What stops faster "Car VS bike" - debate

[mccarthy]

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Seriously? :laughing8:

heres a lil example of what im trying to tell you guys.. oviously it came off the wrong way..

if you try and brake with only your rear tire your not going to stop very fast at all. none of the wieght that makes up your vehicle is being pushed onto that wheel.. you can apply that to anything with wheels that moves and brakes. thats what i meant by high center of gravity during braking..

Your body is that wiegh and high center of gravity on a motorcycle... Its a huge advantage when braking in a straight line! you can move you body in order to put as much of that weight on the front wheel as possible.

when you apply your brakes on your bike have you noticed that your pushing down and forwards on your handle bars...

 

[Kawi-Rex]

Wow.. Do you really believe that?

Let's take your argument and apply to another aspect of driving.. cornering ability. Your argument implies that raising the centre of gravity, therefore putting more weight on the wheel on the side the G-forces seem to come from (ie: the front wheel in a stoppie, the rear wheel in acceleration, the outside wheels in a turn on a car) increases the G-Force. Perhaps you should give the Formula One engineers some lessons as I seem to recall them trying to lower the centre of gravity of F1 cars.

You argument would imply that a Van, SUV or Truck with a high centre of gravity can out-corner a sports car with a low centre of gravity since the high centre of gravity vehicle can get closer to rolling over sooner (and will roll over sooner.) I suspect that most people would agree that it simply isn't true.

..Tom

i think g-force you refer to is momentum but im not quite sure what your arguing it seems that your saying that the center of gravity of a bike is lower in comparison to a car which is not true the center of gravity on a bike is higher up say a 500lb bike has a 200lb rider already you have the center of gravity shifting higher up hence why sport bikes position riders high up and as horizontal to the bike to raise its center of gravity.
As for cornering cars and motorcycles behave completly different in corners were cars try to maintain traction on all fours by lower center of gravity motorcycles controls its center of gravity by leaning closer to the ground going back to why ride position is higher up this provides more leverage to the rider to lean the bike.

 

[SuburbanBWS-R]

I only noticed this thread now, but to answer you question here is a video of a BMWF650GS twin ABS vs a Honda Accord with ABS.

http://www.youtube.com/watch?v=pfffXkoJvUU

They are even in wet. The BMW stops faster in dry by 1 car length.

 

[mccarthy]

I only noticed this thread now, but to answer you question here is a video of a BMWF650GS twin ABS vs a Honda Accord with ABS.

http://www.youtube.com/watch?v=pfffXkoJvUU

They are even in wet. The BMW stops faster in dry by 1 car length.

Thank you so much for posting this video.. Clear this damned thread up

 

[V-Tom]

- they already understand, thats why they adjust the camber of the tires on race cars- in order to use the wieght of the vehicle to its full potential when cornering. lol your really not understanding what im saying and i dont wanna waste more time trying to break it down.

Does anyone here understand that all cars front 2 wheel do 80% of the stopping and are supplyed with 80% of the power when you apply the brakes.. does anyone here watching any kind or motorsport racing. god damnit

I very much understand about camber on the tires.. but that isn't what you are talking about.

Here is what you said:

...a motorcycle can stop faster because it has a higher center of gravity allowing more pressure to be put onto the ground by the front tire when braking.

(My underlining and bold.)

If you don't understand how wrong this statement is then it's pretty hard to have more discussion. But think for a moment: if what you say above is true, then race cars would sit higher. Cars setup for the track wouldn't lowered, they would be raised.

..Tom

 

[Baggsy]

In controlled conditions with an excellent rider a motorcycle can get 1.3 g's of deceleration.

None of us are excellent riders and our roads are not controlled conditions.

I therefore try to make allowance for you to NOT be able to out brake my minivan.

Hopefully, you do the same.

 

[mccarthy]

If you don't understand how wrong this statement is then it's pretty hard to have more discussion. But think for a moment: if what you say above is true, then race cars would sit higher. Cars setup for the track wouldn't lowered, they would be raised.

..Tom[/QUOTE]

Dude your starting to sound like a kid whos trying to play dumb.. .. Something with 4 wheels is completly different, i assumed u understood the physics behind roll and body movement on a car.. A lowered stance provides much more stability in something with 4 wheels... oviously... lowering the wieght on a 4 wheeled vehicle also places more wieght on all the tires rather than "over" the tires which can pull the tires off the ground... which is why suvs roll over more... so what i said before is still very right.

A motorcycle needs to ridden and balanced--- thus its design will be completly different. look at all sport bikes, they have such a high seating position. The rider is part of the physics of the machine becuase it wieghs just about twice his wieght compared to a "passenger" in a 4 wheeled vehicle that wieghts thousands of pounds. It wont make sense if you relate it to something with 4 wheels.



