Somebody on here said "bikes stop slower than cars"

[timsatx]

Looks like somebody needs suspension work.

[rtarp1]

the place i read it was this forum and the guy was giving advice!??

[stevewfl]

the place i read it was this forum and the guy was giving advice!??

Well, you and i both know oh too well that if its posted on the Internetz, it has to be true 

^^^^^^^^^^^^^^that

[martin_14]

If I may...
[vehicle dynamics engineer = on]
Let's assume a couple of parameters:
a) car tires and bike tires offer the same tire/surface friction coefficient, say 1.
b) both have brakes powerful enough to block all the wheels in the vehicle
That said, both vehicles will achieve a deceleration of 1 g and brake in similar distance.
Now let's add aerodynamics. A bike produces nearly no downforce, but sporty cars do. This will add braking power to the rear axle, decreasing braking distance. Just like carrying a passenger on a bike.
An extra advantage of the cars is that there is less weight transference to the front axle due to lower CoG and longer wheel base. This optimizes the use of the contact patches, since the curve that characterizes the relationship between the exerted vertical load and longitudinal force that the tire can develop has a decreasing rate. That is, the more you load the tire, the more longitudinal force it will be able to develop, but with a smaller factor. For example, if you duplicate the vertical load on a tire, it will develop only 1.6 times the braking force, not twice.
[vehicle dynamics engineer = off]
In extreme cases, say a DTM car against an S1000RR, the bike will crush the car in acceleration, but the bike will have to brake sooner and harder at the entry of every curve. The car has a big spoiler in the back that improves braking (so it will brake harder) and increases the speed at which it can take a curve (an F1 car develops 4.5 Gs, no bike can do more than 1.2 Gs), so it also needs to brake less. At the end of some straight the bike will have to brake 300 yards before the curve from 200 mph to 60 mph, while the car will blast past the bike and start braking only 150 yards before the curve from 180 to perhaps 80 mph. Depending on the track, the checkered flag can lean to one vehicle or the other...

[AZBiker]

According to David Hough, the 60-0 stopping distance of a 97 Connie is 108ft.

You will not be able to stop faster than:
Corvette Z06, ZR1 (late models)
Ferrari Scuderia, 458
911, Boxter
Audi R8
Dodge Viper
Nissan GT-R

It takes a lot less skill to stop a cage quickly.

FWIW, that distance for the Connie is about the same as a pre-ABS VFR.

The average meathead could probably get really close to the min stopping distance in a cage.

How many of us are Hough-level riders?

[stevewfl]

If I may...
[vehicle dynamics engineer = on]
Let's assume a couple of parameters:
a) car tires and bike tires offer the same tire/surface friction coefficient, say 1.
b) both have brakes powerful enough to block all the wheels in the vehicle
That said, both vehicles will achieve a deceleration of 1 g and brake in similar distance.
Now let's add aerodynamics. A bike produces nearly no downforce, but sporty cars do. This will add braking power to the rear axle, decreasing braking distance. Just like carrying a passenger on a bike.
An extra advantage of the cars is that there is less weight transference to the front axle due to lower CoG and longer wheel base. This optimizes the use of the contact patches, since the curve that characterizes the relationship between the exerted vertical load and longitudinal force that the tire can develop has a decreasing rate. That is, the more you load the tire, the more longitudinal force it will be able to develop, but with a smaller factor. For example, if you duplicate the vertical load on a tire, it will develop only 1.6 times the braking force, not twice.
[vehicle dynamics engineer = off]
In extreme cases, say a DTM car against an S1000RR, the bike will crush the car in acceleration, but the bike will have to brake sooner and harder at the entry of every curve. The car has a big spoiler in the back that improves braking (so it will brake harder) and increases the speed at which it can take a curve (an F1 car develops 4.5 Gs, no bike can do more than 1.2 Gs), so it also needs to brake less. At the end of some straight the bike will have to brake 300 yards before the curve from 200 mph to 60 mph, while the car will blast past the bike and start braking only 150 yards before the curve from 180 to perhaps 80 mph. Depending on the track, the checkered flag can lean to one vehicle or the other...

Totally unrealistic, too far off to even be a consideration for general purposes.  Tire contact patch area on motorcycle's tire is too minimal. Performance cars have HUGE WIDE contact patches. Once they get into those sizes, bikes are at a loss.

[Stasch]

I recall this too, and have a vague memory of it being in a magazine article that was talking about ABS too. 

The gist of what I recall being said was to the effect of:  "in real world traffic situations, the total time / distance to stopping at speed, measured from reaction time at point of awareness to the point of complete stop was remarkably similar comparing bikes vs. a soccer mom in mini-van."

I don't recall the exact conditions they were referring to but it was more than controlled testing measuring pure braking performance.

The point I took away from it:  They seemed to be staing saying that although bike's have superior stopping power during actual braking - the perception by most riders that they can stop far quicker than cars is often negated by other factors in real world situations.

(edited for spelling).

[snarf]

Would it change anything if i had car tires on my bike?

Sorry I just couldn't resist

[martin_14]

Totally unrealistic, too far off to even be a consideration for general purposes.  Tire contact patch area on motorcycle's tire is too minimal. Performance cars have HUGE WIDE contact patches. Once they get into those sizes, bikes are at a loss.

Why the big fat tires?
a) So they can handle the power without becoming useless after 500 miles.
b) so the grip is higher (smaller slip angle, hence more precision for the handling), but the maximum grip does not change.
They do not provide extra grip at the limit (sticky tires will let go at 1.2 g or so without aero help) but will provide less slip angle (I'm talking about cornering here, but the concept of slip is the same for braking).

The size of the contact patch is absolutely irrelevant for braking distance, or grip in general. What it does change is the way the tire behaves. But peak grip under straight line braking or acceleration is only dependent on temperature, thread, street condition and rubber compound. Porsche made a study regarding this very interesting topic many years ago and they know what they are doing, in my opinion. The reason tires get wider is to modify the rate at which the grip changes with the vertical load, but not the maximum that can be achieved (not significantly, anyway).

As you know, the typical formula used in phisics at school is that F = friction coef. x load, so the size of the contact area plays next to no role.

The longitudinal slip that happens on a tire while rolling is about 1% and it's increased while braking or accelerating. Narrower tires (smaller contact patch for similar diameter and air pressure) will increase the slip more than wider tires when accelerating or braking, but the grip levels that they can achieve are the same.

Simple experiment: put a brick on a table and 2 brick on top of the 1st one, and with a rope hanging off the table and some weight. Determine the weight that you need to move the bricks. Now put all 3 bricks in a row and linked by a rope, while one brick is still tied to a hanging weight off the table. Determine the weight that you need to move the bricks. It's similar. Contact area is 3 times bigger, weight is the same. Longitudinal force is the same.

[T Cro ®]

the place i read it was this forum and the guy was giving advice!??

Cause it is true.... Cars do stop faster than bikes. Why else would we hear "I had to lay the bike down cause a car stopped short in front of me"..... 

[gPink]

Cause it is true.... Cars do stop faster than bikes. Why else would we hear "I had to lay the bike down cause a car stopped short in front of me"..... 

[Son of Pappy]

Cause it is true.... Cars do stop faster than bikes. Why else would we hear "I had to lay the bike down cause a car stopped short in front of me"..... 

Do you still have my addy?  I need a towel to wipe the coffee off of my keyboard!!