Heavy or Light Braking

[MiketheEngineer]

Will you get more brake and tire wear if you quickly apply the brakes or "drag" them coming to a stop say from a set speed of 50 mph??

Obviously - the slower method allows aero and engine braking to help out longer but all things considered - does it make any difference? The theoretical work is the same - so would not the wear be the same??

Just a dumb old Structurual here that likes fooling around with old cars.

 

[MacGyverS2000]

From a theoretical standpoint, the longer you tajke to brake, the less work is being done by the rotors/pads (due to the engine and aero taking some of the brunt).

From a real-world standpoint? Pretty much irrelevant, particularly since brakes are cheap to replace (compared to engine wear, clutch wear, etc.)

Dan - Owner

http://www.Hi-TecDesigns.com

 

[BrianPetersen]

Taking a long time to come to a stop will allow more of the heat to be dissipated by air circulation and conduction through to everything that the brakes are connected to, in addition to letting engine braking and aerodynamics take care of some of it.

I always get very long life out of brake pads and rotors on my cars.

 

[mattsooty]

Also, by using 'engine braking' more, you will also have an extended periods of over run fuel cut off, saving you fuel & therefore cash.

MS

 

[MintJulep]

Highly dependent on the friction material.

Temperature and shear force within the friction material are of greater interest than work. Temperature variation within the material (hot spots) are also important.

 

[patprimmer]

The most expensive single component in running a car is the hourly rate for the operator. It generally out weighs all other variable cost added together.

I am sure it is very dependant on circumstances as to how it nets out at the end of a trip, but late hard braking does save time but costs fuel, tyres and brake components.

Regards
Pat
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[evelrod]

I've got to go with Pat on this one...
Yesterday I was talking to a UPS driver and commenting on the fact that every time he sat in his seat he buckled his seat belt. In this instance he was simply backing his truck up to make it possible for me to leave...in his truck for no more than a minute...

Me---"Safety first, eh"?...his reply---"The company has harassed me for taking those extra seconds to buckle up when they thought it not necessary. Time is money"! Fancy that...comes as no surprise, though.

Rod

 

[pgpada]

I think that if you let your car brake by itself and in the end apply the brakes a little harder than usual is the most cost effective braking.
Because 1 the engine is in high revs so no fuel is going in the engine. So more engine braking
2 Aero does more job at high speed.
3 And shorter pressure on brakesputs less heat on them. even though applied harder.

PGP

PGP

 

[dbecker]

Interesting concept brought up by Pat, time = money I never thought of that. I guess it stands out to me because I drive an hour each way to work.

 

[drwebb]

So how much of that hour is possible to pull back with late braking?

 

[BiPolarMoment]

Absolutely none if you have to wait for the red light...though you'll have more time to text message.

 

[patprimmer]

Every so often late braking can lead to making it through an orange light instead of having to stop. That's the time saver in that situation.

If there is no traffic and you are on a winding country road, late braking and quick acceleration between curves definitely saves time BUT costs in almost every other variable cost.

A lot also depends on speed limits and compliance to them vs cornering speed. ie If there are frequent large changes in speed you can save a lot of time. If they are infrequent and small, the time becomes insignificant, but the cost also becomes insigifican by about the same factor.



Regards
Pat
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[potteryshard]

Unless you're fortunate enough to be able to afford your own country, habitual late braking affects much more than just your individual drive to work.

The measure of a good driver is not only the number of accidents one has, but also the number of accidents one causes. The societal costs of all those accidents that the late braker leaves in his or her wake adds to the indirect cost of operating a vehicle.

In a completely just world, the costs of accidents that one triggers through selfish driving habits would be in some manner charged directly to that person. As it is, all we can do is remind people that absolutely nothing is done in isolation.

 

[BiPolarMoment]

I don't want to get political so I'll keep this short--braking late does not "cause" any more accidents that were not already predicated by inattentiveness of the follower. I think it's disingenuous to assign blame to those that initiate no direct action on yourself.

Pat: do you actually have orange lights in your area or are you making a funny? I only ask because the common usage is "stale yellow" in my recollection.

 

[patprimmer]

In a completely just world, the costs of wasted time [b/] that one causes [b/] through selfish driving habits would be in some manner charged directly to that person. As it is, all we can do is remind people that absolutely nothing is done in isolation.

There you go. Fixed.

Also, in a no traffic situation how does late braking cause others to have an accident. Even in a heavy traffic situation, it is the responsibility of the following driver to maintain a safe distance as you never know when a emergency stop that has nothing to do with late braking practices might be required by the car in front, like a kid on a skateboard shooting out onto the road or a large animal running onto the road.

Regards
Pat
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[IRstuff]

"I think it's disingenuous to assign blame to those that initiate no direct action on yourself."

So, if you see a bullet coming at you, you wouldn't duck? Yes, they hit have hit you anyway, but why wouldn't try to avoid the incident if you can?

TTFN

FAQ731-376

 

[SomptingGuy]

Any driving style that increases a vehicle's acceleration will also increase tyre wear.

Heavy braking often goes with heavy acceleration, so that kinetic energy is wasted. No relevance to wear, but bad for fuel economy.

But if the vehicle really needs to stop, why put the brake discs through more of a thermal/stress cycle than they need?

- Steve

 

[NormPeterson]

With the turn that this thread seems to have taken, I'd prefer that the driver in the car following mine be reasonably familiar with intentionally braking hard rather than only doing so when tripped into full panic mode for whatever reason.


Norm

 

[Higgler]

Whats in use now for cars that apply their own brakes to follow a certain distance behind the car in front of them?

Wonder if they use a G force sensor to put a shaped f=ma breaking force on the passenger to keep their comfort level at optimum?

I know Lexus LS460's have this laser system, I'd expect all the high end cars do too.

 

[potteryshard]

Umm... Point completely missed.

Of course the obligation to avoid rear-ending a hard braking vehicle belongs with the car following.

The point is that unless no other cars are allowed to use the road at the same time, driving is not a solitary pursuit; it is a cooperative endeavor.

Any driving style that fails to recognize the neccessity of the cooperative part of the endeavor is selfish. Whether that is using up people's available reaction time in hard non-emergency braking, not being smart enough to figure out the turn signal lever, meandering along below the speed limit, or just in general acting as if no other vehicles exist all come down to selfishness.

Traffic engineering has long recognized that vehicle flow resembles shock waves near critcal velocity; one person stabs the brakes, and each of the following vehicles has to stop progressively harder as the reaction time cushion is used up, until some poor sap, ten vehicles behind, and who was following at a reasonable distance is presented with a total speed change that is cumulatively impossible to handle.

Talking about the mechanical engineering aspects of hard braking in a race environment is one thing, but talking about the mechanical engineering aspects of non-emergency habitual hard braking on public roadways without simultaneously talking about the traffic and human factors engineering aspects seems irreponsible.

I'm sorry if that view offends anyone, but as Engineers, aren't we trained to look at the whole picture?