good trailbraking article in this months sports car

[SgWRX]

interesting article about trailbraking and slow-in-fast-out. i was thinking about it a week or so ago. i never really got the whole idea of slow-in-fast-out and always used to slam into corners with the brakes on hard while turning. thinking back to a recent auto-x my best laptime was when i was calm and braking before the corners, then turning. seems to be the best starting point for getting better. for slalom, it's best to try and get through all at one speed as opposed to speeding up / hitting the brakes huh? is slow-in-fast-out part of "being smooth"?

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[Homemade WRX]

it works for me...the key is just finding and judging the limit of just slow enough

[adhowe70]

SIFO is the best starting point for improvement. Once you've mastered that, you can slowly increase the amount of trailbraking that is used.

Oh... and the longer the straight following the corner, the less trail braking you'll use (to maximize exit speed all the way down the straight.)

I didn't get fast until I fully embraced SIFO.

Andy H.

[Dark]

http://www.tckc.net/tips_faqs/drivin...techniques.htm

try this web site, it had some basic idea for breakin and accelerating, it also show the race lines for common corners you will see on a race track.

[SgWRX]

Originally Posted by adhowe70

Oh... and the longer the straight following the corner, the less trail braking you'll use (to maximize exit speed all the way down the straight.)

Andy H.

by this you mean, harder on the brakes before the corner? or, just less braking to keep momentum going?

good link

[adhowe70]

Harder on the brakes before the corner. SIFO leads to faster corner exit speeds:

Brake earlier to achieve a slower minimum corner speed. Stay wide longer. When you do start to turn, its a tighter radius (still wide of the apex). But, the radius gets larger and larger as you approach the apex, allowing higher speeds than the trail braking line.

You pay for it up front with SIFO, but get rewarded down the next straight. The balance is how much trailbraking nets you the fastest time. The bigger the bonus to be had after corner exit, the closer the optimum line will be to SIFO.

Aside: For beginners, trailbraking isn't a good plan. Its easy to be overly aggressive and upset the car at corner entry. If you do this, you end up driving a longer line (missing the apex completely) and waiting waaaaay to long to get on the throttle. This is why SIFO is taught first.

[CirrusWRX]

But I think a key point that was mentioned in the "other" thread about this article (please forgive me as I forgot who posted it...) but they focused SO much on the "advantages/disadvantages" using all sorts of measurements and data acquisition and mathematics, but they never delved into the "when is a good time/corner, and when is a bad time/corner."

In other words, they never addressed situations where playing captain late-brake, while on paper reduces the amount of time to get through turn x, it reduces overall speed by y. While the time made up for the speed lost may be very beneficial to your overall lap time through a twisty section, it spells absolute death if you're leading onto the longest straightaway on the entire course.

The previous poster in the other thread gave an example that if you're going to save .2 seconds by trailbraking, but lose 2mph of speed leading onto a straight, you'll ultimately lose lap time if you choose that method over a nice SIFO. So while you're giving up .2 seconds in the corner, you're gaining 2 mph that will ultimately pay back > .2 seconds over your 5-15 second trip down the straight.

[adhowe70]

Yeah, that article needed a serious "your mileage may vary" warning on it. All they really did was prove that trailbraking works in NASCAR.

Good point though... trailbraking is faster from the point where the SIFO driver applies the brakes until the apex. SIFO is faster from the apex until the next braking zone. So, which line is faster depends on how long the braking zones and subsequent acceleration zones are.

The real point they made is that driving less distance (especially at super slow autocross type speeds) is faster. That's all it proved.

Andy H.

[jmott]

did you read it?
slow in fast out was not the quick way. trailbraking was =)

every slalom is different. normally a constant speed is not the fastest way, no.