Anyway im done with this thread. Just look it up if you dont understand me, im not a good teacher at all. An average motorcycle with an average rider outbrakes an average car with an average driver anyday..

 

[Kawi-Rex]

If you don't understand how wrong this statement is then it's pretty hard to have more discussion. But think for a moment: if what you say above is true, then race cars would sit higher. Cars setup for the track wouldn't lowered, they would be raised.

..Tom

are you kiding me don't you understand that bikes and cars don't behave the same. its called optimization engineers compromise one charteristic to greaten another depending on the ratio thats why engines on most sports and race cars are placed in the center mid rear drivetrains. This place the heaviest component of the car in the center and as low to the ground as possible which provides optimal braking and acceleration by transfer weight evenly between the to.
FYI cars turn using there front wheels which requires as much traction on all four wheels. Bikes turn by leaning and the wheels try to up right it self which pulls the bike in the direction of the lean.

 

[*gSTP*]

Sport motorcycles are not designed with just straight line stopping distance in mind. Their design purpose is for track racing. Acceleration, braking, and cornering.

A longer wheel base improves acceleration and braking. Less wheelies. Less stoppies. The downside is that cornering ability is affected. Track times are the determining factor when the decisions are made at the design stage.

The BMW K1300S beat everything due to the long wheel base. Cornering tests using this bike on the other hand will produce different results.

Generally speaking a motorcycle is not the best place to live when emergency braking is required. A four wheel machine will ultimately stop more quickly, give the driver more control (ie the ability to mash the brake pedal with no fear), and will provide a much greater level of safety when the worst happens.

*gSTP*

 

[mike.from.canmore]

Wow.. This thread is getting good.



mccarthy - don't leave the debate. Simply calm down and counter debate as you see fit. It's clear that our opinions on the matter differ completely - but that's no reason leave the debate. It certainly won;t be easy, but if you can prove to me that I am wrong, I will gladly join your side of the argument.

Honestly, his topic is great. it's great because we all "KNOW" what's true - it just so happens that what we each believe to be true/fact - doesn't match what the next guy also knows is certainly a fact.


I do plan on living forever, so I'm not going anywhere - I will continue to attempt to convince people I am right on this subject - much like others who disagree will do the same (all of us think we are right, otherwise you would just post that you have no opinion on the subject).

If someone challenges your post - no need to get defensive - just reply with more facts/details that will enhance your argument.



eg... you posted a YT video showing a bike stopping quicker - http://www.youtube.com/watch?v=pfffXkoJvUU

Good find SuburbanBWS-R = one point for your team.


Earlier - someone posted a link to the Dec 2009 edition of MCN
Where it made it abundantly clear that in there tests - only one single Superbike beat a Honda Civic diesel – typical family hatchback with typical car ABS. All other bikes tested were worse than the civic (yes! it's in the magazine) http://www.motorcyclenews.com/MCN/N...09/December/dec2309-bmw-k1300s-wins-abs-test/

another good find = one point for my team.


Stay with it... change your stance or convince people who think like me that you right - don't just leave it open. The community needs input from everyone.





With respect to what you were saying about weight transfer and the bike being better as a result of that. I totally understand what you are saying - that a car can only reach about 80% weight transfer where a Bike can reach 100% (more is better in your opinion?). BUT you seem to have omitted the fact that the bike (with it's short wheelbase and high CG) is prone to flipping over - where the car is not. So even though the bike can get 100% weight transfer to the front wheel, and it DOES for sure acquire more relative traction - that traction can't be utilized -cause the bike will flip over long before maximum braking(with respect to traction) is reached.

See post #139 - read the link there - sure it's long, but it's quite informative, come back and tell me I'm wrong, or perhaps you might see the light.

 

[V-Tom]

You'll have to read and comprehend the preceding messages to understand what I was saying.

Mccarthy was trying to make the point that a high centre of gravity is what makes a bike stop quicker. This is obviously false and a basic understanding of physics would make it obvious why this isn't true. If you took mccarthy's assertion to its logical conclusion, we would have Vans and SUV's outhandling cars, engineers would raise race cars to improve handling. It's obvious that these assertions are not true therefore mccarthy's original assertion is not true.

As far as were the weight goes in a race car: the weight is centralized to provide a low moment of polar inertia. This enables quicker direction changes. Ideally the weight is kept as low as possible as this minimizes weight transfer in all directions. For Formula One car the weight distribution front to rear is approximately 60 or so percent on the rear wheels. Since there are only two wheels driving the car this optimizes grip for acceleration. Under braking four wheels decelerate the car, so the rearward weight bias also means that weight shift toward the front results in more balances weight distribution and therefore all the brakes can do a more efficient job of braking. (Note that actual weight distribution allows for the different size of tires front to rear and the requirements of each race track as ballast can be moved around to fine tune things.)

