[Deck]

I could deal with that Ducati though, that looks bad ass.

 

[6hunnit]

Generally speaking though, bikes aren't symmetrical. It's not like there's a chain and sprocket on both sides of the bike, nor is there a caliper and rotor on both sides of the rear.
Putting all symmetry aside, I think as long as it's designed well, a side-exit exhaust can look great. -Although aesthetics are in the eye of the beholder.

 

[tary preisser]

Maybe the center high design aided "flickiness"?

I have heard track men say that when the bike goes down, the center exhaust is less likely to damage....

 

[Tpoppa]

The RC213v Moto GP bike is the fastest, best handling, road racing motorcycle in the world at the moment. It has both undertail and sidemount exhaust. Although that exhuast system is made from exotic materials and probably costs more than an entire production CBR600RR.

 

[VoltaicShock]

Generally speaking though, bikes aren't symmetrical. It's not like there's a chain and sprocket on both sides of the bike, nor is there a caliper and rotor on both sides of the rear.
Putting all symmetry aside, I think as long as it's designed well, a side-exit exhaust can look great. -Although aesthetics are in the eye of the beholder.

This is true. I think for me it just stands out so much on the bike that it throws the whole thing off for me.

 

[Bimmerx2]

Generally speaking though, bikes aren't symmetrical. It's not like there's a chain and sprocket on both sides of the bike, nor is there a caliper and rotor on both sides of the rear.
Putting all symmetry aside, I think as long as it's designed well, a side-exit exhaust can look great. -Although aesthetics are in the eye of the beholder.

This is pretty much how I feel about it. The bike is not going to be symmetric, ever, so I just go with what I like. I have three bikes; the 600 with the under tail, a 1000 CBR with the low side exhaust, and a K1600 with cans on both sides down low. Honestly, I never thought about that until just now.

This is true. I think for me it just stands out so much on the bike that it throws the whole thing off for me.

Everyone has to filter down to the choices that matter to them. If the side exhaust is the deal breaker for you then so be it - some guys probably can't stand the under tail configuration. The vast majority probably have a preference but it's so far down the list of what's important that it just doesn't matter.

 

[Miweber929]

Personally I think if this were 10 years ago and the then-new fashion was under tail exhausts you'd be having the same argument that the previous generation side mount exhaust was the way to go. It's not as much about performance but about what's fashionable at the moment.

For those of us who rode sportbikes bike then it wasn't even something you noticed, thought about or even mattered. Manufactures simply placed parts differently on the bike to counteract the pipe (the batteries were usually placed towards the opposite side of the pipe) and when we went down on the right side we had to replace the muffler as well.

Hate to break it down to you but it's really current trends that makes it one way or the other. While under tail pipes do have some advantages, it's by far the heaviest style system out there and has the most weight up high. While side to side weight may be "even" you still have excess heat and heat shielding under the seat you have to deal with not to mention an asymmetrical swingarm to make room for the upwards pipe which have 2-3' extra length to it. And it runs that heat right by the shock.

Not a huge advantage other than looks if you honestly break it down.

My biggest beef with them is the exhaust gets all over you and your passenger far more than a side or under exit exhaust. I don't mind exhaust smell at the track but having to sit in it for 8 hours while at work is annoying compared to when I take the NC700X which is almost nothing.

Mike

 

[Tpoppa]

While under tail pipes do have some advantages, it's by far the heaviest style system out there and has the most weight up high.

While what you are saying about the exhaust is correct, there are more things to consider when talking about mass centralization.

Consider the Buell systems (I've owned 3 of them) that are completely under the motor. The exhaust is low, but the motor has to be mounted a couple inches higher to allow ground clearance for the exhaust. Which affects mass cetralization more... the motor or the exhaust?

There are lot's of engineering solutions for mass centralization. The exhaust, which isn't the heaviest component of the motorcycle, is just one of the concerns.

 

[VoltaicShock]

My biggest beef with them is the exhaust gets all over you and your passenger far more than a side or under exit exhaust. I don't mind exhaust smell at the track but having to sit in it for 8 hours while at work is annoying compared to when I take the NC700X which is almost nothing.

Mike

I smelled more on my 250 with a side exhaust. Then again it was carb not FI

 

[Miweber929]

While what you are saying about the exhaust is correct, there are more things to consider when talking about mass centralization.

Consider the Buell systems (I've owned 3 of them) that are completely under the motor. The exhaust is low, but the motor has to be mounted a couple inches higher to allow ground clearance for the exhaust. Which affects mass cetralization more... the motor or the exhaust?

There are lot's of engineering solutions for mass centralization. The exhaust, which isn't the heaviest component of the motorcycle, is just one of the concerns.

Yeah and no. I agree with what you are saying in principal but like you said there is much more going on under the motor already like the oil pan, headers, suspension linkage, etc. that raising the motor is hardly a thing of several inches (in anything other than say a Buell or a big twin) and more of a millimeter thing that would have a small effect on overall handling. Most of the inline motors already have the headers running under the engine, there is simply more of it. Or some have huge collector boxes: Google a pic of the 90-93 stock VFR750 exhaust, there was a HUGE collector box already under the motor.

While the exhaust isn't the heaviest component, the muffler under the rear seat is at one of the highest points on the bike, the lower the weight, the less it affects handling.

Mike

 

[Sh1ft3r]

The KTM RC8 has it low under the engine, I test drove one and that's something you feel immediatly that the weight distribution is well done underneath you!

 

[VoltaicShock]

The KTM RC8 has it low under the engine, I test drove one and that's something you feel immediatly that the weight distribution is well done underneath you!

