ZX10R vs CBR1000RR - similar designs? mass centralization? handling?

Since I own a 2008 CBR1000RR, I read Sport Rider's review of the new ZX10R with interest and it occurred to me that the ZX might be quite similar to the CBR but with next gen chassis and engine electronics.  Below are the basic specs, copied from Sport Rider's test pages here and from elsewhere.  

I had suspected, incorrectly, that the two might share similar chassis specs.  It turns out that the Honda's chassis, by the numbers, is "quicker" in terms of wheelbase and rake and trail.


2011 Kawasaki ZX-10R
998cc, 76 x 55
Rake/trail: 25.0*/4.33 in.
Wheelbase: 56.1 in.
Claimed wet weight: 436.6 lb.
Seat height: 32.0 in.


Honda 2008 CBR1000RR
999cc, 76 x 55.1
Rake/Trail: 23.3*/3.8 in  
Wheelbase: 55.4 inches
Claimed Wet Weight 440 lbs
Seat Height: 32.3 inches


These specs don't tell the whole story, of course.

So, I'm curious, how do the two compare, in terms of handling?  Does the ZX share the Honda's "mass centralization" theory of chassis design?  

The Kawasaki does share much of the same mass centralization philosophy, but the problem with using specs to try and make a correlation of actual handling characteristics is that weight variations-- where the weight is placed-- will be different (never mind the major difference in rake/trail and wheelbase). Without riding them back-to-back, it would be difficult to make a real comparison.

But all that said, just from memory, I'd say the Honda is still the quickest/easiest to make a steering input, and is probably a little more agile...correlating with its steeper rake, shorter trail and wheelbase.  

I was looking at pics of the 2011 ZX10R I like the dash set up and the adjustable pegs are great. I have been riding the mass centralized bikes for 4 years now first an XB 12 SS Buell then the CR though the bikes are worlds apart from a race bike the mass centralizatin thing is great for steering inputs all of the Buells are a hoot to ride!!!! So put that into the animalistic power plant of a liter Bike WOW I wish I was 20 years younger and 50lbs lighter is all I'll say about that!!!!  

I've been riding the Norton lately.  It weighs about the same as the CBR yet, having a lower center of gravity, it feels much lighter, especially when walking it around or making slow turns in a parking lot, for example.  The Honda is very top heavy by comparison.  That's an almost static comparison; at higher speeds the Honda feels lighter, turns quicker, even with those far wider wheels and tires.

I have much to learn about this subject, the dynamics of weight distribution, chassis geometry, steering, pitch, roll, yaw and all of that.  Maybe I've missed past articles on the topic?  

Here is an Art & Science from a few years ago about moment of inertia and mass centralization. Unfortunately none of the pictures are online.

http://www.sportrider.com/dyno/146_0104_inertia/index.html

This is an interesting topic. When I was at Kawasaki for a briefing on the ZX-10R,  they said that a lot of the reasoning behind a low (or, lets say, not too high) center of gravity was that it makes the bike more difficult to high-side in a corner. Knowing the new ZX-10R was going to have traction control operating as a default, they could make the bike with a higher center of gravity as they wouldn't have that problem.

AT  

Thank you AT, in that article, you wrote -

'In a simplified analysis, the motorcycle rotates about the tires' contact patches, so it would make sense to centralize as much mass as possible close to that axis (low to the ground) . . . . .

. . . . but consider for a moment that the front wheel is steered from under the motorcycle-in the opposite direction of the corner-entering a turn. This would mean that the axis of rotation (the roll axis) lies above the ground and closer to the bike's center of gravity (CoG) during at least a portion of the turn. But having the CoG too low affects a bike's behavior in the middle of a corner, once the bike is leaned in. Honda's 1984 NSR500, with its fuel tank underneath the engine and pipes over top, is an extreme example of lowering the CoG-and Honda reverted to a more conventional layout the following year."

I get the part about it "make[s] sense to centralize as much mass as possible close to that axis (low to the ground)" but it gets foggy for me in your next paragraph.

I can see it if I think of it as a teeter totter, with a dynamic moving fulcrum (roll axis), where one end or the teeter totter is the tire/road contact patch and the other end is the center of gravity  of the motorcycle.  Is that wrong?

Another curiosity, as we increase lean angle, the line of force down through the motorcycle to the contact patch shifts from the center line of the bike to turning side of center.  That is the contact moves from center and toward the direction of lean.  When we hang off, it seems that we moving that line of force back to the center, the lines of force are drawing a triangle?  

The general thinking 30 years ago (or so) was that the bike rotates around the where the tires meet the pavement, so lower weight is better. That's when Honda made the NSR500 "upside down" and found that's not the case. Your analogy with the teeter totter is one way of looking at it - that would mean the bike rotates around a point somewhere in between the tire/pavement and center of gravity. Some people think that the bike rotates around the center of gravity itself. When Honda introduced the '05 CBR600RR I talked to the project leader about where the bike rotates, he said center of gravity.

The force vector that is the sum of weight (gravity) and lateral acceleration (or centrifugal force, if you prefer to look at it that way) should sum to something lining up with the combined bike/rider center of gravity and the tires' contact patch. Otherwise the bike would lean more or less to make that happen. And yes, that should look like a triangle.


AT  

AT, thank you for another thoughtful response.

