59 replies to this topic

[rolf123]

Could someone please explain this to me?

Looking at the onboards over the years, the braking distances in F1 are now less than 100m mostly and I've noticed that drivers will brake in a straight line first but then also while turning and almost to the apex of the corner.

In all other forumlae and in F1 in times gone by (early 90s and before) this was not possible. All braking had to be in a straight line or risk losing the rear.

Now I know that cars had TC and ABS for a while but the braking style is not discernably different this year.

Can anyone explain how they do it? I know that they release braking pressure as they get deeper into the braking zone but F1 drivers have always had to do this due to the loss of aerodynamic grip as you get slower. Surely, this is not the explanation?

[Ross Stonefeld]

Its hard to say for certain without a decent helicopter shot, but I recall Da Matta saying a few years ago in F1 (because of the grooved tire/aero mix) you had to take a corner in a more of a V shape. So maybe thats why it looks like they're carrying heavy braking into the apex.

But all race cars driven at any semi-competitive speed are trail braking. What surprised me somewhat was when I noticed even bikes do. I figured if you had any decent brake on when you turned the front would skid away from you.

[OfficeLinebacker]

Yeah it's trail braking.

The best way to imagine the body movement is to imagine that there is a cable connected from the bottom of the steering wheel which is just long enough to allow full braking with the wheel straight. As you start to turn the wheel, you can't brake as hard.

The idea is that the grip from the front wheels can be used for either braking or turning. You can mix & match, so as you slow down, you turn harder, & vice versa.

[murpia]

It really comes down to driver skill and also driver style.

A driver trail braking in an F1 car will contantly be modulating brake pressure to take account of any or all of the following factors (in rough chronological order) :

build up of brake material temperature,
build up of longitudinal weight transfer,
loss of aerodynamic downforce due to speed loss in a straight line,
changes in engine braking due to rpm drop and downshifting,
build up of lateral weight transfer on initial turn-in,
loss of aerodynamic downforce due to yaw,
loss of longitudinal weight transfer at the apex.

The Valencia track (permanent not the new street circuit) has a number of impressive trail-braking corners, a driver who attempts to 'brake in a straight line and then turn-in' there would lose whole seconds of laptime.

Regards, Ian

[rolf123]

Interesting, so how come I barely noticed this in say the late 80s/early 90s? Even with longer braking distances, were drivers trail braking even then?

You can tell from the engine notes when they finish braking and I never remember any of this during that earlier period...?

Or is this a feature of modern cars? I suspect that modern cars are very forgiving in terms of chassis/suspension handling and ignoring the aero.

[zac510]

Sometimes you have to know it exists to recognise it!

[rolf123]

What I mean is, nowadays at least half of the braking zone is while steering. No way did that phenomenon used to exist. So why did drivers in older eras not take advantage of this? I'm convinced that the cars are more tolerant and forgiving today.

I just wonder how the cars evolved in this direction. Is it the tires maybe?

[Bill Sherwood]

THe drivers would modulate the brake pedal as needed to stop the rears from locking up as they start to generate lateral loads. And the latest F1 cars have a very long wheelbase-to-track ratio so they'll inherently be more stable like that anyway.

[Powersteer]

F1 cars are no where near as tolerant and forgiving. Only thing that seems to make it behave better is the lack of torque on mere 2.4 liters although one might argue the high revving sharp powerband can make things complicated. Besides that, you are either on your racing line or off the track. I think trail braking allows for the front wheels to have more grip so when entering a corner it would help understeer. The amount of downforce on the rear wheels with todays f1 car help pin the rear end from slipping.

Probably it comes down to balancing understeer, oversteer and four wheel drifting, cetain heavy understeering corners ask for more trail brake while higher speed corners ask for less of it. 2¢!

[Lukin]

It's been around as long as tyres haven't been able to generate full lateral grip at the flick of the switch. The nature of lateral tyre grip generation means that you can't go to full lateral grip instantly as you turn the wheel so to maintain the highest amount of total acceleration (i.e. maximise the G-G plot) you have to slow the car down as the car generates lateral grip.

