Been backing off from external BB cranksets for a while now, but I'm sure many STWers have been using for a significant time now.
One of the great praises of the external BB design is their "stifness". That's their only one isn't it? Seeing as the BBs don't seem to last that long and there is no significant weight loss over the older designs.
My question then is - even if the BB is stiffer - once mounted in a frame that flexes under rider pedal input - is the benefit of a stiffer BB really there at all? is there [i]any[/i] benefit?
I'm just wondering if the external BB design fixing something that was never really a broke (excepting ISIS).
I have been running Shimano XT cranks on both bikes for about 3 years now. The Bottom brackets last quite a long time, the XTR ones and Hope ones seem to be very good. BB's are definately better than ISIS, by some significant measure.
Getting cranks on and off is very easy. All in all, I think they are pretty good.
As for stiffness, to be honest I can't tell the difference.
the cranksets are great.
the BB design is bobbins though.
Middleburn & square taper here.
I dont use electricity either.
They're better than they were, and you can get (mostly) a reasonable life span out of a set of external BB's with a bit of care and attention now and again.
And Shimano get to sell more cranksets and replacement external BBs ... they'd probably taken the existing one to it's limit.
But eff all benefit to the MTBer tho?
I've certainly never complained about the stiffness of the BB and noticed frame flex more when mashing the pedals uphill (with a good even stroke 🙂 ).
Well, their job is to sell stuff after all...But in all honesty we've got to where we are because people starting doing stuff on bikes that regular sq taper axles couldn't handle, so they increased the size of that, which stopped folk breaking them, but suddenly bearing life became an issue.
External is an answer to both problems. Progress...of a sort.
Use external on one MTB (steel frame - Soul) and on both road bikes (alu and carbon).
Definitely stiffer (though the MTB is pretty twangy anyway) and I've had no problems with bearing longevity. Mind you, I don't clean my bikes with a pressure washer....
The problem with the external BB';s is that they are sealed from the elements on the outside, but not on the inside.
both my bikes let rear tyre spray find its way down the seatpost into the seat tube and eventually into my BB bearings, no two ways about that. That was until I filled the botttom of each seat tube with a wine cork and some silicon. Job done. BB bearings used to last sub six month, now lasting forever, 18 month+ so far.
Well I went back to my Octalink XT cranks for the winter as my external BB siezed up - never noticed any problem with the older design. Definitely planning to use internal BBs for winter use from now on.
The problem with the external BB';s is that they are sealed from the elements on the outside, but not on the inside.
Ah. Wonder if mine last longer because I put a thick layer of grease on the inside of the cups....
None spin anywhere near as freely as the old square taper in my track bike. without the chain on, that thing spins like a perpetual motion machine....
sq225917: i hope you drilled a hole to let the water out above the cork 🙂
I just have a hole in my bottom bracket shell. Water in, water out! Lovely.
I think they feel a bit stiffer from square taper, but nothing seems to last as long as the square taper bearings.
Having said that just got a year out of my External Shimano BB and now fitted a Hope one which will undoubtedly last longer in our gloriously warm, wet summer
and Ive just got another UN72 of fleabay. Thatll keep me going for another few years 🙂
I've got a brand new deore crankset and internal BB sitting around in the loft if anyone wants it I'm open to offers!
I've been running a sq. taper UN26 BB (£5.50) for 9 months now with still no detectable wear 🙂
Octalinks last for ages too
so they bind. wear relatively faster. and in reality once fitted - they're not that stiff either.
great.
Stiff ? I have no idea about this - the pedals seem to go round without going obviously sideways, and that's good enough for me:-)
i've found them to be a marked improvement on everything I had used before.
using XT on the XC bike and Saint on the DH bike.
not perfect but then nothing is.
i've found them to be a marked improvement on everything I had used before.
can you quantify this ? Do they go round better in some way? My only criterion for BBs is longevity (and freedom from seizure).
There's a fairly substantial weight saving.
HT2 XT weighs less than old Octalink XTR.
Well, the six year old ISIS BB I have in my h/tail seems to be working just fine, new bearings after eighteen months, fitted to new frame around three years ago. Can't comment on the external BB on my SS as yet 'cos it's only around a year or so old, but it's working ok at the moment. Just the way they're fitted, I guess...
define a marked improvement?
i've bought significantly less cranks and bottom brackets since making the swop.
There's a fairly substantial weight saving
unimpressed. a couple of 100gm out of an all-up mass of 90kg is zip-all
[i]i've bought significantly less cranks and bottom brackets since making the swop.[/i]
my sq. taper crank and BB cost me £25 in all and have already done 9 months and still going strong
lucky you.
before HT2 i was destroying cranks and BB's on monthly basis.
Save 100g off every single component and you'll end up with quite a light bike!
It's a lot when you think of it as like for like products, in fact HT2 has always tended to be cheaper than the Octalink systems were when they were current. I've never had an issue with b/b life either, can't understand how people kill them so fast, my Dura Ace in my road bike did 4.5 years, and I've never had an MTB one go in under 18 months.
Save 100g off every single component and you'll end up with quite a light bike!
hardly practical though - I'd prefer to add weight and durability
HT2 XT weighs less than old Octalink XTR.
