bpu699

Stupid question I suppose...

If you lose the brakes, why not just use the emergency parking brake rather than downshifting???

I would think it would work better, you can modulate it, and that's what it's there for?

Also, if you lose the front brakes, you still should have rear brakes ad most cars have dual master pressure ports, no?

ExMB

Cars can have an electric parking. emergency brake or a foot operated one. How do you propose to modulate that one?

mark kibort

if you practice is, it could be effective. but, in most cases you are going very fast, the rear brakes dont slow the car much, so the tendency would be to lock up the rears tossing you in a spin or slide. (could be good , or might not be good depending on the conditions, speeds, track etc) most race cars, dont have e-brakes. downshifting , especially as you slow down to 3rd or 2nd gear, provides enough engine braking to make some hairpin approaches from very high speeds, if there is enough runnout. sure beats just giving up and running straight into the tire or a fence/wall.
the other main reason not to rely on the e-brake, because you are going to be approaching a turn, so you want both hands on the wheel to navigate a early apex type turn approach. (using the turn and possibly a slide to slow the car down)

as far as the back up system..... ive often wondered how that works, because it seems with a blown front brake line , there doesnt seem to be available rear brakes.......at least with my experience of a line failure.

MarcD147

At Sebring in the 12 hour race there was a car that lost brakes. It just stayed straight and hit the wall frontal. Commentators where discussing that was the best way...

Safer than trying to lose speed and create an angle.
footage:

bpu699

I haven't personally ever tried using the parking/emergency brake while moving... May want to try it at least a couple times on a safe street to see what happens...

Downshifting is more natural... but wouldn't you essentially be grenading the motor???

If you are going down a straight at 100+ say in 4th at 6000 rpm or so... brakes don't work... you downshift to 3rd... you are now way past redline, no???

If its a matter of life and death, which it may be, then it really doesn't matter. But all downshifting does is apply a braking force to the rear tires... same, in theory, as the emergency brake...

You obviously can modulate and electronic parking brake or foot brake... but most 80's/90's cars have a center console hand brake... The JDM drifters certainly know how to use it

porscharu

I am not aware of a modern car that doesn't have a dual circuit master cylinder. You would still have your rear brakes.

bpu699

That's was my thought too... Can someone explain?...

If your front breaks over heat/leak/whatever, why wouldn't the rears work? And if so, how would downshifting be "better"?

ExMB

My understanding is that the 2 circuits each control 1 front and 1 rear brake.

Wikipedia

mark kibort

I explained how this happend to me, at laguna. (on video) on the downhill portion approaching the andretti hair pin at 130mph. had i just rode it out, i could have lost the car, but probably (due to the long sand area) been ok and maybe the car would have slowed in time. However, by just practicing and understanding the cars natural characteristic to slow at 130mph, even downhill, you wait ..........blip downshift........wait, start a turn in, blip downshift, to get to 2nd and if things work out, you can stay on track.. if not, worst case you are MUCH slower and any impact with tires or sand , will much less dramatic.

Actually, the force of aero braking and enging braking are quite substantial at 100mph.. so if you just lift, you are almost at the limit of the rear tire braking force anyway.......so, lift wait a second and you can blip again and slowly release the clutch in 3rd (your case) now the rear forces are greater, near max, and start some turn in (as you approach the turn ,which has tremendous decel forces) and blip again and grab 2nd to make the turn... all without the ability to use the brakes... if you have rear brakes stilll effective, sure , use them, and augment it with the engine braking, due to its natural antil-lock characteristics and effect. the main thing, as you say, the engine provides a braking force and it's better to have the hands on the wheel to control it best you can.

I lost mine and the pedal went to the floor and there was nothing happening with any braking force that i could detect. maybe due to the proportioning valve you really need to know its there and push extra hard? it just went to the floor after a blown front line and there was nothing .

even if the do work, downshifting is better as it adds a very controllable and predicable force on the rear tires , and has natural antil lock characteristics. the worst thing you can do is put the car in neutral and ride it out. ive seen that video of the guy that did that, and he ended up blowing out the track gate at sebring and rolling out on to city streets! there is no downside at all by downshifting in that emergency.. just learn how to do it correctly. very easy to practice.

Shandingo

If I am not mistaken, the brake lines on the 2016 RS are hard lines all the way to the calipers. As already mentioned here, replacing them with braided lines can simplify caliper removal and therefore pad changes, but it will not make any difference in terms of performance because the hard lines do not expand at all.

Edit: there must be some part of the lines that is flexible, but it is probably a very short piece, as I believe the hard lines do go to the caliper on the RS, but there should be a flexible piece of rubber hose somewhere further upstream. Still, I doubt you will feel much, if any, difference in pedal feel.

bpu699

Thanks for the explanation... Sounds like you have some skill ...

I think if you find that you don't have brakes in the middle of the starting straight, you can downshift through 3 gears with a 1 second pause in between...

If you find out at the 3rd braking marker...not so much...

So, is the key to test the brakes in the middle of the long straight? Is that what people do?

Because if I found out I had no brakes deep into the end of the straight, I suspect I might have time to downshift 1 gear...

ExMB

AFAIK its a hose from the body to the bracket per the PET, regardless.

mark kibort

assume you mean hard rubber lines (for "hard lines") it has to have a lot of flexibility as the calipers rotate with the wheels. but yes, you are right, there has never been an proof that the bare rubber lines have any expansion over braided. any feel change is due to better bleeding upon installation . however, you can feel them bulge and burst when they go!

actually, that is a good practice, but more for checking if there has been some pad push back.. (meaning, a warped rotor or loose wheel bearing, broken spindle can force the pads back in the caliper) what happens here, is when you apply the brakes, there is no pedal ! it has to be pumped up. usually no time, same effect as brake line burst. SO, yes, thats a good idea. But, when my failure happened i was getting a little suspect of the feel and ran down to the #4 marker, and that was enough time to quick blip downshift... from 4th to 3rd.. start a turn in and blip downshift to 2nd just at the early apex point.... that gave me enough room to slow the car down to 50ish to complete the turn with no off track excursion. again, worst case , even with a # 3 marker event, would have been a slower speed into the traps which is much safer than just giving up and steering through the sand to the tires.

mark kibort

He had PLENTLY OF TIME to do something..... to my points, to bleed off speed and possibly make the turn or at least reduce the force at impact. if you don't practice it or think about it, you wont do it in an emergency. it's something everyone should practice and try when you have a clear track ........ lift, wait, blip downshift, pause, blip downshift and see how much speed you can bleed off in an emergency. However, that Sebring video is a bad situation where another car was clearly in the line of trying to save the turn and car. so, so avoid hitting the car in front, he sacrificed the car..... PLUS, that is a very high speed approach going WOT until the 200FT marker. Had the car not been in front of him , it was possible to save it given the type of turn and the amount of distance to bleed off speed and turn. either way, like i said, worst case, he could have reduced his speed significantly if he had gabbed a gear downward.

MarcD147

He did NOT have plenty of time. He was diving at approx 170 mph into one of the trickiest corners in the US.

Further down the corner the options get a lot uglier.

it looks like he got one maybe two downshifts in and that was as good as it gets there.

He avoided sideways impacts, flips and bounces back into traffic et .