[Ogami musashi]

more simply, i just think the traction circle is far higher than before (=lot's of grip) so that you can simply combine more actions.

F1 tyre's are designed to provide a lot of lateral grip (to the expense of pure longitidinal grip) so with the total grip aviable it is better to trail brake.

[Kalmake]

Better drivers have been trailbraking since the 60's, if not earlier. Maybe some of the turbos or wing-cars were so difficult to handle, that it was not a given.

Famous old quote: "It is amazing how may drivers, even at the Formula One level, think that the brakes are for slowing the car down." -Mario Andretti

[Fat Boy]

Originally posted by Kalmake
Better drivers have been trailbraking since Ben Hur

Fixed.

[rolf123]

Few have offered an explanation why braking has visibly changed on the onboards in the last 15 years. btw I have 20/20 vision!

[Ross Stonefeld]

A larger % of overall grip coming from aero maybe?

[Ogami musashi]

Originally posted by rolf123
Few have offered an explanation why braking has visibly changed on the onboards in the last 15 years. btw I have 20/20 vision!

As i said earlier, and as ross just said again, i think the simple fact the cars have far more grip now just make that you can trade more braking with steering.

and if you can do that, then it is the fastest way for sure.

[murpia]

Originally posted by rolf123
Few have offered an explanation why braking has visibly changed on the onboards in the last 15 years. btw I have 20/20 vision!

First make the assumptions that the slowest point in a corner is still the apex, and that the apexes are still in the same places.

If grip has gone up in the last 15 years, then braking points are now closer to the apexes. This means the proportion of straightline distance that makes up the braking point -> apex distance is much less. Drivers have little choice but to trail brake more.

Regards, Ian

[zac510]

I thought my explanation was spot on!

[DVtriple6]

Very interesting thread. I read through it at work yesterday and until then I thought that braking while turning was a no-no. I'll look into practicing this in a go-kart. Ones skill must always improve.

However, when trailbraking in racing and long races at that. Tirewear? could that become an issue? Logic tells me that when braking and cornering you will loose more rubber than you would if not trailbraking. But then if you regulate brake pressure it may not. Thoughts anyone?

[primer]

Originally posted by DVtriple6
Very interesting thread. I read through it at work yesterday and until then I thought that braking while turning was a no-no. I'll look into practicing this in a go-kart.

Make sure the tires have warmed up lest yer life become exciting.

[DVtriple6]

Originally posted by primer


Make sure the tires have warmed up lest yer life become exciting.

In a rental go-kart mate?

Now I'm tempted to try with cool tires and see what happens. I've only once went off in one of those and that had nothing to do with speed but rather tired arms.

[Ross Stonefeld]

Originally posted by DVtriple6

However, when trailbraking in racing and long races at that. Tirewear? could that become an issue? Logic tells me that when braking and cornering you will loose more rubber than you would if not trailbraking. But then if you regulate brake pressure it may not. Thoughts anyone?

The faster you go the more you're going to wear the tires. You should still trail brake. Just do it earlier or reduce your corner speed or whatever. I don't think the fundamentals of driving change when you're looking after your resources, but rather to what extent you take the performance.

[GeorgeTheCar]

The phenomenon was first well described by Mark Donohue in his book "Unfair Advantage" in his discussion of Friction Circle which he learned about while using the GM testing grounds and instrumentation.

there is a brief description of Friction Circles

http://www.auto-ware.com/setup/fc1.htm

[OfficeLinebacker]

This is good stuff. While I understand the basics of trail braking from the raw performance point of view, I am learning much from this thread. Thank you!

[cheapracer]

Originally posted by GeorgeTheCar
The phenomenon was first well described by Mark Donohue in his book...

I can recall reading reports from Moss in the 50's about it and Clark was a known proponant of the 'V'.

Its been going on forever depending on driver style, its just more visable now because of what Murpia said.

[cheapracer]

Its bugging me, what the 'F' is trail braking anyway?