Originally Posted by SgWRX

interesting article about trailbraking and slow-in-fast-out. i was thinking about it a week or so ago. i never really got the whole idea of slow-in-fast-out and always used to slam into corners with the brakes on hard while turning. thinking back to a recent auto-x my best laptime was when i was calm and braking before the corners, then turning. seems to be the best starting point for getting better. for slalom, it's best to try and get through all at one speed as opposed to speeding up / hitting the brakes huh? is slow-in-fast-out part of "being smooth"?

[jmott]

the time they were measuring WAS total laptime, which includes straights (its an oval remember)

Originally Posted by CirrusWRX

But I think a key point that was mentioned in the "other" thread about this article (please forgive me as I forgot who posted it...) but they focused SO much on the "advantages/disadvantages" using all sorts of measurements and data acquisition and mathematics, but they never delved into the "when is a good time/corner, and when is a bad time/corner."

In other words, they never addressed situations where playing captain late-brake, while on paper reduces the amount of time to get through turn x, it reduces overall speed by y. While the time made up for the speed lost may be very beneficial to your overall lap time through a twisty section, it spells absolute death if you're leading onto the longest straightaway on the entire course.

The previous poster in the other thread gave an example that if you're going to save .2 seconds by trailbraking, but lose 2mph of speed leading onto a straight, you'll ultimately lose lap time if you choose that method over a nice SIFO. So while you're giving up .2 seconds in the corner, you're gaining 2 mph that will ultimately pay back > .2 seconds over your 5-15 second trip down the straight.

[jmott]

ever seen michael schumacher data logs?

trailbraking seems to work at super high f1 speeds too

Originally Posted by adhowe70

Yeah, that article needed a serious "your mileage may vary" warning on it. All they really did was prove that trailbraking works in NASCAR.

Good point though... trailbraking is faster from the point where the SIFO driver applies the brakes until the apex. SIFO is faster from the apex until the next braking zone. So, which line is faster depends on how long the braking zones and subsequent acceleration zones are.

The real point they made is that driving less distance (especially at super slow autocross type speeds) is faster. That's all it proved.

Andy H.

[CirrusWRX]

Originally Posted by jmott

the time they were measuring WAS total laptime, which includes straights (its an oval remember)

An oval is but one example of a course layout. IMO, 99% of the people on this board do not drive ovals. So while the article was talking about ovals, as adhowe pointed out, YMMV- I don't drive ovals so trailbraking into every corner is most likely NOT going to yield the fastest lap time for a given circuit. It's not an exact science, but it's not black magic either. What works well for one track or one car will not necessarily work for a different track with the same or different car.

While the article had some good stuff, all I (and others in the other thread) was trying to say, as with most things in life, it should not be taken as the quintessential be all end all theory of racing.

And please note that Michael Schumacher is:
1. Quite possibly the most talented driver that has ever lived (aka: better than all of us will ever be)

2. Driving a vehicle that in no way shape or form resembles the handling dynamics that most of us are familiar with.

[srf]

The problem with ovals is it doesn't answer the question for compound corners, in which you would probably only trailbrake for the first turn?

Schumacher doesn't hold a candle to Senna.

[CirrusWRX]

Originally Posted by srf

The problem with ovals is it doesn't answer the question for compound corners, in which you would probably only trailbrake for the first turn?

Schumacher doesn't hold a candle to Senna.

Exactly- ovals are boring

Compound corner can mean anything- are we talking increasing or decreasing radius? High speed or low speed corners? "Type 1, 2 or 3" turns? Turn leading onto the longest straight? Turn leading onto the slowest portion of the entire course?

There are just too many unknown's to say that "this is what you do to go fast." That's all I'm trying to say.

And I say Schumacher ARGUABLY- if you want to argue Senna, Petty, Andretti, Fangio, Prost et al. I'd say you have a darned good case. All phenomenal drivers undoubtedly.

[Impreza01]

If one does the physics, trailbraking should theoretically win. The reason is while doing the conventional slow-in-fast-out, you're braking in a straight line and then turning. This increase the amount of time your car is decellerating. With trail braking, assuming you're very good, your resultant acceleration vector is pointing at an angle normal to the center point of the radius of the term. This means the acceleration vector pointing inward from friction and braking vector must equal that vector.

