Dual sus

[Mr. G]

What was the original question again???

 

When to lock out the suspension...

 

 

Yeah sorry just being sarcy, because we really getting off the point.

[techguy]

couldn't tell...

[techguy]

The whole thing boils down to marketing hype, you'll make ANY full suss bob if you pedal in squares. Besides the whole assumption that a full suss robs you of power comes from the early 90's when the suspension designs were k@k and they had things like the unified rear triangle where the whole drivetrain and rear wheel was separated from the main frame, the problem with this was that the saddle height changed when the suspension moved.

[Pappa Bear]

tar

[kosmonooit]

whatever ....

 

Personally I found some of my precious uphill momentum being lost is a big woosh of my lefty, to the point sometimes the bike actually stops when I hit a gras bolletjie and I fall over. Generally I dont bother with the lockout, but, like that last few km of very steep uphill tar road on the Giants Castle, it really does make a tangible difference in conserving your  forward movement, in that pedal power is being transferred to the wheel in torque and not being absorbed in pumping the shock (my reasoning) I guess one could actually measure this.

 

Biggest hassle of suspension locks is remembering to unlock them b4 you  hit the bumps downhill  with the Lefty its a bit tricky since you have to take ur left hand off the bars to do this.

kosmonooit2010-05-26 09:00:38

[Johan Bornman]

From JB:

I think the analogy is off kilter. Squatting under accelleration is completely different from bob during pedaling. Completely.

 

Squatting under accelleration on a motorbike or car causes no power loss. It was mildly irritating on BeeEms but did not affect its accelleration.

 

Bobbing whilst pedaling a bicycle produces lots of power loss. It messes with your rythm as well.

 

I fail to see how a bike is designed so that the rear wheel digs in under accelleration. Rear wheel downforce is a function of the rider's weight and to an extent' date=' the shift in weight caused by accelleration. However, we don't accellerate fast enough to cause any weight shift to the back, so that is moot. We do brake fast enough to cause the reverse though.

 

A comparison of what happens when you brake hard and accellerate hard should make this clear to you.

 

Since you are making some unsubstantiated statements here, perhaps, nuts and bolts you know, you could substantiate your claims and explain why you say what you say?

 

 

 

 

 

[/quote']

 

This is a written medium so I can't help you if you can't read. Please highlight the part of my explanation that you dont understand and I'll try my best to explain it to you.

 

 

[Johan Bornman]

The geometry of the Maestro is designed to resist chain jacking on the rear shock - but this is just one element of many factors affecting suspension kinetics.

I believe the thrust of JB's assertion had more to do with weight shift under acceleration (and correct me if I'm wrong here) and to this end the Maestro won't help a rider shifting weight under hard pedal efforts (like when standing). This will cause "bobbing" easily as much as chain jacking. I'd still like to hear JB's reasoning as to why squatting under acceleration differs between cars and bicycles. Also' date=' some detail on the power robbing that bobbing apparently causes, and why pedal acceleration (I assume seated, to assist JB's assertion) causes so little weight shift as to rule it out of the equation.

[/quote']

 

OK, I think this is the crux of your question.

 

When a car or a motorbike accellerates, the back wheel (I'm assuming rear wheel drive here) experiences a downforce perpendicular to the road. This downforce is due to the shift in weight from the front, to the rear and that shift in weight is because of accelleration.

 

A bicyle accellerates like a slug and doesn't cause a shift of weight to the rear (that's worth mentioning). Use this thought experiment to illustrate the point.

 

1) You are riding pillion on a motorbike and the driver accellerates. You better hold on to him or hold onto the sissy bar or flip over backwards. The accelleration force is noticeable. You can feel it in the fore-aft plane as well as notice it how the vehicle squats.

 

2) You are riding stoker on a tandem and the captain accellerates. You don't even notice it.

 

The bobbing by a cyclist on a suspension bike comes from two forces.

 

1) The torsion on the back wheel makes the bike want to bend so that its bottom bracket moves towards the road. Depending on where the pivots are, the effect is noticeable or not.

