cyccommute 

I'm using the values provided by Fairwheel. They seemed to have made a fair comparison.


Looking at the cranks I've seen, I don't think they are saving much. The metal cranks are swaged which isn't that cheap. And the machining on the other side is more complicated...two pinch bolts, machining on the spindle and machining on the crank arm to fit to the spindle.

cyccommute 

Again, I'm using Fairwheels values. They compare complete crankset to complete cranksets.

Given the choice, would you ride an all steel Schwinn Continental (weight near that of a singularity) or a modern 16 lb super bike? Since weight doesn't matter to you, I guessing the Schwinn...right?

Wanderer

Like him, I don't think a half pound on the proverbial 16# super bike will make a difference..... I carry more water than that in normal use.

IMO, your comparison is likened to comparing a F350 ford, to a Focus..... neither one would notice a half pound.

davidad

Wrong numbnuts.
Two steel Herons. One tour and one road.
Oops! there I go violating rule number two again!

Dave Mayer

Bottom brackets on bikes... What a soap opera. This never fails to demonstrate the sad state of the bike industry, where marketing and flash and deliberate planned obsolescence are passed off as 'progress'.

First off, the test is flawed in the treatment of the square-taper bottom brackets, in that an alu crankset was up against carbon. Not fair. The last generation of Campagnolo square taper carbon units from circa 2005 would have performed very well in stiffness and weight.

Second, the small measured differences in crankarm deflection are inconsequential in the real world, and do not result in energy losses. You get the (small) amount of deflection back during the second part of the pedal stroke.

Following is the tedious chronology of events that lead us up to today.

1. Circa 1995 some dim-bulb marketer (not an engineer) determines that more flash and product turnover is required. He says: "let's look at the lowly bottom bracket". Notwithstanding that the square taper standard had been in place for 50 years, and was plenty light and stiff enough for generations of pro sprinters, who could crank out double the watts that anyone else on this forum. Objective: we need to make it 'stiffer'.
2. First they made the BB spindle a larger diameter. This made the BB bearings smaller and they wore too quickly. (ISIS and Octalink)
3. To bandaid this problem, they invoke a ridiculous kludge: to put the bearings on the outside of the frame, exposed to water and dirt. Now this causes the additional problem of an excessively wide Q-factor and your heels catching on crankarms.
4. To solve these 2 problems, they put the large bearings back in the frame where they belong, which requires a change in frame standards. Hence BB30, BB86, BB whatever. An explosion of incompatible frame, crank and BB standards that are misery to workaround.

This is where we are right now. BTW: my Campagnolo carbon crankset from 2005 is light and stiff and uses square taper. As far as longevity, the BB on my old steel road bike has been in continuous use for over 40 years. Yearly overhauls, and has only cost a few bucks in ball bearings over this time.

HillRider

In fact it did just that. An objective measurement of various bottom brackets by, IIRC, Velo News several years ago showed the Campy square taper cartridge bottom brackets were as stiff as competitive ISIS and Octalink bb and slightly stiffer than some other square taper cartridges. However, as below, the differences were very small from the best to the worst.

+100 This whole stiffness argument is nit-picking at its finest.

ISIS, for the most part yes. Many were poorly made and wore out fast. Octalink, not so much. I've got an Octalink BB6500 in service with over 35,000 miles and it's still in fine condition. In general, Octalinks held up well.

fietsbob

Roger Durham , Late, of Bullseye , managed to sort out the pipe spindle on the Right crank, & his patent had to lapse for the rest of the Companies to begin copying it.

But Bullseye BBs were internal in the standard frame .. a combination of roller/needle bearings for the Load bearing and ball bearings for thrust . laterally.

cyccommute 

Not all of the cranks tested were carbon. Most of them but not all.

As with most things bicycle related in the last 20 years, the driver wasn't road bikes but mountain bikes. Square taper was, and is, a problem on mountain bikes. The retaining bolt is too small and tends to back out leaving you with a rounded taper instead of a square one. That's not good. ISIS and Octalink give more mounting surface and a large bolt that doesn't back out as easily. It wasn't "some dim-bulb marketer" but an engineer who thought that up. And it was in answer to a problem not just to turnover product.

Putting the bearings outside the frame isn't a bad idea. They are much easier to install and work on than internal ones.

As I've stated above, I have ISIS bottom brackets that are still going strong. I seldom see bad cartridge bottom brackets of any kind...even external ones... at my local co-op. The same can't be said for loose ball bottom brackets.

Dave Mayer

? I was riding mountain bikes in the early 80s, close to the dawn of the sport in my 'hood. Real mountain biking in the middle of nowhere where if you have a mechanical, you're walking out long distances in the dark. No vehicle access, no cell phones and nobody to lend assistance. Unless you count the bears. Obviously on square taper crankset/BB setups.

Why should mountain biking be any different in terms of the crankset requirements?

Anyway, I never had a problem with a square taper BB/crankset on these rides. I broke almost everything else including chains, rims, saddles, derailleurs and helmets and collarbones, but never had a crankarm come loose. If you install them correctly, they are reliable.

cyccommute 

Installing them correctly is the problem. They often aren't. I, too, have never had a square taper crankarm come loose while mountain biking but I was very fastidious about torque the bolts. Most people weren't and I've seen lots and lots of hollowed out square taper crank arms. Mountain biking obviously puts stress and strains on bikes that you'll never see on a road bike. People who ride strictly road bikes will never have a litany of broken parts that a mountain bike rider has.

People get a misty eyed about square taper but if they look at the system honestly, it really is a pretty poor way to connect the crank to a spindle. Tighten the bolt too much and you can split an aluminum crank arm. Tighten it too little and the arms can come loose and get damaged. A splined system has a much better interface. External bearing systems take that one step further and use a system that is simple and highly effective to attach the arm to the spindle. Putting the bearings outside the frame isn't even that bad an idea as long as the bearings are of good quality. Failure of external bearings...which isn't as common as many people think...isn't a failure of the system but of the part.