Topic: Do you really want to be low?

[Blaize]

No that thing actually gets allot of disscusion in VW circles, it's a stock body with the better part of a 96 Porsche 911 turbo powertrain, brakes and suspension grafted in. And of course there is nothing at all in the cargo area. It still has a floor but all of the interior is gone. The engine is worked over, and makes around 600 BHP. It belongs to a tuner co. in Germany. They just use it a shows and such, from what I am told it is road legal but you wouldn't want to drive it in traffic.

[rhinoracer]

I don’t see how raising the forks up in your triple tree (lowering the front) makes you loose travel? The bike is still far enough up from the ground before it bottoms out. The forks still have the same amount of travel but the bike sits lower. Right?

I know what you're saying though, and agree.

'Cause the fender will hit the bottom of the triple clamp sooner. You have to limit travel or risk stuffing the fender into the tire and locking it.

[moduleum]

Thanks Geeto67, but I stand by my statement. That's just quibling.
When you lower the bike you've just cut the shape at the tire. It's probably 5% or less of the silouette. Tires don't make a big impression on wind resistance.

it is statements like above that show you are not thinking about aerodynamics in the right way. It is only quibbling to you because the conversation has fast approached the limit of your knowledge on aerodynamics.

Tires do make a large impression on wind resistance, as does rim type or anything else you are trying to push through the air. spoke rims are actually the least efficient because they act like giant fans slicing the wind, as do the treads in the tires, etc.  However lowering a bike doesn't just cover up the tire, it takes the forks out of the wind also and reduces the distance between the fender and the bottom of the fairing. If you think as this area as one large scoop then by shrinking you have decreased the volume of airflow that will travel through it and diverted it around (you have also increased its speed which creates other issues). Since that air normally becomes turbulent and creates different pressure situations when it hits the radiator, the front of the cylinder block, the fan, etc...you have made an dramatic effect on the aerodynamics of the bike, whether someone will feel that physically that is a different story. Drag is actually not a static number it is a number that increases the faster you go. A co-efficient of drag is really measuring how fast the rate of drag increases, if you reduce the rate at which it increases then you are in effect reducing how much resistance there is at a given speed. 

granted aerodynamic changes usually aren't felt in significant amounts until major speeds, it doesn't mean things aren't changing. at 50-60 mph you may not feel it physically but it may start to manifest itself in the form of reduction of fuel consumption, or a lesser propensity to be pushed over by cross winds.

Hmmm...

Some of the things you say are controversial and debatable to say the least.  I'm no aerospace engineer, but I am a mechanical engineer and have taken a several classes (including upper level electives) dealing with compressible and incompressible fluids.

Lowering a bike will not significantly affect pressure or friction drags at street-worthy speeds.  Lowering cars for the Bonneville salt flats is mainly done to reduce flow underneath the car, reducing lift and friction drag.

I would not say that the tires have a large or even a significant impression on the drag of the bike.  Yes, a spoked wheel will obviously invoke higher drag than a solid alloy wheel, but how much of a difference are we really looking at here?  Using a very simplistic approach, by lowering a bike, the frontal area of the bike is not changing, thus not affecting the friction drag.  Pressure drag might be slightly altered by changing the angle of attack on the front fairing, but nothing noticeable below 100mph i.m.o.  Lowering the bike does not also magically fuse the tire with the forks either creating a more streamlined path for air flow.

Also, a coefficient of drag doesn't not measure "how fast the rate of drag increases."  It is a constant that associates an object's shape with a how much force an object will experience under a specified fluid "load."  There is no rate associated with a drag coefficient.

Sorry for the long post.

c/n: Lowering bikes is for tards unless you're doing high speed runs.

[edbikerii]

I guess its good for a laugh, and for publicity if you run a tuner company, but there are easier and cheaper ways to build superior speed and handling.  Imagine what a performer you'd have if you dumped all that time and money into the original '96 Porsche 911 Turbo?