 

2) Our heavy legs and the up-down powerstroke of our  bi-pedal pistons bounce the bike up and down. Our powerstroke is so limited in its range that in effect we just punch down with our legs at a very low cadence. This causes bob. The loss of power can be calculated by the force required to induce the bob (say 200N) times half the time between bobs, times the horizontal travel of the bob - say 60mm.

 

On a motorbike, there is no bob but a once-off squat (BMW example) as you accellerate. This is repeated between gearchanges but not for each revolution of the engine. On a bicycle it is for each revolution of the engine.

 

That makes a big difference in the portion of power robbed by up-down movements.

 

 

 

  

[Johan Bornman]

whatever ....

 

Personally I found some of my precious uphill momentum being lost is a big woosh of my lefty' date=' to the point sometimes the bike actually stops when I hit a gras bolletjie and I fall over. Generally I dont bother with the lockout, but, like that last few km of very steep uphill tar road on the Giants Castle, it really does make a tangible difference in conserving your  forward movement, in that pedal power is being transferred to the wheel in torque and not being absorbed in pumping the shock (my reasoning) I guess one could actually measure this.

 

Biggest hassle of suspension locks is remembering to unlock them b4 you  hit the bumps downhill  with the Lefty its a bit tricky since you have to take ur left hand off the bars to do this.

[/quote']

 

You are right. In conditions like you describe, the bob robs you of a lot of your input. I've attempted to measure it in my repoly to Cyclequip1 - have a look at my reasoning. We may find one or two other factors to include in the formula.

 

All the energy you lost in the bob is transfered to the shock as heat energy and dissipated to the atmosphere. It may even have an effect on global warming. Who knows?

 

 

[parabola]

 

Any good advice : in which situations should the lock out be used? ]

 

I would say that use the lockout on long, smooth climbs, where you will be standing and pedaling hard. On loose climbs if you keep seated and unlocked then the suspension will absorb the bumps and maintain rear wheel traction. Goes without saying that on tar/smooth hardpack you can lock it out. If your shocks (front and rear) are properly adjusted for your weight, then you should only need lockout quite rarely, unless you are a serious racer.

 

Its as simple as using it when the suspension feels too soft and you are bobbing around.

 

Thanks JB and tom893 for the interesting information.

[DirtyFrank]

 

 

 

when you notice 'bunches' being formed around you. like on boring bits like district roads' date=' especially uphill.

 

[/quote']on nice smooth uphills (OK thats relative), where the uphill is full of ruts and stones, its easier sometimes to leave your shock active, but it all comes down to personal preference, try it in training, and you will have a better idea of where it is suitable. What shock have you got by the way, I've an RP23, and leave it on the platform setting (Pro-pedal on) for most of my ride, only releasing it for very rough downhills, and stony and badly rutted uphills.

I get the idea most people are under the impression that these shocks have a lock out...`pro pedal` is not a lockout in the true sense of the word and will still be active under fast compression. Personally I have a dualie with maestro suspension which is supposed to minimize pedal induced bob and I still use the propedal setting for 80% of the time as it does undoubtedly improve pedaling efficiency on reasonably smooth surfaces and when i stand and pedal.

[Headshot]

[QUOTE=techguy]The whole thing boils down to marketing hype, you'll make ANY full suss bob if you pedal in squares. Besides the whole assumption that a full suss robs you of power comes from the early 90's when the suspension designs were k@k and they had things like the unified rear triangle where the whole drivetrain and rear wheel was separated from the main frame, the problem with this was that the saddle height changed when the suspension moved.[/quote]

 

How do you square your first phrase above with the "fact" below? I agree with you its all marketing hype - but disagree that the brands you mention have perfected full suspension design. Its just more hype IMO.

 

Why do you think brands like Specialized, Trek to name two spend hundreds of thousands of dollars developing full suss designs and market them? Because they are better. And while they fit them with shocks that have a platform function it's because thats what the market dictates and if they didn't spec them with a Fox RP23 for example they wouldn't sell the same number, not because the system needs it. Thats a fact.

