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Touring load weight distribution

In reading advice for carrying cargo on a bicycle, whether for touring or otherwise, I see recommendations (such as here) that load should be either evenly distributed between the front and rear wheels, or slightly greater, 60/40, on the front wheel.

Why is this? My intuition says that more load should be on the rear wheel, but my touring experience is limited.

Bonus points for answers with actual physics in them.

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marked as duplicate by zenbike Jan 6 '13 at 8:11

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

2  
I don't think it's a dupe. That question is "How should I load my bike?"; my question is "Why should I load my bike that way?" –  dpassage Jan 6 '13 at 2:59
    
Speaking from experience: Weight on the front wheel makes the bike more stable. The only caveat is that it be firmly attached -- a vibrating load on the front can be real scary. –  Daniel R Hicks Jan 6 '13 at 3:09
    
This answer makes clear why you would load weight one way or the other. bicycles.stackexchange.com/a/309/1259 –  zenbike Jan 6 '13 at 8:12
    
Again, I feel that question covers the "how", but not the "why". @mattnz's answer below includes a lot more information about the "why" - the bit about torque and uphill climbing is particularly interesting. –  dpassage Jan 6 '13 at 16:42

1 Answer 1

up vote 6 down vote accepted

When you sit on your bike, you put more weight on the rear wheel than the front (it's easy to use bathroom scales to see exactly how much). By distributing your cargo 60/40 to the front, you get a more even distribution of overall weight on the tires. This is good for several reasons. The tires (assuming same size) have the same load bearing ability, so having them evenly balanced is better - particularly on a heavily laden tourer. Also if you put to much weight to far back, there is no weight to hold the front down. This negatively affects cornering, inducing uncontrollable under steer, and also affects hill climbing. A tourer usually has an insanely low granny gear, which means it's possible to grind up very steep hills, provided the torque does not lift the front wheel. Pulling wheelies on a fully loaded tourer is something best avoided by all but the most skilled riders.

These are only guidelines. Every rider and bike is different, so you should do what suits you. Don't be scared to experiment - even once you find a way to load that you like. If you don't try something different, you may never find that "better" way...

Forgive me, I will go for the bonus points.

Max Torque induced by Pedal Force on Chain = (Rider Weight * Crank Length) / Small Chainring Diameter.

Torque on back wheel = (Force on Chain * Diameter of Largest Cassette gear ) / Wheel Diameter

Torque to rotate bike = Wheel base * Weight on Front wheel.

Crash === Torque to rotate bike > Torque on back wheel

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Also, weight nearer the steering axis is easier to balance. –  alex Jan 6 '13 at 1:43
    
Matt, thanks, thank helps a lot! Alex, can you expand on that, maybe in an additional answer? Why is that true? –  dpassage Jan 6 '13 at 3:01

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