I have a braking question

That's a good question and I am interested to hear what those more learned than I have to say.

Braking hard or slow will dissipate the same energy. The difference will be in peak brake temperature. Hard braking will have much higher peak temps because the energy is dissipated over a shorter time.

What I don't know is how temp impacts the pads wear rate. My guess is that it has minimal impact

 

I would bet on hard braking, in increments, knocking off 20-30 mph in each increment, with a few seconds cooling between. My 2 cents.

 

Not sure I agree with this one. Theoretically the peak temp with this method should be higher than a smooth steady brake over the same amount of time.

In my previous post I left out any comment about sheer force applied to the pad because it is probably negligible. BUT, multiple braking events would inflict sheer force spikes. I suspect, with no knowledge or data, impulse braking is a bad idea to minimize wear.

My bet is on one steady braking event that uses the entire deceleration zone.

 

My WAG would be; a combination of gentle downshifting and steady braking would be cause the least wear. Let the compression of the motor help with braking.

 

I was thinking more about the temperature build up and not the wear. I readily admit that my reasoning is based mostly on instinct.

 

As pointed out above, it's going to create about the same kinetic effect braking harder v. a little easier - same amount of heat energy is created.

The real difference between steady braking and cycled braking is that the heat will go more quickly into the caliper rather than the bearings/hub with steady braking (instead of cycled). The pad is the main interface and method of transferring heat from the rotors into the calipers and hub and surrounding metal. The longer the pad is in contact with the rotors, the faster the calipers will pick up the heat rather than bearings and hub.

So, pick your poison - do you want to boil the fluid in the calipers, or fry the bearings in the hub??

 

I recently completed a massive big brake upgrade, Wtih F50 Brembos on the front and 360 rears on the back on my old 308, so, i have no worries on track day

The same kinetic energy will be dissipated into heat, whether you brake fast or slow. The shorter the time that you get the job done,the higher the component temperatures will be. It takes time to dissipate the heat.
It is not uncommon to hear that cars that are tracked hard will go through a set of pads in a few track sessions. Street driven cars go many many times that mileage - the difference is the ware that takes place at elevated temperatures.

So to the original question, to it as quickly as possible or do it easy in the distance available ?? I would go with the longer distance, (time) for lower temperatures and less ware.
hth,
chris
Image Unavailable, Please Login

 

Anyone asked Brembo?

 

Is there no appreciable heat dissipation, from the rotor and caliper, to the surrounding air?

 

Yes, of course, but at a much slower rate compared to how fast heat is moving to the brake fluid and other components. Ait is not a good conductor of heat. Metal is. Moving the air helps of course, but it still pales in comparison to conducting heat through metal.

 

Heh. Dig the gratuitous F pic

 

Avoid downshifting, clutches are way more expensive than brakes.

 

Hi Fred,

Eventually, it all goes out into the air. Giving it more time to dissipate the heat makes it easier on all of the compnents.
chris

 

Thanks Dave,

I spent a lot of time trying to get a big brake set up, figured out and balanced.

It wasn't cheap, but when the 360s and 550s are cooking their brakes at the end of the straight, i am closing up the gap that their huge horsepower gained them on the straight.

There is something very comforting about never having to worry about the brakes. If you track you will know what i mean.

chris

 

Any time you can avoid slipping the clutch, either for take off or shifting gears, you will reduce the ware on the clutch, So double clutch to bring the revs up to matching speed and shift - minimal ware.

I forgot to mention that air and mechanical drag also help to slow the car, so the longer you take, especially from high speed, to brake, the easier it is on the brakes.

Having said all of that, slow braking is clearly not the fastest way around the track or the most fun on a challenging road.

Bring the equipment up to the task.

put the pedal down.
chris

 

I can't stand it amymore. It's spelled "wear" not "ware".

Dave

 

He was speaking of hardware on the clutch, nuts and bolts, that sort of thing. What I want to know is who is "amy more????" Is she hot?
Dave

 

From what I have read on "track guy" sites I get the impression that when it gets hot enough brake pad friction material melts and comes off in globs. This would explain how they wear out so fast during track events.

The high heat peaks would also tend to warp the rotors

So I would expect that steady lower-decel rate braking would be better than pulsating heavy.

 

Hit the wrong key, but "wear" is the correct spelling. Ware or wares has nothing to do with brake, clutch, or any other mechanical part wear.

Dave

 

Sorry, it was my bad attempt at humor with "ware" referring to a manufactured item. I'll go back to my day job now.
dave

 

From any aircraft's flight manual about braking after landing, and especially from T.O. F-111-F-1, which I have, the most efficient use of a braking system and the one causing the least wear and least heat pumped into the system, is one hard depression as late as possible, continuing until the desired speed is reached. Any other technique will increase wear and increase the heat load on the brake system.

Taz
Terry Phillips

 

This is incorrect. As long as the rotors are allowed to cool evenly, they will remain true. I get the rotors on my F355 hot enough to cook hot dogs after a 20 minute track session. Yet they last 30 track weekends. In order to cool evenly, they must remain rotating down to 600dF or so, and then allowed to cool without any caliper pressure on them the rest of the way.

A cool down lap is basically manditory to cool the rotors sufficiently so that they will not warp. On my cool down laps, I put the car in 6th gear and cruise through the whole lap without using any brakes, then into 4th drive into the pist without brakes and stop using just a smidgen of brakes.

I, personally, have never had anything come off my pads other than dust and larger particles of dust. The big globs of stuff on the rims are more typically pick-up rubber. This pick-up rubber also gets into the radiators and needs cleaned out now and again.

But, something special when the rotors get up to the point they glow cherry red. At this point, the radiative transport of thermal energy exceeds the convection transfer of thermal energy. This greatly increases the ability to get rid of heat, assuming the pads and fluid will put up with those temperatures.

 

6,000 ft less 4,500ft...

I'd suggest brake hard enough to stop in 1,499 feet, or it might get a load more expensive than brake pads and discs (rotors).

Or am I missing the point?


Just make sure the car gets a long fast run back to the paddock with minimal braking before parking, ie: try to cool the system off between runs. And NEVER leave it parked with the handbrake / parkbrake engaged, as this helps transfer the heat into those pads and calipers leaving you with two hot brakes and two cooling ones.

 

Neat! I didn't know that. Very interesting.