The physics of a bike turning are in some ways different than a car, but the physics of a bike braking and accelerating are very similar to a car, whether you are talking about the car braking, accelerating, or cornering.

Ultimately from a physics point of view cornering forces or braking and accelerating forces are the same thing and can be represented in a simple force diagram. The forces generated will boil down to downward force vs forces 90 degrees to it.

..Tom

are you kiding me don't you understand that bikes and cars don't behave the same. its called optimization engineers compromise one charteristic to greaten another depending on the ratio thats why engines on most sports and race cars are placed in the center mid rear drivetrains. This place the heaviest component of the car in the center and as low to the ground as possible which provides optimal braking and acceleration by transfer weight evenly between the to.
FYI cars turn using there front wheels which requires as much traction on all four wheels. Bikes turn by leaning and the wheels try to up right it self which pulls the bike in the direction of the lean.

 

[mike.from.canmore]

In controlled conditions with an excellent rider a motorcycle can get 1.3 g's of deceleration.

1.3G's of deceleration without the assistance of supplemental downforce? Are you sure about this? (source please).

1.3g's is quite a bit. This is beyond what I would have thought possible without adding downforce.

 

[Kawi-Rex]

My vote is still with a motorcycle reason being:

It can transfer weight to the front wheel more effectivly(Friction equals normal force * coefficient of friction). In a car since the center of gravity is lower and towards the front of the car most of the momentum is used to continue propelling the car forward during braking were as in a sport bike the weight is higher up and cause a higher amount of torque on the front axial which directs that force into the ground more so than propelling the bike forward which is why cars are more prone to skiding than a bike is.

Second reason under continued use even daily use car brakes tend to feel the effects of heat fade fairly quick due to poor ventilation to the rotors example the video the car was continuosly getting worst im sure if they did another test the car would have been 2 car lengths away(i know there was water but that was less of an influence since abs would avoid any skiding). On a bike the rotors are exposed to a continous stream of cool air to keep them at optimal temp.

Third on a modern day average car the calipers that grab the rotors are only a single piston design which is not ideal for strong braking were as in all sport bikes there is a multiple rotor and piston setup usually 2 rotors 12 piston which is comparable to something off a ferrari.

Forth being that most sport bikes are a equipped with sport tires which are ridiculously sticky wear your average car has all season tires which aren't the best in any weather.

 

[mike.from.canmore]

My vote is still with a motorcycle reason being:

It can transfer weight to the front wheel more effectively(Friction equals normal force * coefficient of friction). In a car since the center of gravity is lower and towards the front of the car most of the momentum is used to continue propelling the car forward during braking were as in a sport bike the weight is higher up and cause a higher amount of torque on the front axial which directs that force into the ground more so than propelling the bike forward which is why cars are more prone to skiding than a bike is.

Second reason under continued use even daily use car brakes tend to feel the effects of heat fade fairly quick due to poor ventilation to the rotors example the video the car was continuosly getting worst im sure if they did another test the car would have been 2 car lengths away(i know there was water but that was less of an influence since abs would avoid any skiding). On a bike the rotors are exposed to a continous stream of cool air to keep them at optimal temp.

Third on a modern day average car the calipers that grab the rotors are only a single piston design which is not ideal for strong braking were as in all sport bikes there is a multiple rotor and piston setup usually 2 rotors 12 piston which is comparable to something off a ferrari.

Forth being that most sport bikes are a equipped with sport tires which are ridiculously sticky wear your average car has all season tires which aren't the best in any weather.

OK...

1. - you view weight transfer as a good thing? the reason your rear brake doesn't stop you is because weight transfer occurs. If you could somehow prevent or reduce the weight transfer, you'd be able to stop by using both tires, and eliminate the risk of a flipover (see point 4). (do you think sway bars on cars increase weight transfer in corners??)

2. - yup that's why we have specified many times in this thread that we are talking about one stop. not repeated stops.

3. - cars have a single piston, sure, but with a MASSIVE VACUUM powered booster and the force of a drivers foot/body weight!!! I thought we ALL concluded already that larger brakes/more pistons etc only helped with repeated stops - not one single stop. This is of course off topic (you could start another thread perhaps?)

4. - yup, bikes sure have sticky tires..
so sticky that....