Isn't that what 4wheel drives do downhill on "trails"

The word itself seems to me to be new and trendy to use for a simple thing thats been around forever and is simple physics. Race cars never only ever braked in a straight line.

[OfficeLinebacker]

Originally posted by cheapracer
Its bugging me, what the 'F' is trail braking anyway?

Isn't that what 4wheel drives do downhill on "trails"

The word itself seems to me to be new and trendy to use for a simple thing thats been around forever and is simple physics. Race cars never only ever braked in a straight line.

It means the brake pressure is trailing off as the wheels are turned more.

[rolf123]

I understand the explanations given. You can tell from onboard videos that in today's F1 cars compared to those from 20 years ago, much more of the braking is done while steering. Let's just call this exploting the friction circle as people have said.

What I still don't understand is why the car doesn't often violently lurch out of control? In other classes of motorsport where 90% of the braking is done in a straight line and maybe 10% is done while steering, if you brake too late and try to compensate by doing more of your braking while steering (say 80/20) then it is very easy to lose control. Many cars in motorsport simply don't tolerate more than a tiny bit of braking while steering - they want most of the braking to be done in a straight line.

So, given this, and even if today's cars are more forgiving, how come we don't see more drivers losing control?

I could understand this if it were possible to adjust left:right brake bias but with a 50:50 distribution I just don't understand it? If trail braking really were so easy then why weren't drivers 20 years ago in F1 killing most of their speed during corner entry and approaching the apex, rather than mostly in a straight line and a little on corner entry?

[Ogami musashi]

Originally posted by rolf123
I understand the explanations given. You can tell from onboard videos that in today's F1 cars compared to those from 20 years ago, much more of the braking is done while steering. Let's just call this exploting the friction circle as people have said.

What I still don't understand is why the car doesn't often violently lurch out of control? In other classes of motorsport where 90% of the braking is done in a straight line and maybe 10% is done while steering, if you brake too late and try to compensate by doing more of your braking while steering (say 80/20) then it is very easy to lose control. Many cars in motorsport simply don't tolerate more than a tiny bit of braking while steering - they want most of the braking to be done in a straight line.

So, given this, and even if today's cars are more forgiving, how come we don't see more drivers losing control?

I could understand this if it were possible to adjust left:right brake bias but with a 50:50 distribution I just don't understand it? If trail braking really were so easy then why weren't drivers 20 years ago in F1 killing most of their speed during corner entry and approaching the apex, rather than mostly in a straight line and a little on corner entry?

Apart from advance in stability especially via aerodynamic stability and load transfer mitigation, you can apply the same reasoning.

A loss of control is a loss of grip by one or several tyres. If you do have more grip aviable then the loss of control is less likely simply because, even with load transfer you still have enough grip.

[McGuire]

They are still doing the bulk of their braking in a straight line. However, the straight-line braking distances are now shorter, that's all. But the distance from corner entry to apex is not going to change (not unless they change the track) so it looks like they are on the brakes relatively longer in the corner. But really, nothing about trail-braking has changed significantly.

Eventually, given sufficient technical advances in braking, the driver could stab the brakes hard for an instant at corner entry and then trail-brake to the apex. In fact, when I saw the F1 cars going into the T1 right-hander off the front straight at the first USGP at Indy (after not seeing F1 cars run in person for a number of years) that is what it looked like to me. It was rather stunning, looked like an optical illusion.

[cheapracer]

Originally posted by OfficeLinebacker


It means the brake pressure is trailing off as the wheels are turned more.

Yes I know. Now read my post again like it was written by a sarcastic person.

[cheapracer]

Originally posted by rolf123
Many cars in motorsport simply don't tolerate more than a tiny bit of braking while steering -

WTF??????????? Do you even have a car licence?

Now read McGuires last post and Murpia's post about 34000 times.

