Trail braking. Is it really faster? If so, how and when?

[mollytherocker]

I've never really used this technique before but understand the principle. I recently had some tuition at Silverstone where the instructor (Ex F1 driver) was trying to get me to brake to the apex to give more front end grip; i.e reduce understeer. To be fair, it was raining and we were in an Evora S which is of course mid engined.

This was totally alien to me and just FELT slower.

Braking in a straight line and then smoothly transferring the weight towards the throttle into the apex just seems faster!

Am I dreaming this?

If it really is faster, please explain why.

MTR

[waremark]

It is a fascinating question, but I am not convinced that this forum - about road driving - is the place for it.

[Steve Rance]

Yep, agree. You need to brake late to keep the front springs and shockers loaded all the way to apex. On the road that is not a good plan. If you brake early, it don't work as the nose will unload too early.

[mollytherocker]

I understand the point of loading the front suspension into the corner for more grip but please explain this.

If you are turning whilst braking, the car is diving and thus unloading the rear suspension. Would your speed around (Or into) the corner have to be lower than if the car was on a steady throttle, i.e; balanced?

Or, is it the case that the above IS true BUT the extra grip at the front out weighs this? If so, how? Exit speed would be lower?

I hope I am making myself clear!

MTR

[LeoSayer]

It's only faster if you can start your braking later....thereby getting to the apex quicker than if you had braked in a straight line.

[mollytherocker]

LeoSayer said:

It's only faster if you can start your braking later....thereby getting to the apex quicker than if you had braked in a straight line.

Right..

So, I have to brake later and 'finish' the braking in the corner. My entry speed into the corner is going to be higher AND I will be on the brakes.

So the extra front end grip is going to counteract this?

Apologies if these are dumb questions.

MTR

[Steve Rance]

Nope, modern diff technology, the increased physical grip that modern tyres have and increased chasis control damping technology combined with stiffer chasis and improved suspension geometry often make it a viable option. Many of the quicker race drivers now employ an element of trail braking whatever the layout of the car. Its often very effective but it requires very skillful brake modulation as you are trading many forces acting on the car at the same time. As i said earlier. To do it you need to first brake late and keep the nose loaded from turn in to apex or near it. The ammount of load placed over the front wheels will depend on many different factors. A 911 needs a lot of load on the nose all the way to the apex because dynamically all the weight is in the rear of the car. A front engined RWD car will need less and the rear will unload a lot earlier. Never the less, many pro drivers that i know that drive front engined RWD cars still employ it to very good effect.

[mollytherocker]

Steve Rance said:

Nope, modern diff technology, the increased physical grip that modern tyres have and increased chasis control damping technology combined with stiffer chasis and improved suspension geometry often make it a viable option. Many of the quicker race drivers now employ an element of trail braking whatever the layout of the car. Its often very effective but it requires very skillful brake modulation as you are trading many forces acting on the car at the same time. As i said earlier. To do it you need to first brake late and keep the nose loaded from turn in to apex or near it. The ammount of load placed over the front wheels will depend on many different factors. A 911 needs a lot of load on the nose all the way to the apex because dynamically all the weight is in the rear of the car. A front engined RWD car will need less and the rear will unload a lot earlier. Never the less, many pro drivers that i know that drive front engined RWD cars still employ it to very good effect.

Thats useful, thanks. I think I was looking at it too simply. I understand what this is trying to achieve more clearly now.

As you say, 'you are trading many forces' and I think this phrase has summed it up.

I need to practice!!!!

MTR

[RobM77]

For a graphical explanation of "trading many forces", just look at the friction circle.

I can't find an explanation on the web that doesn't blind the reader with science (my pet hate!), but it's such a simple concept you should be able to picture it. Basically, the car is capable of not just braking, acceleration and cornering, it can actually do combinations of them. All trailbraking is is doing a combination of braking and cornering, just like when you accelerate as you leave the corner, but on the way in.

Bear in mind that blending the brakes into the steering on turn in to achieve a balance is not trailbraking, it's something different. If you come off the brakes and then turn, you'll get monumental understeer, so bringing in the steering as you come off the brakes is the way to avoid this by managing weight transfer. This is not trailbraking.

[7db]

Worth noting that trail-braking will add weight to the nose (at the expense of the rear), helping the turn in, but robbing the vehicle of overall cornering grip, which is maximised with a even distributed weight.

[RobM77]

7db said:

Worth noting that trail-braking will add weight to the nose (at the expense of the rear), helping the turn in, but robbing the vehicle of overall cornering grip, which is maximised with a even distributed weight.

It's always a balancing act between all the benefits and disadvantages. You also gain by being able to brake slightly later, which is actually noticeable, especially in faster braking areas.

