The 'sitting' posture on a motorcycle is a compromise between either loading up the back or loading up the wrists. And this 'loading' is defined more by the relative position of the foot-pegs than the distance between the handlebar and the seat. The one other major contributing element is the front-end ride height.

The higher the speed at which a certain bike is expected to travel through most of its running life, the more is the torso rotated forwards and feet moved backwards. This is in no way connected to the power output of the engine or the ultimate performance capability of the motorcycle. Cruisers have powerful engines but the target cruising speed is low enough for the full-drag spread-eagle position to be viable. Ground clearence issues apart, try riding a cruiser through the twisties at a 150 kph and you'll understand it all. Sportsbikes are not just about fast acceleration, hard braking, quick direction changes and high speeds. Its all this with CONTROL. And so its about a very dynamic and aggressive riding posture with the rider ready for any body movement or control input done reflexively.


Most sportsbikes have riding postures that are like the rider is caught mid-way in a push-up. The forward leaning and tucked in position is not just for aerodynamic purposes as is usually thought. The purpose is to spread the rider's body-weight as much along the bike as possible and also keep him low so as to keep the resultant rider/bike C of G also low. A high C of G poses control problems both during hard acceleration/deceleration and quick direction changes, all the more exacerbated at high speeds that these bikes are meant to travel at. These bikes are NOT comfortable to ride. The ergonomics are not human friendly and yet they remain so for the benefits of handling and control they provide. Also because the rider in not expected to remain sitting in one position for long periods on such bikes. These bikes are meant for taking turns fast and when a rider does that, he hardly sits in one position for long. Weight shifts, foot-peg weighing and moving forwards/backwards on the seat for better control. All this movement doesn't highlight the discomfort of the posture. Use a sportsbike for touring and the 'painful' ergonomics come up front. As during touring, you sit in one position for long periods and any unusual muscle/ligament stresses get amplified.

The 'tourers' have the most rider friendly ergonomics. They follow the middle path between the sports-bikes and the cruisers. The rider is expected to cover large distances with little 'posture alteration' along the way. The 'direction change needs' are for a good response at reasonable speeds without compromising unduly on straight-line stability. The rider sits such that he doesn't need the support of his arms to stay sitting. A small test of 'long-time-on-saddle' friendly ergonomics is (with the bike on the centre-stand) to be able to stand on the foot-pegs and sit back on the seat without needing your arms for support. Try doing that with the rear-sets of a sprots-bike or the forward mounted pegs of the cruiser.

As for the proper (comfortable and control-friendly) arm position on a bike, it is with the rider's elbows level or a little below the handlebar level in a way that gets his forearms parallel with the ground. This is the unweighted position for arms i.e. the arms are there just for the task of steering and controlling the bike and not taking the load of the upper body. Loading with torso weight only happens under braking. And unloaded arms are a pre-requisite for precise steering inputs and feedback sensing. The cruisers do unload the arms but also place the feet so far forward that they no longer can play any role in taking any load off the back.The rider is like a sail catching all the wind at full stretch and this pushes his torso backwards at speed, making him hang on to the handlebars. The reason for large rake and trail with the accompanying long wheelbase is to give sufficient inherent directional stability to preclude a very active role from the rider. They are the 'easy' riders after all....aren't they.

There's an interesting bit of research in this 'research paper'. It is a downloadable pdf document. Just check out the body-position interrelation between various ergonomic/design configurations.

And here's the link to Tony Foale's works.

OF

Kyan: We posted almost simultaneously. The clip-on feeling heavier would primarily be due to the reduced 'leverage' that you are getting from it. I'll site a different example to put this 'leverage' into perspective. The Suzuki Intruder handle is so wide that if used as a lever with a suitably located fulcrum, one can lift more than 2 tonnes with it!.

Reducing handlebar width even by half an inch will appreciably cut down its mechanical advantage as a lever. That and it being positioned lower while being angled 'inwards' increases the 'force' requirement for steering.

Fantastic experiement. I'm able to understand why this happens & Thanks to both you & oldfox.

Going by OF's explanation on rake & trail & your earlier post on converting the stock handle bars to clip ons, I'm just trying to understand something here. I'm assuming that the position from which the handle bar starts is not changed or rather the forks are untouched; but instead of a regular handle bar they're replaced with clip on; this means the offset is not changed & the rake angle is not changed; this means the trail is also not changed. In that case, how will the handling become heavy? May be I couldn't understand somethings here; OF, Kaynmantis, R-Series & nitrosatya - pls help me understand here.

