hard braking before race start... what's it for?

noamkrief

3593951377411601

Hey everyone, I'm new to this forum.


 


You guys notice that after the warmup lap right before the riders get into position they seem to get on the brakes hard for a quick moment about 3-5 times?


 


What is the reason for this? 


I was thinking maybe


1) warm up front tire


2) warm up brakes


3) warm up fork oil


 


But non of those make sense because it's such a short period, it seems "nothing" compared to how hard they brake and warm up the front tires / brakes / fork oil during warm-up lap which they are actually going quite fast...


 


Just curious.


thanks


Noam

Click to expand...

 


It's to seat the brake pucks to the discs so that the brakes are rubbed in good. It is not unknown for a racer to hit the first corner and the lever to go all the way down and have no brakes at all.


 


Edit - Welcome to the forum - Hoping you enjoy yourself here

whammy

3593961377412995

 

It's to seat the brake pucks to the discs so that the brakes are rubbed in good. It is not unknown for a racer to hit the first corner and the lever to go all the way down and have no brakes at all.

 

Edit - Welcome to the forum - Hoping you enjoy yourself here

Click to expand...

George Michael is correct

If you note though, top riders like Bautista dont employ this technique.

JohnnyKnockdown

3593971377413453

George Michael is correct
If you note though, top riders like Bautista dont employ this technique.

Click to expand...

excellent

JohnnyKnockdown

3593971377413453

George Michael is correct

If you note though, top riders like Bautista dont employ this technique.

Click to expand...

AB has never used his brakes on the first lap. Counterproductive to his suicide attempts.

whammy

3593991377414618

AB has never used his brakes on the first lap. Counterproductive to his suicide attempts.

Click to expand...

Someone in the paddock told Bautista that brakes slow you down, so he had his disconnected

Garbin

3594051377418146

Someone in the paddock told Bautista that brakes slow you down, so he had his disconnected

Click to expand...

 


An even better line. Seriously the way the grid is lined up this race we could very well have some drama unfold on the first lap.


 


My eyes will be glued to the screen

noamkrief

3593951377411601

Hey everyone, I'm new to this forum.


 


You guys notice that after the warmup lap right before the riders get into position they seem to get on the brakes hard for a quick moment about 3-5 times?


 


What is the reason for this? 


I was thinking maybe


1) warm up front tire


2) warm up brakes


3) warm up fork oil


 


But non of those make sense because it's such a short period, it seems "nothing" compared to how hard they brake and warm up the front tires / brakes / fork oil during warm-up lap which they are actually going quite fast...


 


Just curious.


thanks


Noam

Click to expand...

 


Brake temperature


Tyre temperature


 


In that order I'd imagine, and I'd be surprised if anything else even came into it,  besides a bit of the psychological stuff.  Certainly do not think it is 'positioning the brake pucks' or whatever it was that someone said

 
whammy

3593961377412995

It's to seat the brake pucks to the discs so that the brakes are rubbed in good. It is not unknown for a racer to hit the first corner and the lever to go all the way down and have no brakes at all.

Click to expand...

The 3 round donuts are pucks or cups or pistons. They push against the


pads which put pressure on the rotor. All 3 pucks must be firmly seated


against the backside of the pads and the friction material rubbed into


the rotors. Not just one but all three else you have no brakes in the


first corner. Don't believe me go ask a racer and make sure you tell


them you thought they were warming the brakes up before a race.

whammy

3599401377840709

The 3 round donuts are pucks or cups or pistons. They push against the


pads which put pressure on the rotor. All 3 pucks must be firmly seated


against the backside of the pads and the friction material rubbed into


the rotors. Not just one but all three else you have no brakes in the


first corner. Don't believe me go ask a racer and make sure you tell


them you thought they were warming the brakes up before a race.

Click to expand...

 


I have read somewhere there is a routine when leaving the pits the first thing the rider does is ensure the pads are against the disc, in case they were pushed back during a wheel change. I assume this is what you are refering to. If not done, its going to be a problem in the first corner of the warmup lap, not the race.


 


noamkrief is asking why brake hard after the warmup lap? Surely they use the brakes during the warmup lap, so the pads are already seated by then. That sharp stoppie style brake thing they do is replicated in other types of racing such as F1 etc, right before the start. I always assumed it was to build up the heat in the carbon discs.

birdman

3604741378262744

I have read somewhere there is a routine when leaving the pits the first thing the rider does is ensure the pads are against the disc, in case they were pushed back during a wheel change. I assume this is what you are refering to. If not done, its going to be a problem in the first corner of the warmup lap, not the race.


