Re: INFO: A Guide On Technical Jargons

That just cleared up all the confusion. Beautiful explanation.

Re: INFO: A Guide On Technical Jargons

Gears are torque multipliers not in the sense that they can add to or subtract from what the engine produces. They are torque multipliers as they change the relationship between the engine RPM and the wheel RPM. Lower gears make it possible for you to increase engine RPM at a faster rate in relation to the wheel RPM while taller ratios allow for a slower rate of increase in engine RPM's compared to road speeds. Which is why every 1000 RPM's in first gear (the shortest ratio) give an additional 4 kph (as an example) compared to the 15 kph increase for every 1000 rpm when in top gear (the tallest ratio). So the torque remains the same for any and every gear but it can be changed i.e. increased and decreased very quickly in lower gears. Hence you get a quicker change in speed in lower gears per unit time which in other words is how acceleration is defined.

So lower geared bikes are quicker to accelerate and the first ratio (or the bottom ratio) is decided upon depending on the end -use of the bike as much as it depends upon the engine characteristics. This is because the bottom ratio more or less decides what and how far the top one would be as you cannot have extremely wide gaps between ratios. Any more than 6 gears would not just make the gearbox too cumbersome to produce and keep reliable but would also be a nuisance for the rider. This complexity can of course be afforded in those huge hauler trucks that have compound gearboxes offering 20 ratios or even more. The huge range of load pulling and gradeability requirements coupled with the need for high fuel efficiency drives up the number of ratios needed.


No, I wrote it exactly as it was meant to be. I know that the '200 hits a true 100 kph in 5th gear. Dropping a couple of teeth will definitely not demand the 5th gear but this is pure conjecture to assume that the ability to pull longer in each gear will necessarily give better 0-100 timing. It may or may not and only a practical test will tell. The Duke's inherent strength lies not just in that excellent engine but also in the perfectly matched gearbox it has. The gear ratios are in perfect sync with the engine in allowing a rapid climb-up of the RPM's under load. Change the ratios and you just might change the rapidity of this RPM gain - possibly adversely affecting the acceleration of the bike. So my words.

Again a little bit more of speculation regarding the gearing of the 390 - I feel they have deliberately chosen overall taller ratios not just in the interest of better fuel economy but also to improve rideability for the average buyer (they are in the business of selling bikes after all) . Ratios as low as the 200 would have made a 390 just too peppy for the average Joe to ride without drastically increasing the danger of not remaining rubber side up for long.

Glad the confusion went. Though I think it would have returned had I not checked myself in time at the end of the post

Suspension and Handling.

Whats the relation between the suspension stiffness and bike handling?
I know a stiffer suspension provides better handling than a softer one because thats what I have "felt" while riding.
It feels like a softer suspension makes the chassis move more and thereby upsetting the handling of the bike.
But what I would like to know is what is the physics behind how suspension affects handling?

Any inputs?

Cheers!!

Re: Suspension and Handling.

Few days back, i was browsing through the fb timeline, and saw a couple of modified sports bikes with really long swing arms.
So that made me think what is the relation with the swing arm length with the bike handling ? Like those with long ones, and what might happen if we make it short ?
Tried to search for the answer but could find anything useful.

what i think is that a longer swingarm might help in keeping the bike planted on the road, thereby making the chances of wheel pop-up very less.
is this the correct reason ?
i have seen a few videos of bike drag racging and they had really long swingarms. From them i concluded this.
some light on this would be sppreciated.

Re: INFO: A Guide On Technical Jargons

Firstly, a longer swingarm means more distance between rear wheel and rider's seat & weight--> You know what happens next. The rider, being so ahead of the rear wheel, disturbs the weight distribution, bringing it forward.
Yes, Wheelies become difficult in such a setup. And even if the engine is capable enough, wheelies on such a setup are more risky.

But, avoiding wheelie is not a big plus, as instead of wheelie it might wheelspin too, which is a dangerous situation if the rider is not prepared as the weight on rear tyre is not so much, and this might reduce grip.


So, there's a bigger picture to such swingarms, than just "avoiding wheelies".

Wheelbase is a parameter of a motorcycle, which means the distance between the contact ground of the front and rear wheel. So, if Karizma has a wheelbase of 1350mm, it means the front and rear wheel are 1350mm apart at their road contact point usually.

For any category of bike, a longer wheelbase makes them "Stable at high speeds" but "slower turning through turns"... Vice Versa is true also. Shorter wheelbase means quicker turning but instability at high speeds.