That's not the complete picture is it? XTR went external-BB a fair while ago.
Compare an XT Chainset with BB non-HT2 with a current HT2 XT chainset then the difference is negligible. They both weigh a little over 850g each.
So no weight saving.
If you're going to be a weight-weenie get it right 🙂
[url= http://weightweenies.starbike.com/listings/components.php?type=cranksets&sortby=manufacturer ]http://weightweenies.starbike.com/listings/components.php?type=cranksets&sortby=manufacturer[/url]
I use both, I am over 16st so believe me there is far more torque going through my cranks than most. I can feel bugger all difference. I think most of it is marketing bollox that people unfortunately buy into. People can tell you there is a significant difference, but in reality it is only shimano and the like who benefit....
[i]My only criterion for BBs is longevity[/i]
Other people's criteria may differ though.(road)Sprinter friends of mine could snap Sqr taper axles, and I seen a few break on heavy landings. Couple of mates that are into dirt jumping don't really care at all about bearing life, as TBH they don't do massive mileage in shite conditions, but axle strength is waayyy more important to them.
sounds like HT2 was designed for a [i]minority [/i]of riders then?
Not really, it's a "one size fits all" solution, Even if you can't feel it, stiffer cranks are better, bearing life is (now at least) acceptable, and fitting them is a piece of cake.
.(road)Sprinter friends of mine could snap Sqr taper axles, and I seen a few break on heavy landings. Couple of mates that are into dirt jumping don't really care at all about bearing life, as TBH they don't do massive mileage in shite conditions
ie not really mountain biking then 🙂
and riding through puddles is?
Even if you can't feel it, stiffer cranks are better
or no different at all...
and riding through puddles is?
if they are on mountains :o)
Well, there'd be no point in making cranks more flexible would there? Does it matter that different disciplines can benefit from the same technology?
pointless argument really
are there many mountains where you ride, because most of your pictures appear to be on big hills.
Well, there'd be no point in making cranks more flexible would there?
hard to say really - perhaps twice as much flexibility as sq. taper might be fine...
Does it matter that different disciplines can benefit from the same technology?
not as such, but I've read a lot about EXBB seizing up in filthy conditions, which I've never seen with older types, so perhaps it's better suited to those other disciplines ?
sq225917-nice tip!
I think early EXBB were pretty badly sealed, newer ones are better, certainly mine have survived a pretty shitty Chilterns' winter without seizing. But essentially I think for really extended longevity, you're right to stick to Sqr taper
HTP404, there's a 50g weight saving, from XT M750 - M770 which, IME also brings better bearing life. I know a lot of people find the opposite, but I trashed Octalink b/bs much more quickly. Seems to be related to weight too, heavy riders seem to fair worse, I'm only 69kg, which seems to help.
At the end of the day, it's not going away, if you don't wanna buy it, don't. I've now got a BB30 chainset, and the bearing life is dire. But I've got a big pile of warranty ones to keep me going for a while!
Other people's criteria may differ though.(road)Sprinter friends of mine could snap Sqr taper axles, and I seen a few break on heavy landings.
Tom Boonen was using sqr taper cranks up until recently - can't recall him snapping any - maybe your freinds should give quick step a call!
However i've seen sqr taper axles break on landings on mtb bikes (only un72 thou)
I think each style BB had it's own advantages and disadvantages.
I quite discount the stiffnes thing for normal XC riding, as you are mostly spinning - and i dare say most decent track cyclists could put down at least 30% more power than most guys on this wesite and efficiency is paramount sucsess in track, and as flexability would reduce effeciency they would be the first to bin them.
Octalink - i always found them very good - it removed the problems of sqr taper (damaging cranks on landings) with very good durability - but slightly less than sqr taper due to smaller bearings.
ISIS - Filth.
External - good idea dogged by poor execution - especially by race face and FSA (my external road FSA BB disintegrated compleatly on a ride the other day) Shimano seem to have the best seals although i've yet to try hope etc.
My conclusion is that sqr taper offers good cheap long life option for those not doing anything to hucky. Octalink similar but can handle more abuse by the rider. And external good for heavy folk and those that jump off stuff - just don't be a knob and jet wash your bike!
The other advantage of external BB's is that the bearings are cheap & easy to replace.
Certainly cheaper than a new BB
The other advantage of external BB's is that the bearings are cheap & easy to replace.
That depends how often you replace them 🙂
ISIS - Filth
There are some good uns as well as the bad - FSA seem to last me fine, and SKF are awesome quality.
HTII have been rubbish in my experience - one lasted 3 rides!
Certainly cheaper than a new BB
cheaper than £5.50 ?
and as flexability would reduce effeciency they would be the first to bin them
evidence please. Even if the cranks DID flex, this would not absorb energy in elastic bending, so it's not obvious that it would affect efficiency
cheaper than £5.50 ?
Where sells BBs for that price?
Where sells BBs for that price?
Secondhand.
Where sells BBs for that price?
UN26 from Parker International
7.15 plus 3.95 postage. You could easily get a decent set of bearings for a tenner 😀
7.15 plus 3.95 postage.
I can't find them on that site any longer, but there was no postage charge.