cranks, as I like BBs that last years, not weeks or months.

    The stiffness argument is marketing pish; there’s no way that you’re average weekend pedalling punter can tell the difference in stiffness between a HTII and Square Taper BB. They may tell themselves that they can, but they can’t.

    orangeboy
    Member

    Do see ht2 left arms that fall off now and then its not that

    Hollow tech uses an internal bb ( octalink )
    hollow tech 2 (ht2) is the external one

    Premier Icon epicyclo
    Subscriber

    why bother upgrading cranks to external BB?

    because it’s hard to find a decent ISIS these days…

    orangeboy
    Member

    Rs8 arms spider and a Phil bb come to just over 600g
    That’s still very light even Useing old technology

    TuckerUK
    Member

    More bearings so better load spreading = longer life

    Really????

    Decent Shimano ST and Octalink BBs have been known to last for over 10 years.

    Junkyard
    Member

    Its lighter…

    not really depends what cranks you use

    stiffer..

    I seriously doubt anyone can tell and your tyres and frame delfect when you hammer it so it makes **** all difference anwyay.

    More bearings so better load spreading = longer life (as long as its a nice BB with good seals = Hope)

    I doubt even the industry calims this as a benefit
    I have square taper BB’s that outlasted the frames – i am pleased to get an external last the season – Hope are awesome to be fair when matched to XTR cranks

    easier to install + remove (especially shimano)…

    I think both sets need a tool to remoce so not sure why you think one is easier than the other – its not QR via wheel nuts now is it?.

    Your crank will never fall off (iv had this with square taper)

    It does

    doesn’t creek like square taper can

    yes no ones cranks creek anymore 😯

    Just a better solution to the problem of cranks

    Its not like press fit I assume the industry dies it because its cheaper /easier to build rather than for us

    FWIW i have 2 x external and 2 x Square. the squares still outlast the hope and the stiffness thing is not something I can detect even though the square is on a SS

    I would not upgrade myself personally for say the BB but i would perhaps if rings went or the crank was fubbared

    Premier Icon ads678
    Subscriber

    I’ve had shimano octalink and ht2 cranks fall off. Probably says more about my grease monkey skills though. Still prefer ht2 though, just seems simpler and a nicer set up. Not really bothered measuring weight savings in grams, i’m too fat for that!!

    Premier Icon ahwiles
    Subscriber

    crank extractors and the piddly fine threads were a nightmare.

    Junkyard
    Member

    You have not tried to remove XTR hollowtech then which uses basically the same method but with an alloy bolt !!

    johnellison
    Member

    I think a lot of it is down to preference again.

    Back in the day I had cranks that fell off and creaked on square taper, and I had cranks that didn’t. I broke/bent some square taper axles, others were fine.

    Similarly I’ve had cranks that fell off and creaked on outboard BBs, and I had cranks that didn’t.

    I’ve never broken or bent an outbard BB spindle though.

    The main issue is bearing life. The further apart a pair bearings are, the better that they will support axial loads, so theoretically they should last longer.

    However, both Shimano and RaceFace outboard BBs were notorious for having cheese bearings although I believe. Hope are way superior though.

    Horses for courses though, innit?

    shermer75
    Member

    The only time I’ve noticed a difference in stiffness was when I had a set of RaceFace freeride cranks for a year or so. They were heavy. Everything else I’ve had (and I’ve had the lot many times over apart from the new press fit stuff) have all pretty much felt the same.

    bigyinn
    Member

    TiRed – Member

    This. The difference is that when your HTII crank falls off, it won’t be trashed and can be reinstalled on the octalink axle. A square taper will be rounded out and will probably be heading for the bin.
    I know im being pedantic, but getting a HTII crankarm on an Octalink axle is quite an achievement!

    shermer75
    Member

    The main advantage is that you’ll never have to deal with a BB seized in your frame again, as the BB will fail long before this has a chance to happen.

    This ^

    Premier Icon transporter13
    Subscriber

    Main issue is strength for me. I was forever snapping square taper axles, didn’t matter which brand or model I used.
    Ht2 is much stronger. I’ve not managed to twist or break any cranks or axles in all the time I’ve had them. I’d happily trade strength over longevity of bearings

    brakes
    Member

    I’ve had to take far more square taper cranks off with a hammer than I have outboard bearing types.
    AND I can tell the difference between square taper cranks and outboard bearing with respect to stiffness on MTB and road.

    Premier Icon Northwind
    Subscriber

    I can feel the difference between my external and internal cranks, but, to be fair there’s also a spec difference- not many directly comparable cranks these days.

    Also, yes I’ve had more trouble with stuck internal BBs, but that’s partly because I’ve never had an external BB last for the best part of a decade.

    OTOH I’ve written off 3 sets of cranks in my life and they were all square taper. Older, sure, so maybe just less good in general.

