Side loads on wheels

"James Annan" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Something that I've been wondering about for some time, and I'd appreciate comments.

Mostly, the loading on a wheel is in plane. However, when riding over rough ground and/or tight
manouevring there sometimes seem to be significant side loads. Sometimes I can feel the wheel
trying quite forcefully to turn under me and of course the ground force is quite close to the
steering axis whereas my hands are a foot out to the

sides

Quoted message said:

on long handlebars. Probably some tacoed wheels can be atttributed to predominantly in-plane
forces, but on the other hand these tacoes do

not

Quoted message said:

necessarily coincide with pinch flats.

What I'm wondering is, what are the biggest side forces that are felt

in

Quoted message said:

MTBing, and a secondary question is what effect does this have on the spoke tension? I've seen
some rough measurements posted here by Jim Papadopoulos (what happened to him) when he leant the
bike to one

side,

Quoted message said:

indicating a substantial increase in tension on the lowest spokes on

the

Quoted message said:

under side as well as the large decrease in the ones on the higher

side.

With biking in general, most turns are coordinated or a crash will result. This usually means the
resultant load of lateral tire traction and weight is always in plane with the wheel. Having said
that, when traveling in a straight line it is possible to shift the bicycle to one side and
compensate by shifting body weight to maintain balance. The resultant wheel load has to pass through
the cg of the bicycle and rider combination to maintain balance. It is possible to exaggerate this
to obtain a large side load but this is really an abuse load as it is not normal riding. Assuming a
lean of ~30 deg from vertical, the lateral load on each wheel would be approximately half the in
plane load.

Phil Holman

"James Annan" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

However, when riding over rough ground and/or tight manouevring there sometimes seem to be
significant side loads.

I have measured between the pad deflection in the "lab" (due to a load applied close to the actual
RCP) and also while actually riding on the road. The results, with no real analysis can be seen at:

tinyurl.com7o9qOpen ↗

Not quite so sure I buy into your "rough road" line of thinking - but anything out of the saddle
will contribute to the loading that you describe.
--
==================
Kraig Willett www.biketechreview.com
==================

James Annan said:

What I'm wondering is, what are the biggest side forces that are felt in MTBing, and a secondary
question is what effect does this have on the spoke tension? I've seen some rough measurements
posted here by Jim Papadopoulos (what happened to him) when he leaned the bike to one side,
indicating a substantial increase in tension on the lowest spokes on the under side as well as the
large decrease in the ones on the higher side.

They aren't large because bicycle riding is a balanced act. Wheels are made with front hubs as
wide as they are because when leaning the bicycle from the plumb line (when pedaling standing),
the lean angle doesn't exceed that of the lateral spoke angle. You can test this by sighting down
to the rim through the hub wile riding in this mode. That is about as far as side loads go in
riding without falling.

Jobst Brandt [email hidden] Palo Alto CA

"Phil Holman" <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

With biking in general, most turns are coordinated or a crash will result. This usually means the
resultant load of lateral tire traction and weight is always in plane with the wheel. Having said
that, when traveling in a straight line it is possible to shift the bicycle to one side and
compensate by shifting body weight to maintain balance. The resultant wheel load has to pass
through the cg of the bicycle and rider combination to maintain balance. It is possible to
exaggerate this to obtain a large side load but this is really an abuse load as it is not normal
riding. Assuming a lean of ~30 deg from vertical, the lateral load on each wheel would be
approximately half the in plane load.

While that is all true, it's not really relevant to what I was asking. Perhaps I could have been
more clear. I'm talking about MTBing on bumpy and/or loose surfaces, where for example the wheels
will often get knocked from one side or slip momentarily.

James

[email hidden] wrote in message news:<[email hidden]>...

Quoted message said:

They aren't large because bicycle riding is a balanced act. Wheels are made with front hubs as
wide as they are because when leaning the bicycle from the plumb line (when pedaling standing),
the lean angle doesn't exceed that of the lateral spoke angle. You can test this by sighting down
to the rim through the hub wile riding in this mode. That is about as far as side loads go in
riding without falling.

Certainly in normal riding I've no problem in accepting this. However I've heard (perhaps somewhat
apocryphal) stories of tandemers folding up the front wheel while climbing slowly up a steep hill or
otherwise manouevring slowly (especially when the front wheel has a disk brake and is therefore
dished and relatively weak). This probably has more to do with large steering excursions and/or
riders lurching about rather than substantial leaning of the bicycle.