No that thing actually gets allot of disscusion in VW circles, it's a stock body with the better part of a 96 Porsche 911 turbo powertrain, brakes and suspension grafted in. And of course there is nothing at all in the cargo area. It still has a floor but all of the interior is gone. The engine is worked over, and makes around 600 BHP. It belongs to a tuner co. in Germany. They just use it a shows and such, from what I am told it is road legal but you wouldn't want to drive it in traffic.

[Blaize]

Oh I totally agree, I wouldn't have spent the time or money on it. But it is cool to see so long as somone else has.

[andy750]

Not sure about the VW bus video but this is a good demo of low car aerodynamics ;-)....watch until the end where it gets really low...

http://videos.streetfire.net/hottestvideos/2/b9f05753-2366-4589-87c9-232c17b3e991.htm

enjoy,
Andy

[Bob Wessner]

I bet she never does clean the car.

[CBGBs]

I have put quite a bit of thought on this opinion. When I posted this thread I felt that this low trend was something that people really hadn't put much consideration into. I figured people who were familiar with the fact that lowering a car is a benefit on the track had carried this over onto two wheels. But this is not so with motorcycles. I've never seen a motoGP bike that was lowered. It may exist but it would be the exception. I knew this would be mildly controversial, but also beneficial, and a popular discussion.

If you look at this thread it all plays out. My judgement of the trend seems totally accurate. You would have to expect that some people would want to defend lowering. The interesting part is how easily it veered off into cars. I'm sure this is where this trend gets its purpose. I don't think it has so much to do with motorcycle drags. This kind of illustrates how little people are actually thinking about how this may effect the bike, and how strong the trend may be. I've got the attitide that if everybody's doin it, then I'm skeptical about it.

If you want to lower your bike because you're short, I'd suggest you try to lower the seat first.
If you want to lower your bike because of performance, I'd suggest you consider whether you really think you can engineer a bike better than Honda.
If you want to lower your bike because it's cool, then just say so. And I won't call you a tard either.

[ProTeal55]

If you want to lower your bike because you're short, I'd suggest you try to lower the seat first.If you want to lower your bike because of performance, I'd suggest you consider whether you really think you can engineer a bike better than Honda.
If you want to lower your bike because it's cool, then just say so. And I won't call you a tard either.

I lower MY cars/bikes because I choose to because they are MINE.
Just like I choose to put a 21'' front wheel on MY cb750. If YOU choose to keep your bike at the stock height (for whatever reason it may be) so be it, because it's YOURS to do with as YOU please..

As I said before, it's all personal preference...

[CrisPDuk]

If you want to lower your bike because of performance, I'd suggest you consider whether you really think you can engineer a bike better than Honda.

As stated in my previous post I have lowered my bike for performance reasons, I also believe the result to be successful, the bike now corners better/quicker than it did before

I do not think that I can engineer a bike better than Honda, but I know that many frame builders in the 70's and 80's definitely could, so there is obviously room for improvement

Personally though I did it just because I'm happy for the line of compromise between comfort and handling to tend more toward handling than Honda maybe originally intended

As an added bonus it looks cool too

[merc2dogs]

 The arguement about engineering better than Honda is based on an incorrect assumption.

  For it's intended market the cb750 was engineered very well.
  But you have to remember that it was designed for mainstream buyers, the the vast majority of whom were looking for straight line stability and comfort, not maximum cornering ability.

 any mass market vehicle is designed for the majority of the buyers, not for a select few who want to push it's design perameters.
  aftermarket, and owner customization drives design at the manufacturing level.
   for example, the chopper craze of the 70's lead to factories turning out the 'customs' of the 80's, and todays 'factory chops' the cafe and road race crowd with their pursuit of speed and handling has led through the years to the crotch rockets
 the huge number of people buying vetter and shoi tour equipment and turning stock bikes into tourers led to the creation of the goldwing and it's like. Very few people left the bike in factory condition, which is one reason it's almost impossible to buy a true 'naked' bike today.

 In my opinion, lowering a bike will improve handling if it's done correcly, done incorrectly and it alters the geometry too badly
 
 There is tons of room to improve the handling of the 750 specifically, and any '70s era bike in general, trussing the swingarm to stiffen it, or swapping to a stiffer one, either aftermarket or from a different bike, gusseting the frame was not too unusual but not overly common to stiffen up the frame. larger fork tubes and better damping, different shocks etc all improve on honda's engineering.

