braking points

[dtype38]

Originally posted by pch
There is your problem. You can't actually begin to accelerate until you can start to unwind the lock - which is usually at the apex.

Err, not quite what I meant...Let me describe this properly:

I have a front heavy car with quite a high centre of gravity. Standing on the brakes simply causes massive weight transfer and locked rears so I have to be very progressive on the pedal. I've found from hard experience that there's no way the old girl will turn in that state, the back is just too light, so I then bleed the brakes off to get the nose up so that I can turn into the corner. As soon as I've turned in I immediately balance the throttle to "set" the car, giving a smoothe ride to the apex aiming to use 100% of the traction available for cornering with no decelerating or accelerating going on at all. Of course as soon as I get to the apex, or more often well before (I use classical cornering lines) I start to apply real power and unwind the lock.

All I can say in defence of my style is that it is designed specifically to overcome the problems of having an underpowered car. My aim has been to get on the power far earlier than anyone else. It seems to have worked so far as I have trouble convincing some of my co-competitors that I'm genuinely 50hp down on their cars when I keep up with them on the straights.

For this year I have rebuilt the car from scratch and have more power and a much lower centre of gravity (the top of my roll cage is 6" lower than last year). It will be interesting to see if this changes my views. My knowledge and understanding is a mear drop in your ocean

[Tim Falce]

Originally posted by dtype38

.....I have trouble convincing some of my co-competitors that I'm genuinely 50hp down on their cars when I keep up with them on the straights.

yeah, right. I believe you Ken

[dtype38]

That mean that I can't borrow your tracking and camber gauges then?

[pch]

Originally posted by dtype38
Err, not quite what I meant...Let me describe this properly:

OK, I assume from your moniker that you have an E-Type. If memory serves - and I may not be correct here, I recall that these have a roll-centre above ground at the rear, which will make it very tail happy going into the corner on a trailing throttle, and your technique as described betrays no fundamental or obvious error, well nothing significant. I'll come to that later ...

As to beating them down the straights with a 50bhp deficiet - that shows you clearly have a good exit technique and that you are probably carrying goo corner speed too.

Jackie Stewart once said, the last thing a race driver learns to do is brake properly, so you are in elite company.

Further, your comments illustrate perfectly the issue of a perfect lap bing made up of teh omptimum set of compromises.

Now to the small issue of apparent misunderstanding.

As you move from a straight line to cornering, the initial cornering forces are relatively small so you can be turning quite heavily on the brakes - then you need to gradually reduce the braking effort as you get further into the turn. 1: you speed will be slower so for any given cornering force you can execute a tighter turn and 2: you are looking to bleed off and trade longitudinal (ie braking) forces for lateral forces. The balance of your car must also be taken into account too. Modern cars fit the braking system to pull down the rear and raise the front, so you may want to have a look at this on your car if the rules allow - but I'm guessing they won't - you have to use the original mounting points.

If you get it right, you can - once set up - turn the car pretty much on the brakes in the same way you can turn the car on the accelerator - but oviously in reverse. One more thing, doing this will cahnge your line. You will need to turn in earlier and approach in a more shallow arc, then turn it quicker at the apex - the price may be terminal speed down the next straight, I suspect it will be which is why the technique is not always the optimum approach.

Incidentally, Alan Prost often braked earlier than others in F1, but braked more gently allowing him to carry more corner speed, Michael Schumacher on the other hand is a big trail braker - so it depends on what works for you and how your car behaves.

NEVER accept what anyone says as gospel - merely something worth looking into and checking out for your self; and do it in prgressive small steps building up to the objective - and always believe the stopwatch.

One final suggestion. Never ever leave a race without analysing what you did, what worked and what you ar egoing to try/experiment with next. And ALWAYS understand WHY something worked or didn't work. Then you build a base on which to test, experiement and adapt - if needs be in the middl eof a race.

Now I really am finished.

[pch]

I meant D-Type, but both share similar suspension traits I believe. Previous caveat applies.

[dtype38]

PCH...

Thanks for all that, lots of it makes good sense and I'll certainly be exploring the possibilities raised when I get back on track.

You were right that I drive a D-type Jag, but its a replica and uses the later independent rear suspension of the E-type, so your first guess on handling characteristics was closer. At the front end is twin wishbones with coil over dampers rather than the early Jag torsion bars.

