Optimizing Bicycle Performance: Where Should Mass Be Removed?

[TSN79]

If we are to remove mass from a bicycle, does it have a better effect to remove this mass from the tires instead of the frame due to rotation and such? One opinion states that this is eminence only during acceleration and not during constant velocity?

 

[FredGarvin]

If you are not concerned with tire strength then this is true simply from the aspect of

$$T = I \alpha$$

If you decrease I, then the required torque for the same angular acceleration is lower. If you are at a constant velocity, the only torque required will be that to overcome reisistances like aerodynamic and rolling.

That being said, from what I have seen, bike tires are pretty flimsy to begin with. Are you really going to be able to take that much off to produce a noticeable result? I would think the frame would be the logical place to start looking, but I am not a cycling enthusiast.

 

[krab]

If you want to reduce the energy needed to get to a certain speed, then it is indeed better to remove mass from the wheels than from the non-spinning parts.

 

[brewnog]

In agreement with what's been said, you will find it easy to remove 'unsprung' weight from a bike by replacing normal (steel beaded) tyres with lightweight kevlar beaded ones. This is cheap, and effective, and you'll really notice it when accelerating and climbing hills.

Then, think about your rims. Carbon composite ones, or just really good lightweight alloys (depending on your riding style) can take a vast amount of weight from the outer reaches of your wheels, and again will improve acceleration, deceleration and hill-climbing performance.

Then, start to think about butted Cr-Mo spokes, and some decent hubs.

Taking 500g off your wheels is FAR more worthwhile than taking 500g off your frame. Fred speaks with wisdom, but is unaware of the benefits of kevlar beaded tyres!

 

[FredGarvin]

A half a kilogram? Yowza. I am amazed that that little bit of mass makes that much of a difference, but I yeild to experience.

 

[brewnog]

Well, most situations probably wouldn't allow quite as much of a saving as as 500g per wheel, but the point remains, removing rotating mass is FAR more effective than removing mass just from the frame.

 

[Danger]

I would think that anything you can do to reduce the mass/resistance of the drivetrain would help to an extent somewhere between that of the wheels and the frame. Low-friction chain/sprockets; composite gears and cranks with biggest allowable lightning holes; maximum-efficiency bearings, etc.. (Personally, though, I'd just put a motor on the bloody thing.)