The big problem is trail-braking is a very advanced technique. People seem to throw it around as if it's as easy to do as slow-in-fast-out.

[ITWRX4ME]

The oval shape of the track has little to do with why I disagreed with the SC article. It was the length of the straights between the turns. In this case, the straights were very short, creating a situation where trailbraking line (and the inside radius line) had a significant advantage over the SIFO line.

[ITWRX4ME]

Originally Posted by Impreza01

If one does the physics, trailbraking should theoretically win. The reason is while doing the conventional slow-in-fast-out, you're braking in a straight line and then turning. This increase the amount of time your car is decellerating.

Not quite. You can actually decelerate quicker in a straight line.

Originally Posted by Impreza01

With trail braking, assuming you're very good, your resultant acceleration vector is pointing at an angle normal to the center point of the radius of the term. This means the acceleration vector pointing inward from friction and braking vector must equal that vector.

The advantage of trail-braking, when it's appropriate to do so, is to move the deceleration zone deeper into the turn. This increases the time you spend at top speed in the preceding straight by combining the acts of braking and turning. This results in sliding through the early part of the turn as the car rotates.

You're then on the throttle a bit later than the SIFO car but you get to the mid point (apex) of the turn faster.

Originally Posted by Impreza01

The big problem is trail-braking is a very advanced technique. People seem to throw it around as if it's as easy to do as slow-in-fast-out.

I agree that it's an advanced technique but I don't notice people throwing it around as if it's easy.

I do think people should learn the SIFO way first because trail-braking puts more variables into the mix when you just starting to learn to go faster. Once you master threshold braking in a straight line, you can incrementally (a few feet at a time) move your braking zone deeper into the corner.

Trail-braking is more error prone. It's way easier to misjudge your entry speed and, at a minimum, blow past the line you need to be on. Worst case you can drive off the end of the track. Somewhere in between, you can spin.

That's why it's critical to understand how to balance your car.

[Impreza01]

Originally Posted by ITWRX4ME

Not quite. You can actually decelerate quicker in a straight line.

Originally Posted by ITWRX4ME

The advantage of trail-braking, when it's appropriate to do so, is to move the deceleration zone deeper into the turn. This increases the time you spend at top speed in the preceding straight by combining the acts of braking and turning. This results in sliding through the early part of the turn as the car rotates.

That's what I meant by the fact you can decelerate quicker.

Originally Posted by ITWRX4ME

You're then on the throttle a bit later than the SIFO car but you get to the mid point (apex) of the turn faster.

Not only that, but if you look at the physics behind it, your acceleration vector is in the direciton you want it to be. When doing SIFO, during hte pure cornering of the turn, you're not gassing it. Assuming your car is at constant velocity, the acceleration vector of the car is pointing towards the center of the radius of turn. However, during trail braking, your acceleration vector is pointing towards the path behind you. When you gas it at the apex, the acceleration vector should be pointing towards the direction you want to go. By some arbitrary point, your terminal velocity is faster on the exit than SIFO.

Originally Posted by ITWRX4ME

I agree that it's an advanced technique but I don't notice people throwing it around as if it's easy.

Maybe it's just the people I've been talking to.

My source of information comes from the magazine Racecar engineering, August 2004, Vol. 14 No. 8. They have the physical diagrams on page 55 and 56. If I have the time, perhaps I'll scan the articles in.

[SgWRX]

i'd love to see that!

Originally Posted by Impreza01

My source of information comes from the magazine Racecar engineering, August 2004, Vol. 14 No. 8. They have the physical diagrams on page 55 and 56. If I have the time, perhaps I'll scan the articles in.

[adhowe70]

Its worth noting that some cars are a helluva lot easier to trail brake than others. A FWD Accord (their test car) is on the easy end of the spectrum. So is an Impreza. I can trailbrake my Scooby all day long with great success.