 Yeah, you can engineer it better.
Ken.

[CBGBs]

If someone could show me low Factory Honda that is made for performance and Handling, there would be a really strong argument. I totally agree with ProTeal, and Merc2dogs I only disagree somewhat. I understand very much the point that a bike can be modified to suit a persons needs or wants, but when I posted this I was thinking about the bike scene in general and how there is a trend of doing this with sportbikes. As an example, a friend has a CBR600RR 2007. He is a novice rider and wants to lower his bike.
There is no way this is going to improve this highly tuned bike.

[ic455]

If someone could show me low Factory Honda that is made for performance and Handling, there would be a really strong argument. I totally agree with ProTeal, and Merc2dogs I only disagree somewhat. I understand very much the point that a bike can be modified to suit a persons needs or wants, but when I posted this I was thinking about the bike scene in general and how there is a trend of doing this with sportbikes. As an example, a friend has a CBR600RR 2007. He is a novice rider and wants to lower his bike.
There is no way this is going to improve this highly tuned bike.

Why does he want to lower it?  Being a novice it certainly can't be for performance reasons?  The CBRs are pretty much ready for racing right out of the box, and are designed for cornering.  In that instance, lowering it would be purely aesthetic or due to short stature.  Tell him not to mess with the beast!

[hopterfixer]

I think these people buy these bikes because the are the "cool" ones to have, not realizing what the RR in the name really is intended for other that it goes fast.  I would bet the lowering thing is purely aesthetic, the guy will not race it other than between stoplights.  I wonder if people were saying the same things in the seventies when all of those long hairs were putting 6 over front ends and all of the other popular chopper mods of the day, "why the hell would he do that, that bike was built that way for a reason".  Chalk it up to youthful ignorance.   

[Geeto67]

I said it before and I'll say it again, a lot of guys lower their sport bikes because it makes them easier to ride. cbrs, yzfs, zx, etc are all wheelie prone bikes, lowering them helps control that. It probably doesn't help them in the twisties but it also means they won't 12 o'clock the thing pulling away from every stop light.

the best way to figure out why someone is doing something is to ask them and not guess. I was surprised when the above answer was why a bunch of guys at my buddy's work lowered their sport bikes.

[Jinxracing]

Regarding the whole "low center of gravity equals more stability" thing...

Coincedentally I've recently been having some interesting discussions with my uncle about this very issue. He's a builder of recumbent motorcycles in WA state and was telling me about some handling issues they were having. For one thing, a low center of gravity does not ensure improved stability. We're talking extreme designs here (similar in theme to the Gurney Alligator), but apparently as the center of gravity moves closer to the ground the speed of transition from left to right increases, since there's a shorter "lever" inhibiting that transitional motion. This transitional speed can become so fast as to render the bikes almost unridable.

He's realized that the hiccup in his thinking had to do with thinking that motorcycles operate under the same dynamics as a four-wheeled vehicle, where lower almost always is better. However, a four-wheeled vehicle while turning operates in yaw and exhibits a very small amount of lean (the less the better) and that lean is more of an unwanted byproduct of physics than anything else. Obviously, motorcycles handle because they lean...the more the better in fact. I'm not an engineer, so bear with me, but he's saying that a motorcycle has a longitudinal rotational axis that runs forward-to-back, in the neighborhood above the crankshaft center height. I don't know how this axis is determined, but I do remember reading a Honda technical article awhile back about their "mass-centralization" design philosophy with the original CBR900 (Fireblade to you Brits) and pulling as many heavy engine and chassis components in tight to the longitudinal rotational axis to improve handling and stability. CG wasn't even a factor compared to their desire to center the mass around that invisible axis. The previous comments about clipons making a bike feel as though it handles better could be explained by this theory; lower bars moves your body mass closer to the rotational center of the bike, therefore improving handling and stability.

Also, when you read articles about magazine testers and racers turning fast lap times, it's quite common to hear them mention lowering the front and/or raising the back to affect weight transfer to the front wheel and oftentimes raising the suspension at both ends to increase cornering clearance. I can't remember a single occurence of them lowering a bike's suspension to gain stability or lower lap times. Unless of course you're drag racing which is a whole 'nother kettle of fish. 

