Arrey Sir I am there on the forum everyday, I just dont post very frequently

As the p220 carb version is launched and it is said to be fastest than the previous one i.e Fi and in India too
I want to know that if Fi is the latest technology then why they have made the carb version faster ?
Does the carb thingy overcomes Fi in terms of speed??

@^^^^ The 220 was turned in a carb from a Fi one to save cost so sales increase . the extracted more power out of the engine as they plonked a large 32 mm carb [Zma has a 29mm one ] and also reworked engine and gearing a bit .
but a good Fi system with a good ecu mapping will always be more efficient than a carb and provide more power .

Bajaj choose Carb as price in the end is what matters in India .

but im sure bajaj will get a Fi bike with price around 1 -1.5lakhs rs in future

I would like to add to this info. We know a softer suspension dives more compared to a stiffer suspension. Why exactly is this dive not wanted? After all it looks cool to watch a bike rebound from the suspension after a hard stop!

Brake dive to a certain extent is beneficial. When the front end dives, weight transfers to the front which increases grip at the front. If there is no front end dive (panic braking where suspension does not get time to load up or using too stiffer spring) the tyre skids. Also brake diving reduces overall wheelbase and makes the motorcycle turn quicker (trail braking with the front brake).

Now, what happens when there is too much dive? The suspension bottoms out. A sudden force can now easily get applied on the tyre, now that there is no cushioning effect. Result is a skid if the rider is careless with the brake! Also, too drastic change in the wheelbase can catch the rider unaware and make the bike oversteer suddenly in the middle of the corner. Also too much oversteer tendency means that the bike will feel twitchy on that long curve and the rider will need to hold the handle tightly! Thus the bike feels as if it wants to fall in the corner. Rider is stressed while cornering.

So, we do need dive. But too much of it is bad, as it can be dangerous for a novice rider! And stiffer spring is more forgiving on the rider.

Stiffer springs (in general and not wrt brake dive) also provide more feedback and helps prevent sudden unwanted weight transfer due to bumps etc. This is the only benificial part.

So, we choose a balance between the two.

Cheers on that one, Mr OF! But actually, I had mentioned the straw and the wooden stick to point out the 'feedback' from those setups. I didn't actually mean the straw to be softer spring setup and the wooden stick to be the stiffer springs!!


I am not sure on this one, sir. Actually, I meant the R15 has a Linked type suspension which means that it has a link between the swing-arm and the rear suspension. The link acts like a lever for various loads. The lesser the load the higher the lever ratio, and softer the suspension becomes and the whole dampening system is soft. But greater the load, the lesser the lever ratio, and harder the suspension becomes, therefore hardening the dampening system. I don't think this is pre-load as this is more linear whereas pre-load is more incremental. I might be wrong though.


@abhijeet: I have to disagree on your point where you say the 'diving' of a suspension reduces the overall wheelbase. Why would the wheelbase decrease due to suspension travel? As you know the wheelbase is the distance between the centers of the front and rear wheels. If you are talking in the sense that the compression of the springs results in the retarding movement of the front wheel closer to the center of the bike, then this phenonmenon happens in each bike temporarily each time brake is applied and should not be regarded as change in wheelbase.

Also, if your theory of more suspension travel resulting in better brake feel is correct, then how can you justify a bike with a softer front setup (whose suspension travels more) skidding easily when you apply sudden brakes. See, just take an example of motorcross bikes and a supersports. For both these bikes, the front rake (the angle made by the shocks/forks with the vertical line) is almost the same. The motocross has far more suspension travel than a supersports. But even so, a supersports will brake far more efficiently than a motocross. Ask any stunter, it is much harder to pull of a stoppie in a motocross than a supersports. Why? Because the suspension travel will make the bike drive and induced load come upon the tires suddenly, not giving them enough time to grip, making them loose traction easily. Whereas, the supersports suspension being stiffer, will not travel as much, and the induced load will not come upon the tires suddenly, giving them time to grip. As mentioned by OF earlier.

I agree with the last part though where you say that the suspension needs to be a compromise between the two.

