[j e SS e]

I've been saying since I've had to work on them; it's unfixing something that works beautifully in the first place.

Externals, IMO, have more to do with marketing, business and R&D guys keeping their jobs than an improvement to an existing system, which it clearly is not.

 

[j e SS e]

I think you have some good points and some that are not so good. First, on a mountainbike, you cannot use a square taper BB with loose bearings, no seals, and oil. It just won't last long. Sure, it will feel great for the first ride, but after that it will get gunked up. But it does bring up one of the main complaints about external BBs, namely the drag associated with the bearing and seals. This is definately noticable when spinning the cranks by hand, but I am not sure how much of a difference it actually makes will riding. I am not sure what you mean by less points of contact, I assume you mean less balls in the bearing? I don't think that is correct. I would think the external BB, because it uses larger I.D. and O.D. would have more balls, or at least larger balls which can support more load. As far as spindle wobble, I would think you would get less with the external BB system. Basically because the spindle is supported further out and because the spindle itself is much stiffer. Now I agree that if the BB shell was wider to the point that the bearings ended up in the same place as an external BB system, that would be better than everything else. I am not familiar with the BB30 system, maybe that is what it does.

I think the needs of Keirin racers are drastically different than that of MTB riders. A little extra drag is perfectly acceptable if it results in longer lasting bearings and a stiffer system.

Mark

Enough with all the "balls" and "loads", we're talking bike parts here.....

One problem is everyone's obsession with q-factor. It seems like everyone wants their feet tied together rather than spread apart a bit for better balance and power.

The other problem is everyone's obsession with stiffness. Whatever doesn't bend will break. There needs to be some flex to help bear the load. Bridges flex. Skyscrapers flex. If they didn't they would fail prematurely. Crank/BB/Spindles need to have some flex in there somewhere, too. Especially with increasingly "laterally stiff, vertically compliant" frame designs.

Narrower and stiffer but lasts as long or longer ain't gonna happen.

Internals are much better supported and the bearings, typically, last much longer.

The industry is loving it though, think how many more BB they sell now than when everything was square tapers that last forever.

When things work too well, in any industry, the tendancy is to "improve" the design, which results in something that requires more maintenance and/or replacement. It's how they make more money. Manufacturers don't make as much money with product designs that don't need maintenance or replacement.

 

[j e SS e]

Terrible connection. Terrible logic.

Not really, the point is what doesn't bend will break. Bridges and bicycle drive trains are very similar in that they have forces exerted on them which have to be transferred. If the force is greater than what can be transferred and absorbed you have increased material fatigue and failure.

It's pretty basic, really.

How long to you think a rigid bike would hold up in a DH race?

Same principles apply, the energy has to go somewhere....in this case it's absorbed rather than sent through the bike and rider where it would inflict some damage.

Another oxymoron is that everyone wants stiffer frames and parts, but a smoother ride.

Problem is, all that impact energy has to go somewhere...and I see an awful lot of premature failures on these boards, especially frames.

I've explained my reasoning, can you explain yours, re: "terrible logic" ?

 

[j e SS e]

I thought about that, but there are 140mm suspension forks on 26" wheel bikes and I haven't heard that they were causing the same level of headset problems as 29ers. Although 1.5 headsets are available, 1 1/8 is still remains standard.

That 140mm is absorbing most of the energy before it gets to the HS.....

Most 29ers are run either rigid or with relatively little travel, so more energy goes straight to the HS with less buffer, this is compounded by the fact that it is a longer lever.