What's the point of exterior bb bearings?

[ChrisButch]

most people hate PF30/BB30, because - the latter especially - they're renowned for being as creaky as hell.

Isn't that because of the press-fit design? Threading would probably deal with that problem without losing the other advantages.

[robc02]

Do you know what causes the creaking?

I have seen one or two attempts explain it (just Google "creaking Pressfit BB" - or something similar). It seems to boil down to small movement between the BB shell and the bits that press into it, due to one or the other (or both) parts being at the extreme or even outside their tolerance.

Suffice to say that Hope now supply an aftermarket version (http://www.hopetech.com/product/press-fit/) that includes a two part threaded sleeve that the bearings fit into. They say "Cups pressed in and held in place by a screw-in centre tube to prevent slipping and play".

[[XAP]Bob]

A decent bearing set will cost about 20 quid, a bearing supplier should charge 8 - 10 quid each for SKF bearings in the right size.

£20 isn't bad if they're well sealed and will last as long as S/T if there were other advantages.But TBH if the only other advantage is a little more stiffness it isn't worth it IMO.I don't buy the 'quicker to remove for cleaning' either as I've never needed to remove a chainset to clean it,my cranks get removed once every blue moon usually to turn the inner ring around or replace it.
It would cost me less than £80 to replace a UN54 S/T BB and a Stronglight/XD2 triple chainset,with a choice of Spa's own good quality 7075 middle and outer rings and a steel inner.In all honesty I don't think that can be bettered.

I didn't say it was a deal breaker, in fact I said I'd continue replacing like for like, but it is an advantage.

It's a workshop job, but having had a crank wobble out on me, I appreciate the lack of that particular failure mode. Since I don't throw road soup at my bb I don't lament the seals either....

[pete75]

The improved stiffness is worth it.

Now this guy managed on square taper and even cottered cranks so if they're not stiff enough for you just how powerful a rider are you?

[reohn2]

.......I didn't say it was a deal breaker, in fact I said I'd continue replacing like for like, but it is an advantage.....

My comments weren't aimed at anyone in particular,I've seen posts on other threads about the pros of OBB's and TBH I've never yet been convinced of any claimed advantages they offer.

[jb]

He would have had the best available at the time, any flex, he would have put up with, as every body else had to.

Just as modern riders are putting up with problems that won't exist in the future & which we don't even recognise as a problem today.

[pete75]

He would have had the best available at the time, any flex, he would have put up with, as every body else had to.

Just as modern riders are putting up with problems that won't exist in the future & which we don't even recognise as a problem today.

If something isn't recognised as a problem then surely it isn't one. Name some problems we have today which won't exist in the future...

[Brucey]

I used to hanker after a stiffer frame, a stiffer crankset, stiffer everything. When I finally got stiffer parts I realised that whilst stiffer was better (not sure how much) when I was kicking out ~1kW for a few seconds, it didn't do me any good the rest of the time. In fact it might have made things worse.

People run faster on slightly bouncy racetracks and it may be that people ride faster on slightly springy bikes....

cheers

[mick skinner]

Now this guy managed on square taper and even cottered cranks so if they're not stiff enough for you just how powerful a rider are you?

Image

The record was broken though.

[pete75]

Now this guy managed on square taper and even cottered cranks so if they're not stiff enough for you just how powerful a rider are you?

Image

The record was broken though.

Which record?

[jb]

He would have had the best available at the time, any flex, he would have put up with, as every body else had to.

Just as modern riders are putting up with problems that won't exist in the future & which we don't even recognise as a problem today.

If something isn't recognised as a problem then surely it isn't one. Name some problems we have today which won't exist in the future...

tyre's puncture
chains need lubrication
Wheel spray (but mudguards are awkward)
no indicators
no brake lights
no easy way to see what's behind
You get wet
you get cold
you get too hot
and many more, its just that we accept them as the norm at the moment.

[[XAP]Bob]

brake lights are available...

[pete75]

He would have had the best available at the time, any flex, he would have put up with, as every body else had to.

Just as modern riders are putting up with problems that won't exist in the future & which we don't even recognise as a problem today.

If something isn't recognised as a problem then surely it isn't one. Name some problems we have today which won't exist in the future...

tyre's puncture
chains need lubrication
Wheel spray (but mudguards are awkward)
no indicators
no brake lights
no easy way to see what's behind
You get wet
you get cold
you get too hot
and many more, its just that we accept them as the norm at the moment.

1. Tyres don't puncture inner tubes do. Solid tyres are available.
2. Metal against metal will always need lubrication. If you don't like oily chains buy a bike with a belt drive.
3. And just how will that be stopped without guards which I've never found awkward anyway.
4. Have you no arms? Flashing indicator systems have been made for bikes for years - never sell in any great numbers because most people regard them as a pointless gimic.
5. Actually B&M make one
6. There is unless you have something wrong with your neck and can't turn your head . Even then there are mirrors available.
7. Waterproofs have been on the market for many years.
8. Ditto for warm clothes
9. Exercise generates heat in the body. Without some sort of air conditioning system which requires power you can't avoid it.

[JohnW]

The point is that the old square taper job had its problems one of which was that the exact position of the chain ring could not be determined. With hollow tech and its siblings the precise chain line for any given axle can be known.

The trouble with the design is trying to fit precision bearings into a manky threaded hole with any hope of alignment & a delicate seal sitting next to a crank arm that's continually snow ploughing crap into it.

When the traditional threaded shell is ditched for something more suitable for this type of bearing then hollowtech type set-ups will be fine.

I'm sorry jb, no offence, but I don't identify with what you say.

[JohnW]

Yeah, great, lets have lots of progress.......
Bottom bracket bearings have always been inside the frame, out of the way.....lets re-design the whole thing, frame and all, so the bearings are outside in just about the filthiest place on a bike.......
headset bearings have always been outside the frame, we'll re-design all that too, and put those bearings inside the frame, and while we are at it we'll make the steerer and head tube ever bigger and bigger, so we can make the steerer out of unsuitable materials......
whats next?.....if we put the hub bearings outside, rather than these old-fashioned inside bearings, we could probably make wheel dish even worse...
.....pedal bearings are a bit of a challenge, if we put those outside it will reduce ground clearance, but just think we could have an excuse to re-design the entire shoe/pedal interface.....
forks have been slender and flexible for about a century.....change all that, we'll have great stiff forks (and handlebars) and all the numpties will ride with padding in their gloves and on their bars and tractor tyres
And we can't have the riders deciding what cycle parts they will use, we will design them so nothing is compatible with anything else......

Colin - would you sum all that up by saying that whilst we've had plenty of improvement on bike parts/components/designs etc down the years, not all changes have been improvements................?

There's another one to add to your list : ".........if we make all components in a groupset different from the components in all other groupsets, and then make each groupset obsolete in less time than it takes to wear them out, then we can get even more money out of the suckers.................?