Also would like to add another question. Consider a sports bike & what happens if the clip ons are removed & a regular handle bars are fitted so as to attain a street bike sitting position? I hope I wouldn't be altering the rake angle here right? Eventually I wouldn't be altering any of the bike's engineering as such right? I know its a weird question, but still I'm trying to understand little deeper on the subject. So it would look something like the attached pic. Pls help me understand this one too. Tks.

@aargee: My reply to kyanmantis' query (and now yours) probably got lost at the bottom of my post. So I am reproducing it here below.
Post #50
Also have seen the attachment to your post. Even if the width of the handlebar is the same, you have raised its 'height'.....This raising acts as a torque multiplier. So in ref. to the pic in your attachment, the R1 would be far easier to steer. Though of course such a mod would be detrimental from control point of view as the other elements of its ergonomics remain as per the low-set clip-ons. Imagine your arms raised high and your body rotating forwards because your feet are resting on rear-sets.

In Kyan's experiment with clip-ons on the ZMA, even though all other geometry parameters remain the same, just reducing the width of the handlebars or their height or both shall have a noticeable effect of the force needed to steer the bike.

Thanks OF. I think I missed out understanding the above part. Thanks for reiterating it further. Yes, I'm able to get a better picture of how reduction in the width of a handle bar affects the steering; also it helps to give a better understanding to comparing it as a lever example.

Sorry that I couldn't get the above part; so I just sent them for processing in the back of my mind . It will come back in the foreground to seek more clarifications & ofcourse with lot of questions. Thank you so much for providing clear answers with simple examples.

@@Nitrosatya - Pls come up with more stuff; we need to listen/discuss/debate more

another factor making the steering feel heavier while using clipons is weight distribution.
clipons, if lower than stock bars will put more of your body weight on the front wheel. that causes the steering to feel heavier to turn at very low speeds. the heaviness will almost disappear at higher speed.

the bars have no effect on rake or trail. but because they make a big difference to the weight distribution and cg, it is worthwhile to experiment with different bars to find the optimum position for your body type.

as for modifying the factory geometry, i would not recommend changing ...say... an r1's ergonomics. but our commuting oriented bikes are much less optimized for performance, so major gains are possible.

cheers

@aargee: There are many different types of clip-on handle bars. Some are directly fitted on top of the shocks, while other are designed to be bolt on to the slots where stock handle bars are attached. Their design will also differ from one manufacturer to another.

Here's a rough illustration on how my clip-on look like against the stock. You can clearly see the off-set are changed. oldFox has already mentioned that length of handlebars can also attribute to change in hardness. Yes, my clip-on are slightly shorter than stock.

Now this get me to thinking. As the illustration shows the clip-on moves the handle bars away from the fulcrum, away from the rider. Result = heaviness in steering (even considering that my clip-on are slightly shorter than stock, I feel it shouldn't make the amount of change I felt in heaviness, say as I would had I cut off a little bit of my stock handle bars to match the width of the clip-on). Now what if the opposite is done. What might be the effect?

@braindead: I agree body weight could also contribute to heavy feel. But as I noted earlier. It is still heavier with clip-on without leaning against the handle.

Oh!!! I thought the red circled one matters for the offset position; are you saying that the blue one is responsible for the offset? I'm asking this because, in this pic, I'm unders the impression that the offset position is not changed at all. Pls correct my understanding.

Going by the classical definition of Torque=Force x force arm ; it is just that the distance from the center of headstock to the bar end matters. I think the heaviness in steering resulted from shortening of length of the handle bars.

Btw let us not make this a very technical thread. Let us keep ourselves at styling. My aim to start this thread was to educate fellow riders on international styling trends which i think will make us demand better designed bikes!

Perhaps my understanding of offset is not correct. More knowledgeable person can correct me. However what I mean is illustrated in the diagram below. The diagram shows front portion of bike viewed from top.
The handle bars have been reposition in an exaggerate manner to highlight my thoughts.
(A) This position shows normal position. The grip is almost in perfect alignment with the rake as well as the 'fulcrum' point. The fulcrum point can be the top portion of the forks or the area where handle bars are bolted to the forks.
(B & C) These position shows handle bars being pulled back 'B' and pushed forward 'C'. The grip is out of alignment with rake as well as the 'fulcrum' point.