    I don’t think many people really compare the two fairly- internal fans want to believe that XT BBs last 5 minutes, which if it was ever true isn’t true now. And external fans want to believe that their mighty thighs will bend an internal one. It all seems to be about imagined differences.

    orangeboy – Member

    Rs8 arms spider and a Phil bb come to just over 600g

    And the BB alone costs as much as a complete XT crankset with BB and rings.

    Saccades
    Member

    epicyclo – Member

    why bother upgrading cranks to external BB?

    because it’s hard to find a decent ISIS these days…

    Could you ever find decent ISIS BB’s 😉

    Junkyard
    Member

    I’ve had to take far more square taper cranks off with a hammer than I have outboard bearing types.

    so you are saying they are more secure 😉

    AND I can tell the difference between square taper cranks and outboard bearing with respect to stiffness on MTB and road.

    I think lots of people claim this but I would love to see some double blind trials done as i dont think anyone really can they just think they can. This “placebo” affect is true for many thinks not just expensive MTB parts we have just bought.

    slimjim78
    Member

    The stiffness argument is marketing pish; there’s no way that you’re average weekend pedalling punter can tell the difference in stiffness between a HTII and Square Taper BB. They may tell themselves that they can, but they can’t.

    [quote]I would love to see some double blind trials done as i dont think anyone really can they just think they can. [/quote]

    I can tell also.
    Back to back swaps on my steels frames, a stiffer platform is instantly noticable. I would pish on a pepsi challenge.

    Much easier to fit/remove/maintain also.
    If you require new cranks/bb, I wouldnt hesitate to recommend an external set up.
    No real expeirience of Shimano though, SRAM GXP / Hope has been superb.

    Death to square taper. Nasty ancient stuff.

    cynic-al
    Member

    What junkyard said. I only converted when my STs were creaking when jumping – I reckoned they might not last.

    brakes
    Member

    I know I can, and that’s good enough for me.
    as an example I went from an FSA Carbon Team Issue ISIS crank (not square taper, but this is about inboard and outboard) to Shimano 105 with HTII and the difference was very obvious.
    what I had previously assumed was a flexy frame was actually flexy cranks/BB.

    Junkyard
    Member

    its like when folk tell me they can tell forks flex and maxles are stiffer.

    I agree they think they can I am less convinced that they can.

    acehtn
    Member

    HTII is easier to work with.
    When i switched over i thought i had made a terrible mistake as shimano BB’s didn’t last any better than the ISIS i ditched.
    Raceface DH bb was just as bad but more money.
    Had some Enduro bearings fitted to the Raceface cups about 6 years ago, getting a bit rough now 🙂

    Have seen HTII crank arms drop off. Have seen a couple with M10 bolts through the spindle to keep the arm’s together.
    And know of one saint crank that got the spindle/axle bent.

    On cost and used them before, going back to octalink as i can get a new chainset and bb for around £50 and already have the fitting tool and an old bb (for more xc type riding)

    brakes
    Member

    its like when folk tell me they can tell forks flex and maxles are stiffer.
    I agree they think they can I am less convinced that they can.

    with forks it’s about how they track, not about whether you can feel them flex.
    with cranks you can feel that more of your effort is going towards pushing you forward, rather than feeling the axle/ crank arm flex.
    it’s not about the individual items flexing it’s about the result that higher/lower stiffness has on how the bikes feels.
    I find it difficult to tune a bike’s suspension because I find it hard to appreciate the subtle differences in settings, whereas stiffness is more appreciable.

    Premier Icon hatter
    Subscriber

    Depends on who you are, I’m a big heavy biffer so HTII was a godsend, I was forever killing axles and rounding off square tapers(yup, even Middleburns, ISIS was stiffer but the BB’s were beyond dreadful, HTII was a huge improvement.

    If you’re a light weight rider who puts huge miles in then a set of Middleburns with Nice Ti-axled Phil Wood Or Royce BB would be damn near perfect for you, they wouldn’t last me 5 minutes.

    Horses for courses.

    TuckerUK
    Member

    what I had previously assumed was a flexy frame was actually flexy cranks/BB.

    See, I’m fairly positive that isn’t true (having seen a guy put a square taper axle in a vice and try to twist it). What I think HTII does is reinforce the bike’s BB shell and stiffens the frame in that area.

    TiRed
    Member

    but getting a HTII crankarm on an Octalink axle is quite an achievement!

    Doh! me bad. Of course I meant HT 😳 . My HT crank fell off in a race once. Tried to put it back on in situ to no avail (was fine once I’d got back to the garage). But as I’d completed a lap and was the third of three singlespeeds, I placed on the podium. I have rounded square taper cranks too. They went in the bin.

    In fact, I passed over octalink and have gone straight to HT. My UN52’s are all fine after 10 years and none are as smooth as the serviced cup and cones on the Dawes Super Galaxy tandem.

    Van Halen
    Member

    i have a scar on teh inside of my left leg from a square taper snapped axle that is an eternal reminder to me that hollowtec external bb`s are better than square taper.

Viewing 40 posts - 1 through 40 (of 46 total)

The topic ‘why bother upgrading cranks to external BB?’ is closed to new replies.