[jw130270]

After sitting on a 1987 CBR600 and a new modern day 2009 CBR600, why does the old bike seem to have a lower center of balance? The old CBR is technically heavier than the new model....

I'm a noob... but is a higher center of balance actually better for cornering? I don't think so, but I might be wrong... :bitchslap


thanks in advance everyone!!

 

[Nero Diablo]

The older bike will sit a lot lower to the ground, modern sports bikes are "jacked up" to improve conering clearance the older bike will also have more wieght on its rear wheel and not as much on its front. Improves drive but doesn't help tracking the older bike will be much longer as well. In 1987 there was no such thing as 600 super sport racing 600 wasn't a race class at all so the 600's of the time were simply smaller versions of the sport tourers so the geometry and setup will be more oriented towards that. If you wanted a race rep you bought a 750 or a 500 smoker. A slightly higher centre of gravitiy will help tip but not stablity in but like most things on a bike it will be a compromise.

 

[jw130270]

I see.

thanks for the advice! :beer

 

[04zx6r]

I actually owned a 88CBR 600 Hurricane for my first bike. Didn't feel heavy or slow to turn as I owned it, but when I bought by '04 ZX6R a couple years later, holy crap what a difference!

Now as to why, dunno, bike engineers are smarter than I, all I know is that the bike with 16 years newer technology works better. Imagine that

 

[benroe]

Modern bikes are much more radical in terms of steering geometry, and you sit on rather than in the new bikes as well. Having said that, I would love to run up on a used fzr1k from the 89 breed in good shape!!

 

[baldheadeddork]

The older bike will sit a lot lower to the ground, modern sports bikes are "jacked up" to improve conering clearance the older bike will also have more wieght on its rear wheel and not as much on its front. Improves drive but doesn't help tracking the older bike will be much longer as well. In 1987 there was no such thing as 600 super sport racing 600 wasn't a race class at all so the 600's of the time were simply smaller versions of the sport tourers so the geometry and setup will be more oriented towards that. If you wanted a race rep you bought a 750 or a 500 smoker. A slightly higher centre of gravitiy will help tip but not stablity in but like most things on a bike it will be a compromise.

There actually isn't a notable difference between the ground clearance on the two bikes. Look at these two pictures and you'll see what I mean.

Both bikes have seventeen inch wheels and the bottom of the bodywork hits almost the same point, which means the ground clearance is very similar between the two.

Also, the key to increasing cornering clearance regarding the engine is to make the bike narrower at the crankshaft. Think about it. But this hasn't been a practical concern for a long time. The limit on cornering clearance for the last 20 years has been the foot peg assemblies, and that is constrained by ergonomic requirements. I've been in this for almost 30 years and I can't remember a sportbike in the liquid cooled era that would deck the case in cornering.

And there definitely was 600 supersport racing in the late 80's in AMA/CCS and WERA, and it was very big. The CBR600 wasn't developed from a sport-touring bike. The way it looked was just the best way the factories knew how to make a 600 sportbike at the time. The 500GP bikes of that era had the same kind of bulbous styling as the CBR.



About the question from the OP: That's a good question because on paper the new CBR looks like maybe it should have a lower cg. The first-gen CBR had a steel frame that weighed a lot more than the aluminum frame on the new bike. The new engine has the cases cast together with the cylinder block, and the head is quite a bit smaller and it weighs less than the head on the old bike. Also, look at the suspension, tires and wheels. The new bike has much wider wheels, larger diameter brake rotors, heavier calipers, inverted forks with larger diameter tubes, which have a lower center of mass than the old style of forks. The new CBR is clearly lighter at the top of the bike, but most of the stuff on the bottom is much larger and probably not much lighter overall, if at all. The new CBR does have the undertail exhaust, but the OEM silencers on new bikes are magnitudes lighter than the lead-packed exhausts on bikes back in the 80's. I guarantee that even if you throw in the new exhaust canister, the weight savings from the new aluminum frame are several pounds greater than the old CBR frame.

I bet that if you calculated the center of gravity for the bikes by themselves, the cg for the new CBR might actually be slightly lower than the old bike. But when you put a rider on them, everyone who's been on both would agree the '09 feels much more top heavy.

