From square taper to hollowtech II BB. Advantages?

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rockyraccoon
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From square taper to hollowtech II BB. Advantages?

Postby rockyraccoon » 9 Nov 2011, 8:03pm

Any real advantages in replacing my current bottom bracket square taper (shimano 2300 chainset) for a hollowtech II bottom bracket with shimano 105 chainset/cranks on my road bike?

I've got a spare 105 chainset/cranks but to replace my current one (2300) I'd need to purchase the hollowtech BB. Is it really worth replacing them? What difference would it make? Cheers

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meic
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Re: From square taper to hollowtech II BB. Advantages?

Postby meic » 9 Nov 2011, 8:31pm

Why not give it a try and find out?

It will only cost £12.

http://www.chainreactioncycles.com/Mode ... elID=67221

My external BB has lasted 2800 miles so far which some claim is good going for them.
Yma o Hyd

irc
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Re: From square taper to hollowtech II BB. Advantages?

Postby irc » 9 Nov 2011, 8:56pm

rockyraccoon wrote:Any real advantages in replacing my current bottom bracket square taper (shimano 2300 chainset) for a hollowtech II bottom bracket with shimano 105 chainset/cranks on my road bike?

I've got a spare 105 chainset/cranks but to replace my current one (2300) I'd need to purchase the hollowtech BB. Is it really worth replacing them? What difference would it make? Cheers


I find the Hollowtech BB stiffer. But I'm a heavy rider 14-16 stone. Lighter riders might not notice the flex on square taper. It was only a marginal problem for me when standing out the saddle.

I had square taper cranks loosen in use on a couple of bikes. Not a problem with Hollowtech.

Hollowtech BBs allow easy crank removal with just an allen key.

As for longevity? I replaced the BB on my tourer at over 10000 miles. I was replacing the cranks anyway which came with a new BB. The LBS mechasnic said the driveside bearings were on the original BB were still fine. The non drives were worn but usable. I hadn't noticed any issues in use. One caveat is that 8000 of those miles were in the dry climate of summer touring in the USA. Use in typical wet UK conditions may give a shorter life. My frame was faced before the original BB was installed. I have read that failing to do this can shorten bearing life if the frame isn't perfectly square at the BB.

But having said all that unless you have issues with your current BB or are replacing a worn BB or crankset why change something that works for you?
No one believes more firmly than Comrade Napoleon that all animals are equal. He would be only too happy to let you make your decisions for yourselves. But sometimes you might make the wrong decisions, comrades, and then where should we be?

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Erudin
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Re: From square taper to hollowtech II BB. Advantages?

Postby Erudin » 10 Nov 2011, 1:35am

Similar experience to irc, also a heavy rider. I fitted a Shimano Tiagra Hollowtech II Triple Chainset and bb to my winter/audax bike. I find it stiffer when out of the saddle on a steep climb/sprint, and gear shifting smoother. I have not had a chain derail/crank loosen since fitting them, but did with the previous square taper setup (fitted a dog fang chain catcher). Have not had problems with the square-taper set-ups on my mtbs or racer but the winter/audax gets ridden in worse weather and for longer.

Removing/installing the cranks is quick and easy, if the chainset is filthy It can be quickly removed for degreasing/cleaning. Installing and removing the bb is easy using a breaker bar and Hollow Tech 2 BB Socket Installation Tool, find its gives lots more leverage/purchase than my square taper spanner fit bb tools.

Only issue I have is how good the seals on the bottom bracket are, but companies like Hope are now making compatible external bottom brackets with labyrinth seals and replaceable bearings.

BigG
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Re: From square taper to hollowtech II BB. Advantages?

Postby BigG » 10 Nov 2011, 8:52am

Surely the square taper axle is much stiffer than the frame. If there is any flex, then it is likely to be the frame flexing, not the axle. This would be the same for both types of axle. The wider spacing of Hollowtech-type bearings should bring an advantage, but I have never had any problems with the square taper systems over 40 or more years - and I weigh over 15 stone.

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hubgearfreak
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Re: From square taper to hollowtech II BB. Advantages?

Postby hubgearfreak » 10 Nov 2011, 9:52am

BigG wrote:Surely the square taper axle is much stiffer than the frame. If there is any flex, then it is likely to be the frame flexing, not the axle.


no no no. having read the (it's stiffer) posts from those that have converted, i thought i'd do a test.

so, put into the vice a square taper axle, and you know what, it wobbles and flexes like a steel rule :lol:

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Si
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Re: From square taper to hollowtech II BB. Advantages?

Postby Si » 10 Nov 2011, 11:09am

so, put into the vice a square taper axle, and you know what, it wobbles and flexes like a steel rule :lol:


does it make a 'boioioioing' sound just like Zebadee when you twang it?

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Mick F
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Re: From square taper to hollowtech II BB. Advantages?

Postby Mick F » 10 Nov 2011, 11:13am

I agree about the BB axle flexing rather than the frame, though I've never done the Zebedee Test in a vice.

Anyone I've spoken to/read about, says that going to "modern" external bearings makes the thing stiffer.

I've always been aware that when pushing hard in a high gear, the chain on the outer ring will catch on the front mech. This is axle flex, not frame flex.
Mick F. Cornwall

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531colin
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Re: From square taper to hollowtech II BB. Advantages?