Two points of interest which come into my handling characteristics are the differential and the front wishbone geometry.

The former is a Jaguar Powerlok diff which has limited slip during braking and neutral power application, but as the name implies, becomes a fully locked axle under load. (This is great for starts because any wheelspin is exactly equally distributed to the back wheels and stops at exactly the same time for both wheels making it very easy to control). It does, however, give horendous understeer if power is applied while cornering. Hence my classic lines of in-deep, turn quite hard, and straighten up on the power very early... BTW I think I said that I could "keep up" with my opposition on the straights, not "beat them" as you suggested.

Going forward to the front wishbones: As supplied by the kit manufacturer the upper is shorter than the lower, as would be expected, but the pair were essentially parallel and horizontal. As you may know this means for smallish deflections the wheel moves up and down parallel to the car, and with the spring rates I use, it takes quite a tight corner to get enough body roll for the camber to change much. The long and the short of it is that under braking the tyres stay pretty flat to the road giving excellent grip, for hairpins and tight corners I get good grip, but on high speed turn ins (first corner at Snetterton being a particular problem) I get into the brown trousers arena until I've generated enough turning force to get some body roll happening. Not nice. My solution to this is that I've moved my upper inner wishbone pivots down and in considerably (in a line towards the lower inner pivots) and lengthened the wishbones to give much more camber change at smaller body roll angles. I've also lowered my CoG and stiffened the spring rates to try and reduce overall pitch and roll. The downside I'm expecting from the change is that heavy braking will tend to lever the outer edges of my tyres off the road as the nose drops thus reducing my braking grip. To compensate for this I'm using less static camber (about 0.5 deg) and the heavier spring rates I mentioned. Welllll... according to the CAD model I've made of my front suspension and taking the castor angle I've set, I should never be able to get my front tyres at more than about 0.7 deg from vertical regardless of what I'm doing in the car. So given that I'm using 60 profile tyres (Yoko A032Rs)hopefully that means I'll never be short of grip up front.

The proof of the pudding, of course, will be the number of visits to the scenery

[R59]

Cor, did I stir a hornets nest?

Any road, up, as I said, you have all of the theories, simulation software, engineers, and degree's under your belt, but does that make you a better driver, with the ability to judge the situation.

In a perfect world, the track is clean, and we always follow the racing line. The tarmac has perfect characteristics, the tyres have been scrubbed in to perfection, and you can do it all with robotic precision.

In the real world, the track is dirty, we can't always follow the line (because of the previous), the tarmac is variable, and the tyres have probably been abused.

That's why (love him or hate him) Michael Schumacher is top dog in F1. The car is spot on, the support is fantastic, but Michael seems to extract 110% out of the car by using his ability over the technology.

The other ability that many drivers lack, is the ability to get the best out of their chassis. I for one know that I still have lots to learn. To contradict the "engineer" who seemed to point a finger at me for "being a know-it-all", I guess I'll stop learning when they put the final nail in the coffin. I raced the same car for almost 15 years, and every year found more time, not just by improving the old bucket's spec, but by listenening to drivers who know more than me.

So, withtout the aid of a trackside analysis package, including full telemetry, etc..., I use seat of the pants, coupled with a lap-timer, and a speedo! You know when you've done it better!

I bought a set of corner weight scales this year, as my new car is much more critical in terms of setup. I used to scrounge the use of someone else's before.

Never be afraid of technology, a bad workman blames his tools, and if you don't know how to use your tools, you are just as likely to cause more damage with them, than without them.

Where there is no sense, there is no feeling. So they say.

Rob.

[dtype38]

Racing59 has just added to my belief in my own pesonal pet theory... That there as many ideas about the "right" way of going about motor racing as there are people who go motor racing! .... Would be a dull old world otherwise eh?

On a more serious note, I think personal circumstances and backgrounds greatly affect the way each of us approach our racing. Pesonally I have an engineering background, but due to other committments can't do much more than about 15-18 races a year, with little hope in hell of actually going testing. Naturally that means I try and use theory and simulation to make the most of the track time I do get.

I respect that some drivers are in the reverse position of enjoying more bum-in-seat-time than theories and can achieve just as much, maybe more, with that approach. I would love to go testing on real tracks every weekend, but I can't so I have to use what I have. Does tht make me a worse driver? Dunno, but at least I don't have a chip on my shoulder about it.