Diving does reduce the wheelbase. This "temporary" phenomenon helps a bike to turn in quicker in corners and at a higher speed. As we know a shorter wheelbase results in a flickable bike. This particular technique is called trail braking. Also, we do not need to apply full brake to observe this. Lightly loading the front is enough.

A motocross bike may not stoppie, but it does stop as fast. It can not stoppie as the cushioning effect due to the suspension prevents the rear from rising up. So, in fact it will skid less compared to a sportsbike. I did not say brake FEEL, I said it results in better braking. If you do not agree with me on this point, please explain why stiffer suspension will result in better braking.

Firstly, it is no "google" gyan.
Secondly, My main point was that high speeds cause wobbles anyways (obviously). A long swingarm however ensures the least disturbance to the rest of Chassis. This was my point. Anyways ... I guess I need to work on my explanation.

and this situation "Short wheelbase & long swingarm" results in a best of both worlds situation, accd. to Bike UK. Of course, other factors impact too.

Ok, I have one question to ask. Take a cycle without any suspension, and one with a front suspension.

Now if I brake hard, which one will stoppie easily? The one without any suspension. (No cushioning effect)

If I slam the brake hard, which one will skid? Again the one without any suspension. (No cushioning effect and no weight transfer)

Agree with me? That was what I meant.

Stiffer suspension ONLY will not result in better braking. There is alot more to this, as far as I can see. The front rake is a factor, the tire compound is a factor, the weight of the bike, the CG of the bike, the rider himself, in fact we are missing the main thing, the brakes themselves that factor into how to brake better.

The phenomenon you and I are talking about has nothing to do with bike geometry. Its not because of the dive due to softer springs that makes the bike turn quicker. Its because as you brake before a turn, trail braking as we call it, the weight of the bike is transferred to the front tyre gradually and therefore a greater grip is achieved while turning, and slowly the riders taper off the brakes to carry better speeds throughout the turn. First of all, this is a motorcycle riding technique used in long sweeping corners. This technique is not commonly used in tight corners as you are suggesting. Also, the decrease in wheelbase as you say it is not the reason for the bike to turn easily. The steering geometry of the bike changes.

See bro. Let's not get worked up here. I don't have to agree to you, and you don't have to agree to me. At the end of the day, we all are trying to better our biking knowledge through this thread. As far your above example goes, it is not that simple, in my humble opinion. You cannot compare stiff suspension with no suspension. But this will go on. Happy riding! I hope OF clears this out.

I had considered all such factors to be same.

My friend, if the bike suspension is stiff as a brick, will weight transfer occur? No. Weight transfer occurs only if the front end dips down compared to its original position. So, suspensions needs to be soft to cause weight transfer. Of course too much weight transfer due to very soft suspension will result in oversteer as the rear end looses grip.

And it is used in tight corners as well. Nothing to suggest that it can be used in long curves only. The steering geometry change you are talking about is this wheelbase change only - more specifically the trail of the bike changes. (Hence the name trail braking).

Edit - No, I am not at all worked up. Just wanted to know why you see it that way. After all discussions lead to gain in knowledge. It is an interesting aspect of motorcycling. My aim was just to say that stiffer suspensions is not the holy gail in handling as it is made out to be. Too stiff suspensions can have detrimental effects too.

Anyways, want to hear what OF has to say regarding this.

wosh.........and I thought I knew every aspect of braking, biking, wheelbase , electricals etc. But my mates have made me think otherwise.

My humble request to all who are reading this and who all are/will be posting in the thread.... lets not let our egos clash, lets make this a platform to discuss and learn. ( am trying to potray myself as Future Mod of xBhp, right now am happy being a Mood (Iri) tator.)

as for the braking wrt to suspension...my point of view is a lot of things work for a common goal. why would a particular bike do a stoppie and why some other wont(easily) we can not just talk about the Brake Dia and the suspension only. it has a lot to do with the rake, with the travel, definitely the tyres, the weight/ CG of the vehicle too.

Old fox... It seems we are waiting for you to say the last word

OT:

I totally agree with you on this one. But if you were referring to me and abhijeet's posts as egos clashing, then let me just clarify that it was a mature discussion with good spirit in the interest of biking and nothing else.

