Wednesday, November 14, 2007

Magnesium Wheels, worth it?

I'll try to keep this small.

The primer for today's post is yesterday's PezCycling News article on a test run done by Chris Manatan on the Extreme Power bike...Click to read.

In this setup, you would think Chris should really be satisfied with the setup he has, instead he chooses to switch his Fulcrum racing wheels (690 gram front, 850 gram rear) with a pair of American Classic Magnesiums (1150 grams or so per pair...) and makes the following statement :

"Now in fairness to Fulcrum they make a slightly better wheel than their Mavic cousins the Ksyrium but I am not a sloppy guy that will notice that the American Classics do have more side flex. I am not a low power guy either, and simply notice the FAR snappier acceleration and better, quicker handling of the lighter American Classic and Zipps (even Zipps CSC training clinchers) more than I notice any better stiffness of the Fulcrum. This was a great example of how important wheels are to a bike. I would say that wheels are more important than most of us give them credit for…"

True and true... but I think this statement has been grossly overestimated, for the simple fact that today (forget about Pro's , they're given what to ride) most of us ride 600-2000 dollar pair of wheels that are quite light and aero... and the differences between them are very small. Magnesium wheels maybe 200 grams lighter, but you will pay the high premium due to its insane production costs (its a rough one to weld, and it can catch fire)...

And we also know that due to the small weight differences between the two sets of wheels, the difference in rotational intertia (or rotational weight) is going to be pretty small. Try measuring rotational inertia, you'll get something like 0.1 or something, something you can't even count ! Any lightweight wheel today requires both energy to move it linearly, and a still smaller component of energy to move it rotationally. I'm pretty sure the difference between that second component for both these wheels is negligibly small. In energy tems, it might require a rider to put for 2 or 3 more watts of energy to accelerate, but then think about it. How much time do we spend on the bike actually accelerating? And are our pedal strokes really smooth, like a motor driving the cranks? People are being fooled. Think about this. You're paying probably a 1000 dollars more to shave off a one digit number of Watts from your efforts. That's a load of crap.

Magnesium may be slightly less dense than aluminium, but its less stronger and less stiffer. Its Young modulus is quite small. And durability issues? It corrodes, its pretty unstable with heat, and I'm pretty sure no one needs Magnesium to win races.

But bike companies, and some people who don't think, like to fool you with junk and ask you to pay more to cover its production costs and profits. This is another reason I stopped reading reviews :) I only look at them for the pictures.

So top wheels in today's market have hardly much difference between them. To say that a 1000 dollar wheel has "FAR" snappier accelaration than another 1000 dollar wheel is just making fun of us readers. How much is FAR? Obviously designers from a top wheel company like Fulcrum aren't foolish to drop all mass into wheel rims.

Subjectiveness and false reports have always been a part of bike reviews and I believe it requires engineers to come up with specific numbers (which being very small for today's high standard products).

:) ... I guess all of this does not matter when you have the money, right? Still, its all for little which is my point. I guess inadequecy of training, and poor performances make people think that buying high priced equipment can actually help them someway.

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