Bear with me on this -

Maybe this is similar to a car stuck in the mud, you get a 4x4 as a lever and you get a rock as a fulcrum and you stick the short end of the lever under the car but . . . . the rock sinks in the mud  . . .  the fulcrum moves.

So, to continue with our motorcycle as teeter-totter analogy, the fulcrum is the center of gravity, and it is not fixed; it is dynamic, it moves in some proportion with, and according to, the rider's weight shifts and inputs.  Hanging off, lowers the CG, lowers that fulcrum, but it also moves it away from the center line and to the inside, the side that the rider is hanging off.  Peg weighting also moves the CG, that fulcrum, toward the side that is being weighted.  Interestingly, weighting the outside moves the CG/fulcrum toward, and maybe even across the centerline, to the outside.  Our contact points with the bike, the pegs and the handlebars and the sides of the gas tank and the seat are all variously and dynamically the rider's end of the teeter totter, levered against the CG/fulcrum, and thereby against the contact patch.

Maybe that's wrong.  Maybe we actually move the contact patch a lot.  Think of how we can flick a 600 pound package so quickly.  Maybe it's best to think of that CG/fulcrum as mainly fixed (laterally) and a solid point against which we really move the contact patch, a bunch, to steer the bike.  

Do we hold the long end of the lever?  I guess so, that's what a high side is about, the short end (the contact patch), taking control.  

I know that a motorcycle does rotate or pivot at the CG, because when I had a Honda MB5 (50cc two-stroke sold in '81-'83), you could flick the bike so aggressively into a turn by countersteering the handlebars that the front tire (not sure about the rear) would momentarily lift off the ground before setting the contact patch back down to the outside of where it was before you initiated the turn when the bike begins to corner.  

A couple of things to think about:

Depending on how you sit on and steer the bike, you are making the lever different, but your only option to change the contact patch is to lean the bike over more or less. I think for the most part the bike rotates around the CG, but at times - like a highside, as you say - it can rotate around somewhere closer to the contact patches.

How you sit on the bike can definitely move the CG around. If you sit up straight, the CG is higher and can make the bike easier to turn, but you've also de-centralized a lot of mass, which can make the bike harder to turn. Which has more effect can depend a lot on the bike and rider.

Pushing on the pegs or tank won't change the CG, but it definitely changes how your weight interacts with the bike. Consider that the engine mounting points don't matter when it comes to its contribution to CG, but their position can really change how the engine contributes stiffness to the chassis.

AT  

Yes Kento, I saw Rossi crash doing that - on the entry to turn 2 at Indianapolis in 2009; turn 1 is a left and turn 2 is a close following right; it appeared that when he picked the picked the bike up from turning left to flick it onto the right side, the suspension unloaded, daylight under the front wheel, it came off the ground.  He flicked the bike right onto the ground, onto its right side.

That makes me realize realize that suspension action also moves the location of that CG/fulcrum relative to the contact patch; that leg of the AT's triangle changes length, dynamically, as the suspension shortens or lengthens.  

AT, don't you think that the CG/fulcrum is dynamic?  That is, would you agree that as the rider moves her mass around, forward/rearward, side to side, high to low, peg weight right or left, that the CG/fulcrum moves too?  Or, in so moving are we just adjusting the length of, and pounds of pressure applied at, our end of the lever?  

xbacksideslider:
AT, don't you think that the CG/fulcrum is dynamic?  That is, would you agree that as the rider moves her mass around, forward/rearward, side to side, high to low, peg weight right or left, that the CG/fulcrum moves too?  Or, in so moving are we just adjusting the length of, and pounds of pressure applied at, our end of the lever?

Yes, the CG definitely moves around, but I think we're starting about two different things here. Where you sit and your position helps determine the CG. Where you grab onto the handlebar and where you put your feet on the pegs can change how much leverage you have over the bike.

When you push on the pegs or the tank, or try and put more weight on one side or the other, the CG does not change - your actual body has to change position for that to happen. Back to the engine analogy: It doesn't matter where the mounts are, the CG is where it is.

AT  

xbacksideslider:
Yes Kento, I saw Rossi crash doing that - on the entry to turn 2 at Indianapolis in 2009; turn 1 is a left and turn 2 is a close following right; it appeared that when he picked the picked the bike up from turning left to flick it onto the right side, the suspension unloaded, daylight under the front wheel, it came off the ground.  He flicked the bike right onto the ground, onto its right side.


It might've appeared that way if you were there watching in person, but actually, Rossi's Indy 2009 crash was due to his getting into Turn 2 too hot trying to get back past Lorenzo. He got off line by a just a bit, and apparently the grip is very poor off the racing line (all the riders were complaining about it that year-- and still complain about it). As he tried to turn it in on the brakes, the front end tucked. They showed a bunch of replays on it during the MotoGP live feed (not Speed). What you might have seen was his front tire hitting one of the bumps just before it let go.  

Thanks guys, I feel like I'm stealing your valuable time . . . .

Kento, without benefit of seeing the live feed replays, I defer.

AT, I can't get my head around the idea that the CG does not move lower when I move my weight from the seat to the pegs.  I get the idea that the path of my weight to the ground is defined by the chassis but my head rebels at the idea the point of input of my weight, seat vs pegs, has no import on chassis dynamics by way of a movement of the CG.