Another way of approaching the question would be to ask: what sort of side loads will a wheel stand
before it does fail? Obviously it will also depend on the simultaneous in-plane load. There's no
question that MTB wheels do see some side loads, this may be better considered as a case of
near-crashing rather than just riding along. I think it's fair to say that _some_ tacoed wheels are
probably the cause of a crash, rather than its result. Ie the rider would have expected to stay
upright but the wheel folded up.

James

James Annan said:

Quoted message said:

With biking in general, most turns are coordinated or a crash will result. This usually means the
resultant load of lateral tire traction and weight is always in plane with the wheel. Having said
that, when traveling in a straight line it is possible to shift the bicycle to one side and
compensate by shifting body weight to maintain balance. The resultant wheel load has to pass
through the cg of the bicycle and rider combination to maintain balance. It is possible to
exaggerate this to obtain a large side load but this is really an abuse load as it is not normal
riding. Assuming a lean of ~30 deg from vertical, the lateral load on each wheel would be
approximately half the in plane load.

Quoted message said:

While that is all true, it's not really relevant to what I was asking. Perhaps I could have been
more clear. I'm talking about MTBing on bumpy and/or loose surfaces, where for example the wheels
will often get knocked from one side or slip momentarily.

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop, most likely crashing in the event. The lateral force on
the wheel would be generated by rider leg mass that causes a side force between saddle and
ground contact patch. The rider's mass on the saddle cannot develop a side load on the ground
contact patch.

Jobst Brandt [email hidden] Palo Alto CA

James Annan said:

Quoted message said:

With biking in general, most turns are coordinated or a crash will result. This usually means the
resultant load of lateral tire traction and weight is always in plane with the wheel. Having said
that, when traveling in a straight line it is possible to shift the bicycle to one side and
compensate by shifting body weight to maintain balance. The resultant wheel load has to pass
through the cg of the bicycle and rider combination to maintain balance. It is possible to
exaggerate this to obtain a large side load but this is really an abuse load as it is not normal
riding. Assuming a lean of ~30 deg from vertical, the lateral load on each wheel would be
approximately half the in plane load.

Quoted message said:

While that is all true, it's not really relevant to what I was asking. Perhaps I could have been
more clear. I'm talking about MTBing on bumpy and/or loose surfaces, where for example the wheels
will often get knocked from one side or slip momentarily.

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop, most likely crashing in the event. The lateral force on the
wheel would be generated by rider leg mass via the pedals that causes a side force between saddle
and ground contact patch. The rider's mass on the saddle cannot develop a side load on the ground
contact patch.

Jobst Brandt [email hidden] Palo Alto CA

James Annan said:

Another way of approaching the question would be to ask: what sort of side loads will a wheel
stand before it does fail? Obviously it will also depend on the simultaneous in-plane load.

Forgetting the in-plane load for a moment (I know, it slackens the spokes, yadda yadda, but I doubt
this matters with a well-built wheel), have you ever made a field repair to a potato-chipped wheel
by whacking it on the ground? The amount of bashing a normal wheel will take (or needs, once
potato-chipped, in order to be trueable) is pretty damn impressive.

Quoted message said:

There's no question that MTB wheels do see some side loads, this may be better considered as a
case of near-crashing rather than just riding along. I think it's fair to say that _some_ tacoed
wheels are probably the cause of a crash, rather than its result. Ie the rider would have expected
to stay upright but the wheel folded up.

For me, this definitely falls in the category of things I am not going to worry about while mountain
biking. I don't ride a tandem, but still find it hard to believe that even a tandem will do this
without extreme measures.

Quoted message said:

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop, most likely crashing in the event. The lateral force on the
wheel would be generated by rider leg mass via the pedals that causes a side force between saddle
and ground contact patch. The rider's mass on the saddle cannot develop a side load on the ground
contact patch.

The handlebars provide a handy lever for applying torques, and for that matter the pedals are
(mumble) distance from the bike centerline.

I think we are talking somewhat at cross purposes here. Your comments are (I think) basically
considering a near-equilibrium situation, which is reasonable enough for most road riding (and most
off-road riding too). But when just riding along, I can easily apply a large impusive downward force
on one side of the handlebars, at will. This generates a sideways reaction force at the ground. The
total impulse is limited, but I see no trivial upper limit on the momentary forces I can apply. Of
course there is no particular reason for me to do this while just riding along on level ground, but
when bumping over rough ground I can certainly feel the wheel being knocked from side to side in my
hands (since the side forces are close to the steering axis, this suggests they could be quite
large). I can also feel myself putting substantially more weight on one end of the bars and then the
other, as I try to keep balanced. Maybe this is close to crashing, but I think it's also pretty
normal for MTBing. It's not stuff that could be ridden no-hands.