My S2000 is at the hard end of the spectrum. I drive a line that is much closer to SIFO when I'm in my S2000... Upsetting the back end of the car has dire consequences: an inability to use the throttle without instigating the spin cycle.

[ITWRX4ME]

Originally Posted by adhowe70

Its worth noting that some cars are a helluva lot easier to trail brake than others. A FWD Accord (their test car) is on the easy end of the spectrum. So is an Impreza. I can trailbrake my Scooby all day long with great success.

My S2000 is at the hard end of the spectrum. I drive a line that is much closer to SIFO when I'm in my S2000... Upsetting the back end of the car has dire consequences: an inability to use the throttle without instigating the spin cycle.

Great point. And another one glossed over in the article. It's entirely possible for two cars to take different lines through a turn with both going as quickly as possible for that car. Swap lines and they'll both choke.

Edit: At Shenandoah I was trying to learn the best line around the track by following faster cars. There's one turn that everyone used a late apex, as it leads onto a long gently sweeping uphill curve (going under the bridge).

I would consistently find myself losing significant ground to other cars because I had far less lateral grip on that line. The second day, after I was more comfortable with the rest of the track, I started working on that turn.

The late apex line forced me to enter slowly and build speed through the turn. But I could never build enough speed that I had to use all of the track on the exit. A quicker entry on the same line caused too much sliding.

So, realizing that there was more room on exit, I tried taking an earlier apex with a slightly higher entry speed. This line put me a full car width to the right of the other line. Low and behold, the pavement was almost imperceptibly canted to the inside of the turn at that point. Now I had more cornering grip so I could pass through the turn at a higher speed.

That early apex obviously forced me to run out of track quicker, but it translated into at least 5 mph in increased exit speed.

Completely counter intuitive. And I never would have seen that pavement difference had I not tried that line.

[kfoote]

Originally Posted by ITWRX4ME

...Low and behold, the pavement was almost imperceptibly canted to the inside of the turn at that point. Now I had more cornering grip so I could pass through the turn at a higher speed.

That early apex obviously forced me to run out of track quicker, but it translated into at least 5 mph in increased exit speed.

Completely counter intuitive. And I never would have seen that pavement difference had I not tried that line.

[hijack] This is a great example of why you should walk a track that you have never been to before, to pick up things like this. Sometimes it's also good to walk it after you have been on the track, as you can pick up things that you just can't see when you're in the car going 50+ MPH. I've got about 15 track days at Lime Rock, and probably 30 laps walking the track. When I walked it last Friday night between qualifying and the race, there were a few things that I picked up that I had either never noticed before or had forgotten about. I went out for the walk to check something very specific in Big Bend, but I also picked up new information on the left hander and how the different track surfaces dry with respect to one another.

[GarySheehan]

THEORY: Trailbraking is ALWAYS faster as it allows the driver the opportunity to keep the tires on the outside edge of the traction circle.

REALITY: Trailbraking is only faster if it is done properly. If you are slower while using trailbraking, you haven't completely mastered it yet.

Gary
Sheehan Motor Racing
www.teamSMR.com

[ITWRX4ME]

Originally Posted by GarySheehan

THEORY: Trailbraking is ALWAYS faster as it allows the driver the opportunity to keep the tires on the outside edge of the traction circle.

REALITY: Trailbraking is only faster if it is done properly. If you are slower while using trailbraking, you haven't completely mastered it yet.

Gary
Sheehan Motor Racing
www.teamSMR.com

Yeah. I see what you mean.

[adhowe70]

Originally Posted by GarySheehan

THEORY: Trailbraking is ALWAYS faster as it allows the driver the opportunity to keep the tires on the outside edge of the traction circle.

REALITY: Trailbraking is only faster if it is done properly. If you are slower while using trailbraking, you haven't completely mastered it yet.

Gary
Sheehan Motor Racing
www.teamSMR.com

Word!