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Old 07-12-08, 05:34 PM   #1
Bassanio
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Confused on Bicycle Science!!!

Newbie here. I've been doing a lot of research on the top bicycle brands and parts and I can't seem to understand some of the science or terminology.

Can someone explain to me why it is good to have your bike stiff (elastic modulus?)

What is paired spokes? The site says paired spokes allow for fewer spokes but the diagram has more spokes than the conventional.
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Old 07-12-08, 05:36 PM   #2
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PS: trying to see if bontrager wheels are better than Zipp wheels or if it's the same as deciding what rims you want for your SUV.
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Old 07-12-08, 05:46 PM   #3
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Basically the more flexible the frame, the more energy you expend is absorbed by the frame. Here's a link that will do a much better job of explaining it:

http://www.bikethink.com/Frameflex.htm
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Old 07-12-08, 06:35 PM   #4
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If you are new to cycling, I'd forget about spending wasted dollars on something you aren't familiar with and get strong, relaible equipment. After you have been riding for a while, you will get a better understanding of how things work and the results. Then you can make a better judgment on what's good and bad.

Yes, it's like trying to find out what wheels to go on a SUV. You need to decide what use you want to put the item to, and the effects that will have (durability, weight limits, speed, comfort, etc etc).

Oddly, the guy who lent his name to the wheels you refer to, Keith Bontrager, came up with the saying: "Cheap, strong, light -- pick any two". It's sound advice, even though those products with his name are reported frequently not to reflect it.

Paired spokes is a lacing pattern that tries to overcome the apparently inherent weakness in low-spoke counts. If you don't know, I would steer well clear of them and opt for something like a good quality Ultegra hub/Mavic Open Pro or Velocity Aerohead rim at 32H with minnimum two-cross but preferably three cross.
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Old 07-12-08, 09:30 PM   #5
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Modulus of Elasticity, aka Young's Modulus, is the measure of stiffness of a material. All steels are 30 million psi, all aluminum is 10 million psi, all titanium is 16 million psi, and carbon fiber varies but as I recall most is in the range of 50 million psi.

Since bike frames need to first be stiff, then light....tubing diameters are largely dictated my their material. You probably have noticed how small the tubes are on a steel frame and how large they are on aluminum...now you know why....since the stiffness of the tube increases as a cube of the diameter, a slightly larger tibe is required for lower modulus materials.
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Old 07-15-08, 07:14 PM   #6
Bassanio
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i feel so enlightened. thank you for your posts
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Old 07-15-08, 07:45 PM   #7
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It's 2-wheels and a dirty chain, don't make it sound like caviar.
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Old 07-15-08, 10:45 PM   #8
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"Your frame has exceeded its modulus of elasticity."

Translation: "Your frame is f*****d up!"
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Old 07-16-08, 02:22 AM   #9
Rowan
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Quote:
Originally Posted by Bassanio View Post
i feel so enlightened. thank you for your posts
Are you taking the p!ss? Or is it an honest answer?
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Old 07-16-08, 05:31 AM   #10
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Quote:
Originally Posted by Rowan View Post
Are you taking the p!ss? Or is it an honest answer?
from the tone, sounds like there may have been a bit of trolling going on.



that said, for the most part, s/he got helpful replies without all the condescension......there's hope for bf yet!
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