And with all due respect to OF and other highly knowledgeable people in xBhp, I think discussions from less knowledgeable members with differing point of views should be encouraged because if you can substantiate your views like both of us did, it relates to more thought process required while doing your research about bikes.

I am sure most of us will agree on this fact which applies to all: 'Learning never stops'.

Sorry for the long OT, let's back to the discussion.!

So far so good Abhijeet with just a couple of exceptions. It is true that we need 'some' dive to allow for 'cushioned' or 'graded' weight transfer onto the front contact patch. And that too stiff a front would be almost akin to a bottomed spring. This was actually the reason for the decline of the once favored 'anti-dive' systems (the Honda TRAC and the Kawasaki AVDS). Too stiff a springing would make the wheel chatter and skitter over small bumps.

It is also true that there is a certain reduction in the wheelbase which increases instability which in turn contributes to some extent in making the bike easier to turn in (more 'flickable). But the major contributor here is the reduction in the bike's 'trail'. See fig below:



The front suspension compression under braking reduces trail (the steering head drops lower and the contact patch spreads rearwards) and this reduction in trail leads to quicker direction changes.

So in conclusion, we tread the middle path by 'tailoring' some amount of dive into the front suspension to get the best of braking without compromising on comfort and inducing too much instability.



Pranay: I'd thought you were asking about the 'pre-load' thing.

As for what you've stated above, the 'link and lever' suspension has links and levers just to multiply the available suspension travel. A shocker/damper compresses just about a couple of inches before bottoming out. To get 4 inches of wheel travel with the same shocker unit requires the use of some sort of linkages and levers. The 'progressiveness' of the suspension comes from what are called 'variable rate' springs. The spring coils, visually speaking, are far apart towards the top of the spring and get closer together towards the bottom of the unit. The top coils get compressed easily under light loads while the bottom coils deflect less and need higher loads to compress. So, on the whole, the coil spring acts like a 'soft' spring under light loads and as a 'stiff' spring under heavy load. More expensive units also provide variable damping but then that would be another story.

There seems to be some mis-conception about 'trail braking' here. I'll start with a diagram that I've taken from a book 'Sport Riding Techniques' by Nick Ienatsch.



The orthodox riding technique staees that we finish all our braking and gear shifting while the bike is upright, enter the turn on constant throttle and just past the apex, feed in the throttle progressively. But the preferred method now is using 'trail braking'. Trail Braking is a technique where the rider progressively reduces his braking force as he gets deeper into the turn and closer to the apex. This progressive and smooth reduction in braking is to use a progressively larger share of traction for turning, a need that hits its maximum at the apex, where the braking input is reduced to zero. Trail braking has two major benefits: 1. It allows for braking while turning, allowing the rider more control over his situation. and 2. The rider can carry speed deeper into the turn and by slowing progressively towards the apex, has more reserve traction to trade for the same needed for turning.

Post-apex, progressively openng the throttle makes for gradual rearward weight transfer allowing the rear tyre time to gain traction and transfer power for acceleration.

In practice, the overlap between trail braking and powering out is a smooth blend, always balancing the available traction to the traction needs.




Ref to the bold part: weight transfer 'causes' front end dive. Weight transfer is NOT the result of front end dive. Again a fig below:



Weight transfer WILL occur even with no suspension springing at all, ex. the bicycle. The bicycle skids (on loose surface) or does a stoppie(on tarmac) because with no suspension to 'gradually' load up the front tyre, a sudden load forces it to stop. If the tyre grips, the whole bicycle rotates around the front contact patch that acts as a pivot. If the tyre does not grip (i.e. the coeficient of friction between the tyre and road is small), the it locks up and skids.

And abhijeet, hope I've managed to clear the air about the 'trail braking' part. And yes, trails braking is a useful skill, whatever the turn is like.

An incessant curiosity for things not known is anytime welcome at my end.

Ride long and safe...

OF

wow!!!

This thread is getting better & better.....its clearing lots of doubts for people like me....

OF, your explanation to things.....i'm awestruck....thanks a lot for the Gyan!!

Thanks a lot to all contributing here, I am sure it will help lot of us in xbhp...