Initial Braking; Slap Them On Or Squeeze Them Quickly?

I was having a conversation with my fabricator friend about the Foxbody Mustang brakes.

The Mustang seems to respond better to aggressively applying the brakes, much like a single seater with downforce or a Modern car with ABS. 

The brakes on Datsun; with it's six inch wide bias ply tires and short wheelbase, need to be squeezed, on albeit quickly squeezed. 

Basically if you slap the brakes on in the Datsun you'll lock a tire up; it needs a split second longer to get to maximum braking. Slapping them on also upsets the chassis. If you measured it it would probably be a hundredth of a second delay but it's a delayed application nevertheless.

So out of curiosity I'm trying to see how folks with different cars approach their braking? Call it a bit of a survey.

I think by nature I'm programmed to quickly squeeze them on rather than just stomping the pedal.  

How the car reacts to a quick stomp will depend a bit on the tires, pedal force required for lockup, and how the chassis behaves under hard braking.  Assuming straight line braking, a chassis that's more stable under hard braking, tires that break away more progressively at the limit, and higher brake pedal effort will all contribute to a car that doesn't mind having the pedal stomped as you're less likely to over-do it and lock a tire or get the car out of sorts. 

For ABS cars I stomp them hard and fast if I'm going in a straight line on smooth pavement, if I need to start braking while I'm still turning or on a rough patch of pavement or if the car doesn't have ABS, control is more important so I squeeze them on as quickly as I can without risking lockup (edit: Or in the case of ABS, surprising yourself with a sudden burst of directional skipping) or upsetting the chassis. For either one, it's even more important to release the brakes smoothly and not too quickly to keep the nose from popping up and unloading the front wheels on corner entry.

Quick squeeze. Ancient ABS means just jamming on it increases the likelihood of ice mode.

GameboyRMH said:

For either one, it's even more important to release the brakes smoothly and not too quickly to keep the nose from popping up and unloading the front wheels on corner entry.

As an instructor I nag nag nag about a smooth pedal release.

Basically the answer is "as fast as you can get away with." How quickly you apply the brakes is going to depend a lot on a couple of factors: Load transfer, traction distribution and brake balance. For example, a Z51 Corvette we were testing a couple weeks ago would get ABS intervention in front if I went too hard on the initial brake application. It wanted to build the load a bit more slowly. The front tires are a lot narrower than the rears, and it's rear-biased with regards to weight distribution, so it wanted some time to properly load those front tires to deliver maximum traction. On the other hand, with our front heavy BMW 435i with a square tire setup, you can spike that pedal as fast as you want and it just squats and stops.

So if you're looking for the edge, I'd say find it by exceeding it and then backing off slightly, especially if it's a newer car or something with generally good brakes, because they'll let you get away with mistakes better than something that's really balance sensitive. 

And I'll definitely second the comment on release. Brake release is a skill that everyone needs to master because it pretty much defines the entire cornering posture after it. It's a skill I don't think we give enough importance to.

JG Pasterjak said:

Our front heavy BMW 435i with a square tire setup, you can spike that pedal as fast as you want and it just squats and stops.

This describes the Mustang. I am also new to this realm, having spent 33 seasons in the 1600lb Datsun, 10 seasons in the F-Mod / F500 and 3 seasons in the D-Sports Racer.

Sure I drive student's front engine V8 cars but I obviously don't flog them like they are mine.

This thread makes me wonder if I'm doing it wrong, haha

For my Elise (ABS), I get peak decel early in the braking zone and then it drops linearly through to turn-in. I like the strong initial application because it has a very rearward CG - like 64% or so. As the weight quickly transfers to the nose, both axles are eventually at 50/50 and then slightly nose-heavy. The heavier the initial stab, the more evenly the braking burden is spread between the four tires throughout the braking zone because it can slow more before the nose gets heavy. ABS for this car is very senstive to a lot of factors, but with my current wheels, pads, and tires, it is very happy. I don't get early intervention, but it usually starts to step in a little towards the middle, and it definitely kicks in when I can trail strongly because the inside gets light.  

This car also is very draggy and has strong engine-braking, so some of that early peak could also be from those two factors. I should look and see if I can spot the coast-down decel between letting off the throttle and getting on the brakes. Overall, braking peak is about 10-15% more than the lateral peaks. 

Edit: I should also add that, that I tend to overbrake. I'm very much on the rarer side of cooked, to quote Shelby in Ford vs. Ferrari, so oftentimes the drop in decel is just because I notice I am over-slowing and need to pull back a little. I imagine I would be quicker with less initial braking in these cases purely on account of less braking. Ideally, I'd have less tapering off if I braked later. 

On the Integra with ABS, I have a good feel for it and just stomping it hard works great on it. 

The Civic with a similar brake setup without ABS, I am still trying to learn and figure it out, and can say I am struggling the non ABS brake feel outside of street driving. 

The MK6 GTI, I can get away with stomping, but encountered what felt like "ice mode" at the last autocross I went to on my last run. Surface changed from smooth asphalt to some sort of rough somewhat gravely surface and brake pedal got hard, and it didnt feel like it wanted to stop. I had issues with the part of the course all day I noticed...

In reply to aw614 :

You're pretty doomed to get ice mode when there's gravel because it detects the wheel decel is far more rapid than it should be. Even with ramping up brake pressure, it'll still lock going over the gravel and inform the ABS that it's on a low grip surface. You're best bet is to release and reapply the brakes so it 'resets'. 

In reply to cyow5 :

This is my standard answer on how to hone in braking points:

When to brake is as simple this; if you are still threshold braking when you should be transitioning to trail braking, which typically happens as you turn in, then you’ve left it to late.

As for when to let off the brakes; if you over rotate the car you’ve left the brakes on to long. If you let off the brakes and the car drifts wide of the apex you’ve come off the brakes to early. 

The reason I'm out braking people is not wholly a case of braking later; it's a combination of having mastered trail braking, which allows me to enter corners at a higher speed, and nailing the turn in points.  If you have the turn in point truly nailed you can ratchet your brake point down until you've left it to deep. After that you take it back a notch.

When I'm new to a track or car I start by approaching the brake zones less aggressively with my focus on finding out the true corner entry speed. Doing that allows me to set my turn in points and all the rest falls into place.