 


noamkrief is asking why brake hard after the warmup lap? Surely they use the brakes during the warmup lap, so the pads are already seated by then. That sharp stoppie style brake thing they do is replicated in other types of racing such as F1 etc, right before the start. I always assumed it was to build up the heat in the carbon discs.

Click to expand...

 


It would definitely be for a last second chance to heat the discs/tyre. They would have already done a couple of braking applications from 200kph on the warmup so it's a bit late to seat the pads. Also remember the guys on the front row have to wait a while for everyone else to grid up so every last degree will help.

Garbin

3594051377418146

AB has never used his brakes on the first lap. Counterproductive to his suicide attempts.

Someone in the paddock told Bautista that brakes slow you down, so he had his disconnected

Click to expand...

When one of the tech guys told Bautista not to forget the brakes this time, he said " who you want me to break ? "

birdman

3604741378262744

I have read somewhere there is a routine when leaving the pits the first thing the rider does is ensure the pads are against the disc, in case they were pushed back during a wheel change. I assume this is what you are refering to. If not done, its going to be a problem in the first corner of the warmup lap, not the race.


 


noamkrief is asking why brake hard after the warmup lap? Surely they use the brakes during the warmup lap, so the pads are already seated by then. That sharp stoppie style brake thing they do is replicated in other types of racing such as F1 etc, right before the start. I always assumed it was to build up the heat in the carbon discs.

Click to expand...

OK I see that there is some misunderstanding and that is my fault. I have a tendency of not explaining things fully. I will go thru again and try to add details that were omitted. Before each race the pads, rotor and tire are replaced on the bike with brand new ones. In order to replace them the pucks need to be pushed all the way down into the caliper. The pucks fit extremely tight in the caliper bores so tight in fact that they suffer from a condition known as stiction. This tight fit is necessary to keep the caliper from leaking fluid when it gets hot and expands creating loose tolerances. The bike takes to the track on the first lap out called sighting lap at a nice slow pace so the fans can "sight" their favorite rider by paint scheme and colors. The bikes align on the grid and then do a warmup lap at an elevated speed but not yet racing speed. This lap has added some heat to the caliper that might have a puck with a stiction problem. This heat is needed in the caliper to help overcome any stiction. Approaching the grid at a slow speed the rider will do a series of bunny hop brake applications. Slow speed is the best way to free a puck because it allows vibrations from the rotor and pads to be transferred to the caliper and that vibration will cause the puck to jump against the backside of the brake pads.You will not get the vibrations at an elevated speed, they occur at slow speed only. If stiction is present then it will be known instantly because the brake lever will fall down against the throttle. And the next pull of the brake lever will restore itself to a full lever.


The bunny hops at slow speed serve one other function although not as important. The same vibrations that freed the puck will cause minute cracks in any glaze that has formed on the new rotor and new pads. New clutches and brakes are prone to developing a glaze. We have all seen how quick a clutch can go just launching off the starting line. Those minute cracks will allow the brakes to shed the glaze and it looks exactly like the black dust we wash from our mag wheels on our Corvette.


One other thing, brakes do not need to be heated up. They are a heat engine within themselves and can create huge amounts of heat very quickly. If you have ever been to a night race then you will have seen how fast they can generate heat. They can go from ambient temperature to glowing red in a fraction of a second. The problem has always been shedding the heat generated by brakes ie Cal's sheet aluminum air ducts on the end of his forks at Silverstone.


If you have benefited from this please remember to help me out when I need it cause I know for a fact I do not know everything MotoGP

Whammy, all more or less correct although I suspect (like birdman) in MGP, as in club racing, that any 'stiction' issues are resolved LONG before the final grid formation and the low-speed stoppies are the equivalent of an ice hockey goalie adjusting his cup before the drop of the puck, even though he already knows his nads are protected!


 


Regarding the other point, carbon-fibre disks do indeed require an initial heat build-up to function at their optimal level.


 


As to the 'glaze', even at club-level you 'dress' pads and disks prior to installation to eliminate this issue.

A short story


You visit your uncle in the big city and he drives you around to show you all the sites. You notice he has his left foot on the brakes while he is pointing out the numerous things of interest. After thirty minutes he approaches a stop sign but instead of stopping short of the sign he over runs into the intersection and pretends he needs to pay more attention to his driving. Both of us know that is hogwash and know exactly why he ran out into that intersection. His brakes had glazed.


