ideal average time to full brake force for track
07-01-2010, 12:43 PM
#16
Advanced
How do you know (in real time, at each relevant corner) that you are applying the desired maximum braking pressure and in the desired time?
In other words, now that you know the information exists, how do you plan to use it to improve your driving?
07-01-2010, 03:21 PM
#17
Rennlist Member
This is the answer from Chris Meissen at OptimumG:
> > Yes typically you want to build brake pressure as quick as possible.
> > The reason for this is that initial braking is typically done in a
> > straight line with little lateral acceleration. Therefore to achieve
> > the best performance you always want use your tires at their maximum
> > capability.
> >
> > So initially when you brake in a straight line you want to immediately
> > be using the brakes and tires at their peak performance. When you
> > start entering the corner you will want to ease off the brakes as the
> > lateral acceleration of the vehicle increases. As the lateral grip
> > provided from the tires increases the longitudinal grip capability
> > will decrease.
> >
> > So even though you don't have a extremely stiffly sprung race car, you
> > will still get the maximum speed from initially braking as hard as
> > possible, as long as you don't lock the brakes up or lose the
> > stability of the car.
By losing the stability of the car, I mean that some cars under hard
> > braking may have a tendency to spin because the real wheels can become
> > almost completely unloaded. You are correct that with a properly setup
> > 911 this shouldn't happen, since a 911 has the majority of its weight
> > on the rear wheels.
> > Yes typically you want to build brake pressure as quick as possible.
> > The reason for this is that initial braking is typically done in a
> > straight line with little lateral acceleration. Therefore to achieve
> > the best performance you always want use your tires at their maximum
> > capability.
> >
> > So initially when you brake in a straight line you want to immediately
> > be using the brakes and tires at their peak performance. When you
> > start entering the corner you will want to ease off the brakes as the
> > lateral acceleration of the vehicle increases. As the lateral grip
> > provided from the tires increases the longitudinal grip capability
> > will decrease.
> >
> > So even though you don't have a extremely stiffly sprung race car, you
> > will still get the maximum speed from initially braking as hard as
> > possible, as long as you don't lock the brakes up or lose the
> > stability of the car.
By losing the stability of the car, I mean that some cars under hard
> > braking may have a tendency to spin because the real wheels can become
> > almost completely unloaded. You are correct that with a properly setup
> > 911 this shouldn't happen, since a 911 has the majority of its weight
> > on the rear wheels.
Another point to add to what is said here: To lock the brakes at 150 MPH takes more pressure and more pedal effort than at 60 MPH. This is part of the reason for on like a lion and off like a mouse. From my personal experience in anything from a spec miata to a Cup Car this is always true. Quick on the brakes with usually max pressure very quickly to squeezing off the brakes as the car decelerates.
07-01-2010, 04:26 PM
#18
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kfyork,
To answer your question: My plan is to try using a target of ~0.2 sec for this time instead of 2.0 sec for this time. I probably will never learn to fit together all the many other things that are involved in making an optimal turn, but identifying this particular approximate target was my goal in starting this thread.
Art
To answer your question: My plan is to try using a target of ~0.2 sec for this time instead of 2.0 sec for this time. I probably will never learn to fit together all the many other things that are involved in making an optimal turn, but identifying this particular approximate target was my goal in starting this thread.
Art
07-01-2010, 04:26 PM
#19
Rennlist Member
Seriously, you can feel threshold braking. And you can tell by your steering inputs/seat how much traction the car has in the corner. If you were threshold braking into T1 at the Glen, and then mid corner it felt like a "non event" - you're probably going slow in the corner.
Next time, brake a little later, release at the same time, and carry 2 MPH faster in the corner and see how it feels. Maybe it'll feel like horrible understeer, and you'll have to delay getting on the throttle to avoid tracking out early... In that case, in mid corner, it wasn't a "non-event" but rather an "event".
This kind of "feeling" and "analyzing" will help you find the "limit". Some people can find it faster than others - and some people can correct at the limit (to make it business like usual) better than other people.
07-01-2010, 05:58 PM
#20
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07-02-2010, 06:50 PM
#21
Three Wheelin'
Guys, happy you all found the Optimum G "Tech Tip". One item not mentioned is that the car has maximum downforce at top speed (I know it is minor compared to F1, but it is your maximum never the less). Friction is directly proportional to the vertical load down on the tire. So, maximum downforce creates maximum grip in braking. As you slow, you lose some downforce so your braking limit is less.
IMHO, you should not consider going to max braking in 0.2 seconds without fully analyzing how quickly you can go from full thottle to starting the brake pressure to move. These two items are very important together.
IMHO, you should not consider going to max braking in 0.2 seconds without fully analyzing how quickly you can go from full thottle to starting the brake pressure to move. These two items are very important together.
07-02-2010, 07:50 PM
#22
NASA Racer
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Another point to add to what is said here: To lock the brakes at 150 MPH takes more pressure and more pedal effort than at 60 MPH. This is part of the reason for on like a lion and off like a mouse. From my personal experience in anything from a spec miata to a Cup Car this is always true. Quick on the brakes with usually max pressure very quickly to squeezing off the brakes as the car decelerates.
07-02-2010, 09:41 PM
#23
Rennlist Member
You'd want to maintain close to steady pressure until you turn in (start to trail brake). There the "string from the bottom of the steering wheel to the brake pedal" analogy is helpful. The more you turn the wheel, the more you release brake pressure. You leaving something on the table if you back off from threshold braking before you trade some longitudinal grip for some lateral grip by turning in.
07-03-2010, 04:02 AM
#24
Rennlist Member
I have to assume pads and pad material are relevant too. My understanding is that with Carbon Metallic pads you actually have to 'feed' them off, if that doesn't sound backwards. I realise that the original question was about how fast you can/should get to brakes once off the throttle but this also doesn't account for heel and toe shifts. If you have a car that relys on rpm rather than torque or has short gearing, then you are more often than not downshifting into most corners anyway, so how does this discussion allow for these events?
I also agree that VR's answer is the best!
I also agree that VR's answer is the best!
07-15-2010, 11:02 AM
#25
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Usual racing principals apply -
Brake as late as possible and as hard as possible
Data Analysis reveals that very hard braking from very high speed yields the highest -G numbers
Stomp on the pedal means 80kg plus, which is easier if your leg isn't straight to start with and you can press back against the seat (hard in some single seaters).
As nothing is ever easy, you must remember not to over brake, or arrive in the corner unbalanced
R+C
Brake as late as possible and as hard as possible
Data Analysis reveals that very hard braking from very high speed yields the highest -G numbers
Stomp on the pedal means 80kg plus, which is easier if your leg isn't straight to start with and you can press back against the seat (hard in some single seaters).
As nothing is ever easy, you must remember not to over brake, or arrive in the corner unbalanced
R+C