Based on all of this second-hand information, I'm weighing in with the "lowering your bike might make it look better or easier to put your feet on the ground, but doesn't do much for handling or stability" crowd.

[mlinder]

I said it before and I'll say it again, a lot of guys lower their sport bikes because it makes them easier to ride. cbrs, yzfs, zx, etc are all wheelie prone bikes, lowering them helps control that. It probably doesn't help them in the twisties but it also means they won't 12 o'clock the thing pulling away from every stop light.

I thought that was what being able to control your clutch and throttle was for.

the best way to figure out why someone is doing something is to ask them and not guess. I was surprised when the above answer was why a bunch of guys at my buddy's work lowered their sport bikes.

If pros can turn sub 3-second 0-60's on these bikes without lowering them and putting the front end at 12:00 or later, your buddies don't need to lower their bikes. They need to either learn how to control their bikes, or get something (a lot) slower.

[Geeto67]

I said it before and I'll say it again, a lot of guys lower their sport bikes because it makes them easier to ride. cbrs, yzfs, zx, etc are all wheelie prone bikes, lowering them helps control that. It probably doesn't help them in the twisties but it also means they won't 12 o'clock the thing pulling away from every stop light.

I thought that was what being able to control your clutch and throttle was for.

the best way to figure out why someone is doing something is to ask them and not guess. I was surprised when the above answer was why a bunch of guys at my buddy's work lowered their sport bikes.

If pros can turn sub 3-second 0-60's on these bikes without lowering them and putting the front end at 12:00 or later, your buddies don't need to lower their bikes. They need to either learn how to control their bikes, or get something (a lot) slower.

be a smartass all you want about proper riding skill, some of these guys just don't have that much restraint. they bought the ticket for the super fast ride and they want it, they just don't want to soil their undies while doing it. To give you an idea of the kind of riders they are, they are the kind of drivers who in a car will pull to the shoulder at a stop light and try and beat the car in the right lane to get around them.

And as for sub 3 second 0-60 times, I don't know where you are getting that number but I can guarantee you if someone is doing that on a stock suspension sport bike they are doing it all on one wheel. Even the magazines lower the bikes for acceleration tests. These usually involve sliding the forks up or ratcheting them down, and sometimes even lowering links in the rear. some of them even use dyno calculations and don't actually run the bikes at all. They don't exactly tell you how they get their numbers but it is not always as above board as you think. It isn't only the magazine's fault a lot of this depends on the testers and the writers. These are all straight line kind of tests, and while they may go into great detail about how they setup their bike for the road course, they hardly mention what it takes to run the number (the one exception was the zx636 test in cycle world where they showed you exactly how much was to be gained by lowering the bike and having kawi's hired gun Gadson (sp) ride the thing.

[dusterdude]

i went to the prostar race here in april,just about all the guys riding stock suspended busa`s and zx`s had one hell of a time keeping the front end down.

[mlinder]

i went to the prostar race here in april,just about all the guys riding stock suspended busa`s and zx`s had one hell of a time keeping the front end down.

Geetos buds are riding on the street. They shouldn't have trouble keeping the front end down on the street.

And Geeto, some day your buds are going to meet someone like me, and as they try to pass someone on the shoulder, that someone is going to make sure they end up in the ditch or headfirst into a telephone pole for being an ass. I've done it, and I'm sure others have too. Tell your friends to be careful, because they're not the only crazy #$%*s out there.

[Geeto67]

i went to the prostar race here in april,just about all the guys riding stock suspended busa`s and zx`s had one hell of a time keeping the front end down.

Geetos buds are riding on the street. They shouldn't have trouble keeping the front end down on the street.

And Geeto, some day your buds are going to meet someone like me, and as they try to pass someone on the shoulder, that someone is going to make sure they end up in the ditch or headfirst into a telephone pole for being an ass. I've done it, and I'm sure others have too. Tell your friends to be careful, because they're not the only crazy #$%*s out there.

