Why is the weight of a bicycle so important?

[egbert]

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

[wildoliver]

Think about it like this. Would you sooner carry 10kg or 20kg on a long walk? It may be a small percentage but who likes pushing extra weight?

Also heavy bikes feel numb.

[ewenm]

If you're fit and trained, then your weight is optimised for maximum performance - so your weight gives you the best power. The bike is merely a tool to convert that power into movement, it doesn't provide any power so you want it to be as light as possible.

[Asterix]

ewenm said:

If you're fit and trained, then your weight is optimised for maximum performance - so your weight gives you the best power. The bike is merely a tool to convert that power into movement, it doesn't provide any power so you want it to be as light as possible.

...and as stiff as possible so that all of the power generated by the rider is directly transfered to the wheels and not dissipated/wasted through the flexing of the frame.

[ewenm]

Asterix said:

ewenm said:

If you're fit and trained, then your weight is optimised for maximum performance - so your weight gives you the best power. The bike is merely a tool to convert that power into movement, it doesn't provide any power so you want it to be as light as possible.

...and as stiff as possible so that all of the power generated by the rider is directly transfered to the wheels and not dissipated/wasted through the flexing of the frame.

I always smirk when I see someone pounding away on a cheap full suspension bike with the suspension bouncing away eating up the energy, pivots flexing, etc. IMO suspension isn't worth it until you can afford a decent system with lockouts.

Light and stiff road and mountain bikes are the best (again IMO).

[BigLepton]

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

It's to make them easier to pick up everytime the rider is knocked off ignoring red lights and left turning lorries. . . . . . . .

[eldar]

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

Try pushing a Harley......

[egbert]

I figured that all the weight of my body can be converted into power by standing up and pedalling so I can use my 90kg to my advantage at times but I'm interested to know the science behind why the weight of the bike is so important, 10% of unsprung weight may be a lot but it's only 1% of the overall.

[M400 NBL]

ewenm said:

Asterix said:

ewenm said:

If you're fit and trained, then your weight is optimised for maximum performance - so your weight gives you the best power. The bike is merely a tool to convert that power into movement, it doesn't provide any power so you want it to be as light as possible.

...and as stiff as possible so that all of the power generated by the rider is directly transfered to the wheels and not dissipated/wasted through the flexing of the frame.

I always smirk when I see someone pounding away on a cheap full suspension bike with the suspension bouncing away eating up the energy, pivots flexing, etc. IMO suspension isn't worth it until you can afford a decent system with lockouts.

Light and stiff road and mountain bikes are the best (again IMO).

Suspension bouncing, seat so low that their legs barely straighten more than 90 degrees, rust chains and rubbing break pads....but the lucky buggers always seem to have the wind behind them

I personally prefer rear shocks on account that i've had it for so long. Having swapped bikes with a mate that had borrowed a bike with the above description, minus any suspension (he struggled to move the thing) it felt like my bones and internal organs were moving where usually the suspension would take the shock. I do have a lockout butI prefer around 250psi. However I would lockout if riding more than my daily 6 mile commute and wanted to be somewhere as fast as possible.

Edited by M400 NBL on Sunday 28th September 11:47

[M400 NBL]

egbert said:

I figured that all the weight of my body can be converted into power by standing up and pedalling so I can use my 90kg to my advantage at times but I'm interested to know the science behind why the weight of the bike is so important, 10% of unsprung weight may be a lot but it's only 1% of the overall.

If you were a robot, it would matter less....but as a human you will get tired faster and be less effective from the 1st second.

But as you would have read already, the weight isn't the only factor to consider. I personally think wheels (and their bearings) are one of the most important. I often find myself free wheeling behind other cyclists that appear to be using an awful lot of effort....and yet I have to use my brakes to prevent myself going into the back off them.

The weight will be more of a facor with any upward inclines.

Edited to say that I even free wheel faster than some of the old rickety road bikes with meag thin tyres (1")...and mine are mtb wheels with 1.5" tyres....but I wouldn't get close to a new decent road bike with even thinner tyres. I used to run 1" conti's but found my commute (at my old company) was far too bumpy... so I kept getting punctures. But Christ it waseasy to accelerate from a stand still.

Edited by M400 NBL on Sunday 28th September 11:51

Edited by M400 NBL on Sunday 28th September 12:37

[john2443]

Imagine trying to pedal your car along - it would be very hard work, probably impossible.
Now imagine pedaling a motorbike - still hard work, but possible.

So, the lighter the thing is you are pedaling the easier it becomes, I agree that the difference beomes marginal if you're trying to save 100g on a 3kg bike, but it you are racing and might get beaten by 1/100th of a second, every little bit helps.

[PooPoo]

Ive just gone from an aluminium Kona to a steel Orange P7! (i'll let you know!)

[Rocket Pepper]

eldar said:

Try pushing a Harley......

Oh trust me, I have. A few actually. Then I bought a Buell. And I've pushed that some miles over the last ten years too. Luckily though, the Buell is dripping in carbon so a little lighter than when I first bought it.

Here's my 'heavy' push bike.

[cottonfoo]

Rocket Pepper said:

Here's my 'heavy' push bike.

That's quite nice, how much does it weigh?

[King Herald]

eldar said:

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

Try pushing a Harley......

Why do they add hundreds of pounds of lead to land speed record cars??

[singlecoil]

King Herald said:

eldar said:

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

Try pushing a Harley......

Why do they add hundreds of pounds of lead to land speed record cars??

Probably to make them heavier, either that or protection against Kryptonite

[Munter]

King Herald said:

eldar said:

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

Try pushing a Harley......

Why do they add hundreds of pounds of lead to land speed record cars??

Because weight has little to do with top speed given a fixed ammount of thrust.....on the flat.

Riding a bike you'll get tired and need to go up hills and stop and start.

[Stu R]

King Herald said:

eldar said:

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

Try pushing a Harley......

Why do they add hundreds of pounds of lead to land speed record cars??

To counteract the lift force? Something a harley will never need worry about

[Norman G. Potato]

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

It may be a similar concept to the weight of ones' wife. Only required for the odd ride, but the less roly poly the better.

[ian in lancs]

egbert said:

Why is it that the weight of my bicycle is so critical to performance despite being less than 10% of the overall weight of bike and rider?

Is it unsprung weight that is the issue? Why is it so important?

Weight: climbing hills and acceleration both adversely affected by mass. Important if the only engine is human. Incidentally rider weight is more important - a bike may weigh 10kg but a person 80kg+. Steering response is also affected by front wheel mass (gyroscopic effect resists turning moment).

Unsprung Mass: impacts the agility of the suspension to react to bumps. Minimal unsprung weight gives a smoother ride.