I think the answer is how the bikes position your body on them. The new CBR has a seat height that is slightly (0.6") higher, but the big difference is the height of the clip-ons and the relationship between the seat height and the clip-ons. Look at the two pictures above. The clip-ons sit a good two or three inches higher than the seat on the 89 CBR, but they're at the same height on the 09. This means the upper half of your body (which weighs the most) will be pushed towards the front tire, which increases the feeling of having a high center of gravity. The pegs are also higher, which raises the of your legs when your on the bike and that pushes the overall cg higher.

About lower cg being better for handling, you'd think so but it doesn't work that way. Honda built a NR bike in the early 80's that mounted the gas tank under the engine to lower the cg and it was practically unrideable.

 

[Nero Diablo]

Cutting the cases on the late 90''s 900 honda's for the serious racers wasn't unusual, whilst they might of been racing 600's in one country the factories hadn't quiet geared up with the international focus that exists now. The older bikes were still about everyday transport rather than ultimate track performance. Bike geometry is somewhere between a complex science and vodoo so having simple blanket idea's doesn't work.

 

[inpayne]

If you ever heard of "mass centralization" then that is what the newer bikes do. Yes they are lighter, but the weight that it does have, is better placed.

 

[jw130270]

There actually isn't a notable difference between the ground clearance on the two bikes. Look at these two pictures and you'll see what I mean.

Both bikes have seventeen inch wheels and the bottom of the bodywork hits almost the same point, which means the ground clearance is very similar between the two.

Also, the key to increasing cornering clearance regarding the engine is to make the bike narrower at the crankshaft. Think about it. But this hasn't been a practical concern for a long time. The limit on cornering clearance for the last 20 years has been the foot peg assemblies, and that is constrained by ergonomic requirements. I've been in this for almost 30 years and I can't remember a sportbike in the liquid cooled era that would deck the case in cornering.

And there definitely was 600 supersport racing in the late 80's in AMA/CCS and WERA, and it was very big. The CBR600 wasn't developed from a sport-touring bike. The way it looked was just the best way the factories knew how to make a 600 sportbike at the time. The 500GP bikes of that era had the same kind of bulbous styling as the CBR.



About the question from the OP: That's a good question because on paper the new CBR looks like maybe it should have a lower cg. The first-gen CBR had a steel frame that weighed a lot more than the aluminum frame on the new bike. The new engine has the cases cast together with the cylinder block, and the head is quite a bit smaller and it weighs less than the head on the old bike. Also, look at the suspension, tires and wheels. The new bike has much wider wheels, larger diameter brake rotors, heavier calipers, inverted forks with larger diameter tubes, which have a lower center of mass than the old style of forks. The new CBR is clearly lighter at the top of the bike, but most of the stuff on the bottom is much larger and probably not much lighter overall, if at all. The new CBR does have the undertail exhaust, but the OEM silencers on new bikes are magnitudes lighter than the lead-packed exhausts on bikes back in the 80's. I guarantee that even if you throw in the new exhaust canister, the weight savings from the new aluminum frame are several pounds greater than the old CBR frame.

I bet that if you calculated the center of gravity for the bikes by themselves, the cg for the new CBR might actually be slightly lower than the old bike. But when you put a rider on them, everyone who's been on both would agree the '09 feels much more top heavy.

I think the answer is how the bikes position your body on them. The new CBR has a seat height that is slightly (0.6") higher, but the big difference is the height of the clip-ons and the relationship between the seat height and the clip-ons. Look at the two pictures above. The clip-ons sit a good two or three inches higher than the seat on the 89 CBR, but they're at the same height on the 09. This means the upper half of your body (which weighs the most) will be pushed towards the front tire, which increases the feeling of having a high center of gravity. The pegs are also higher, which raises the of your legs when your on the bike and that pushes the overall cg higher.

About lower cg being better for handling, you'd think so but it doesn't work that way. Honda built a NR bike in the early 80's that mounted the gas tank under the engine to lower the cg and it was practically unrideable.

wow... when you post the old generation and new generation together, you really see the how dynamically those bikes have changed cosmetically.


