17 replies to this topic

[F1Frog]

I read that Stirling Moss used trail-braking in his Lotus and didn't understand why the other drivers didn't do the same.

 

Did Stirling Moss 'invent' trail-braking? Or was he simply the first to do it in Grand Prix cars?

[Charlieman]

It may be best to discuss this topic as 'induced oversteer', although there are other descriptions. Drivers have different ways of explaining how it worked for them.

 

The first acknowledged practice of the technique would be the 1920s when motor racing surfaces had become more consistent.

 

In the late 1990s or early 2000s, drivers in the junior categories raced in cars which responded best to gentle inputs on steering, brakes and throttle. The designers minimised customer demise. In Formula One, cars were designed to respond best to more abrupt driver inputs. For the last 20 years, F1 cars have needed really late brake braking.

[Bloggsworth]

IIRC, Moss said that braking into the corner effectively extended the length of the straight. I'm sure a lot of drivers do it unconsciously, I didn'y realise that I did it until I locked the inside rear wheel of my Manta as I turned into a corner which, incidentally, informed me that a front roll/sway bar link had broken. On FWD cars, of course, trail braking is de rigeur, neccessary to destabalise the rear end and negate terminal understeer.

[D-Type]

What exactly does "Trail braking" mean?

[GregThomas]

To the best of my knowledge it's a term mainly used in motorcycle racing. The technique of keeping the front brake on lightly ( "trailing" the brake ) while turning in to the corner means the forks are compressed which reduces trail letting the bike turn easier.  Trail is the geometric measurement of the offset between the tyre contact patch and the point where the steering axis meets the road. Less trail means quicker steering.

The term seems to have been appropriated for use any time braking is continued close to a corner apex.

In the Moss/Pomeroy book on The Grand Prix Car, the technique is certainly discussed - but at no point does Moss name it trail braking

 

I was taught to drive by my father who was accustomed to beam axle cars. His rule was that you never braked on a corner as this could potentially lock the steering.

I suspect that Moss's development of the technique coincided with the evolution of suspension systems where it became possible.

[Gene]

I seem to remember Mark Donohue giving a fairly extensive description of "Trail Braking" in his book "The Unfair Advantage".

[GreenMachine]

It is a thing in low level club car racing .

[Roger Clark]

Moss described his braking technique in the Design and Behaviour chapter on 2.5-litre Cooper and Lotus cars. As mentioned above, he didn't use the term trail braking. He said that was a technique he developed late in his career but doesn't say when. He said that the key was the transition from braking to power in such a way as to avoid upsetting the balance of the car. Extreme sensitivity was required. He felt that the technique gave him a real advantage over his rivals. Given Moss's competitiveness since 1955, I think it's unlikely that any other drivers were using the technique, Fangio possibly excepted. I couldn't say whether this is what other people mean by trail braking.

[F1Frog]

My definition of trail-braking (and please correct me if I am wrong because it is just based on what I have read), is that, instead of braking in a straight line before the corner, then easing off the brakes while turning in, the driver turns into the corner and brakes while turning, thus attempting to cause oversteer in the corner and make the back end step out so that you can make the corner and get the power down again. I had read that Stirling Moss used to do this and didn't understand why he was the only driver doing it. Then Jim Clark did the same during the 1960s.

 

However, this might not be accurate, and I am mainly interested in what was unique about Moss' braking, whether he was the first to do it, and why others didn't do the same (I assume the last is just because it is particularly difficult to pull it off).

 

Thank you to everyone who has helped so far.

Edited by F1Frog, 11 April 2023 - 12:08.

[Sterzo]

My definition of trail-braking (and please correct me if I am wrong because it is just based on what I have read), is that, instead of braking in a straight line before the corner, then easing off the brakes while turning in, the driver turns into the corner and brakes while turning...
 

That's my understanding too, and the "trail" element is that you do ease the brake as you turn but keep braking lightly. Common in karting too.

 

 

I was taught to drive by my father who was accustomed to beam axle cars. His rule was that you never braked on a corner as this could potentially lock the steering.

I suspect that Moss's development of the technique coincided with the evolution of suspension systems where it became possible.

That sounds plausible, in that stiffer chassis with softer coil springing bring greater control, so braking while turning is less likely to induce unwanted effects than it would be with flexible chassis and stiff leaf springs.
 

[GreenMachine]

Trail braking has to be seen in the light of the friction circle, whereby the concept is that there is a limited amount of friction available from the tyres, and that has to be apportioned between lateral and fore/aft friction.  You can use it all braking, but none is then available for lateral loads (ie cornering).