Changing the swingarm is the easiest method to change wheelbase- this is much easier, and so far the best commonly accepted method to have a hugely different wheelbase. So, swingarm length depends on what you want- Straight line Stability or turning radius.


A person wanting to participate in an indoor competition will choose a smaller swingarm & wheelbase for quick turning, because he won't touch high speeds inside a room. But he will need to turn quick!

On the other hand, a drag racer who will go upto 220 kmph will benefit from a longer wheelbase, as it will give him stability to manage the vehicle as it touches high speeds.

Examples of quick turning bikes:- Hero's Commuters, TVS Apache 150, Yamaha Crux, etc. (less than 1300 mm)

Examples of long wheelbase bikes: FZ1, Bandit 1250S, Suzuki Hayabusa, Suzuki Intruder, etc... (1400+ mm)

"In the middle" examples: P220, Karizma, Duke 200, etc. (1350~ mm)


There was a guy who set the world record for highest speed on a modified Suzuki Hayabusa, he set 502~ kmph on a deserted airstrip. He too had a huge long swingarm installed, as the stock swingarm of Hayabusa might have not helped his case beyond 300 kmph.
Even then he said that he didn't know what was happening and he was bouncing around the place, etc. This is what stability means.

That's why touring bikes should have good wheelbases, so that they can remain calm at high speeds. Take a Apache 150 or junior Pulsar on a tour and you will see how unstable they feel beyond 110 kmph. Of course, frame matters too, but you can't change frames everyday.

Handling is finding yourself in "control" of the vehicle. Better handling means better control, even under worse conditions.

While riding, some of your purposeful movements (weight shift, etc.) act as instructions for the motorcycle to change direction. What soft suspension does is that:

1. it dampens your actions, so they don't translate into the same control that hard suspensions give. You don't feel your actions are helping to "control" the bike. Your lean angles while turning will not inspire confidence,

2. When you apply the front brakes, the entire chassis "nose-Dives" forward as the front suspension contracts. When you accelerate hard, your rear suspension contracts so you can feel the frame lift from front, but you can't feel the front wheel at all- whether its in air or not.

3. Racing or hard riding, you won't "feel the road" with such a soft setup. That means, you won't get feedback from the road, and won't be able to judge the grip properly too.

4. On corners, on a soft setup, you will feel bouncy through the corner. One corner is ok, but if you have to pass through some fast corners one after another- you're going to be confused.
Compare this to a harder suspension where you'll feel the bike to be taut and within control.


Basically, a suspension's deciding values are:
preload value, its decided on the basis of weight of rider and initial stiffness. Its to maintain the suspension poise even under heavy weight.
compression is how quickly it will get compressed,
rebound damping is how quickly it will "rebound" to normal after getting compressed,
travel is the maximum length that the suspension can be compressed under heavy usage,


My opinion is that for best handling, a suitable frame is a must. And secondly, its NOT true that hardest suspensions will always give you good handling.
If that was true, we would've had racing bikes & cars without suspensions at all.

My opinion is that a suspension setup should be "road & usage suitable". Its like a lego piece: right suspension on the right roads.


Going to Off road? Long travel low damped soft suspensions will let you control the bike, while riding a hard suspension here will only shake and destabilise you continuously.
Going to a racetrack? High quality hard suspensions is the way to go. Here, soft suspensions will only slow you around corners.

I think @Old Fox sir can explain the suspension thing better...

Re: INFO: A Guide On Technical Jargons

^^ really nice explanation.
I always thought of this as only to avoid wheelies in drag races, now i know better. Thank you.

BTW, i would have loved to study under you finished my college in June only.

Re: Suspension and Handling.

Beautiful explanation Samarth bhai...though there is another perspective I'd like to add on - there are a group of stuntmen who love to "drift" their bikes. For their stunt purposes, they must purposefully let their rear wheels spin hard without burning out the tyres. In such situations, a custom "extra long" swingarm helps the purpose. Definitely not for road use, though.

Re: Suspension and Handling.

^^^ Very beautifully explained Samarth
I was able to visualize everything you said so well and relate it to the riding experience. Hats off to you and a big thanks!!

So in analogy the difference between a hard and soft suspension is like the difference in trying to play a game with a joystick made with hard plastic or soft bendy rubber.

Helps in understanding a lot.

Cheers!!