WHAT WILL THEY LOOK LIKE IN 20 YEARS IN THE FUTURE??? :cheers

 

[BeeGee]

The older bike will sit a lot lower to the ground, modern sports bikes are "jacked up" to improve conering clearance the older bike will also have more wieght on its rear wheel and not as much on its front. Improves drive but doesn't help tracking the older bike will be much longer as well. In 1987 there was no such thing as 600 super sport racing 600 wasn't a race class at all so the 600's of the time were simply smaller versions of the sport tourers so the geometry and setup will be more oriented towards that. If you wanted a race rep you bought a 750 or a 500 smoker. A slightly higher centre of gravitiy will help tip but not stablity in but like most things on a bike it will be a compromise.

i beg to differ. Early 600s were based on the 400 japanese market counterparts. The 600 ninja, FZ600 which were followed by the 87 Hurricane and then the 88 Kan-o-tuna and then the 89 FZR600: None of these bikes had a sport touring oriented geometry.

 

[dreyna14]

Motorcycles aren't cars and don't have lateral weight transfer like a car does. CG height above the ground and it's effects aren't as trivial in the case of a bike. However, before I get flamed by people who don't know better, a lower CG can give the rider more moment arm for easier transitions or correction of line simply by shifting your weight. Also, since all forces act on and around the CG, very fast transitions to lean will cause a higher CG bike to lose some grip as a result. Gravity acts on the CG and rotations are about it. The wheel wants to rotate off the ground but gravity pulls the CG back downward along with the tires. A high CG means greater velocity of the contact patch as it travels around the CG. However, the higher CG will make countersteer easier since the greater moment arm of the tires pulls them to the outside of the turn easier. It's not as straightforward as is it for cars. There is more compromise in bike, IMO, and will depend on so many factors, including the one sitting in the seat.

All this is transitional, once established in the lean, there is no difference. For example, any bike at a static lean angle of 45 degrees with respect to the CG and contact patch will be pulling one lateral g, no exceptions (as long as there's no tire slip). CG height will play no role, it's simple trigonometry. Lateral force is the tangent of the angle the CG makes with the ground and contact patches of the tires. Notice I said CG, leaning off the bike shifts the CG towards the inside of the turn increasing the effective angle.

Right now the biggest issue with motorcycle handling is the gyroscopic forces from the front wheel. This is just a transition issue and affects speeds in places like quick chicanes at higher speeds and the reason why you have to counter steer with so much force in those situations. Counter act that front wheel's rotation and you'll have a bike that will transition like no other.

 

[benroe]

+1, have you guys seen the bike with the counter rotating disc brakes?? They said it is almost unstable. There is a fine line the engineers walk with gyro effects.

 

[jw130270]

+1, have you guys seen the bike with the counter rotating disc brakes?? They said it is almost unstable. There is a fine line the engineers walk with gyro effects.

What bike make and model would this be?
sounds interesting...

 

[inpayne]

Well all sportbikes are "almost unstable" that's the point.

 

[Bpro]

I had an 87 Honda Hurricane, and you could definitely run out of ground clearance even with aftermarket springs and good tires. I was always kinda proud of the holes ground through the lower fairings where they swelled out to cover the engine cases.( not to mention the beveled footpegs/shifter/brake lever)

The problem wit the hurricane was keeping traction exiting hard out of corners. There was not much swing arm angle to begin with, and you could easily bind up the rear suspension and spin up the wheel. with the stock shock there was no easy way to correct this. Alot of folks blamed the skinny tires, but with the chassis set up properly the stock sized tires performed as well as anything else in the day.

one interesting thing about the early CBR's is that they evolved fairly slowly and parts from more modern machines were easily adapted. I installed set of F3 forks, F2 swing arm, brakes and wheels and a Fox shock to mine and it was an absolute dream on the local backroads.

 

[dreyna14]

What bike make and model would this be?
sounds interesting...