James

James Annan said:

Quoted message said:

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop

Experimented with monostay forks once. The first versions were unridable at low speeds because of
flex. To me that indicates that at low speeds significant sideforces are fed into the wheel to
keep upright

--
Marten

<[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop, most likely crashing in the event. The lateral force on the
wheel would be generated by rider leg mass via the pedals that causes a side force between saddle
and ground contact patch. The rider's mass on the saddle cannot develop a side load on the ground
contact patch.

Not disagreeing with that last sentence, but what if you stand up, and push the bike to one side as
you keep going forward - doesn't that give a lateral force?

Not that its usually sensible or useful to do such a thing, but I see kids on MTBs and BMXs doing it
fairly often.

Benjamin Weiner said:

Quoted message said:

Another way of approaching the question would be to ask: what sort of side loads will a wheel
stand before it does fail? Obviously it will also depend on the simultaneous in-plane load.

Quoted message said:

Forgetting the in-plane load for a moment (I know, it slackens the spokes, yadda yadda, but I
doubt this matters with a well-built wheel), have you ever made a field repair to a potato-chipped
wheel by whacking it on the ground? The amount of bashing a normal wheel will take (or needs, once
potato-chipped, in order to be trueable) is pretty damn impressive.

Impressive! Yes, that is about all it is. Anything you can do with such violence can be done far
better and with more control, statically. That is, a bent wheel should be laid on the ground, with
the biggest wow toward the operator, pressing down on either side of that point with the hands or
knees near the diameter. If the rim looks salvageable, do this only after loosening all spokes about
a half turn to one turn, regardless of whether they are tight or loose. You can read about this in
"the Bicycle Wheel" and how and why it works. I have done this on several occasions on the road, far
from anywhere, for tourists who had a collapsed wheel.

Quoted message said:

Quoted message said:

There's no question that MTB wheels do see some side loads, this may be better considered as a
case of near-crashing rather than just riding along. I think it's fair to say that _some_ tacoed
wheels are probably the cause of a crash, rather than its result. Ie the rider would have
expected to stay upright but the wheel folded up.

Quoted message said:

For me, this definitely falls in the category of things I am not going to worry about while
mountain biking. I don't ride a tandem, but still find it hard to believe that even a tandem will
do this without extreme measures.

An overloaded wheel (too few spokes, not enough tension) can easily collapse under trivial side
loads, the kind common in bicycling. That is why tension and number of spokes is important. Most
riders don't know how close they are to wheel collapse with low spoke count wheels, but that doesn't
matter since most riders don't demand much from these wheels. That came to mind when hearing a
four-strut Spinergy wheels go by with rattling 'spokes', the rider being sure they were safe. These
wheels were initially tension spoked but lost that tension with age and were still widely used in
that condition.

home.interlynx.net~pjduOpen ↗

Jobst Brandt [email hidden] Palo Alto CA

James Annan said:

Quoted message said:

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop, most likely crashing in the event. The lateral force on the
wheel would be generated by rider leg mass via the pedals that causes a side force between saddle
and ground contact patch. The rider's mass on the saddle cannot develop a side load on the ground
contact patch.

Quoted message said:

The handlebars provide a handy lever for applying torques, and for that matter the pedals are
(mumble) distance from the bike centerline.

I thin you should do some calculations on how much lateral force you can put on the wheel that way.
Besides, it should be apparent that if there is a side load, it must cause lean in the plane of the
bicycle. Pushing down on a pedal while pulling up on the bars is a closed loop and does not involve
the wheels.

Quoted message said:

I think we are talking somewhat at cross purposes here. Your comments are (I think) basically
considering a near-equilibrium situation, which is reasonable enough for most road riding (and
most off-road riding too). But when just riding along, I can easily apply a large impulsive
downward force on one side of the handlebars, at will.

I don't believe it. What do you call large force? Compare the lever length of a half bar and the
distance to the road. Besides, as I said, this force is offset by the pedal force. If it weren't,
you would fall off the bicycle.

Quoted message said:

This generates a sideways reaction force at the ground. The total impulse is limited, but I see no
trivial upper limit on the momentary forces I can apply. Of course there is no particular reason
for me to do this while just riding along on level ground, but when bumping over rough ground I
can certainly feel the wheel being knocked from side to side in my hands (since the side forces
are close to the steering axis, this suggests they could be quite large). I can also feel myself
putting substantially more weight on one end of the bars and then the other, as I try to keep
balanced. Maybe this is close to crashing, but I think it's also pretty normal for MTBing. It's
not stuff that could be ridden no-hands.

