Thorn Cycles Forum
Community => Thorn General => Topic started by: Swislon on December 19, 2013, 03:48:12 PM
-
Have we done this before?
External bottom bracket bearings or square taper?
I lean towards square taper for longevity but am I stuck in the past or is there real evidence out there that proves the point?
I have external on my other audax bike and it has lasted a good 7 years but now requires changing. I never changed previous square taper just the bearings.
Am I being a Luddite here?
Steve
-
I vote for square taper. Those external bearings are supposed to be better because they're bigger, but they've just become another fashion item, while square tape bottom brackets are now a highly reliable, inexpensive generic fitting. The Kinex bottom bracket fitted by both the top German bike brands retails for under ten euro... I have some on my bikes, and they're superb.
-
Good question Steve, this is something I've been pondering over lately as hopefully I'm in the market for an Audax next year. I was going to go with the proven reliability of square taper but it seems that is an old fashioned option. I'll be interesting to hear from owners of external type BB's as to there opinions of them. I think that Andre has a very nice Royce Square Taper BB on one of his bikes, that would be my No1 choice if the funds allowed.
Neil
-
Have we done this before?
External bottom bracket bearings or square taper?
Yep! A quick Search of the Forum archives using the string "External" (no quotes) will bring up most past references. For example: http://www.thorncycles.co.uk/forums/index.php?topic=7289.msg46639#msg46639
Just a general reminder to new members and those who may be seeking information quickly...I wrote and posted a little tutorial on quickly and effectively searching the Forum and posted it here: http://www.thorncycles.co.uk/forums/index.php?topic=4390.0
Steve, I deliberately chose to fit Sherpa and the Nomad with external-bearing BBs to see how they'd fare and so each of the bikes would be fully modern. I found (as I had expected) the Shimano external-bearing BB did not last long in my use, so I replaced it with a Phil Wood unit I had waiting in the wings for when the Shimano failed. So far, so good on the Phil, but it should be noted my 14 or so other bottom brackets (including several Phil units) are square-taper and exceptionally long-lived, especially compared to the Shimano external unit I've had.
The *idea* of an external bottom bracket makes a great deal of sense and I like it very much from an engineering standpoint. What lets it down in general is not all manufacturers design appropriately for maximum life. Many use smaller, fewer bearings and then fail to seal them properly against weather/water and compound the problem with soft bearing cups. The result is as expected. Designed with an eye toward preventing these problems, the outlook is encouraging. I just need to put more miles on mine to see if it comes anywhere near the exceptionally high mileage I have on some of my square-taper units.
Hope this helps.
Best,
Dan.
-
I've been running a Shimano external on my Trek for a couple of years. Commuting all year round in all weather I've had over 4K miles out of it so far and never given me any problems and still going strong. For my new Club Tour I've got a Hope stainless steel external which I'm expecting to be just as reliable.
I should add that I dont expect to get the same mileage from an external as I would from a square taper.
-
Steve,
One more note I forgot to mention above: If you go with an external-bearing unit, please be aware they are *very* sensitive to bearing preload; too much will quickly kill them. Typically, the preload adjustment is best used only to secure the left arm to the spindle and takes almost no torque at all. If you install the unit yourself, be sure to keep this in mind else it won't last long. I think this is the single biggest determinant in bearing life for external units.
Best,
Dan.
-
Another point to bear in mind is that the bottom bracket shell should be faced for an external bottom bracket to be fitted correctly, Thorn faced my Club Tour frame for no extra charge.
-
Real good point, Chris, and I think a large factor in the good service life of your external unit. The Nomad made that part easy -- the anodized alu eccentric was turned square in relation to the threads and no paint to worry about -- yay!
Best,
Dan.
-
The Shimano SM BB51 which I had on my Audax failed between 3000 - 4000 miles. My LBS commented this was the norm and not to expect any more. Somewhere someone also mentioned the external nature of them makes them more vulnerable to water getting in - but then they cost around £20.
Steve, you're not being a Luddite, I think these things should last much longer.
Grrrrrrr.
-
I did a 500 mile unsupported tour in summer of 2012 around Glacier National Park. That is in Western USA, lots of steep mountain climbing, but all on pavement.
There were a few flat tires, one person had a spring in a front derailleur break and the only other equipment failure was an external bottom bracket.
If it was me, I would likely stick with whatever works with my crankset instead of replacing cranks. If I replaced it with something else, I would also factor in the cost of tools if they were different.
All my bikes have square taper. When I built up my Nomad this past spring, I chose a square taper Shimano cartridge bottom bracket, I got the cheapest one they had that had a metal (not plastic) bushing for the left side.
I got a Vuelta crankset compact complete for about $30 USD, it was cheaper than crank arms elsewhere. I do not think I have ever heard of a square taper crank arm failing, so I see no reason to pay a lot for this component. I am using a different ring than came with it, the chainring was about $10 USD.
I considered trying to set up my Nomad with old style cups and bottom bracket spindle so that I could disassemble and regrease (instead of cartridge), but I was unable to find anyone that would sell me the right spindle for that setup. This might not be a labor saving device, but for an expedition bike it made sense to me to have something that can be disassebled and regreased.
-
My nineteen year old Kona MTB has the original square taper BB, which in spite of little maintenance, still works perfectly. This was a deciding factor when choosing parts for my Raven.
-
Hi All,
Square taper BB do out last new External type BB by about 10 to 1.
I work in one of the LBS and we replace alot of External type BB and More of the Newer BB30 tyre BB :o
BB30 BB last about 3 months to a year.
External type BB last 1 to 2 years.
Square taper BB's last 1 to 15 + years :( we can not make money replacing BB,s Here :o
Happy Cycling
Pete 8)