Postby 531colin » 10 Nov 2011, 11:35am

Mick F wrote:................. when pushing hard in a high gear, the chain on the outer ring will catch on the front mech. This is axle flex, not frame flex.


Surely not with Campag, Mick? I'm shocked! :shock:

I thought the marketing RA! RA! RA! for those big tubular axles was that they didn't wind up when you push the left pedal down.?

Anybody out there really know which is stiffer, a BB axle or a bunch of tubes stuck round the bracket shell? (any responses which don't start with "it depends what you mean by stiffer" will be discounted)

reohn2
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Re: From square taper to hollowtech II BB. Advantages?

Postby reohn2 » 10 Nov 2011, 11:40am

Mick F wrote:...........I've always been aware that when pushing hard in a high gear, the chain on the outer ring will catch on the front mech. This is axle flex, not frame flex.


I'd say its more like bearing "flex"
Square Taper is the durable(20,000+miles for UN54) system,flex doesn't concern me unless its excesive,which it isn't.
I'm glad Hope are giving extenal BB owners who cycle in all weathers(heaven forbid) hope,by producing quality bearings for what,by all accounts,should be a good system.
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CREPELLO
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Re: From square taper to hollowtech II BB. Advantages?

Postby CREPELLO » 10 Nov 2011, 12:08pm

reohn2 wrote:
Mick F wrote:...........I've always been aware that when pushing hard in a high gear, the chain on the outer ring will catch on the front mech. This is axle flex, not frame flex.


I'd say its more like bearing "flex".
Mmm. An interesting concept, but can I ask, what exactly is "bearing flex"? And why would it appear that external BB's are less prone to it than square taper BB's?

Edwards
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Re: From square taper to hollowtech II BB. Advantages?

Postby Edwards » 10 Nov 2011, 12:18pm

I have been know to use an old square taper axle as a drift even as a lever with a bar on one end. It did not flex that much, so what type of axle is it that flexes? The fixed cup with the bearings in or the older adjustable cup with a solid bar one?
Keith Edwards
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BigG
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Re: From square taper to hollowtech II BB. Advantages?

Postby BigG » 10 Nov 2011, 12:39pm

hubgearfreak wrote:
BigG wrote:Surely the square taper axle is much stiffer than the frame. If there is any flex, then it is likely to be the frame flexing, not the axle.


no no no. having read the (it's stiffer) posts from those that have converted, i thought i'd do a test.

so, put into the vice a square taper axle, and you know what, it wobbles and flexes like a steel rule :lol:

I put my square taper axles (one Phil Wood and one Shimano UN52) in a vice and couldn't detect any flex even with all of my weight on an 18" wrench. (The work bench moved a little, but not as far as I could tell the axle.) However, I can bend my frames noticeably (all 531 original - not 531c, two butted, one plain) with my 15 stone on one pedal only. I have no problems with the chain rubbing on the front mech if properly centred; but I do use a friction only front mech (Suntour) which is probably easier to centre. Both the axles checked and my third axle, a Kajita, are solid, not hollow; but unless the walls are particularly thin, this would not make much difference to the stiffness.
Perhaps the slight movement of my workbench masked the flexing of the axles; but I don't think so.

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hubgearfreak
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Re: From square taper to hollowtech II BB. Advantages?

Postby hubgearfreak » 10 Nov 2011, 12:45pm

Si wrote:does it make a 'boioioioing' sound just like Zebadee when you twang it?


yes, exactly. and if you had several vices and several bb axles protuding from the vice by differing amounts, you could have a xylophone type thing going on


boioioioing, boioioioing, boioioioing, boioioioing, boioioioing, boioioioing, boioioioing - any one for a game of i'll name that tune?

reohn2
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Re: From square taper to hollowtech II BB. Advantages?

Postby reohn2 » 10 Nov 2011, 12:49pm

CREPELLO wrote:Mmm. An interesting concept, but can I ask, what exactly is "bearing flex"? And why would it appear that external BB's are less prone to it than square taper BB's?


I wouldn't think a solid s/taper axle would flex(I could be wrong) so I conclude that if theres any flex/movement in a S/taper BB it would be in the bearings as they are inboard of the BB shell ie; closer together on the axle than external bearings,as MickF says if the chain is catching on the f/mech cage under load it must be the BB and not the frame thats flexing.
That is unless its the c/ring thats flexing which is possible with say a 48t on a 110BCD c/set there would hardly any on say a 36t ring on the same BCD c/set.If I detect any flex its usually in the 48 ring on extreme chain angle ie;big ring second gear, but its small.I cannot detect any with by feel ie; though the feet,though I'm not a big strong rider and I don't climb these day out of the saddle usually,preferring to twiddle than mash.
All that said if some riders can detect flex,external bearings with hollow large diameter axles are a good idea.
Its the bearings that are at fault IMO,in that(by all accounts) they aren't weatherproof and are in plastic housings which doesn't bode well for such a highly stressed part.
If Hope can make a durable external bearing set that lasts and doesn't cost the earth then they and users are on a winner ie; a stiffer and durable external bearing BB.
I think its got to be remembered that for most people durablity over a slight,almost undetectable flexing wins out every time,especially for tourists.
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