Please review where these forces arise and how they are applied to the bicycle. The deformation of
the bicycle is not in the wheels as you perceive it.

Jobst Brandt [email hidden] Palo Alto CA

W K Hyagillot said:

Quoted message said:

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop, most likely crashing in the event. The lateral force on the
wheel would be generated by rider leg mass via the pedals that causes a side force between saddle
and ground contact patch. The rider's mass on the saddle cannot develop a side load on the ground
contact patch.

Quoted message said:

Not disagreeing with that last sentence, but what if you stand up, and push the bike to one side
as you keep going forward - doesn't that give a lateral force?

Yes, and that has been mentioned here often. The amount of side load is shown by the lean angle of
the bicycle and that angle stays within the lateral spoke angle. While standing you can sight
through the front hub to the rim and note that the rim centerline does not go outside of the flanges
unless you are specifically trying to do that.

Quoted message said:

Not that its usually sensible or useful to do such a thing, but I see kids on MTBs and BMXs doing
it fairly often.

So what. I do that to test whether a wheel has any spoke twist by coasting along slowly and leaning
as far as I can off center while standing on one pedal. The wheel withstands this easily.

Jobst Brandt [email hidden] Palo Alto CA

Jobst Brandt said:

Quoted message said:

Quoted message said:

That is the same as the case described. To cause significant side load on the wheel, requires
sliding sideways into a solid stop

Marten Gerritsen demurred:

Quoted message said:

Experimented with monostay forks once. The first versions were unridable at low speeds because of
flex. To me that indicates that at low speeds significant sideforces are fed into the wheel to
keep upright

I don't think so. I'd imagine that the problem was lack of torsional rigidity in the fork blade,
introducing hysterisis to the steering. This would be most noticeable at low speeds, where steering
corrections are of larger magnitude.

Sheldon "Bifurcated" Brown +-------------------------------------+
| Natural laws have no pity. | --Robert A. Heinlein |
+-------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

Sheldon Brown said:

Jobst Brandt said:

Quoted message said:

>That is the same as the case described. To cause significant side load on the wheel, requires
>sliding sideways into a solid stop

Marten Gerritsen demurred:

Quoted message said:

Experimented with monostay forks once. The first versions were unridable at low speeds because
of flex. To me that indicates that at low speeds significant sideforces are fed into the wheel
to keep upright

I don't think so. I'd imagine that the problem was lack of torsional rigidity in the fork blade,
introducing hysterisis to the steering. This would be most noticeable at low speeds, where
steering corrections are of larger magnitude.

Don't believe it, and anyhow you can't feed very much torque through the contact patch. And it
doesn't mesh with the feeling of the fronthub bending towards the pedals at turn in and popping back
again once the turn starts

Marten

In article <[email hidden]>, M-Gineering import & framebouw

Quoted message said:

Sheldon Brown said:

Jobst Brandt said:

>>That is the same as the case described. To cause significant side load on the wheel, requires
>>sliding sideways into a solid stop

Marten Gerritsen demurred:

Quoted message said:

Experimented with monostay forks once. The first versions were unridable at low speeds because
of flex. To me that indicates that at low speeds significant sideforces are fed into the wheel
to keep upright

I don't think so. I'd imagine that the problem was lack of torsional rigidity in the fork blade,
introducing hysterisis to the steering. This would be most noticeable at low speeds, where
steering corrections are of larger magnitude.

Don't believe it, and anyhow you can't feed very much torque through the contact patch. And it
doesn't mesh with the feeling of the fronthub bending towards the pedals at turn in and popping
back again once the turn starts

Correct me if I'm wrong, but this would be the result of the monoblade fork failling to hold the hub
perpendicular to the plane of steering. That's a very different situation than a standard fork which
loads the hub basically equally on both side of the wheel. The problem you describe is with the fork
being inadequate to the design task and would make a single track two wheel vehicle like a bicycle
very difficult to ride.

I would think that with all the load concentrated on one end of the axle, the wheel would be loaded
quite differently than with a normal fork. A much larger diameter fork would seem necessary as would
a larger diameter stub axle and a much less flexible attachment method than a bicycle-style dropout.
After all, this becomes basically a 100 mm lever with bending forces acting in multiple directions
from vertical load, braking loads and turning loads.