The only thing I reconise that some of you may be talking about is the transition from turning in under brakes to coasting before accelerating - generally somewhere before the apex depending on about a squillion different variables not the least the radius shape of the corner. At the old, old Calder tarck I braked and turned and slid all the way to the apex as it was a massively reducing radius all the way to it - and I died every lap doing it and every race had to be stopped because every race car lost control every lap doing the same. In fact thats why racing was really banned in Swedan, those darn Swedes kept braking while turning and crashed at every corner. Then those mongrel Swedes and their Finnish cousins later started jamming thier left foot on the brake pedal while actually going through the apex, wow I don't know how any of them are even still alive today.

[Bill Sherwood]

It's a bit hard to see, but I do it on a few corners in qualifying at the Malaysian 12-Hour at Sepang.



Mainly at the end of the front straight.

Not all corners are best trail-braked into, some are though.

I also trail-brake at times in my racing car, which has a terrible track:wheelbase ratio (about 1.5:1) and if done carefully it's controllable. The longer Mallock Mk31 I'm building will be far better though as through the longer wheelbase there's less weight transfer and so it will be more stable on turn-in, regardless if I trail-brake or not.

[McGuire]

Originally posted by cheapracer


Yes I know. Now read my post again like it was written by a sarcastic person.

That would make a hell of a sig line.

[rolf123]

Cheapracer, everyone here has been constructive and yet you throw some kind of cheap shots. Suits your name I suppose. Let's talk like adults please.

[primer]

Originally posted by rolf123
Let's talk like adults please.

It does seem that you aren't really serious about this topic. :

As far as I can tell, everyone trail brakes ALL the time. Track or road, race car or road car, me or my grannie Sure the amount of force you apply on pedal as you reach the apex might vary, you might modulate in various different ways, but to me straight line braking sounds like exception rather than rule. Are we even talking about the same thing?!

Not trail braking sounds so incredibly.....wasteful. Take almost any sporty car or a go-kart and go to a track with some amateur drivers. If you only brake in straight line and then coast to apex, on most courses you'd be the slowest person around. You'd probably also cause an accident or two as people run into your back under braking.

[OfficeLinebacker]

The natural inclination in a road car is to increase brake pressure as the car is decelerating. That is the opposite of trail braking.

[Catalina Park]

When I was working on a ground effect Formula Pacific in the early 80s the driver made the comment that with the grip the car had he could brake all the way to the apex unlike with the old Formula 2 cars of the 70s that he had driven.
So I don't think that it is a new idea to be braking up to the apex.

I know a lot of tracks where you have to brake during a corner. When Wakefield Park was built all the braking areas were in curves, they have since straightened out most of them to spoil the fun.

[Todd]

Originally posted by Ross Stonefeld
What surprised me somewhat was when I noticed even bikes do. I figured if you had any decent brake on when you turned the front would skid away from you.

It is because of the nature of the front fork. The rider needs to keep the front suspension compressed while transitioning from brake dive to lateral acceleration. Because bikes lean, the fork perceives both brake dive and lateral acceleration as compressing forces, and if you release the brake before turning in, the spring in the fork rebounding will destabilize the contact patch. Good riders are the ones who can release the brake at a rate which keeps the fork compressed during this transition, therefore keeping the total force on the contact patch fairly constant. There are some other things going on too, like the steering axis being more vertical with the bike leaning forward, but the advantage of keeping the tire loading constant is simple enough.

[Powersteer]

Race bikes has a slipper clutch system designed around trail braking. The wheelbase to CoG ratio of a race bike is so high compared to a car that limit is a matter of going over rather than losing grip so to brake as late as possible requires lots of trail braking and whatever loss of traditional race line happens, the acceleration of a bike makes up for it.

Todd full covered controlling trail braking.

[fester82]

What nobody has mentioned so far is the prevalence of left braking that also lends itself to trail braking. With new transmissions, straight cut gears, and clutches that don't need to be used except getting started - you might as well use that other apendage for something. Heel and toe braking and double clutching will become a lost art all to soon!


Fester

[cheapracer]

Originally posted by rolf123
Cheapracer, everyone here has been constructive and yet you throw some kind of cheap shots. Suits your name I suppose. Let's talk like adults please.

