KITS - The weight acting on a bike

[kitchenman]

When a bike is designed isn't weight the most important factor? If you draw a line then would it look like this:



If there is a single line that can be drawn then isn't the answer to the question where is the best place to put my kit - ON THE LINE?
If anyone suggests putting anywhere else shouldn't the stock answer be (in the words of Walter in the Big Lebowski) OVER THE LINE! ?

 

[flecc]

Bikes aren't critical of rearward weight bias though, so rear hub motors aren't a problem in weight terms. A high carrier battery can affect stability when manhandling the bike, but not very much when riding, so that's why these positions for motors and batteries are common.
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[Deleted member 4366]

There is an ideal weight distribution and balance point, but it's not critical in most situations and is insignificant compared with the rider's weight and position. A nicely balanced bike wil handle nicely. Too much bias to the rear can cause the front wheel to lift when going up steep hills, which can be overcome by leaning forward. Too much bias to the front can cause heavy steering, but steering geometry in the chasis design has a bigger effect on it. On an ebike there's little to worry about except in extremes - like riding in snow, mud and very having very heavy batteries on a rear rack overhanging the back wheel.

 

[kitchenman]

Bikes aren't critical of rearward weight bias though, so rear hub motors aren't a problem in weight terms. A high carrier battery can affect stability when manhandling the bike, but not very much when riding, so that's why these positions for motors and batteries are common.
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Flecc, Do you know if there is a line? Has anyone on the forum designed a bike or know anyone who has? Lets say there is and its called the "weight line"(WL). The designer has made the bike so it performs best even when extra weight is added to the WL. So, if you want the bike to perform at its best then you need to install your kit on the line. Isn't that so? I accept that its ok to install it either side of the line because.. well .. people do. They don't seem to be riding round in circles or doing wheelies! .. or maybe there are some funny stories relating to getting it completely wrong? That would be interesting.

 

[kitchenman]

There is an ideal weight distribution and balance point, but it's not critical in most situations and is insignificant compared with the rider's weight and position. A nicely balanced bike wil handle nicely. Too much bias to the rear can cause the front wheel to lift when going up steep hills, which can be overcome by leaning forward. Too much bias to the front can cause heavy steering, but steering geometry in the chasis design has a bigger effect on it. On an ebike there's little to worry about except in extremes - like riding in snow, mud and very having very heavy batteries on a rear rack overhanging the back wheel.

A point is part of a line. But I'm not sure that your point is on my line! Can you tell me more about the ideal weight distribution and balance point? Perhaps I should get a book on bike design or perhaps there are some web resources you can point me at? ...
Thanks ..

 

[Deleted member 4366]

For a normal road bike for commuting and pleasure, the best position for the centre of mass of the bike and rider would be somewhere around half way along the line joining the centres of the wheels. Where to add weight depends on the geometry of the bike e.g. where the saddle and handlebars are. Ideally all mass should be located at the above-mentioned position, but that's not possible.

 

[flecc]

There's really no fixed line since there are other variable factors such as frame geometry, seating position, steering angle, wheel diameter and importantly, centre of gravity.

That many of these is not too critical on bikes, and especially e-bikes, is due to the low speeds involved. On motorcycles these factors are far more important, for example a 200 mph Moto GP bike's handling can be radically altered by changing the front wheel diameter by one inch, something that would barely be noticed on a bicycle.

It is possible to get funny effects. As d8veh says, wheelies on steep hills due to rear weight bias can easily happen, and my Q-bike is a good example of that. On that 20" wheel bike with rear hub motor and battery just ahead of the rear wheel, the seating position is somewhat rearward as is normal on a folder. The rear weight bias is desirable for control of the very large and heavy trailer loads it pulls.

But a standing start pedal thrust up a 22% hill in the 35" bottom gear with full throttle on the powerful SB motor results in a huge wheelie, only stopped from turning turtle by my leaning forward, body almost touching the handlebars. Of course that's extreme, few have to ever start on such a hill and I only do it to demonstrate the bike's capabilities.

N.B. Reply crossed with d8veh's post.
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[kitchenman]

But a standing start pedal thrust up a 22% hill in the 35" bottom gear with full throttle on the powerful SB motor results in a huge wheelie, only stopped from turning turtle by my leaning forward, body almost touching the handlebars. Of course that's extreme, few have to ever start on such a hill and I only do it to demonstrate the bike's capabilities.
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Next time your demonstrating please let me know and I'll come along with my camera(s)

 

[flecc]

Next time your demonstrating please let me know and I'll come along with my camera(s)

I'm fortunate enough to have that 22% as a tarmac footpath next to my home, very handy. Last demonstration to a member was some while ago, to Tim of 50cycles.
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