Frankly I have never been able to see why anyone bothers with trying to make this design work. The
benefits seem relatively few. Mike Burrows has been at it for years and hasn't been able to convince
any manufacturer totake this on on a large scale commercial product. He used it on the Lotus bike,
on the Windcheetah, the RatCatcher and his current cargo bike (front and rear, with the wheels not
in the same line), and he tried with a plastic utility/shopper bike that he piched to Giant about 5
years ago.

[email hidden] wrote in message news:<[email hidden]>...

Quoted message said:

James Annan said:

The handlebars provide a handy lever for applying torques, and for that matter the pedals are
(mumble) distance from the bike centerline.

I thin you should do some calculations on how much lateral force you can put on the wheel
that way.

If I push on the end of the handlebar towards the contact patch with an impulsive load of X, then
the reaction at the ground is roughly X vertically and X/4 laterally (30cm half-width of bar, at
1.2m height). If I pull up on the other bar at the same time, the angle of the net reaction force is
even wider. Of course there is also a net reaction on the rider too, but the change in his momentum
depends on the duration for which the force is applied, as well as its magnitude.

Quoted message said:

Besides, it should be apparent that if there is a side load, it must cause lean in the plane of
the bicycle. Pushing down on a pedal while pulling up on the bars is a closed loop and does not
involve the wheels.

Again you seem to be talking about steady(ish) loads applied for some time. I'm talking about the
impulsive forces which are certainly much greater, but are of course only applied very briefly.
Bottoming out a suspension fork requires typically double the rider's weight on the fork alone, and
pinch flats imply an even greater force. Rim dings and bent handlebars presumably require even
greater forces since these events are rarer, but they still do happen. Surely these forces are
_predominantly_ in the plane of the bicycle, but I see no justification for the assertion that the
net effect of these forces necessarily lies within the spoke bracing angle. If you like, perhaps you
can consider them to be a succession of sharp steering corrections where the bicycle is not leant in
plane with the rider. This seems to me to be pretty much what happens on some bumpy descents.

James

James Annan said:

Quoted message said:

Quoted message said:

The handlebars provide a handy lever for applying torques, and for that matter the pedals are
(mumble) distance from the bike centerline.

Quoted message said:

Quoted message said:

I thin you should do some calculations on how much lateral force you can put on the wheel
that way.

Quoted message said:

If I push on the end of the handlebar towards the contact patch with an impulsive load of X, then
the reaction at the ground is roughly X vertically and X/4 laterally (30cm half-width of bar, at
1.2m height). If I pull up on the other bar at the same time, the angle of the net reaction force
is even wider. Of course there is also a net reaction on the rider too, but the change in his
momentum depends on the duration for which the force is applied, as well as its magnitude.

Hold it! Let's make a free body diagram and see where the loads arise. You cannot unilaterally push
down on one bar-end unless you unload another area or lean off the bicycle to that side. I don't
dispute that off center loads occur, only that they are not what you propose and are insignificant
in magnitude.

Quoted message said:

Quoted message said:

Besides, it should be apparent that if there is a side load, it must cause lean in the plane of
the bicycle. Pushing down on a pedal while pulling up on the bars is a closed loop and does not
involve the wheels.

Quoted message said:

Again you seem to be talking about steady(ish) loads applied for some time. I'm talking about the
impulsive forces which are certainly much greater, but are of course only applied very briefly.
Bottoming out a suspension fork requires typically double the rider's weight on the fork alone,
and pinch flats imply an even greater force. Rim dings and bent handlebars presumably require even
greater forces since these events are rarer, but they still do happen. Surely these forces are
_predominantly_ in the plane of the bicycle, but I see no justification for the assertion that the
net effect of these forces necessarily lies within the spoke bracing angle.

I didn't say necessarily but only that they do so. That is why hubs are as wide as they are. This
width takes care of the 99.9th percentile of occurrences.

Quoted message said:

If you like, perhaps you can consider them to be a succession of sharp steering corrections where
the bicycle is not leant in plane with the rider. This seems to me to be pretty much what happens
on some bumpy descents.

No, not unless you are purposely trying to skid the wheel sideways. That is the way most non-crash
wheel collapses are achieved. Skid on dirt, turn the wheel crosswise and hit an obstacle. It
behooves the rough terrain rider to get good at not doing this. My MTB is my road bicycle is my
touring bicycle and it goes everywhere. Collapsing wheels is not one of my worries and hasn't been
over many years.

Jobst Brandt [email hidden] Palo Alto CA