The new 16" front wheel

The overall outside diameter will be the same but with tire profile that gives a larger contact patch while lent over, the bike is easier to turn because the actual wheel rim is 0.5 inches smaller and is therefore lighter.

<div class='quotetop'>QUOTE (Tom @ Mar 22 2007, 04:56 AM) <{POST_SNAPBACK}><div class='quotemain'>The overall outside diameter will be the same but with tire profile that gives a larger contact patch while lent over, the bike is easier to turn because the actual wheel rim is 0.5 inches smaller and is therefore lighter.
Ya, the wheel will be lighter, but the tires weight will be more? So, the whole wheel and tire package will weigh about the same as before. I think it's all for the larger contact patch as you have mentioned.

Remember last year, when some riders had a wide front wheel? Or maybe it was the tire. I wonder if they will still play around with this?

I understood that the whole point of the smaller rim was to reduce the gyroscopic effect to assist turning - and that the increased grip and the resulting 'front end ch-ch-ch-ch-chatter' was merely a by-product of this ?

The whole point of the 16" front is to help guys get more front grip/feel on corner entry and hold more speed mid turn. The outer circumference of the tyre, the part that is in contact with the road when the bike is completely upright is the same as before. Because the rim is smaller the circumference around the 'shoulder' or edge of the tyre is less thus allowing for a bigger contact patch when fully lent over.

How the tyres, front or rear, affect the rate of turn of the bike depends more on the profile. A rounder profile will be lazier to turn in whilst a pointier profile will turn much faster, like the bike almost wants to just fall onto it's side. The trade off is, if you've got a tyre that allows you to change direction real quick, you sacrifice stability, especially in fast turns, same as messing around with chassis settings. The difference a 0.5" smaller rim will make to gyroscopic forces of the wheel spinning, affecting how the bike turns, is negligible compared to the difference made by playing around with different tyre profiles and constructions.

Michelin experimented a lot with front tyres last year. It was the wider front tyre that really made the Yamaha chatter big time, the extra grip on corner entry being the main culprit, that's why Rossi and eventually Edwards went back to the more traditional narrower profile, why they still had chatter problems for a few races after that remains a mystery. It took the 2005 chassis to come out of retirement to fix it in the end.

Interesting read Babel, thanks.

Skidmark, are you an engineer?

<div class='quotetop'>QUOTE (Babelfish @ Mar 23 2007, 12:05 AM) <{POST_SNAPBACK}><div class='quotemain'>I wonder how much higher if at all the tire walls are. I haven't been studying close up lately but remember from the 17" days that the clearance from rim to aspahlt was only a few millimetre. That doesn't give much room for flexing in the vertical direction.I'm not sure what you're asking here fish.

<div class='quotetop'>QUOTE (Babelfish @ Mar 23 2007, 12:05 AM) <{POST_SNAPBACK}><div class='quotemain'>To me it seems like the "added feel" in the entry of turns might just as well be the added suspension higher side walls can give while hard on the brakes and allready leaned over.

Close to maximum compression and with an angle that make the suspension ineffective an added suspension in the tire could make a difference, I think.

On the first part, any tyre will flex a certain amount. It's not an active part of the suspension but it does have an effect. To put it simply there are a few principles about tyre construction. A stiff carcass won't flex easily which means it transfers more energy to the susension and won't overheat as readily which in many cases is the way you want a tyre to behave. The stiffer you make the tyre, the heavier it has to be. Make it too light and the tyre will absorb more energy itself, flex way too much and heat up. Ever ride a bike on a soft tyre? It gets really hot, same idea.
On the second part, I take it you mean when a bike is at max lean. If your suspension is ineffective at this point you will fall off.

<div class='quotetop'>QUOTE (Racejumkie @ Mar 22 2007, 10:54 PM) <{POST_SNAPBACK}><div class='quotemain'>Skidmark, are you an engineer?Just nerdy about the tech stuff jumkie

<div class='quotetop'>QUOTE (Babelfish @ Mar 23 2007, 12:34 PM) <{POST_SNAPBACK}><div class='quotemain'>Not really. The suspension is inneffective at maximum lean angle.Fish, you used to race didn't you? Well if you did I'm going to assume you weren't fully awake when you typed this. If not I'd really like you to explain that one.

<div class='quotetop'>QUOTE (Babelfish @ Mar 23 2007, 12:34 PM) <{POST_SNAPBACK}><div class='quotemain'>As mentioned above, with the 17" there are only a few mm from rim to asphalt at maximum lean angle. That leave very llittle room for flexing as the tire has more or less allready maxed out it's flex. With a smaller rim they may have some more distance and thereby some more room for the tire to flex. It doesn't need to be softer, it just get more room to do it's job. Or maybe the smaller rim just compensate for more lean angle and leave the distance at the same despite more lean.Ok I know now what you mean, and you can bet Michelin and Bridgestone look at every possible option in terms of tyre behaviour. But I believe the problem you percieve of ineffective suspension mid turn couldn't possibly exist.

<div class='quotetop'>QUOTE (Babelfish @ Mar 23 2007, 02:18 PM) <{POST_SNAPBACK}><div class='quotemain'>But of cource it does. I'm not saying it doesn't work, it just doesn't work by far as good as it does when the bike is straight or as good as it could if someone could find a contruction that work with the same vertical stroke regardless of lean angle, without adding weight and still suspending the horisontal forces in a turn. There has been all kind of experiments to improve suspension in corners including spring/damper on the axel bolt's and stuff like that, but they all fail in some way or the other. So, insted of altering the basic disign the producers try to decrease the friction among other things.
Any way, i think the most critical part is the entry, on the brakes and leaned over. Thats where the suspension it is very close to max at the same time as the feel for the front is essential.Fair enough, but you've evaded my first point and changed your opinion, if I am to be totally honest. In fact the only time the suspension on a bike does nothing at all is flat out on a straight.