My interpretation of 'offset' was the position of the grip against the point where handle bars is bolted to the forks. But as you pointed out in my previous diagram. The offset can be changed by changing the position of these bolted area.

Anyway, my point is that such change in grip position as shown in the pic can have different effect.

My sincere apologies to nitrosatya for inadvertently hijacking his thread in this manner. Since it seemed inappropriate to leave things hanging in mid-air, I take the liberty of this one last post which attempts to clear the confusion.

I guess there has been confusion over the forces involved in turning the handle. It is difficult to visualize in three dimensions what one sees on paper i.e. 2D. The figure below should help with that comprehension.



The difference between case 1 and case 2 is the height of the handle above its point of rotation. A raised handlebar (stock) is in effect a longer lever arm than a straight handlebar (clip-ons). The Resultant force that actually turns the steering head is the resultant of two force vectors in case 1 compared to just one force in case 2. So the rider in case 1, for applying a certain torque at the steering axis, needs to apply a smaller force than he would need in case 2. In short, all things being the same including the linear handlebar length, the handle would feel lighter in case 1 and heavier in case 2.

OF

i am sorry but your explanation is flawed.

provided the handlebar is sufficiently stiff, there is not going to be any difference in the steering effort for the same width of the handlebar.
the resultant length of lever arm you show in the picture cannot be right. thats because the resultant lever arm will always be perpendicular to the axis of rotation, no matter its location.

at this point we need to separate static and dynamic steering effort.

static steering effort is the effort required to turn the steering when the bike is not moving (or moving very slowly). friction of the tyre is the biggest contributor to this effort. the tyre friction is caused by the size of the contact patch, compound of the tyre and load on the tyre.
a lower handlebar will increase this effort because it will cause more weight to be placed on the front wheel, increasing friction.
a fatter tyre will have the same effect as lower handlebar on the static steering effort.

dynamic steering effort is the effort required to turn the steering when the bike is moving. the steering effort is the result of the self correcting tendency of the bike thanks to the trail. the handlebar has no effect on this effort.

but static steering effort does not vanish once the bike is motion but reduces gradually to a negligible value with increase in speed.

a human factor that we can consider is that maybe a person perceives the steering effort to be more if there is too much load on the wrists.
perceptions are not necessarily the truth.

cheers all

@@nitrosatya - Sorry to have asked more questions on handlebars that deviates from this topic altogether.

I've a request to OF - can you create a new thread on handlebars? Probably, we can all ask the Mods to move the appropriate replies to the new post & still keep discussing on styling here & handle bar discussion there?

I guess my explanation relating the forces involved directly to the bar length is not right. The effort was in the interest of simplicity but has apparently skewed the physics involved. Thanks a lot for pointing it out.

However, the physical forces involved in case of a 'raised' bar, even if rigidly mounted are resolvable into two. One, the torque perpendicular to the axis of rotation and the other a torque that tries to rotate the handlebar forwards on its mounting. What gets to the steering head is the resultant of these two forces. Steering inputs, seen at one bar end for simplicity, are both a forward/backward and up/down push or a pull in combination. To turn left for example, the rider pushes forward and downwards on the left grip to countersteer. The lever arm remains the same as you've pointed out but the forces involved differ between a straight-bar and a raised bar.

There is some contradiction between the two sentences quoted above. However what you say about the static steering effort getting reduced drastically is quite true. A major reason being the far smaller steering angle required for turns at speed than when the bike is at crawl speeds. That, when coupled with gyroscopic precession, almost feels like the bike is turning by itself.

And yes, lowered bars put more weight on the wrists and as a result the force needed to turn the handle has the added factor of also turning the heavily loaded wrists. This 'additional' load results in a heavier handle.

Done. Muddling up the two topics would have ruined both.

@braindead - appreciate the view you've provided; though a simple thing that I notice everyday , but couldn't get the inner meaning as much you've explained above; I've few questions to help me in understanding the below...
1. I couldn't get the point on how a lower handlebar will increase the static steering effort. Could you help understand with a pic pls?
2. With a very thin tyres & (just imagine a huge engine plonked on a thin bike for understanding sake) at very high speeds the vehicle tends to feel very light & as if to throw you off - is this the phenomenon where in the steering effort goes to completely negligible state?
3. I'm unable to understand how the load is more on the wrists. It will be YES when you apply throttle to turn your wrists, but for steering how? I usually feel the pain at the triceps portion just under the shoulder or over the elbow. Is this not the case?