 

In trail braking, the concept utilises unused friction on corner entry - that is the sum of lateral and braking is less than 100% of the available friction, and the balance is taken up by extending braking into corner entry phase, easing off as the apex is approached and lateral loading is approaching the 100% friction available.  We are all familiar with the application of the concept on corner exit, where over-use of the accelerator overloads the friction available at the rear, and the rear tyres slip.

 

At least, that is how I understand it.

[john aston]

My definition of trail-braking (and please correct me if I am wrong because it is just based on what I have read), is that, instead of braking in a straight line before the corner, then easing off the brakes while turning in, the driver turns into the corner and brakes while turning, thus attempting to cause oversteer in the corner and make the back end step out so that you can make the corner and get the power down again. I had read that Stirling Moss used to do this and didn't understand why he was the only driver doing it. Then Jim Clark did the same during the 1960s.

 

However, this might not be accurate, and I am mainly interested in what was unique about Moss' braking, whether he was the first to do it, and why others didn't do the same (I assume the last is just because it is particularly difficult to pull it off).

 

Thank you to everyone who has helped so far.

 I recall reading an article by Peter Windsor about Clark's driving technique in which I'm pretty sure that he described Clark's style as 'classical' - getting all the braking done in a straight line before turning in , having reapplied power . I never saw Moss or Clark race in period so cannot be sure . But it is almost universal now and people like Senna and Schumacher were exceptional exponents. In my track day sessions in Caterhams I tried very hard to tell my foot to stay on the brake  to the apex but the damn thing never did what it was told . It feels counter- intuitive-  which possibly explains why I drove a desk and not a Lotus 79.  .

[john wood]

Further on Jim Clark’s braking/cornering technique. This from ‘Jim Clark at the wheel’ (1963) - “…most people run deep into a corner before turning the wheels to go round. In this way you can complete all your braking in a straight line, as everyone recommends you do, before setting the car up for the corner; but I prefer to cut into the corner early and even with my brakes on to set up the car earlier. In this way I almost make a false apex because I get the power on early and try to drift the car through the true apex and continue with this sliding until I am set up for the next bit of straight..."

[Roger Clark]

Is Peter Windsor's description of Jim Clark's style, as reported in John Aston's post, consistent with John Wood's quote from At The Wheel?

[cpbell]

Further on Jim Clark’s braking/cornering technique. This from ‘Jim Clark at the wheel’ (1963) - “…most people run deep into a corner before turning the wheels to go round. In this way you can complete all your braking in a straight line, as everyone recommends you do, before setting the car up for the corner; but I prefer to cut into the corner early and even with my brakes on to set up the car earlier. In this way I almost make a false apex because I get the power on early and try to drift the car through the true apex and continue with this sliding until I am set up for the next bit of straight..."

In this regard, Jim was more in the Prost/Button mould with a geometric line and an earlier, false apex, whereas the modern style is to trail brake, take late apex and complete the rotation quickly.

[F1Frog]

Is Peter Windsor's description of Jim Clark's style, as reported in John Aston's post, consistent with John Wood's quote from At The Wheel?

To me they appear completely contradictory. The 'at the wheel' description is what I thought trail-braking was, and what I believed Clark's driving style was. Perhaps it changed in the later years to fit Peter Windsor's description? Or perhaps he could just do both and changed it constantly depending on the corner?

 

Anybody know?

Edited by F1Frog, 21 April 2023 - 21:18.

[Doug Nye]

Unfortunately I was always too much in awe of Jim Clark to ask him in any detail about driving technique - nor in fact do I believe he would have been forthcoming in great detail to a spotty herbert eager young 'reporter', because he always seemed unconscious of (indeed puzzled by) the innate skills which he plainly had in abundance but which most of his rivals could seldom even approach.

 

However - I do have vivid memories of him in one of the Whit-Monday Formula 2 races at Crystal Palace, when his car's brakes whistled distinctively on every lap as he hurtled into the right-hander at North Tower Crescent.  The whistling was sustained after the car had visibly turned into the corner, but not so far as the apex - by which time it was sitting down on its outside rear wheel and Jimmy was balancing it through on a progressively opening throttle. Again, one could hear the sound, i.e. the rising engine note.

 

From the top of the timber sleeper-protected bank on the outside of the corner the process - highlighted by that sound track - seemed absolutely magical.  Poetry in motion, in fact.

 

Yes - you can say I was (and remain) A Fan.

 

DCN

[Roger Clark]

It is probable that Jim Clark's style evolved during his career.  Stirling Moss and Jackie Stewart have both written how they developed new techniques towards the end of their careers.  It is also likely that the best technique for an early 25, with very little surplus power, was not  the same as for a 49 with double the power, delivered very suddenly.