[StephenRae]

Originally posted by billywhiz1
Has anyone got information or a formula that can determine the effect on lap times, by using different braking points into a very slow corner from speed, such as a hairpin??

Judging by all that has gone before, the direct answer to your question is...no! Unless you have access to telemetry created by the quickest driver on the day, preferably in your car you cannot get a definitive comparison...but wouldn't that take all the fun out of it?

[pch]

Originally posted by racing59
Cor, did I stir a hornets nest?

It was I read as a derogatory dismissal of theory and the implication that I was talking sh*/ because I didn't have any experience that stirred it for me, but then I may just have taken your remark wrongly - its very easy to do in such areas.

Reality certainly IS different to modelling, but each has its place. You start with theory and adapt in the light of experience - that is the quick way to the optimum. It also builds understanding - which enables better responses to situations. If you know why something happens you are more likely to get a good realworld compromise. All of which is precisely WHY MS is able to do his stuff. In fact everything I have heard about MS indicates that he is incredibly technical in his approach to his racing - as are all the successful drivers I know whatever level they were running at.

You can have all the skill in the world, but if you are don not realise you are going in the wrong direction then its no use.

Let me give you one real example from a few years ago - braking related. I was having major problems with locking rear wheels. We mucked about with a variety of master cylinders, bias valve settings etc. We just could not get it to work properly. So I wrote a spreadsheet to calculate base settings taking account/allowing for various front and rear msater cylinder sizes, brake caliper piston size/configurations, rotor diameters, CoG, wheelbase, aero d/f, static weight distributions and various target deceleration rates.

What I discovered was the advise I had been given on the required master cylinder sizes (from a 'forget theory, work on practice' type person) was wrong - which was why we could not get the stuff to work properly. Used the base settings and next time out we were within half a turn on the bias valve. If I had done that from the start I'd have been far better off.

But don't take my word for it - Valentino Rossi and Mick Doohan were both recently interviewed about what made a good bike racer (arguably two of the greatest of all time) and while both said many things in common - the significant point in terms of this discussion was 'always understand why a crash occurred'. To understand you need to know the theory and how that is affected by practice.

[StephenRae]

Originally posted by pch



Let me give you one real example from a few years ago - braking related. I was having major problems with locking rear wheels. We mucked about with a variety of master cylinders, bias valve settings etc. We just could not get it to work properly. So I wrote a spreadsheet to calculate base settings taking account/allowing for various front and rear msater cylinder sizes, brake caliper piston size/configurations, rotor diameters, CoG, wheelbase, aero d/f, static weight distributions and various target deceleration rates.

What I discovered was the advise I had been given on the required master cylinder sizes (from a 'forget theory, work on practice' type person) was wrong - which was why we could not get the stuff to work properly. Used the base settings and next time out we were within half a turn on the bias valve. If I had done that from the start I'd have been far better off.

Surely it doesn't take a degree in maths to figure out you need a bigger master cylinder to the rear to reduce the bias? and as for 1/2 a turn on the balance bar being detectable...I don't think so...

[dtype38]

Originally posted by StephenRae
Surely it doesn't take a degree in maths to figure out you need a bigger master cylinder to the rear to reduce the bias?

Hmmm... here's an interesting one we found with our cars. My team mate and I in similar cars were both getting problems locking the rear brakes. We tried putting bigger rear master cylinders on, and smaller front ones, and it didn't make any difference. What seemed to be happening was the more we biased the brakes to the front, the more weight transfer we got under braking, hence still the tendency to lock the rears. We eventually solved it by going pretty much back to where we started, but lowered the back of the car about 1/2" - 3/4" on its ride hight. Hey presto the problem went away. Just goes to show there's more than one way to skin a cat.

[StephenRae]

dtype...that's sort of the point I was making, as you proved just changing the bias is not the end of the story. I guess that is why race engineers spend so much time de- briefing drivers even though they theoretically know more about what the car is doing than the he does!