Headshot2010-05-26 14:26:57

[Fitter]

The geometry of the Maestro is designed to resist chain jacking on the rear shock - but this is just one element of many factors affecting suspension kinetics.

I believe the thrust of JB's assertion had more to do with weight shift under acceleration (and correct me if I'm wrong here) and to this end the Maestro won't help a rider shifting weight under hard pedal efforts (like when standing). This will cause "bobbing" easily as much as chain jacking. I'd still like to hear JB's reasoning as to why squatting under acceleration differs between cars and bicycles. Also' date=' some detail on the power robbing that bobbing apparently causes, and why pedal acceleration (I assume seated, to assist JB's assertion) causes so little weight shift as to rule it out of the equation.

[/quote']

 

OK, I think this is the crux of your question.

 

When a car or a motorbike accellerates, the back wheel (I'm assuming rear wheel drive here) experiences a downforce perpendicular to the road. This downforce is due to the shift in weight from the front, to the rear and that shift in weight is because of accelleration.

 

A bicyle accellerates like a slug and doesn't cause a shift of weight to the rear (that's worth mentioning). Use this thought experiment to illustrate the point.

 

1) You are riding pillion on a motorbike and the driver accellerates. You better hold on to him or hold onto the sissy bar or flip over backwards. The accelleration force is noticeable. You can feel it in the fore-aft plane as well as notice it how the vehicle squats.

 

2) You are riding stoker on a tandem and the captain accellerates. You don't even notice it.

 

The bobbing by a cyclist on a suspension bike comes from two forces.

 

1) The torsion on the back wheel makes the bike want to bend so that its bottom bracket moves towards the road. Depending on where the pivots are, the effect is noticeable or not.

 

2) Our heavy legs and the up-down powerstroke of our  bi-pedal pistons bounce the bike up and down. Our powerstroke is so limited in its range that in effect we just punch down with our legs at a very low cadence. This causes bob. The loss of power can be calculated by the force required to induce the bob (say 200N) times half the time between bobs, times the horizontal travel of the bob - say 60mm.

 

On a motorbike, there is no bob but a once-off squat (BMW example) as you accellerate. This is repeated between gearchanges but not for each revolution of the engine. On a bicycle it is for each revolution of the engine.

 

That makes a big difference in the portion of power robbed by up-down movements. 

 

What drivel!

What causes this massive weight shift from the front to the back of a car under acceleration???

This is a phenomenon known as load transfer and has nothing to do with a shift of weight. There might be a small weight transfer caused by small CoG displacement as a result of suspension pitch change, vertical suspension travel or tyre contact patch deformation, but that is all.

How would this weight shift work in a solid suspension vehicle under acceleration? Or a vehicle witjh a massively long wheelbase??

Since this is a written medium, as you say, stop writing drivel and answer the question please. Quote some references, don't offer some pathetic, badly thought-out thought experiment.

FYI the load shift phenomenon is exactly the same with a bicycle. Speed of acceleration simply goes to quantum of load shift but does not somehow negate load shift. When you sit on a pillion and the motorbike accelerates, the pillion rider experiences inertia, not weight shift!! When you are a stoker you are pulling on handlebars and pushing down on pedals - how on earth do you compare the two phenomena. Did you apply yourself at all to this answer, or are you simply unraveling your ignorance here and thinking everyone sucks up your nonsense?

The torsion on a bicycle rear wheel will want to move the rear wheel forward, not the BB down. The resultant will be determined by pivot placement. On some designs this chain jacking will want to compress the shock. This causes bobbing. Our pedal action causes as much forward-backward motion as it does up-down. This causes bobbing. You say this robs power and you offer a quantitative equation to measure this. Please could you offer some substantiation of this, other than your speculative and questionable equation.

Now please explain how in similar vein, on an unsuspended road bike, the deformation of a BB from side-to-side has never been shown or measured as a loss of power? You say all the energy of the shock compression is lost as heat and dissipated into the atmosphere, contributing to global warming? You evidently don't understand the concept of kinetic energy stored in the air spring of the suspension component, most of which is returned to the rider as the unit rebounds. Either this or you are being deliberately disingenuous. Either way, your responses are sheer nonsense.