Now let's revisit stiction and the stuff I left out when I was trying to fix things. If stiction can be present when applying brakes then the same stiction will be present when releasing the brakes. The warm up lap will have the same effect as your uncle's scenic tour. So now we know that the riders are looking for more than one kind of stiction and are also checking to see if their brakes release quickly and cleanly. Stiction is stiction whether moving in or out of the caliper. No brakes into the first corner will be an "OH ...." thing whereas brake fade into the first corner will be a "Whoa" thing. Stiction in or stiction out.


Now on to brake warming. It don't matter if Valentino Rossi himself tells you he is warming the brakes just laugh at him. He is either pulling your leg or is repeating an urban legend he has heard from someone else. Those brake rotors can go from a surface temperature of 70F to 1200 F in less than 1/4 second. They don't need warming up cause they are self warming. If you were to tell me they needed to go through a heat cycle to improve their performance I might bite on that one. But brake warming in itself is a farce.


These are the things I have seen in my lifetime and of course coming to me for answers is like going to a doctor. You really need to get a second opinion. I've not been here long enough for you to have reason to trust my judgment or advice.


 


Note - I do consider this a good exchange between members and a benefit to all.

Are you really saying that MotoGP brakes work just great from cold? I think you wrote that twice. Self warming? You could say that tyre surfaces, and we know how lovely cold tearing is to a slick.


 


You know that the like of carbon-carbon brakes work better when stinking hot? The hotter they get, the more temp gradient is available and thus the more kinetic energy they can convert to heat in a given time (power). That goes for all brakes, it's just that Carbon-Carbon meet their thermal limits at higher temperatures than steelies/cast.


 


Carbon-Carbons don't need a deposit of pad material on the disc, pad - carbon, disc - carbon. Different concept to steel/cast discs. Your uncle story? Any racer dragging their steels to the point of glazing needs to take up another sport.


 


Stiction? $60K brakes and the seals are preventing the pistons from retracting to the point where your lever comes back??


 


MickD, Tom, etc got it right.


 


The only binding or weird lever feel brakes I've experienced were some ISR 6 pots I ran for one meeting on my RS....and the binding wasn't from seal stiction...it was from the stupid design with 6 separate pads. Which, if they were worn at all, would twist/.... in the caliper and make the response really inconsistent. The rattley floating disc that come with them also cauised this with the little pads getting easily knocked-back. Scary and .....

Ahhh, yer reading my posts again...


 


From MGP.com:


 


Although the lighter carbon discs are therefore preferable to their steel alternatives when they are working correctly, they are far more temperature sensitive. Their functionality is virtually non-existent until the discs and pads are heated to their premium operating temperature, and while they heat up quickly, rider caution is required during sighting and warm-up laps, and even the first couple of corners in a race.


 


I could find more urban legends...


 


F1 carbon brakes build temperature at a rate of 100°C/tenth of a second for the first half second of breaking AND THEN start to work. Having carbon brakes 'pre-heated' prior to the drop of the flag is both prudent and necessary.

Mick D

3605001378291012

Ahhh, yer reading my posts again...


 


From MGP.com:


 


Although the lighter carbon discs are therefore preferable to their steel alternatives when they are working correctly, they are far more temperature sensitive. Their functionality is virtually non-existent until the discs and pads are heated to their premium operating temperature, and while they heat up quickly, rider caution is required during sighting and warm-up laps, and even the first couple of corners in a race.


 


I could find more urban legends...


 


F1 carbon brakes build temperature at a rate of 100°C/tenth of a second for the first half second of breaking AND THEN start to work. Having carbon brakes 'pre-heated' prior to the drop of the flag is both prudent and necessary.

Click to expand...

 


 


exactly, and in the rain, they can't use carbon brakes because they don't get warm enough for breaking efficiency.

I assumed it was to warm up the brakes as well, F1 drivers do a similar thing when they get back to the grid after the warm up lap as well. I'd want to be damn sure my brakes were going to work just fine when I hit a corner at the speed they go.

Braking is to heat carbon rotors to optimal temp for a consistent response prior to lights out.


Pads are seated well before race start. It's not a issue. FYI, riders do at least 2 laps before the start where brakes are used significantly.


F1 uses a carbon ceramic hybrid brakes, which are more temperature stable, sharper and more expensive. This is outlawed in GP, mostly due to a small propenstiy toward chipping but partly due to cost and usability.