[MarkG]

I've read with great interest, all the responses to my original question about braking points. The responses have made me more aware of how little I know about the science of a car. I understand about the 'feel' of a car of course, like weight transfer, understeer, oversteer etc, but can only guess at car-setup solutions that would save me having to compensate in my driving. Like all racers, I will always strive to make the car/driver combination quicker, and that includes sorting out my own weakness (slow corner hard-braking) and attempting to analyse the car behaviour and changing setup. Until that day I set record laps at ease consistently (and who of us can do that???) I will seek those advantages that I can, that are beyond just 'seat-of-the-pants'. Seat-of-the-pants is great fun but if one is competitive by nature(and we wouldn't race if we weren't) and one wants to be competitive against racers with more knowledge, then one has to look beyond seat-of-the-pants.

[pch]

Billywhiz, if you can get hold of it, I would recommend reading Race Car Vehicle Dynamics - its sort of the industry's text book on the subject.

You will need good maths to follow - but it will cover off pretty much everything you will need to know.

The first 20-25 pages are on how a contact patch works for example.

There is quite a bit on aero design and lots on suspension (such as Ackermann, anti-dive and squat, trade-off factors etc.) If that is too much - and it is for most people (its around 1000 pages IIRC) then try one of the other less technical publications - might actually be a better start in fact.

Also Sports and Competition Driving (by Paul Freyer) - I am not too sure of the title, it is something like that - is a very good intro with the added benefit of linking it back to the driver and also covers off mental prep and related matters.

[R59]

If it's books you want, there are quite a few US publications, mostly for "Stock-Cars", but they give lots of very useful information in a fairly easily understandable form.

One has to learn to walk before you can run.

I have various Bosch handbooks (full of lots of really useful techincal information), and I lent one to a friend to help him diagnose a problem on his car. He tried to understand the book, but brought it back and was stumped as he couldn't grasp the maths.

I lent him a "Stock-Car Engineering" book, and he came back with a grin on his face. Fixed it. In a very agricultural sense, but fixed none the less.

Setting up a race car, ie: a proper race car with proper adjustable everything, can be a complete nightmare for a novice. You can easily make the wrong adjustments, and then end up making dozens more before you end up with a complete mess.

I had an old DOS based program called "racecar" or something like that, which was great for helping setup center of gravity, roll centres, ackermann, bump steer, etc.... You could simulate it, providing you put the right information into the program first.
Rubbish in, rubbish out.

I certainly don't think that anyone on here has been talking sh.t, in fact, I this discussion, I would say that I have picked up yet more information, and in true Wyle Coyote form, I shall decend into the workshop with my chalk and slate and attempt to work some magic.

And yes, Race Car Vehicle Dynamics is a great bible, certainly not bedtime reading though!

Rob.

[MarkG]

thanks pch and racing59, I'll check out the books. My maths *was* ok at one time, I'll see if it still is

[R59]

Let us know what you do, and what you find, as it's always good to have someone else's practical experiences, that is, if you don't mind sharing!!

[pch]

Originally posted by racing59
Let us know what you do, and what you find, as it's always good to have someone else's practical experiences, that is, if you don't mind sharing!!

Definately.

Can I also suggest any of the Carol Shelby (?) books eg Race to Win, Tune to Win and a number of others. They are less technical than RCVD and my be more accessible. I may have confused the author, but the book titles are correct and I know several people who have found these VERY helpful.

[gfm]

Well done billy whizz - ask a decent question... Just to underline what I said at the begining, don't get hung up about late braking, but generally try to do less of it! Best books IMHO are
Ayrton Senna’s Principle of Race Driving
Denis Jenkinson The Racing Driver
Paul Frere Competition Driving
Pierro Tarufi The Technique of Motor Racing.
You also need something on sports psychology like Terry Orlick In Pursuit of Excellence, because if your heads in the right place, good things happen.
A sister to this 10/10ths board is a mag called Circuit Driver and the website has some stunning common sense stuff. The circuit guides are perfect.
By the way, who are you going to watch this weekend? There are three geniuses with their heads in the right place, out at work right now IMHO : Lance Armstrong in the Tour, Rossi in Moto GP, and Schumacher Ferrari of course. Just get out there and compete.

[dtype38]

Billywhiz1 - If you would be interested in a slightly more entry level version of "Race car vehicle dynamics" then the SPEEDPRO SERIES book "How to build and modify sportscar and kit car suspension and brakes" by Des Hammill is a good beginners guide. It goes through all the basic car structure and dynamics stuff in easily accessible terms and also gives some excellent ways of doing quite accurate setup without expensive equipment. Well worth a look... if you can't find it elsewhere I think its in the "Burton Power" cataloge.