 

[Johan Bornman]

 

What drivel!

What causes this massive weight shift from the front to the back of a car under acceleration???

This is a phenomenon known as load transfer and has nothing to do with a shift of weight. There might be a small weight transfer caused by small CoG displacement as a result of suspension pitch change' date=' vertical suspension travel or tyre contact patch deformation, but that is all.

How would this weight shift work in a solid suspension vehicle under acceleration? Or a vehicle witjh a massively long wheelbase??

Since this is a written medium, as you say, stop writing drivel and answer the question please. Quote some references, don't offer some pathetic, badly thought-out thought experiment.

FYI the load shift phenomenon is exactly the same with a bicycle. Speed of acceleration simply goes to quantum of load shift but does not somehow negate load shift. When you sit on a pillion and the motorbike accelerates, the pillion rider experiences inertia, not weight shift!! When you are a stoker you are pulling on handlebars and pushing down on pedals - how on earth do you compare the two phenomena. Did you apply yourself at all to this answer, or are you simply unraveling your ignorance here and thinking everyone sucks up your nonsense?

The torsion on a bicycle rear wheel will want to move the rear wheel forward, not the BB down. The resultant will be determined by pivot placement. On some designs this chain jacking will want to compress the shock. This causes bobbing. Our pedal action causes as much forward-backward motion as it does up-down. This causes bobbing. You say this robs power and you offer a quantitative equation to measure this. Please could you offer some substantiation of this, other than your speculative and questionable equation.

Now please explain how in similar vein, on an unsuspended road bike, the deformation of a BB from side-to-side has never been shown or measured as a loss of power? You say all the energy of the shock compression is lost as heat and dissipated into the atmosphere, contributing to global warming? You evidently don't understand the concept of kinetic energy stored in the air spring of the suspension component, most of which is returned to the rider as the unit rebounds. Either this or you are being deliberately disingenuous. Either way, your responses are sheer nonsense.

 

[/quote']

 

If I call it load transfer, I'm told no-one understands what I say. If I simplify it to weight shift, then I'm told I talk drivel.  You in fact referred to weight shift yourself. Control your emotions and debate like a gentleman.

 

The global warming quip is just that, a quip. You are right, I shouldn't have said ALL in that sentence, some of the energy goes elsewhere other than into the suspension. However, I don't agree with your assertion that most of it is returned. I think most of it is lost. The purpose of the shock is after all to damp and it does so on the compression and rebound stroke. Significant energy is lost.

 

I don't know where BB sway entered the argument. Take it up elsewhere.

 

You seem to find a problem with my weight shift/load transfer analogy of a tandem and a motorbike. Let me change it, the stoker DOESN'T hold on. Will she fall off the back? I don't think so.

 

As for the BB  moving down...reconsider what I said and take into account  that the BB will want to move down because the chain wants to shorten the distance between BB and rear hub. If the link is flexible and biased downwards like in a suspension bike, it can only go down.

 

The original question was when to use lockout and the answer is to use it when the suspension starts to rob you of your input or interferes with your stride.

 

 

 

 

 

 

[Robrider]

 

The geometry of the Maestro is designed to resist chain jacking on the rear shock - but this is just one element of many factors affecting suspension kinetics.

I believe the thrust of JB's assertion had more to do with weight shift under acceleration (and correct me if I'm wrong here) and to this end the Maestro won't help a rider shifting weight under hard pedal efforts (like when standing). This will cause "bobbing" easily as much as chain jacking. I'd still like to hear JB's reasoning as to why squatting under acceleration differs between cars and bicycles. Also' date=' some detail on the power robbing that bobbing apparently causes, and why pedal acceleration (I assume seated, to assist JB's assertion) causes so little weight shift as to rule it out of the equation.

[/quote']

 

OK, I think this is the crux of your question.

