They pedal going downhill on their light carbon bikes

[earlestownflya]

This. I tend to freewheel quicker than most of my friends. I putthis down to having a better maintained bike, with silky smooth bearings, and nothing at all to do with a high Beer and Pies factor.

exactly right

 

[themosquitoking]

I thought the OP was questioning why he (not pedalling) was going faster than them (pedalling) - such that he had to brake to avoid hitting them, when he assumed the weight difference wasn't enough to have that much of an effect.

I reckon he's drafting efficiently.

 

[Kestevan]

Fat Lads Advantage.......

 

[markharry66]

Except on long bike rides I always pedal down hill try and keep legs moving at all time with on set of old age I am always worried about the on set of rigamortis setting in.

 

[mjr]

Except on long bike rides I always pedal down hill try and keep legs moving at all time with on set of old age I am always worried about the on set of rigamortis setting in.

I do the opposite, actually (despite what I wrote earlier), because I think there's more chance that I've died on a long ride and just not noticed yet

 

[jefmcg]

but i find myself having to brake to avoid running into them on the descents.

If you have to brake to avoid hitting them, then you are drafting them. Thus going faster for the same work.

 

[totallyfixed]

If you have to brake to avoid hitting them, then you are drafting them. Thus going faster for the same work.

This is the most likely of all explanations, makes a huge difference.

 

[Milkfloat]

This. I tend to freewheel quicker than most of my friends. I putthis down to having a better maintained bike, with silky smooth bearings, and nothing at all to do with a high Beer and Pies factor.

Same wheels on different bikes I go faster downhill on the heavier bike and slower uphills.

 

[Dogtrousers]

@Accy cyclist ... you're not an alien are you?

I only ask this because the thread title reminds me of what the aliens say in the Smash advert. "They peel them with their metal knives, and then they smash them into bits" versus "They pedal downhill on their carbon bikes ".

Coincidence? I think not.

 

[Milkfloat]

Right to go all scientific.

"Downhill

During descents, the negative slope of the hill in the power equation reflects the addition of gravitational potential energy to the power generated by the cyclist. In a freewheel (passive) descent, the cyclist's speed will be determined by the balance of the air resistance force and the gravitational force. As the cyclist accelerates, sv2 increases. Once kaAsv2 (plus the negligible power term associated with rolling resistance) increases to match giMs, the cyclist will reach terminal velocity. Any further increase in speed must be achieved by adding energy through pedaling. However, on steep hills, terminal velocities may reach 70 km·hr-1. At such high associated values of sv2, even the application of VO2max would result in only a minimal increase in speed.

Terminal velocity can be solved for in the cycling equation above by setting power at 0. If one assumes the rolling resistance term is also 0, and that there is no wind blowing (v = s), then the equation becomes:

kaAs3 = -giMs
or s = (-giM/kaA)1/2

Thus, the terminal velocity is roughly proportional to the square root of the ratio of M/A. Scaling reveals that larger cyclists have a greater ratio of mass to frontal area. They therefore descend hills faster as a consequence of purely physical, not physiological, laws. Since the larger cyclist has a greater mass, gravity acts on him or her with a greater force than it does on a smaller cyclist. (Note: A common misconception is to note the equal acceleration of two different sized objects in free fall in a vacuum, and assume that the force of gravity on both is equal. The force on the more massive object is greater, being exactly proportional to mass, which is why the more massive object is accelerated at the same rate as the less massive one.) While the larger cyclist also has a greater absolute frontal area than the smaller cyclist, the difference is not as great as that for their masses. Thus, the larger cyclist will attain a greater s3 before a balance of forces results in terminal velocity.

With lighter cyclists climbing hills faster due to their greater relative VO2max, and heavier cyclists descending faster due to their greater M/A ratio, one might assume that equal performances would occur in races involving equal up and down segments. However, ascents take longer than descents, so a speed advantage to small cyclists on the acsents produces a greater time advantage than large cyclists obtain on the descents. For this reason, smaller cyclists are generally superior competitors on hilly road races." http://www.sportsci.org/jour/9804/dps.html#downhill

If you cannot be arsed to read it - it basically says heavy bloke/bike is faster than light.

 

[Dirk]

Right to go all scientific.

"Downhill

During descents, the negative slope of the hill in the power equation reflects the addition of gravitational potential energy to the power generated by the cyclist. In a freewheel (passive) descent, the cyclist's speed will be determined by the balance of the air resistance force and the gravitational force. As the cyclist accelerates, sv2 increases. Once kaAsv2 (plus the negligible power term associated with rolling resistance) increases to match giMs, the cyclist will reach terminal velocity. Any further increase in speed must be achieved by adding energy through pedaling. However, on steep hills, terminal velocities may reach 70 km·hr-1. At such high associated values of sv2, even the application of VO2max would result in only a minimal increase in speed.

Terminal velocity can be solved for in the cycling equation above by setting power at 0. If one assumes the rolling resistance term is also 0, and that there is no wind blowing (v = s), then the equation becomes:

kaAs3 = -giMs
or s = (-giM/kaA)1/2

Thus, the terminal velocity is roughly proportional to the square root of the ratio of M/A. Scaling reveals that larger cyclists have a greater ratio of mass to frontal area. They therefore descend hills faster as a consequence of purely physical, not physiological, laws. Since the larger cyclist has a greater mass, gravity acts on him or her with a greater force than it does on a smaller cyclist. (Note: A common misconception is to note the equal acceleration of two different sized objects in free fall in a vacuum, and assume that the force of gravity on both is equal. The force on the more massive object is greater, being exactly proportional to mass, which is why the more massive object is accelerated at the same rate as the less massive one.) While the larger cyclist also has a greater absolute frontal area than the smaller cyclist, the difference is not as great as that for their masses. Thus, the larger cyclist will attain a greater s3 before a balance of forces results in terminal velocity.

With lighter cyclists climbing hills faster due to their greater relative VO2max, and heavier cyclists descending faster due to their greater M/A ratio, one might assume that equal performances would occur in races involving equal up and down segments. However, ascents take longer than descents, so a speed advantage to small cyclists on the acsents produces a greater time advantage than large cyclists obtain on the descents. For this reason, smaller cyclists are generally superior competitors on hilly road races." http://www.sportsci.org/jour/9804/dps.html#downhill

Damn! Beat me to it.............

 

[TheJDog]

on steep hills, terminal velocities may reach 70 km·hr-1.

Much higher than that. I've hit over 100 kph in the Alps, and that guy Stöckl hit well over 100 mph down the side of a volcano.

 

[glasgowcyclist]

@Accy cyclist ... you're not an alien are you?

I only ask this because the thread title reminds me of what the aliens say in the Smash advert. "They peel them with their metal knives, and then they smash them into bits" versus "They pedal downhill on their carbon bikes ".

Coincidence? I think not.

Snap!

I was just about to say the same thing..



GC

 

[Dogtrousers]

If you cannot be arsed to read it - it basically says heavy bloke/bike is faster than light.

That was really interesting. And it made sense too!

But as with all things weight related, and not related to top level athletes, the waist of the rider is a bigger contributor than the frame material.

 

[mustang1]

Pedal all the time it clears the acid from your legs after the climbs and stops them stiffening up before the next climb. Personal preference entirely but that's one reason for doing it.

Yeah. Recently I've turned the afterburners up a notch and my legs burn up when I'm on a downhill. Since there's traffic I plonk the gears into high and gently continue the pedaling motion (I need the resistance).