Bicycle spokes may be easily bent if put under a bending load or will buckle if put under compression, but they don’t stretch when put under tension. The rim is also fairly weak without the spokes and can be pushed or stretched out of round, but it still has some stiffness and its circumference won’t easily change if it is distorted in this way.

When you sit on a bicycle, the hub tends to be pulled toward the ground. The spokes above the hub are under tension, transmitting the force to the top of the wheel rim. This would make the wheel rim collapse into an oval if it could do so without the sides of the rim to the front and rear of the bicycle sagging outward in the process. However, the spokes going to the forward and rear part of the wheel rim prevent the rim from going pear-shaped in this way.

The spokes are also not fastened to the center of the hub but to either side. This prevents the hub from deflecting sideways because half the spokes will be under greater tension if the hub tries to deflect in that way.

Finally, the rim cannot rotate with respect to the hub because the spokes don’t run exactly radially from the hub to the outer rim. Instead, the hub flange is comparatively wide so that half the spokes are under tension if the rim tries to rotate forward with respect to the hub and the other half are under tension if it tries to rotate backward. Either way, the rim is not free to rotate.

Physics Bicycle Wheel? You are trying to raise a bicycle wheel of mass m and radius R up over a curb of height h. To do this, you apply a horizontal force F.

a) What is the least magnitude of the force F that will succeed in raising the wheel onto the curb when the force is applied at the center of the wheel?
b) What is the least magnitude of the force F that will succeed in raising the wheel onto the curb when the force is applied at the top of the wheel?
c) In which case is less force required, the first (a) or the second (b)?

A) Both applied force F and weight W exert opposing torques, both pivoting in the point where the wheel touches the edge of the curb. Briefly stated, force F will succeed to lift the wheel if its associated torque is greater than the torque due to weight. In mathematical terms,

L = r x F + r x W.

All terms in the equation above are vectors. L is the resulting torque; r x F is considered positive. F will lift the wheel whenever L > 0.

As much can be said without resorting to a figure. Please follow these directions:
1. Draw a circle.
2. Draw a cross-sectional view of the curb, on the right side of wheel. Curb height h should be smaller than wheel radius r.
3. Draw a line from the center of circle to the point where the circle touches curb edge. Label this line “r”.
4. Both F and W are supposed to act on the center of the circle. You may tentalively draw both, F as a horizontal line, directed to the right; W pointing down from the center.

A solution can be found either following a geometrical approach (in terms of r and h), or else by trigonometrical means (in terms of the angle between r and the horizontal -or vertical. Much more often than not, those who post Physics problems in Y!A know the answer beforehand. I have no way to know if the answer you got -I’m sure you do- is in a trigonometrical, rather than geometrical, format. However, since h is mentioned in the problem statement, the latter alternative seems to me more likely.

Since F and W are perpendicular, one horizontal and the other vertical, resolve r into its horizontal and vertical components. These will be the effective “lever-arm” for each of theseforces. The vertical component is readily found in terms of r and h: it is just (r – h). The horizontal component can be found by Pythagoras’ Theorem. We have (in scalar format):

L = F(r – h) – W ?[r? – (r – h)?]

Minimum value for F can be found letting L = 0 and solving for F. The resulting algebraic expression is too cumbersome to be included here, and I think it is hardly necessary to do so. Besides, there are several algebraic manipulations possible. Likely, I would end with a different -albeit equivalent- expression.

b) When F is applied to the top of the wheel, the effective lever-arm for F increases to 2r – h. Refer to figure, or, rather, draw a new one. Join the uppermost point on the wheel to the contact point between wheel and curb edge. Now, persuade yourself that the vertical component of this line equals wheel diameter – curb height, or 2r – h.

Torque due to W remains as before. Consequently,

F(2r – h) = W ?[r? – (r – h)?].

Least F is found solving for F.

c) Clearly, with increased leverage, it would be easier to lift the wheel onto the curb in the second case. This is not apparent from the formulas, however.

For this purpose, the solution in trigonometric form offers much better insight. Here they are:

1st case: F = W / tan ?, where ? is the (clockwise) angle r makes with the horizontal.
2nd case: F = W cos ? /(1 + sin ?)