They are not my friends, they are co-workers of my friends, and I feel they are squids. So many times I have tried to help them out and ended up just throwing my hands up and walking away. One of them I helped out after he got 10 tickets in his car for everything from wreckless driving to speeding and as soon as he gets his license back he goes out and buys a gsxr 1000.

As far as riding on the street and not having trouble keeping the front end down....ha. I have 12 years continuous street riding expirence, and several years on top of that racing motoX, and drag bikes, and even more drag racing cars. I have self control, no desire to stunt, have good throttle and clutch control, have an '86 1000R ninja in the stable, attend MSF safety classes, the works. A buddy of mine lent me his new '06 R1, and I had trouble keeping the front end down. Stoplights weren't so bad, but I did manage to accidentally wheelie the R1 4 times, along the same route and speeds that I normally ride my cb750. Granted I don't ride one everyday so there are habits that I don't have yet that someone who rides everyday would have but still, the bike makes 150hp and weighs less than 400lbs. 

These new Liter bikes are completely unreal, In urban riding situations they are literally grenades with the pins pulled. That being said I am thinking of selling off a couple of my cb750s and buying a zx10 (or a ducati sportclassic). I have my cb750 to commute on and as toys sportbikes are a lot of fun.

[mlinder]

i went to the prostar race here in april,just about all the guys riding stock suspended busa`s and zx`s had one hell of a time keeping the front end down.

Geetos buds are riding on the street. They shouldn't have trouble keeping the front end down on the street.

And Geeto, some day your buds are going to meet someone like me, and as they try to pass someone on the shoulder, that someone is going to make sure they end up in the ditch or headfirst into a telephone pole for being an ass. I've done it, and I'm sure others have too. Tell your friends to be careful, because they're not the only crazy #$%*s out there.

They are not my friends, they are co-workers of my friends, and I feel they are squids. So many times I have tried to help them out and ended up just throwing my hands up and walking away. One of them I helped out after he got 10 tickets in his car for everything from wreckless driving to speeding and as soon as he gets his license back he goes out and buys a gsxr 1000.

As far as riding on the street and not having trouble keeping the front end down....ha. I have 12 years continuous street riding expirence, and several years on top of that racing motoX, and drag bikes, and even more drag racing cars. I have self control, no desire to stunt, have good throttle and clutch control, have an '86 1000R ninja in the stable, attend MSF safety classes, the works. A buddy of mine lent me his new '06 R1, and I had trouble keeping the front end down. Stoplights weren't so bad, but I did manage to accidentally wheelie the R1 4 times, along the same route and speeds that I normally ride my cb750. Granted I don't ride one everyday so there are habits that I don't have yet that someone who rides everyday would have but still, the bike makes 150hp and weighs less than 400lbs. 

These new Liter bikes are completely unreal, In urban riding situations they are literally grenades with the pins pulled. That being said I am thinking of selling off a couple of my cb750s and buying a zx10 (or a ducati sportclassic). I have my cb750 to commute on and as toys sportbikes are a lot of fun.

I wasn't implying that you were doing this. With something as powerful as an R1, I'd def spend some time learning the bike before I started cracking open the throttle. I'm sure it'd get squirrely on me the first few days as I learned it. I'm not saying that's an issue. But if someone trouble keeping the front end down on their zx11 after a year of ownership, they deserve the wrecks they will inevitably have.

[754]

Newbie here, 1st post!!

I have a 73 836cc Honda., with a fairly stock frame

Lowered about 6 inches, stretched 6 inches.

The frame where the kickstand mount was is about 4 inches off the ground


I would like to see the better engineered bikes Honda built that can get off the line  better than this.

Part of why I did it was to bracket race, but then put it back on the street.

IMO I would rather get off the line hard w/o spinning or lifting the wheel (and risking a ticket), and have never found myself going Quicker from backing off during a wheelie.

Also you can push the bike a short distance with one hand, the CG is that low..try that with a stocker..

The day I finally got my low pipes back (sold them with a bike), I lowered the bike about 3 more inches, and picked up, 2.5 or 3 tenths in the 1/4... not bad for an afternoons work...

To each their own, but someone did ask about lowering...

754