Just looked at some pictures of the KTM RC8 and I do like that. I am fine with it "hidden" like that.

 

[le0nng]

I'm surprised that nobody mention the pros of having an underseat exhaust as compared to the exhaust on the sides.

When your bike tips over, you'll save your underseat exhaust from damages!

 

[wibbly]

Why does everyone think that lowering the cg on a bike is the best thing?

Looking for intelligent answers please

 

[rinonz]

Why does everyone think that lowering the cg on a bike is the best thing?

Looking for intelligent answers please

Interestingly enough; lowering the cg can have a negative effect.

Honda experimented with NS500 in 1984
http://www.pinterest.com/pin/302093087478069313/

The result was a bike that understeer; he still won the championship but it wasn't an easy win

Re: suspension yea or nay
Postby rgn » Sat Apr 19, 2014 7:00 pm

The 1984 Honda NS500 of Freddie Spencer had the experimental underslung tank, it handled well enough to achieve forth in the championship out of a field of 27 riders, but it did have some problems changing direction, and with understeer. Next year honda turned the bike the right way around and Freddie won both the 250 and 500 titles in 1985. Here's a fun vid of the bike and Freddie in action.

I'm sorry for going off topic but here's some nice pictures
http://www.deejay51.com/honda_racebikes_pg_4.htm

There was a documentary about the NS and NSR500 history that talked about the issue with the underslung tank; I just can't find it anymore.
*Edit*
Not documentary but some webpage with words
http://www.superbikeplanet.com/NSR500.htm

The '84 NSR's problem wasn't lack of speed - the bike was a wheelspin-crazy rocketship, 140 horses was a big number back then. No, its downfall was the willfully innovative 'upside-down' chassis design - fuel tank mounted below the engine with expansion chambers sweeping back above the engine, for a low center of gravity. But motorcycle dynamics aren't that simple - the NSR's center of g was too low so the bike wouldn't transfer weight into and out of corners to aid front and rear traction. The low-slung fuel load also sloshed forward under brakes, pushing the front like crazy, causing major understeer. And the NSR was a mechanic's nightmare - imagine trying to change plugs or jets beneath those burning hot pipes. So much for superior engineering.

 

[Lyoha]

Honestly when you have a 150lb+ rider on top of a bike, a few extra pounds mounted a foot lower or higher really won't make much of a difference. I like the CBR's undertail for its aesthetics and helps to know that when I do go down, I won't have to worry so much about replacing exhausts. Unless of course it's a massive flop and the sub-frame gets twisted. But by then there are other issues to worry about than if an exhaust pipe is screwed.

 

[smokinjoe73]

It is more fashion than function. Ducati realized this and tried to go back to lower exhast and non single sided swingarm but the consumers all complained so the went back. (not forever but still).

Motogp uses underbelly which Eric Buell knew already. Lower wieght is always better but have you seen the VFR1200 or 800? Honda as of late have made some real butterball fat bikes.

Maybe its too many committees or groups of engineers?

 

[wibbly]

Lower weight is not always better. The raciest bikes have the engines mounted high in the frames. Having a slightly higher cg will allow for lower lean angles and also help with weight transfer.


Erik buell did some absolutely retarded stuff with his bikes, he was trying to be different, not necessarily better.

 

[wibbly]

And typically under mount exhausts are only found on dry sump bikes. The lack of an oil pan makes room for exhaust down there. They COULD mount the engine lower, but that isn't better

 

[PdubRR]

Why does everyone think that lowering the cg on a bike is the best thing?

Looking for intelligent answers please

Proper question. I'll try my shot at a proper answer.
As Rinonz pointed out, a maximally lower CoG was thought of at one point to be beneficial for a bike. I have a good story in an old MCN Sport on that NS500 and why car designers always screw up bikes. That upside down bike was the benefit of a partnership with ELF who were big in auto racing and an embarrassing lesson was learned. Unlike cars a low center of gravity is not key to motorcycle performance, at least ones that have to handle in corners. Enter the idea of mass centralization which Honda has been crusading for years since. That's more the idea that all of the mass of a motorcycle should be concentrated as much as possible into something like a bowling ball centered between the wheels at their hub axis. The more mass that radiates away from that point (exhaust, fuel tank, rider) the more it's going to affect how that bike changes direction around that central mass in a positive or negative way. Obviously a rider is an object of mass you can't really redesign for the bike but the rider can use his mass to positive effect (move over front of bike to reduce wheelie, rearward in braking, and the obvious one of leaning off the inside in turns to allow the bike to require less lean angle) or if totally clueless screw that all up and even the best set up GP bike won't help them.
Now what does this all have to do with an under tail or side mounted exhaust? Plenty. The exhaust is a static mass. It's also one in the case of an under tail configuration that's about as far away from the center of mass as is the rider's head. A side mounted exhaust isn't as far and a stubby GP style or under engine one even less so. Still this is a big reason why they use titanium in the GP exhausts as it reduces the mass of those items further from center of mass. Is all of this going to make a big deal in your street bike? Not so much by itself but say if you took a CBR600RR and removed the subframe designed for two up riding and the heavy stainless steel under tail exhaust canister & pipes then replaced them with a titanium race system and minimal subframe it would be noticeable. At least noticeable to a racer who's flopping it to max lean angle in one direction to another at race pace. For street riding not so much. I put my OEM exhaust back on the bike from the Yoshi RS-5 slip on it had when I bought it and it hasn't made me any faster in the canyons or made it ill handling.

BTW-That ELF partnership also brought the single sided swingarm to the idea of Honda race bikes then to be adapted to their production race & sport bikes; an idea so nifty Ducati adapted it too to the 916 but that's another story.