Note that for ? < 45?, F > W, in the first case. Also, F = W if ? = 45?, and F < W if ? > 45?. On the other hand, in the second case F < W is always met, since both sin ? and cos ? lie in the range 0 to 1. Thus, the numerator will be typically < 1, while the denominator is guaranteed to be > 1. The resulting fraction will in every case be less than unity.

Diameter Of One Bicycle Wheel Is 28 Inches And Its Spoke? Diameter of one bicycle wheel is 28 inches and its spokes run from the hub (or center) to the edge of the rim. The diameter of another bicycle wheel 21 inches. What is the difference in inches between the length of the spokes of the two wheels?

There are many more complexities to a question like this. Do the spokes truly radial to the hub and rim or do the cross over the other spokes? How many times do the spokes cross over other spokes?

28″ and 21″ are likely the relational size at the tire bead. What are the actual inside diameters of each rim?

What is the diameter of each hub? The spokes don’t originate from the axle but from a flange on the hub which is of some diameter. Each make and model of hub is slightly different and will differ between front and rear hubs and can even differ from the left to right flange on the same hub.

What is the distance from the left flange to the right flange on each hub and what is their relation to the center of the axle and to the center of the dish of the wheel? Is it a front wheel or a rear wheel? Is it a disc-brake equipped hub?

Now that you know a little more about the complexities of spoke lengths and wheel sizes, perhaps you should do your geometry homework yourself. If you are truly building wheels and want to know the spoke length differences, I suggest you read some articles that Sheldon Brown wrote.

A Smaller Bicycle Wheel? I am in the process of researching the creating and specs of a bicycle to create a more minimalistic cycle. Can anyone tell me how the size of the size of the wheel affects the ease of use and other things. It would be much easier on the creation process if i could slim down the wheels alot
I am in the process of making a bike that is its own bike rack in the sense that it fits into a brief case once folded. I have basic sketchs down and such but the wheels are still a problem for me due to their size. I have done some exploring and find a bike that is close to the concept im looking for but far from the look. Its called the Strida. It delivers a smaller wheel diameter and folds very compactly but if quite ugly and looks far from a bike.

What i am making can be called a “commuter bike” made for a person like me that lives far from college and rides a bike around campus but has a problem with putting a bike on a rack.

hope this helps and wasn’t to a.d.d. and all over the place
I am in the process of making a bike that is its own bike rack in the sense that it fits into a brief case once folded. I have basic sketchs down and such but the wheels are still a problem for me due to their size. I have done some exploring and find a bike that is close to the concept im looking for but far from the look. Its called the Strida. It delivers a smaller wheel diameter and folds very compactly but if quite ugly and looks far from a bike.

What i am making can be called a “commuter bike” made for a person like me that lives far from college and rides a bike around campus but has a problem with putting a bike on a rack.

hope this helps and wasn’t to a.d.d. and all over the place
I am in the process of making a bike that is its own bike rack in the sense that it fits into a brief case once folded. I have basic sketchs down and such but the wheels are still a problem for me due to their size. I have done some exploring and find a bike that is close to the concept im looking for but far from the look. Its called the Strida. It delivers a smaller wheel diameter and folds very compactly but if quite ugly and looks far from a bike.

What i am making can be called a “commuter bike” made for a person like me that lives far from college and rides a bike around campus but has a problem with putting a bike on a rack.

hope this helps and wasn’t to a.d.d. and all over the place
sorry got impatient and click it to many times lol

Well I can tell you about using smaller wheels because I use smaller wheels on my rides, I use the 16x 1(19-349) size and a 20x 1(19-451) at 120psi and I also use the standard 20 x 406 tires at 100psi. All the wheels are highly responsive, fast and ride equally as well and all use the standard bicycle components, gears, shifters etc. The thing about using smaller wheels is that everything you do such as turns, braking, shifting all seem to happen at a accelerated or faster rate so I’d take that into consideration. The other thing you may want to consider in using smaller type wheels in your bicycle would be chain-rings. Smaller wheels have a disadvantage when climbing so I’d go to a triple crank set, it should give you back some gear ratios you may need.
Some one also mentioned that smaller wheels would not be as fast or harder to ride, I have to disagree. If the bike is set up right it can be faster with less effort. Just change the crank-arms out from the standard crank-arm length of 172.5 to a smaller crank-arm say a 165 that’s the size I run and increase your large chain-ring from a 53 tooth to a 61 or 64 tooth with a 11-32 tooth rear cassette you can have all the speed with less effort you want. I hope some of this helps you out and Good luck with your creation, lets us know how it works out.