Re: INFO: A Guide On Technical Jargons

Thanks Arijit for appreciating, and also thanks for the very good example (in bold).
In fact, your example will be more useful than mine, while explaining a new member... Hard plastic gives better control and button feedback, so its like hard suspension in a way.

Another analogy could be that hard suspension is like a nut bolt attachment, and soft suspension is like rope knot arrangement.... (somewhat?).

Thanks for appreciating.
Yes, that's true. Some might choose bigger swingarms for drifting safely, as the bike still won't change direction or lose stability that easily.
Short swingarms, and ultimately short wheelbase makes the setup very responsive for drifting...

Yes, not for roads definitely. Or the rider must be ready for a huge turning radius.

Re: INFO: A Guide On Technical Jargons

Hey guys, this thread is very informative and interesting!!
I wanted to know What causes vibrations in a bike? For example the rtr series. What causes the handlebar, foot pegs to vibrate in the rtr series? Technical reasons for these vibrations?

Sent from my Blade using xBhp Connect mobile app

Re: INFO: A Guide On Technical Jargons

I don't know how it could be avoided, senior members can comment on this better, but as fas as vibrations are concerned, every mechanical machine will vibrate.
What are vibrations in the first place ? Every body has its own natural vibrations and when the machine parts move, forced vibrations are induced in the parts. These are what we feel from the machines. This is the case with smaller and simpler machines.
In our IC-engines, the number of moving parts is very large and most face alternating vibrations/ forces. For a perfect (i.e. Vibration free operation) all the forces acting on the parts have to be balanced (i.e. There should be no residual forces). The engineering design of each and every part plays an important role in this. The allowances should be extremely low (i.e. The precision of the dimensions should be very high). With high percision parts, the vibrations present in the machine would be low.

Also, you might have heard about the balancer shaft or something like that in technical specs of cars/bikes. What are these ? They are used to balance out the unwanted or unbalanced vibrations and give a smooth operation.
One important thing, there can be no machine which has zero vibration. What we can do is minimize the amount of vibrations, but we can never stop them fully. We can also try to damp the vibrations before reaching the user, but they will always be there.

It may not be much, but i tried [MENTION=32286]psr[/MENTION] sir.. Is there anything wrong with what I have written ? Would love to correct my info if I am wrong.

Re: INFO: A Guide On Technical Jargons

Wow! This thread is really very useful and imformative for a newbie like me...


Bike Riding > Meditation...

Re: INFO: A Guide On Technical Jargons

When people say that vibrations are natural to RTR, they're right. That's because the engine is meant for high revving and has no rev limiter either.
Also, an important part seen in most modern bikes is the (engine) balancer. RTR has no balancer. Hence, the residual forces within the engine aren't nullified and transferred to the frame of the bike. More so, the engine isn't mounted on rubber bolts and grommets.

This is what I feel is the main cause of RTRs feeling vibey!

Re: INFO: A Guide On Technical Jargons

Excellent explanations right there!!

To add, may I suggest resonance?? Maybe the engine vibrations of the RTR have just the right frequency to cause the handlebars to resonate? Thats probably the reason the vibrations are large enough to be actually felt. I dont have an RTR and I cant opine specifically, but this does seem plausible. Maybe the whole bike frame doesn't resonate (that would probably be disastrous!), but certain components like the handlebars or footpegs do. Most bikes have weights on the ends of the handlebars to prevent the vibrations.

Re: INFO: A Guide On Technical Jargons

Regarding suspension , the harder the setup the less the chance the tire has of bouncing on the Tarmac and hence more the grip...When ever a wheel goes over a raised part of road, the wheel is pushed upwards , and the wheel depending on the rise rate and damping setting ,goes higher and rise above the road level..The speed, the suspension setup, weight of vehicle , and the bump in the road ,all contribute to this . When the wheel clear the surface , there is no further upward push from surface, and it starts to come down to make contact with the road again..
There is a time gap when the wheel leaves contact with surface and the time it lands back , when there is NO TRACTION or CONTROL over that wheel...If the suspension is setup stiff then the time gap becomes less or is totally eliminated..ie., the wheel is always in contact with the road ,giving better grip and control.The down side of such a stiff suspension will be a very hard ride...The F1 cars have very stiff suspension and each manufacturer has his own way of doing it.....
Here is RED BULL team F1 car suspension..

This is with common spring in the middle with individual dampers for left and right suspension

here is another type, with individual springs with damper..



here is a simple diagram to explain the F1 suspension...In Actual real time application the suspension are more complicated with different arrangement depending on the driver and the TRACK.