motorcycle weight vs. stopping distance

[kml]

Cut and paste from;
http://www.promocycle.com/documentations/studies-eng/freinage_a.pdf
on page 17


"The presence of a passenger does not seem to have a significant effect on the maximum braking capacity of a motorcycle in a straight line"


cheers
ken

 

[Alsterbator]

Same rider, same day, same conditions...

So you're saying that if we take the braking system off of a Busa and dump it onto a 600, take the tires off the Busa and put it on the 600... the 600 now has same braking distance as the busa did before we took the brakes and tires off of it?

Really?

Find anywhere where I have said that and I'll give you a cookie...
How does same rider, same, day, same coditions and now you want to throw a different bike in there but swap braking systems. Whatever.

 

[danath 34]

you say no, then you say yes?

he said "during a maximum braking event". If hes just riding around town sure he can brake earlier and/or harder to compensate for any added weight, but in a maximum braking event you cant brake earlier or harder

I think thats the key, right there.
And more weight doesnt always improve traction.
On acceleration, yes it does help by adding more traction. Thats because the weight is downwards towards the ground, forcing the tire into the pavement more, improving grip.
However, when braking or turning, the inertia of the extra weight is going forward (when braking) or to the side (turning), which the tires have to then compensate for, and more traction is used up.

 

[MelodicMetalGod]

So, based on the MSF article posted up, it seems that it may be that traction increases sufficiently with weight while the limiting factor may be the breaking systems ability to apply enough force at some increased weight threshold. If so, the only question that I have is:

"What is the exact proportion of traction increase with weight increase?"

 

[Alsterbator]

Alster, bro, you need to pull yer head outta the book and try and apply real world logic. According to you everyone in the AMA should be riding Busa's. A dump truck shouldnt need any more breaking distance full than when empty. A cement truck has the same breaking performance full or empty. You keep overlooking maximum breaking. Yes I can break in 40 feet from 20 miles an hour alone or 2 up WHEN NOT AT MAX. I can not break in the same distance at max breaking if I am heavier. Remeber that based on your theory the opposite would have to be true as well. Im here to tell you that on the same bike, a lighter rider accelerates faster in the same distance!

I have applied this very question with the only variable being a passenger and was successful in proving the the theory. Thats all the real world logic I should need.

 

[jellyrug]

So, based on the MSF article posted up, it seems that it may be that traction increases sufficiently with weight while the limiting factor may be the breaking systems ability to apply enough force at some increased weight threshold. If so, the only question that I have is:

"What is the exact proportion of traction increase with weight increase?"

Lets say your Busa has a soft sticky tire with a coefficient of friction of 0.8

Lets say your busa weighs 573 lbs and you lock both wheels with the brakes while the bike is stationary.

To move your Busa, you will need 573 x 0.8 = 458 lb force to break traction.
If you weigh 200 lbs. you will now need (573 + 200) x 0.8 = 618 lb force to break traction.

So, to answer your question, the coefficient of friction remains constant and the proportion of traction increase is directly proportional to the weight increase.

 

[MelodicMetalGod]

Lets say your Busa has a soft sticky tire with a coefficient of friction of 0.8

Lets say your busa weighs 573 lbs and you lock both wheels with the brakes while the bike is stationary.

To move your Busa, you will need 573 x 0.8 = 458 lb force to break traction.
If you weigh 200 lbs. you will now need (573 + 200) x 0.8 = 618 lb force to break traction.

So, to answer your question, the coefficient of friction remains constant and the proportion of traction increase is directly proportional to the weight increase.

Well, if that is correct, then the limiting factor would seem to be the braking systems ability to apply a large enough stopping force to accommodate increased weights. Again, at some point, a threshold of failure will be reached and heavier weight will require greater stopping distances.

 

[Shane45]

You calculations are static which ignore to much.

Go with the super exageration, it makes it easier to see. A fully loaded cement truck CAN NOT stop in as short a distance as an empty cement truck. AN elephant on a busa can not stop in as short a distance as a mouse on a busa. the heavier the object the more it takes to stop it, start it or make it change direction. Alster, if you could stop in the same distance at max braking 2 up or single, then you simply werent at max breaking.