Where Can I Find Bicycle Wheels To Buy Online? Moreso what i’m trying to figure out is if i can replace the back wheel on my bike i’ve bought from Wal Mart. It’s a Mongoose XR-75 26″ Mens mountain bike. Everytime I try to find wheels all i get is more bikes brought up, and i’d like to just buy a new wheel.

I seem to have bad luck with the back wheels on my bikes. First one i had the cart pushers at wal mart bent the wheel to hell. Second the axle snapped. And this one i went off a curb and landed on the exact wrong area to land, the road was raised higher then the gutter area by a good two inches and I landed right on the corner of it, doing so put a pretty good bend in my wheel. I know I should be more careful but they’re generally cheap bikes, so it’s not too big a problem, I just would like to see if I could buy a new wheel rather than a new bike. : /

Google “bicycle wheel sets”, you’ll be able to search for new wheels from there. the problem you will have online is most wheel sets will have 9 or 10 speed cassettes. my guess is yours is a 7 speed cassette. also, most rear wheels will cast close to the original cost of this bike! since you seem to enjoy riding a bit aggresively, STOP WASTING YOUR MONEY! start saving for a properly fitted bike at your LBS! a solid entry-level hardtail MTB (a dual suspension bike that’ll take your brand of abuse will cost more than $1000) for $300-$500. by the time you add up what you’ve spent on repairing your wallywood bike, you’ll be well into that number anyway. good luck either way!

Why Don’t Bicycle Wheels Buckle? Bicycle spokes are easily bent. When you sit on a bicycle, how come the wheels don’t collapse?

View CommentBicycle spokes may be easily bent if put under a bending load or will buckle if put under compression, but they don’t stretch when put under tension. The rim is also fairly weak without the spokes and can be pushed or stretched out of round, but it still has some stiffness and its circumference won’t easily change if it is distorted in this way.

When you sit on a bicycle, the hub tends to be pulled toward the ground. The spokes above the hub are under tension, transmitting the force to the top of the wheel rim. This would make the wheel rim collapse into an oval if it could do so without the sides of the rim to the front and rear of the bicycle sagging outward in the process. However, the spokes going to the forward and rear part of the wheel rim prevent the rim from going pear-shaped in this way.

The spokes are also not fastened to the center of the hub but to either side. This prevents the hub from deflecting sideways because half the spokes will be under greater tension if the hub tries to deflect in that way.

Finally, the rim cannot rotate with respect to the hub because the spokes don’t run exactly radially from the hub to the outer rim. Instead, the hub flange is comparatively wide so that half the spokes are under tension if the rim tries to rotate forward with respect to the hub and the other half are under tension if it tries to rotate backward. Either way, the rim is not free to rotate.

View CommentPhysics Bicycle Wheel? You are trying to raise a bicycle wheel of mass m and radius R up over a curb of height h. To do this, you apply a horizontal force F.

a) What is the least magnitude of the force F that will succeed in raising the wheel onto the curb when the force is applied at the center of the wheel?

View Commentb) What is the least magnitude of the force F that will succeed in raising the wheel onto the curb when the force is applied at the top of the wheel?

c) In which case is less force required, the first (a) or the second (b)?

A) Both applied force F and weight W exert opposing torques, both pivoting in the point where the wheel touches the edge of the curb. Briefly stated, force F will succeed to lift the wheel if its associated torque is greater than the torque due to weight. In mathematical terms,

L = r x F + r x W.

All terms in the equation above are vectors. L is the resulting torque; r x F is considered positive. F will lift the wheel whenever L > 0.