JohnnyP636, I did a search on this forum for "stoppie" and found this image from this thread . hope you don't mind.
http://www.gtamotorcycle.com/vbforum/showthread.php?t=90569&highlight=stoppie



This is much less common

 

[DY]

caboose already explained how a lower CoG will help a motorcycle brake with the diagram 50 pages back. its called torque. Vtom is correct and this discussion lacks some serious physics. and facts.....:confused1:

 

[mike.from.canmore]

caboose already explained how a lower CoG will help a motorcycle brake with the diagram 50 pages back. its called torque. Vtom is correct and this discussion lacks some serious physics. and facts.....:confused1:

Some people don't get it though... give 'em a chance, they'll come around.
It's an absolute definitive maybe

 

[raginduck]

Without reading through all the posts...

Does anyone have any numbers regarding the braking distances of modern sport bikes?

Also, what are people considering to be an "average" car when comparing?

 

[Kawi-Rex]

Ok if you guys decided to throw out every other aspect of braking and think just about weight transfer during braking not cornering not accelerating a bike can transfer alot of weight to the front wheel yes to the point of flipping if your not careful thats why you practice threshold braking. The physics of braking in a car and bike is similiar the front wheel(s) do almost all the braking if you guys have knowledge of automotive brake systems there are fail safes so that if a brake line is to fail there is always one front and one back working not to keep the car going straight but to always have a front brake. Weight transfer is what gets both objects to a stop if a car didn't transfer weight to the front wheels they wouldn't be as affective since the force of friction is directly related to the amount of force holding the tires to the ground(normal force) x the coeffient of friction of the tires. At cruising a car is balancing its mass at its CoG and the front tires has a force of friction say "F" under braking the momentum is being shifted towards the front of the car some going downward into the ground multipling "F" by the amount of force be exerted perpendicular to the ground and the reset (most) of it pulling the car forward. That momentum is transfered to the front were it can be used to increase the force of friction hence increasing the amount of braking that can be applied before the front tires broke lose and started to skid. But because the CoG is just above the the wheel height from the center it can't transfer momentum as affect as a motocycle were the CoG is higher up and more momentum is transfered to the ground than is used to pull the bike forward.

For those who keep bring up why engineers are building race cars lower to the ground its because they aren't designed to only brake there designed to go fast and corner fast. increasing the CoG would make it impossible to corner at speed but better for braking but there are better ways to over come braking by adding spoilers front lips for downforce and larger dia. rotors with multi piston calipers. Sway bars are designed to maintain the car level and reduce weight transfer(not eliminate) which is bad in a corner since you need traction at all four wheels in fact drivers brake hard before a corner to transfer weight to the front which gives the front tires more traction to allow them to point to the exit quicker and smash the gas. On a sport bike high CoG plays a different role it allows the rider to use more leverage to lean the bike in a turn if the CoG on a bike was lower it would be next to impossible to lean a bike in a turn given that centrifugal force would be to great to overcome at speed. Its been a while since i rode but last time i turned i think I leaned and used my high center of gravity relative to the bike as leverage. If you guys can't get around to realizing CoG plays different roles in different scenarios this thread is going nowhere.

 

[*gSTP*]

Hi Mike.from.canmore

Thanks for starting this thread. It seems that many are misinformed on the topic.

That is not good because a misinformed rider is an accident waiting to happen.

The bright side is this thread may help someone avoid an unscheduled get off.

More than enough real world data is available on the topic. There is no need to get into long physics explanations. Stopping distances are available and published for all production vehicles. Many of the physics explanations being posted are just simply incorrect.

*gSTP*

 

[mikbusa]

After doing some research, it does appear that motorcycles, do have better braking distances on average, according to http://www.mcnews.com/mcn/technical/200801perfindex.pdf - looks like a majority of the bikes are braking right up there with the sports cars with a few exceptions.

Some interesting results, some of the heavy weight cruisers stop shorter than many sport bikes, dual sports have some of the longest stopping distances. That disputes the theory that a high center of gravity is an advantage. 2 tires stop better than 1.


Sports car distances: http://www.motortrend.com/roadtests/112_9705_track_testing_event_part3/60_to_0_braking.html
PORSCHE 911 TURBO 111 ft
FERRARI F355 114 ft
TOYOTA SUPRA TURBO 115 ft
CHEVROLET CORVETTE 116 ft
MITSUBISHI 3000GT VR-4 116 ft
ACURA NSX-T 120 ft
DODGE VIPER GTS 129 ft

Read more: http://www.motortrend.com/roadtests...vent_part3/60_to_0_braking.html#ixzz0cRc3gg3D

The problem is with the bike stopping distances, these are likely achieved in ideal situations likely at a track. In an imperfect world, a car can safely stop on all kinds of crap that will put a bike sliding out of control.

Like *gSTP* said, don't get too confident.

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