"1kg Reduction in Weight will lead to a 1% increase in Speed in the Hills"

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Squashednuts
Posts: 250
Joined: Tue Apr 25, 2017 11:12 am
Location: Christchurch New Zealand

by Squashednuts

I read this in a local road cycling magazine.

The article states that "everything else being equal, a 1kg reduction in weight will lead to a 1% increase in speed in the hills" and refers to this as being Reid's law.

I've searched the Internet for Reid's Law and find the main reference is the initial article.

It seems to stand to reason that loosing body weight will make it easier to go up hills; power to weight ratio.

Have other people found that weight loss has such a linear link to an increase in speed up hills?

Does Reid's Law exist?

C36
Posts: 143
Joined: Fri Mar 03, 2017 3:24 am

by C36

I have no idea what reid's law is but 1kg = 1% is totally nonaccurate since the slope angle enters in the force equation (the reaction of the road has a component that pushes you backward). Give me some time to run the maths.


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by Weenie


Marin
Posts: 2574
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

You can go to kreuzotter.de for the calc.

If you + your bike = 100kg, 1kg off will of course take approximately 1% off your time on a steep climb.

If you're lighter, even more.

blaugrana
Posts: 5
Joined: Wed May 24, 2017 9:49 pm

by blaugrana

Well, the percentage of increase in speed will surely depend on the initial weight of the bike+cyclist to begin with, so that "law" is clearly not true from the mathematical point of view (it might be a reasonably good approximation in some cases, but I have not done any calculations).

As an example, if we have two cyclists, and one weights (including the bike) 50kg and the other 100kg, both with the same power to weight ratio, if we remove 1kg from both, the power to weight is not the same anymore (and therefore the % of speed increase won't be the same).

haynesdavid1988
Posts: 17
Joined: Fri Jan 20, 2017 8:39 am

by haynesdavid1988

Someone is out to sell magazines

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