Back on topic, the 16" tyre subject. There must be endless possibilities in terms of different tyre constructions and subsequent handling properties though the development of tyre construction to that Nth degree may be pointless. Teams are only allowed 31 tyres at a race weekend under the new regs so they want tyres to be good accross a broader band of conditions so a more 'standard' tyre config might be what a team/rider would look for and make finer adjustments with the chassis. Who knows.

I got no "info, but I do have an opinion.

I think they are going for higher aspect ratios to reduces the chances of chatter. Tires with higher aspect rations have more flex and can be profiled for a bigger contact patch. Given that tires and chassis are developed seperately, one cannot predit when chatter will occur, unless the bike is on the track. Given that the 800cc willl be leaning farther than the 990ccs, it only increases the chances of chatter (due to reduced suspension effectiveness at those greater lean angles) . Also, the

I watched the movies, The doctor, Kentucky Kid... And while the movie wa ok, the interviews in the Special Features section with Michelin and Bridgestone were eye opening. did you know that Michelin brings 1,000 tires to each race? they did talk about chatter and stuff too.

<div class='quotetop'>QUOTE (skidmark @ Mar 23 2007, 01:28 PM) <{POST_SNAPBACK}><div class='quotemain'>Fish, you used to race didn't you? Well if you did I'm going to assume you weren't fully awake when you typed this. If not I'd really like you to explain that one.That was my first point, in response to...
<div class='quotetop'>QUOTE <div class='quotemain'>Not really. The suspension is inneffective at maximum lean angle. You need a vertical force and dampning to absorb bumps but have a suspension where only 30% of the movment are vertical because of the lean.I'd really like to hear your take on this.



<div class='quotetop'>QUOTE <div class='quotemain'>No i didn't. Just because you thought "ineffective" ment "not working" doesn't mean that I wrote it. And I think I know enough english and logic to be on safe ground there.Ok my mistake, let's take the "not working at all" part out of the equation. I still disagree on the ineffective part. Having the suspension front and rear behaving just right mid turn is what lets you carry speed, it takes quite some time to understand how to get it right. Jesus, I'm not interested in getting into a row with you over it, but I am challenging your view, that's why I'm here.


<div class='quotetop'>QUOTE <div class='quotemain'>I didn't get your point there.See that's just silly.

<div class='quotetop'>QUOTE <div class='quotemain'>At close to 60degrees lean angle the properies of the fork has dramatically changed with regard to any vertical forces compared to straight up. That’s not entirely correct. The fork does the same thing at 60 degress as it does at 20 degress or any degrees, it’s properties cannot be changed. The fork can only travel on one axis, the only thing that ever changes is the forces acting upon it. The lesser of these forces being the vertical. The force exerted on the damping in a fork/shock to control the stored energy in the shock/fork spring(s) mid turn on a racing bike is far greater than any force on the vertical axis which is always 1g.



<div class='quotetop'>QUOTE <div class='quotemain'>The first rule of a fork is that it should never bottom out. Springs are adjusted to just avoid bottoming out at the toughest braking at the track. So the first rule is…. but the most important parameter is… These two points sort of go against each other, two different adjustments, different properties. Help me out there.<div class='quotetop'>QUOTE <div class='quotemain'>In other words, the most important parameter are calibrated based on straight up, or close to straight up function.Do you mean when the bike is static?
But yeah I think Roberts Snr and kel Carruthers started playing around with two or three different springs in the same fork in the mid seventies designed to leave just that little bit of travel before bottoming out under heavy braking, just in case the bike came across a bump on the way into a turn.




<div class='quotetop'>QUOTE <div class='quotemain'>Then to what happens at high lean angle:
1. To completly soak up a 1 cm bump the fork must move aprocimatly 66% longer = 1.66cm.
2. Because of the lean angle a vertical force are only working with 33% effekt on the spring, and the spring apear 66% harder ( at the same time as it should move 66 longer.
3. The fork is allready loaded due to g-forces. This is similar to soak up bumps under hard braking, a tough job to begin with, even harder because of two points above.Fish I gotta call you on this. Where are you getting your info? You’re assuming a lot of simple physiscs ( action and reaction ) applies which is true up to a certain point. But there’s much more to it than that. You’re not taking the damping in the fork and the amount of energy that can absorb into account at all, and that‘s a pretty damn important factor, how do you account for that? A fork must move 1.66cm?



<div class='quotetop'>QUOTE <div class='quotemain'>4. In addition the forces also has to fight stiction due to higher friction between outer and inner leg. The fork are still holding the full weight of the front, but now the weight (and movments) are also pushing on the seals and bushings bending the complete leg. I don't know to witch degree the last point is an issue as modern materials dramatically reduse the friction, but at the same time the lean angles are larger and forces higher.Totally negligible compared with the factors we're talking about and worth 0.000001s a lap. Slippery forks and trick suspension materials are about about consistancy and predictability of performance as components heat up. Ever feel the shock on a race bike just after the bike's come in, it get's hot.


Dude, in my view, there are some serious flaws in your points and I mean that with no offence or patronising intended. You said you were involved in roadracing, well talk to me brother! I love debating tech stuff, much as I might bore some people to death around here and I'm not always right. Just I gotta pull you on some stuff cos I don't get it.