It's a prototype/technology demonstration bike. It has adjustable rake and trail and is quite rideable, supposedly, even at extreme settings. The great thing with the counter-rotating assembly is that you can "tune" the steering by changing the gear ratios inside the front wheel. This will alter the speed of the brake rotors to the rider's preference.

 

[ZxHunteR]

why does the old bike seem to have a lower center of balance?

It doesn't. It has a lower seat height and probably was low on gas.

 

[coolatula]

I actually owned a 88CBR 600 Hurricane for my first bike. Didn't feel heavy or slow to turn as I owned it, but when I bought by '04 ZX6R a couple years later, holy crap what a difference!

Now as to why, dunno, bike engineers are smarter than I, all I know is that the bike with 16 years newer technology works better. Imagine that

I too owned a 88 Hurricane 600 and as has been said even though it may be a little heavier they FELT like they were much lower to the ground when you were on it. The rider sat a little lower on the bike which gave them the feeling of a much lower center of gravity. Ground clearance suffers compared to the newer bikes that came out after it and mine in stock trim had a suspension that would be way too soft for a track/race machine. The F2/F3s seem much taller,more race focused,but probably have a BETTER actual center of gravity than the Hurricane even though it may not feel like it.

Also as was mention these bikes were VERY MUCH raced and raced in very hotly contested series/events to boot! The CBR600 were very,very competitive despite being down on power to say the Yamahas,but made up for it in being a all-around more balanced machine.

On paper they were weren't nothing to write home about,didn't do any one thing extremely well(except win lots and lots of races!),didn't make a lot of power,but when you add up all the engineering,components and hardware the sum of the parts totaled up to to one great machine. It was a master piece in that it accomplished so much with so little. I personally believe it is one of Hondas best engineered bikes and one of the best production bikes ever produced given it's not dripping with top shelf components,building materials or state of the art engineering.

 

[PhilB]

I too owned a 88 Hurricane 600 and as has been said even though it may be a little heavier they FELT like they were much lower to the ground when you were on it. The rider sat a little lower on the bike which gave them the feeling of a much lower center of gravity. Ground clearance suffers compared to the newer bikes that came out after it and mine in stock trim had a suspension that would be way too soft for a track/race machine. The F2/F3s seem much taller,more race focused,but probably have a BETTER actual center of gravity than the Hurricane even though it may not feel like it.

Also as was mention these bikes were VERY MUCH raced and raced in very hotly contested series/events to boot! The CBR600 were very,very competitive despite being down on power to say the Yamahas,but made up for it in being a all-around more balanced machine.

On paper they were weren't nothing to write home about,didn't do any one thing extremely well(except win lots and lots of races!),didn't make a lot of power,but when you add up all the engineering,components and hardware the sum of the parts totaled up to to one great machine. It was a master piece in that it accomplished so much with so little. I personally believe it is one of Hondas best engineered bikes and one of the best production bikes ever produced given it's not dripping with top shelf components,building materials or state of the art engineering.

I had an '89. One thing that they were that was something to write home about was practically damn indestructible. I named mine Rasputin, because it just would not die. The previous owner had been a squid who just thrashed it, and during his ownership it had also been stolen and stripped and recovered; I bought it from impound for practically nothing after he got it confiscated over his suspended license. During the ten or so years I owned it, it was backed over by at least six cars, plus I hit three cars with it; it kept getting uglier, but kept running. I finally gave it away a few years ago to a guy I knew who had done me some favors and who needed some cheap transpo. It had about 80K on it then. He's still riding it, and I sometimes still regret giving it away.

The only thing I did not like about it was that the 2-piston sliding caliper front brakes were weak. (Which is exactly why I managed to hit those three cars with it; it had as much power as my Ducati, and was generally as fast, and I would forget and ride it like that, until I got caught out by the fact that I was used to the capability of the 4-piston Brembos on the Duc.)

PhilB

 

[coolatula]

A couple other observations about the Hurricane 600 I had. It had one of the smoothest running engines I've ever seen on a inline four. Also the carbs were so spot-on from the factory that most F.I. systems could only wish for response that quick and smooth. I just can't say enough of how much a truly remarkable machine it was given what the designers had to work with at the time.