As much can be said without resorting to a figure. Please follow these directions:

1. Draw a circle.

2. Draw a cross-sectional view of the curb, on the right side of wheel. Curb height h should be smaller than wheel radius r.

3. Draw a line from the center of circle to the point where the circle touches curb edge. Label this line “r”.

4. Both F and W are supposed to act on the center of the circle. You may tentalively draw both, F as a horizontal line, directed to the right; W pointing down from the center.

A solution can be found either following a geometrical approach (in terms of r and h), or else by trigonometrical means (in terms of the angle between r and the horizontal -or vertical. Much more often than not, those who post Physics problems in Y!A know the answer beforehand. I have no way to know if the answer you got -I’m sure you do- is in a trigonometrical, rather than geometrical, format. However, since h is mentioned in the problem statement, the latter alternative seems to me more likely.

Since F and W are perpendicular, one horizontal and the other vertical, resolve r into its horizontal and vertical components. These will be the effective “lever-arm” for each of theseforces. The vertical component is readily found in terms of r and h: it is just (r – h). The horizontal component can be found by Pythagoras’ Theorem. We have (in scalar format):

L = F(r – h) – W ?[r? – (r – h)?]

Minimum value for F can be found letting L = 0 and solving for F. The resulting algebraic expression is too cumbersome to be included here, and I think it is hardly necessary to do so. Besides, there are several algebraic manipulations possible. Likely, I would end with a different -albeit equivalent- expression.

b) When F is applied to the top of the wheel, the effective lever-arm for F increases to 2r – h. Refer to figure, or, rather, draw a new one. Join the uppermost point on the wheel to the contact point between wheel and curb edge. Now, persuade yourself that the vertical component of this line equals wheel diameter – curb height, or 2r – h.

Torque due to W remains as before. Consequently,

F(2r – h) = W ?[r? – (r – h)?].

Least F is found solving for F.

c) Clearly, with increased leverage, it would be easier to lift the wheel onto the curb in the second case. This is not apparent from the formulas, however.

For this purpose, the solution in trigonometric form offers much better insight. Here they are:

1st case: F = W / tan ?, where ? is the (clockwise) angle r makes with the horizontal.

2nd case: F = W cos ? /(1 + sin ?)

Note that for ? < 45?, F > W, in the first case. Also, F = W if ? = 45?, and F < W if ? > 45?. On the other hand, in the second case F < W is always met, since both sin ? and cos ? lie in the range 0 to 1. Thus, the numerator will be typically < 1, while the denominator is guaranteed to be > 1. The resulting fraction will in every case be less than unity.

View CommentDiameter Of One Bicycle Wheel Is 28 Inches And Its Spoke? Diameter of one bicycle wheel is 28 inches and its spokes run from the hub (or center) to the edge of the rim. The diameter of another bicycle wheel 21 inches. What is the difference in inches between the length of the spokes of the two wheels?

View CommentThere are many more complexities to a question like this. Do the spokes truly radial to the hub and rim or do the cross over the other spokes? How many times do the spokes cross over other spokes?

28″ and 21″ are likely the relational size at the tire bead. What are the actual inside diameters of each rim?

What is the diameter of each hub? The spokes don’t originate from the axle but from a flange on the hub which is of some diameter. Each make and model of hub is slightly different and will differ between front and rear hubs and can even differ from the left to right flange on the same hub.

What is the distance from the left flange to the right flange on each hub and what is their relation to the center of the axle and to the center of the dish of the wheel? Is it a front wheel or a rear wheel? Is it a disc-brake equipped hub?

Now that you know a little more about the complexities of spoke lengths and wheel sizes, perhaps you should do your geometry homework yourself. If you are truly building wheels and want to know the spoke length differences, I suggest you read some articles that Sheldon Brown wrote.

Good luck!

