Octalink

[silva]

Interesting positive take on octalink. Encouraging. But am puzzled as to what your square taper issue was. Did you check/retighten the cranks after a bit of riding? Good practice I think.

I never checked/retightened, for 2 years, before recently a crank arm broke, and my replacement required dozens retensionings, the first ones being after every street.
I think that if a crank would sit loose on the taper, the taper quickly would wear off / get rounded off, manifesting the problem, and I haven't seen as such.
So I highly doubt a nontensioned crank would be the cause of offcentering all that time.
The chain tension variation (2 cm up and down difference) was already present from the bikes acquisition / new.
And a later replacement of the crankset also didn't change it.
But again, I'm judging with a singlespeed bias, with gears a spring based chain tensioner "equalizes" the chain tension. An eccenter, or wheel backwards in its mount, not.
So my positive take on octalink should be seen in this particular case.
And also, it still has to be proven on the new bike.
The problem with the new bike was a frame that limited chainring size, causing the need for a longer axle. A longer axle has some mechanical consequences, all towards the negative.

 

[Drago]

But they are no more shielded than external bearings. The only place water can get in is through the seals on the axle which is subject to the same spray off the front wheel on either system. It does not matter how far the body of the bearing protrudes from the bottom bracket.

Having said that, my preferred system is square taper. Good quality bearings (UN55, Centaur) last for ages and fitting is a doddle.

External bearing have a greater surface area directly exposed. Theoretically there isn't a lot in it, but the reality is that despite having larger bearings and more of them the lifespan is, like for like, typically quite poor compared to ISIS, Octa, or the various standards of square taper. There has to be a reason for that.

 

[Blue Hills]

Must admit to not being a fan of isis after my experience with one on a dahon speed pro sportsbike. Never had a bb fail so soon.

 

[davidphilips]

Hope you are wrong about ISIS Blue hills? Just bought a second hand ISIS chainset from Ebay and have been thinking i got a great deal? Time will tell, have no experience of them but looks good £41 delivered complete with BB?FSA SLK Carbon Chainset 110bcd 52/38T ISIS

 

[Blue Hills]

Hope you are wrong about ISIS Blue hills? Just bought a second hand ISIS chainset from Ebay and have been thinking i got a great deal? Time will tell, have no experience of them but looks good £41 delivered complete with BB?FSA SLK Carbon Chainset 110bcd 52/38T ISIS

Maybe you will fare better - mine was a no name thing fitted to a dahon speed pro - not a cheap bike but dahon was known for some dodgy sourcing.
I do though have memories if reading that isis was inferior to octalink.

 

[Pale Rider]

Maybe you will fare better - mine was a no name thing fitted to a dahon speed pro - not a cheap bike but dahon was known for some dodgy sourcing.
I do though have memories if reading that isis was inferior to octalink.

I think ISIS is deemed to be inferior because it has a small bearing race which means each bearing has to work harder in turn making it wear faster.

The view of my local bike shop is you can't get past square taper, although like many components there are cheap and nasty square tapers.

Anything with Shimano written on it will do the job.

In theory, an external bearing with its larger surface area should last even longer.

But as observed upthread, there doesn't seem to be any evidence of that.

I suppose there might be a rigidity benefit.

 

[Smokin Joe]

I think ISIS is deemed to be inferior because it has a small bearing race which means each bearing has to work harder in turn making it wear faster.

The view of my local bike shop is you can't get past square taper, although like many components there are cheap and nasty square tapers.

Anything with Shimano written on it will do the job.

In theory, an external bearing with its larger surface area should last even longer.

But as observed upthread, there doesn't seem to be any evidence of that.

I suppose there might be a rigidity benefit.

The drawback with external bearings is they are prone to wear from even the smallest degree of mis-alignment when fitted to the frame. The self contained cartridge units on square tapers don't have that problem.

 

[Pale Rider]

The drawback with external bearings is they are prone to wear from even the smallest degree of mis-alignment when fitted to the frame. The self contained cartridge units on square tapers don't have that problem.

My local bike shop has a frame facing tool.

Even a coat of paint can make a difference, so I am told.

I wonder if anything that needs that degree of setting up accuracy wouldn't be more suited to Concorde rather than a bicycle.

 

[Smokin Joe]

My local bike shop has a frame facing tool.

Even a coat of paint can make a difference, so I am told.

I wonder if anything that needs that degree of setting up accuracy wouldn't be more suited to Concorde rather than a bicycle.

The answer would be to use self aligning bearings. A few years ago I did see an advert for them, but it is a shame the manufacturers don't fit them as standard.

 

[davidphilips]

Any one else watch Hambini on utube? Hes an engineer that makes bottom brackets etc after watching some of his videos he would put you of some makes of even expensive bikes due to misalignment of bottom brackets.

 

[Threevok]

I think i mentioned this before, but facing the frame makes no difference if you have a threaded BB. Press fit however is a different matter

 

[faster]

I think i mentioned this before, but facing the frame makes no difference if you have a threaded BB. Press fit however is a different matter

Maybe you did mention it before, but you'd have been wrong then too.

For external threaded BB's facing the frame to correct misalignment (if there is any!) is critical.

Facing the frame is irrelevant for press fit, but the bores the bearings press into being correctly aligned is equally critial.

 

[Threevok]

Maybe you did mention it before, but you'd have been wrong then too.

For external threaded BB's facing the frame to correct misalignment (if there is any!) is critical.

Facing the frame is irrelevant for press fit, but the bores the bearings press into being correctly aligned is equally critial.

You could face the frame any angle you like. The BB will follow the angle of the threads, plus there are also the spacers to consider , which are not exactly flat either.

 

[faster]

You could face the frame any angle you like. The BB will follow the angle of the threads, plus there are also the spacers to consider , which are not exactly flat either.

There is enough play in the threads to mean that this isn't the case. The BB will always follow the face except where the threads and face are massively out of line, which is unlikely.

I have no idea which non-flat spacers you are talking about.

 

[Threevok]

There is enough play in the threads to mean that this isn't the case. The BB will always follow the face except where the threads and face are massively out of line, which is unlikely.

I have no idea which non-flat spacers you are talking about.

There is no play in the threads, if there was, you could wiggle it up and down. If you have that much play in your BB then alignment is the least of your worries.

I'm surprised you have no idea about the soft plastic spacers. You get three, which you place two on one side and one on another (depending on chainline you require).