 

When a car or a motorbike accellerates, the back wheel (I'm assuming rear wheel drive here) experiences a downforce perpendicular to the road. This downforce is due to the shift in weight from the front, to the rear and that shift in weight is because of accelleration.

 

A bicyle accellerates like a slug and doesn't cause a shift of weight to the rear (that's worth mentioning). Use this thought experiment to illustrate the point.

 

1) You are riding pillion on a motorbike and the driver accellerates. You better hold on to him or hold onto the sissy bar or flip over backwards. The accelleration force is noticeable. You can feel it in the fore-aft plane as well as notice it how the vehicle squats.

 

2) You are riding stoker on a tandem and the captain accellerates. You don't even notice it.

 

The bobbing by a cyclist on a suspension bike comes from two forces.

 

1) The torsion on the back wheel makes the bike want to bend so that its bottom bracket moves towards the road. Depending on where the pivots are, the effect is noticeable or not.

 

2) Our heavy legs and the up-down powerstroke of our  bi-pedal pistons bounce the bike up and down. Our powerstroke is so limited in its range that in effect we just punch down with our legs at a very low cadence. This causes bob. The loss of power can be calculated by the force required to induce the bob (say 200N) times half the time between bobs, times the horizontal travel of the bob - say 60mm.

 

On a motorbike, there is no bob but a once-off squat (BMW example) as you accellerate. This is repeated between gearchanges but not for each revolution of the engine. On a bicycle it is for each revolution of the engine.

 

That makes a big difference in the portion of power robbed by up-down movements. 

 

What drivel!

What causes this massive weight shift from the front to the back of a car under acceleration???

This is a phenomenon known as load transfer and has nothing to do with a shift of weight. There might be a small weight transfer caused by small CoG displacement as a result of suspension pitch change, vertical suspension travel or tyre contact patch deformation, but that is all.

How would this weight shift work in a solid suspension vehicle under acceleration? Or a vehicle witjh a massively long wheelbase??

Since this is a written medium, as you say, stop writing drivel and answer the question please. Quote some references, don't offer some pathetic, badly thought-out thought experiment.

FYI the load shift phenomenon is exactly the same with a bicycle. Speed of acceleration simply goes to quantum of load shift but does not somehow negate load shift. When you sit on a pillion and the motorbike accelerates, the pillion rider experiences inertia, not weight shift!! When you are a stoker you are pulling on handlebars and pushing down on pedals - how on earth do you compare the two phenomena. Did you apply yourself at all to this answer, or are you simply unraveling your ignorance here and thinking everyone sucks up your nonsense?

The torsion on a bicycle rear wheel will want to move the rear wheel forward, not the BB down. The resultant will be determined by pivot placement. On some designs this chain jacking will want to compress the shock. This causes bobbing. Our pedal action causes as much forward-backward motion as it does up-down. This causes bobbing. You say this robs power and you offer a quantitative equation to measure this. Please could you offer some substantiation of this, other than your speculative and questionable equation.

Now please explain how in similar vein, on an unsuspended road bike, the deformation of a BB from side-to-side has never been shown or measured as a loss of power? You say all the energy of the shock compression is lost as heat and dissipated into the atmosphere, contributing to global warming? You evidently don't understand the concept of kinetic energy stored in the air spring of the suspension component, most of which is returned to the rider as the unit rebounds. Either this or you are being deliberately disingenuous. Either way, your responses are sheer nonsense.

 

 

I'll have a go at this one...

 

I will agree that the weight shift is due to the acceleration forces, not the shift of weight (although i think its just semantics)...

 

With out acceleration the only force on the wheels is due to the weight (mass x gravity). so as the bicycle/car accelerates the acceleration force (or inertial force) acts backwards (mass x acceleration).

 

The total force acting on the wheels is then a function of the resultant force (the combined force of the 2 accelerations)

 

See diagram below:

 

This is where I have to agree with JB becase of two reasons:

 

1) the acceleration of the bicycle is really really small. No matter how hardcore you think you are, its just not that much. So, yes, it is still there... and yes, it will cause weight shift.... but i would guess (not fact) that tilting yr head slightly back would have a simliar effect. Also remember, we not talking about track cycling acceleration, we talking about riding uphills.