As an Adult I expect you to offer an assumption, a question, a proposal or counterproposal, an observation, hell, even with my ego I will listen to advice, but if you make a clear and concise statement as you did, then thats what I will reply to.

[cheapracer]

Originally posted by Catalina Park


I know a lot of tracks where you have to brake during a corner. When Wakefield Park was built all the braking areas were in curves, they have since straightened out most of them to spoil the fun.

If I'm not mistaken Australia has the worlds ultimate braking corner where the cars start to brake at the apex at 300 km/h while cornering all the way down to 80km/h and then actually transfer the load from the outside tyres to the other side while braking into the following corner. Of course I am talking about Caltex Chase at Bathurst.

Of course as many Ozzies know, it does go very wrong there sometimes (another FWD sucks bit of proof too!)
http://www.youtube.c...feature=related

Any fond memory of the 'Chase' Bill?

[Bill Sherwood]

Originally posted by cheapracer
Any fond memory of the 'Chase' Bill?

It was no big deal in the Celica - we'd belt through it in 6th at about 230km/h (at about 0.7G lateral, so more speed was quite possible) and then brake for the LH'er. I used 4th gear but most of the guys used 3rd for the LH'er - I lost a little bit of time doing that but all of us changed into 5th at nearly the same point down into the last corner so I figured it was worth doing that for less stress on the car for 12 hours.

[Catalina Park]

The chase was fun in the HQs and Production car V6 Commodore. You are travelling slow enough (about 200 kph) to get it mostly settled after the corner before standing on the brakes. The braking area is uphill after a dip so you can get a lot of load on the tyres and slow it down very well.

Actually the fastest car I have driven through the chase was an AU Falcon XR6 with three people in the car and a boot full of medical gear.

[cheapracer]

Originally posted by Catalina Park


......and a boot full of medical gear.

Are you saying you don't trust your own driving?

[F1Champion]

Not to hijack the thread but over the last couple of days I've been thinking about steering and how the suspension is fixed and all the steering happens essentially at the corners of the car with the turning of the wheels. What can't F1 teams design a suspension/steering setup where the whole front axis turns around its centre point? For example imagine you are a driver watching your front tyres and you turn into a right hand corner and the front axis would tilt towards the right with the right front tyre getting closer to you while the left tyre would get further away from you. Is there a rule against this?

[OfficeLinebacker]

Originally posted by F1Champion
Not to hijack the thread but over the last couple of days I've been thinking about steering and how the suspension is fixed and all the steering happens essentially at the corners of the car with the turning of the wheels. What can't F1 teams design a suspension/steering setup where the whole front axis turns around its centre point? For example imagine you are a driver watching your front tyres and you turn into a right hand corner and the front axis would tilt towards the right with the right front tyre getting closer to you while the left tyre would get further away from you. Is there a rule against this?

If you're still braking when that happens, wouldn't a computer (a mechanical one isn't out of the question) have to modulate the braking (on the front at least) so as to keep the car from spinning?

I also believe such a system is illegal (the rules about the wheels being so far from the centerline and whatnot apply at all times, even in turns), but assuming it wasn't, I think it'd be a pretty neat trick to accomplish.

Has it been done?

Is the idea similar to Smokey Yunick's 1964 Indy entry?
(image courtesy fireballrobers.com)

[desmo]

Can you imagine any sanctioning body allowing that sort of innovation today?

They'd tell you it's "impossible" and cost trillions.

[McGuire]

Originally posted by F1Champion
Not to hijack the thread but over the last couple of days I've been thinking about steering and how the suspension is fixed and all the steering happens essentially at the corners of the car with the turning of the wheels. What can't F1 teams design a suspension/steering setup where the whole front axis turns around its centre point? For example imagine you are a driver watching your front tyres and you turn into a right hand corner and the front axis would tilt towards the right with the right front tyre getting closer to you while the left tyre would get further away from you. Is there a rule against this?

You mean like a hay wagon or a Radio Flyer?