View CommentA Smaller Bicycle Wheel? I am in the process of researching the creating and specs of a bicycle to create a more minimalistic cycle. Can anyone tell me how the size of the size of the wheel affects the ease of use and other things. It would be much easier on the creation process if i could slim down the wheels alot

I am in the process of making a bike that is its own bike rack in the sense that it fits into a brief case once folded. I have basic sketchs down and such but the wheels are still a problem for me due to their size. I have done some exploring and find a bike that is close to the concept im looking for but far from the look. Its called the Strida. It

deliversa smaller wheel diameter and folds very compactly but if quite ugly and looks far from a bike.What i am making can be called a “commuter bike” made for a person like me that lives far from college and rides a bike around campus but has a problem with putting a bike on a rack.

hope this helps and wasn’t to a.d.d. and all over the place

I am in the process of making a bike that is its own bike rack in the sense that it fits into a brief case once folded. I have basic sketchs down and such but the wheels are still a problem for me due to their size. I have done some exploring and find a bike that is close to the concept im looking for but far from the look. Its called the Strida. It

deliversa smaller wheel diameter and folds very compactly but if quite ugly and looks far from a bike.What i am making can be called a “commuter bike” made for a person like me that lives far from college and rides a bike around campus but has a problem with putting a bike on a rack.

hope this helps and wasn’t to a.d.d. and all over the place

I am in the process of making a bike that is its own bike rack in the sense that it fits into a brief case once folded. I have basic sketchs down and such but the wheels are still a problem for me due to their size. I have done some exploring and find a bike that is close to the concept im looking for but far from the look. Its called the Strida. It

deliversa smaller wheel diameter and folds very compactly but if quite ugly and looks far from a bike.What i am making can be called a “commuter bike” made for a person like me that lives far from college and rides a bike around campus but has a problem with putting a bike on a rack.

hope this helps and wasn’t to a.d.d. and all over the place

View Commentsorry got impatient and click it to many times lol

Well I can tell you about using smaller wheels because I use smaller wheels on my rides, I use the 16x 1(19-349) size and a 20x 1(19-451) at 120psi and I also use the standard 20 x 406 tires at 100psi. All the wheels are highly responsive, fast and ride equally as well and all use the standard bicycle components, gears, shifters etc. The thing about using smaller wheels is that everything you do such as turns, braking, shifting all seem to happen at a accelerated or faster rate so I’d take that into consideration. The other thing you may want to consider in using smaller type wheels in your bicycle would be chain-rings. Smaller wheels have a disadvantage when climbing so I’d go to a triple crank set, it should give you back some gear ratios you may need.

View CommentSome one also mentioned that smaller wheels would not be as fast or harder to ride, I have to disagree. If the bike is set up right it can be faster with less effort. Just change the crank-arms out from the standard crank-arm length of 172.5 to a smaller crank-arm say a 165 that’s the size I run and increase your large chain-ring from a 53 tooth to a 61 or 64 tooth with a 11-32 tooth rear cassette you can have all the speed with less effort you want. I hope some of this helps you out and Good luck with your creation, lets us know how it works out.

Where Can I Find Bicycle Wheels To Buy Online? Moreso what i’m trying to figure out is if i can replace the back wheel on my bike i’ve bought from Wal Mart. It’s a Mongoose XR-75 26″ Mens mountain bike. Everytime I try to find wheels all i get is more bikes brought up, and i’d like to just buy a new wheel.

I seem to have bad luck with the back wheels on my bikes. First one i had the cart pushers at wal mart bent the wheel to hell. Second the axle snapped. And this one i went off a curb and landed on the exact wrong area to land, the road was raised higher then the gutter area by a good two inches and I landed right on the corner of it, doing so put a pretty good bend in my wheel. I know I should be more careful but they’re generally cheap bikes, so it’s not too big a problem, I just would like to see if I could buy a new wheel rather than a new bike. : /

View CommentGoogle “bicycle wheel sets”, you’ll be able to search for new wheels from there. the problem you will have online is most wheel sets will have 9 or 10 speed cassettes. my guess is yours is a 7 speed cassette. also, most rear wheels will cast close to the original cost of this bike! since you seem to enjoy riding a bit aggresively, STOP WASTING YOUR MONEY! start saving for a properly fitted bike at your LBS! a solid entry-level hardtail MTB (a dual suspension bike that’ll take your brand of abuse will cost more than $1000) for $300-$500. by the time you add up what you’ve spent on repairing your wallywood bike, you’ll be well into that number anyway. good luck either way!

View Comment