 

2) The weight shift force is ONLY due to acceleration, which is the changing of speed. So if you are going at a constant speed, then that force dissapears completely. So in this context, most people say they lock it out while climbing, which is where theyexperience the bobbing, they will be at a constant speed.

 

So considering all that, I would say weight shift due to acceleration plays very little role in when to lock out your shock

 

[Headshot]

Guys, read this end to end - its the best you'll find on bike suspension. A tad out of date now, but it really helps see through the BS marketing and hype bike manufacturers and journos sprout

 

http://www.rdrop.com/~/twest/mtb/pathAnalysis/index.html

[Fitter]

If I call it load transfer, I'm told no-one understands what I say. If I simplify it to weight shift, then I'm told I talk drivel.  You in fact referred to weight shift yourself. Control your emotions and debate like a gentleman.

 

More drivel.

I used your term "weight shift". You brought it up, not me. Now you, the master of "use the right term"want to hide behind your own ignorance with some fatuous response about being told you're not being understood? Who told you this? And you have the gall to talk about debating? Like a gentleman? Do me a favour, don't mistake me for a fool and refrain from handing out advices - it'll be a cold day in hell before I'm in need of advice from the likes of you.

 

The global warming quip is just that, a quip. You are right, I shouldn't have said ALL in that sentence, some of the energy goes elsewhere other than into the suspension.

 

However, I don't agree with your assertion that most of it is returned. I think most of it is lost. The purpose of the shock is after all to damp and it does so on the compression and rebound stroke. Significant energy is lost.

 

Back to some answers: I'm not concerned with your speculation about what quantum of energy is lost or returned in a suspension system. I'd like some actual data. This is what debating like a gentleman is about, isn't it? You said, in one sentence:" All the energy you lost in the bob is transfered to the shock as heat energy and dissipated to the atmosphere." Tell me this isn't drivel? The purpose of the shock is to control the movement of the rear axle relative to the rest of the frame and it does so primarily through the use of springs - these are air-compression chambers whose shaft speed is further controlled - under both compression and rebound - by damper circuits. The kinetic energy stored in the springs is not somehow lost through the separate damper circuits - it is simply controlled. I really don't think you understand suspensions ......

 

I don't know where BB sway entered the argument. Take it up elsewhere.

 

This is elsewhere. My BB analogy, for your famously articulate mind, was simply that - an analogy about power being lost in kinetic instances. Like the kinetic instances of an air spring loaded up under compression.

 

You seem to find a problem with my weight shift/load transfer analogy of a tandem and a motorbike. Let me change it, the stoker DOESN'T hold on. Will she fall off the back? I don't think so.

 

What has this got to do with your assertions regarding weight shift? Let ME change it - what if the stoker was sitting vertically and not clipped in - simply balancing? Want to take a bet on what happens when the bike accelerates forward? Again, obfuscation masking the drivel.

 

As for the BB  moving down...reconsider what I said and take into account  that the BB will want to move down because the chain wants to shorten the distance between BB and rear hub. If the link is flexible and biased downwards like in a suspension bike, it can only go down.

 

More drivel and self-serving bootstrapping! Under chain forces the axle wants to meet the BB so vectors can be both forward and down but depending on the link configuration, the load transfer and front fork extension, there can be a resultant chain jacking upwards into a shock.

 

The original question was when to use lockout and the answer is to use it when the suspension starts to rob you of your input or interferes with your stride.

 

Well, this is your answer. Others say don't use the lockout because it doesn't rob you of your input (a nice, technical term that, from the tech wiz) or interferes with your stride  (whatever this might mean, technically). Yet others design complex compression-damping technology to limit the movement under rider input but not trail input. Lockout is exactly that - might as well have a rigid for all the traction benefits you'll be getting. I'd suggest using lockout when riding your MTB on the road.