Trailbraking is also car dependent, with some cars responding well to it, some cars requiring it (I'm told Carrera Cup cars for example), and some cars not getting on well with it at all. Druids at Brands is a classic example - there's one line where you go deep, turn back and get on the throttle early, and there's another line where you trailbrake in on a narrower line, so you're covering less distance but don't have the same angle on corner exit. It's car (and tyre!) dependent in that particular corner, so a driver needs to be flexible enough to experiment (something I can often be accused of not doing enough of!).

[mollytherocker]

7db said:

Worth noting that trail-braking will add weight to the nose (at the expense of the rear), helping the turn in, but robbing the vehicle of overall cornering grip, which is maximised with a even distributed weight.

This was what I understood, which is what caused my confusion. It would seem that this is a simplistic view and the fastest method is dependant on multiple factors!!!

MTR

Edited by mollytherocker on Wednesday 9th March 23:44

[Mr Grayson]

Trail braking can work nicely on the road too, but obviously it reduces the safety margin from the position where entry speed is low enough for the corner before entry, as when using the SOCC. It does make the car turn in nicely though. Put very simply, you brake and turn in, and as the bend opens, you transition from brake to throttle and let the steering unwind. When it works, it feels beautifully balanced. The entry speed can be considerably higher than it is when using the System.

[RobM77]

Mr Grayson said:

Trail braking can work nicely on the road too, but obviously it reduces the safety margin from the position where entry speed is low enough for the corner before entry, as when using the SOCC. It does make the car turn in nicely though. Put very simply, you brake and turn in, and as the bend opens, you transition from brake to throttle and let the steering unwind. When it works, it feels beautifully balanced. The entry speed can be considerably higher than it is when using the System.

I must confess I don't trailbrake on the public road, but I'd like to add to the above that I use a standard (but non "system") technique on the road (blend brakes into steering, steady throttle to apex, then unwind and bring throttle in), and that also works very well indeed (for me at least).

[mollytherocker]

RobM77 said:

Mr Grayson said:

Trail braking can work nicely on the road too, but obviously it reduces the safety margin from the position where entry speed is low enough for the corner before entry, as when using the SOCC. It does make the car turn in nicely though. Put very simply, you brake and turn in, and as the bend opens, you transition from brake to throttle and let the steering unwind. When it works, it feels beautifully balanced. The entry speed can be considerably higher than it is when using the System.

I must confess I don't trailbrake on the public road, but I'd like to add to the above that I use a standard (but non "system") technique on the road (blend brakes into steering, steady throttle to apex, then unwind and bring throttle in), and that also works very well indeed (for me at least).

Thats more the trad style isnt it? You are just blending the transition more to try to keep the car steady?

MTR

[Phisp]

RobM77 said:

I must confess I don't trailbrake on the public road, but I'd like to add to the above that I use a standard (but non "system") technique on the road (blend brakes into steering, steady throttle to apex, then unwind and bring throttle in), and that also works very well indeed (for me at least).

Would you still select the appropriate gear at the same point in time, as if following IPSGA, but use H&T to rev match?

[RobM77]

O/T because I'm purely talking about road driving now.

RobM77 said:

I must confess I don't trailbrake on the public road, but I'd like to add to the above that I use a standard (but non "system") technique on the road (blend brakes into steering, steady throttle to apex, then unwind and bring throttle in), and that also works very well indeed (for me at least).

MollyTheRocker said:

Thats more the trad style isnt it? You are just blending the transition more to try to keep the car steady?

MTR

That's right, yes. I'm trying to achieve a smooth gentle transition to a balanced state.

Phisp said:

Would you still select the appropriate gear at the same point in time, as if following IPSGA

No, and this has been the subject of many heated discussions on here! I work by the following rules on approach to hazards and corners:

a) Keep the revs in a useful range that's also kind to the engine, so for my 320d that means above about 1300rpm, and for the Lotus above about 1700-1800rpm. I do the former so that I have control and stability should I need to take unexpected avoiding or close-limit action or bumps etc cause an instability; and the latter obviously out of sympathy to my car, because both my cars are very high geared and won't take top gear below about 15-20mph without sounding like they're about to vomit a furball out!

b) I don't change gear close to a hazard. The closer you are to a hazard, the less time you'll get to respond if that hazard develops. I always expect the unexpected, because it's the unexpected that causes accidents... For example, when 30 yards from the vanishing point of a corner you'll get far less time to respond to a vehicle on the wrong side of the road than when 60 yards from it. The same goes for a parked van and someone stepping out from behind it into your path. Because of this increasing danger with decreasing distance, I try and get gearchanges out of the way earlier so I've got both hands on the wheel and the brake covered when I'm near the hazard. I would never do as many advanced drivers do, which is change gear just before I made the decision to accelerate - i.e. right on top of the hazard, or perhaps on the give way line of a roundabout (as someone posted a police driver doing on here once when we last discussed this). Of course, there's much less of an argument for this with an auto blipping paddle shift, because you only have very minor dynamic considerations with change gear, and the greater concern of both hands on the wheel and a foot covering the brake already apply throughout the gearchange. With a traditional manual car though, I'll be making my final approach to the hazard with both hands on the wheel, and usually my foot covering the brake.