 

[jellyrug]

Well, if that is correct, then the limiting factor would seem to be the braking systems ability to apply a large enough stopping force to accommodate increased weights. Again, at some point, a threshold of failure will be reached and heavier weight will require greater stopping distances.

Correct, if your brakes fail, you will take a lot longer to stop.

Here is a linky that explains this whole thing a lot better than I can. Somewhere it says that mass has nothing to do with stopping distance, which is kind of correct, not 100% accurate but close.

ABOUT THE MOTORCYCLE BRAKING

 

[the_1]

As for as truck drivers go. A loaded truck stops qicker than any unloaded ive ever been in. That is what i know for certain. This is bikes and i like the open discussion. I 1st went with the more the wait deal but cdl trucks r in a totally diff class. I would say this though. If u had mechanicl scale that the 1st has a riderand then the 2nd did not. Id have to believe that the 1 that had the rider on would stop faster. If this was the exact everything.

 

[jellyrug]

So if we now throw all the debates and theory out the window, don't ya think this fellar would have stopped a whole lot sooner if he doubled the weight with a big butt passenger? This is what happens with Busa tires and Busa brakes on a 600cc.

 

[UncleSteve]

put one of these beauties on the back of your busa and see if you can stop in less distance.
Her weight transfer would crush your boys against the gas tank and cause you to scream a lung out onto the pavement, your spine would invert causing the electrical pulses that fire the muscles in your hands and feet to quit, you then unwillingly release the front and rear break .......increasing your total stopping distance.

It could happen...

 

[Mr Bogus]

awww Steve? uke:

 

[shadetree57]

I'd never thought this tread would go this far although the information is great. The best answer so far to me is twotonevert's. It really shows his interest. I'm sorry, I laughed for quite awhile. maybe everyone else just passed it by. Personally i hate abs braking systems. Be carefull out there everyone.

 

[jellyrug]

I have lots of padding, no problem, they are so cute those girls.

Send them my picture and do you have a phone number for one of them?

Also, if you look at my picture, you will know I have experience with weight and stopping distance. In fact I'm regarded as an expert.

 

[UncleSteve]

mine was bad, yours is off the scale...

 

[MelodicMetalGod]

Correct, if your brakes fail, you will take a lot longer to stop.

Here is a linky that explains this whole thing a lot better than I can. Somewhere it says that mass has nothing to do with stopping distance, which is kind of correct, not 100% accurate but close.

ABOUT THE MOTORCYCLE BRAKING

To clarify, my point was not that the brakes fail completely but that at some point (weight increase) the brakes would no longer be able to apply enough stopping force to achieve maximum braking, thus, longer stopping distance is required at some threshold of weight.

 

[greyrocket]

 

[jellyrug]

To clarify, my point was not that the brakes fail completely but that at some point (weight increase) the brakes would no longer be able to apply enough stopping force to achieve maximum braking, thus, longer stopping distance is required at some threshold of weight.

In the real environment there are some factors we have not considered in previous posts. The coefficient of friction between rubber and asphalt is not linear. A cold tire has a lower coefficient of friction than a warm tire, hence Nascars warm their tires, so do drag racers. However, as the rubber warms, at a certain point the coefficient of friction reduces drastically. When a tire skids, the heat generated on its surface is excessive, hence we lose a lot of traction. This is why ABS helps.

So getting back to splitting hairs on weight and braking distance, with more weight the grip will be better, due to more heat, to the point where traction is broken, thereafter it will be worse. So, with ABS and more weight stopping distance will be shorter, but if traction is broken without ABS, stopping distance will be longer.

Your view is one of semantics, if brakes are overloaded to the point where they cannot break traction (no ABS) we can consider them as failing, or fading.

 

[Over_Easy]

The above article falls in line with what we have said. There will be a breaking or tipping point for the weight/brake pressure/traction equation. So the answer is yes and no.