So, both the above mean that I don't follow the advanced driving method of slowing in top, then changing to an appropriate gear before accelerating away. Instead I will change down as I approach (often skipping gears, so perhaps 6th, 4th, 2nd), make the final approach with both hands on the wheel and the car ready to accelerate (or brake), and then accelerate away again when safe to do so. I guess it's still CMSBGA, but just with a different speed profile and technique difference.

Phisp said:

but use H&T to rev match?

This depends if braking is required or not. I do not let the need to H&T or avoid BGOL make this decision for me; instead my only thought process is whether I need to use the brakes to slow and whether it would be safer to keep a foot on the brake on approach to a suspicious hazard. I then change gear accordingly - if I'm braking at the time then I'll use H&T to rev match, and if I'm not braking then I'll do an off-brake rev match. Brakes always come first in my priority list though. Advanced driving is primarily about avoiding accidents, and to this end, use of the brakes to shed lots of speed quickly is very often a good thing to do, and is certainly more important than whether you've used BGOL! Ergo, I'll let the need to cover or use the brake pedal lead any decision.

So for example, if there's a cat crouched under a parked van in front of me and I'm covering the brake in case it runs out, I won't come off the brake to rev match a gear change because I've been told I shouldn't BGOL (thus risking the life of the cat and the happiness of its owner just to follow the system! ), I'll keep my foot on the brake, eyes on the cat (as well as elsewhere to avoid target fixation of course - another common cause of accidents), and use H&T to select a lower gear before the engine labours or I lose useful revs for control. I use H&T in this situation because I want to keep the brake covered in case the cat runs out, but I need a lower gear for reasons of control and mechanical sympathy.

Sorry for the long post - I hope that makes sense!

Edited by RobM77 on Thursday 10th March 11:45

[Steve Rance]

RobM77 said:

yes: It's always a balancing act between all the benefits and disadvantages. You also gain by being able to brake slightly later, which is actually noticeable, especially in faster braking areas.

Trailbraking is also car dependent, with some cars responding well to it, some cars requiring it (I'm told Carrera Cup cars for example), and some cars not getting on well with it at all. Druids at Brands is a classic example - there's one line where you go deep, turn back and get on the throttle early, and there's another line where you trailbrake in on a narrower line, so you're covering less distance but don't have the same angle on corner exit. It's car (and tyre!) dependent in that particular corner, so a driver needs to be flexible enough to experiment (something I can often be accused of not doing enough of!).

Yep a driver will be nowhere in Carrera cup if he doesnt trail brake. An example is braking into the esses after the back straight at Snetterton. It's a 6th gear braking zone and a sharp 3rd gear entry into the complex. My data showed that 70% of the braking was done after turn in with initial braking at 90 meters which is very late. The trick is to carry a lot of brake all the way after turn in. The rear gets horribly loose and you need to be as light on the tryres as possible but if you are gentle and modulate perfectly it can be done. Get it wrong and its a huge accident. I was lucky and never had a big off whilst trailing but I've seen it cause some huge accidents. If you get the bias set up right it helps a lot. As a guide, i'd be about 75% brake well after turn in of most corners and bleeding to zero at apex, then immediately flat at apex. Saves a huge amount of time on entry and settles the car nicely for throttle application. Worked on it a lot with my instructor who works with several F1 drivers. They all trail. With modern diff, chasis and tyre technology you can ask a lot more of the rear even when it's unloaded providing you have the skills to do it. It is regarded as an essential skill in most forms of top level motorsport these days. A mate of mine who is a FIA GT factory driver for a well known manufacturer of front engined RWD cars finds a lot of time trailing in. To get it right though, it is a skill hard learned especially if you have to deal with no ABS and an adjustable bias at the same time.

Edited by Steve Rance on Thursday 10th March 13:27

[RobM77]

That's interesting Steve, thanks. Trailbraking is something I want to work on this year to try and get a bit of time into some of the corners. I'm racing a mid engined single seater, obviously with no ABS.

[Steve Rance]

RobM77 said:

That's interesting Steve, thanks. Trailbraking is something I want to work on this year to try and get a bit of time into some of the corners. I'm racing a mid engined single seater, obviously with no ABS.

You will find loads of time trailing in a single seater, wind the bias further forward though or you will lock your rears on turn in.