Bruce McLaren on Setting up a GP Car

The following is taken from MOTOR RACING magazine, from two articles published in the May and June 1965 editions.  I have combined the two articles.  The first, by John Bulmer, a motor sport journalist was his views on how he thought GP cars would be set up for particular circuits.  At the end of the article he invited responses from those in the know and Bruce McLaren wrote the second article in response to the first.  So while the first article is of less value than the second, it is necessary to include it to understand Bruce's article.  In addition, those parts of Bulmer's suggestions which are not contradicted can carry more weight.

Monaco

John Bulmer - Monaco has always struck me as a circuit calling for considerably less understeer than most others. In two places in particular - ­the Gasworks and Station hairpins - the re­quirement would seem to be a tight corner­ing radius coupled with the ability to put on the power quickly and smoothly without having to resort to a deliberate violent oversteer. The cars which I have timed the quickest in these places have been those which have shown just a little understeer going into the corner, the understeer being then gradually neutralised, perhaps just to the point of slight oversteer under power coming out.

It is a circuit which puts a tremendous strain on transmissions, even when the driver is probably using only four speeds of his gearbox. and one which demands instant engine pick-up out of slow corners. Many an engine has stammered its way off the leader board at Monaco through poor pick-up. On the score of brakes, these have to work very hard four times a lap -­at the two hairpins. the Mirabeau turn above the station, and at the chicane. It is at the chicane, in particular, that a driver must have complete confidence in his brakes; here, he is travelling very fast, and the slightest pulling will upset his line into what many experts consider to be the most demanding point on the course.

Bruce McLaren - Certainly you want controllability. In other words you want the car to go exactly where you point it. You want the tail to flick or slide out the moment you ask it to. You don't want understeer; you don't want a car that's going to plough ahead in a straight line. So first of all you change things so that you have a lot more oversteer than you had at Silverstone a week or two earlier.

You shouldn't do this just by fitting a big rear roll bar, because that will just tend to destroy traction on the inside rear wheel. Similarly, you don't want the shock absorbing to be too severe. When you arrive at the top of the hill before the Casino, then go round the roundabout before shooting down past the Tip Top, you don't want to be pulling the wheels right off the ground. One snag on this circuit is that you are liable to bottom the nose on the upwards slope into the Tobacconist's Corner, because you hit the brakes hard just about the time you arrive at the ramp. This really buries the car down on the front bump stops when you have full tanks.

One thing which I always find helps a bit at Monaco is to sit up a little bit higher in the cockpit, perhaps pushing the steering wheel forward an inch or so, and lifting the back of the seat a bit. You can see kerbs a little better that way.

John's description of the hairpin technique was pretty much perfect, and here the whole secret of coming out of the hairpin quickly is your low gear ratio and the way your fuel injection carburates, if you see what I mean. You've got to have the engine spinning fast enough to give you plenty of torque when you open the throttle at the apex of the corner, and you also want it to come on smoothly and cleanly; if the engine coughs or splutters there you've lost half a second straight away. Fuel injection has been quite a help over the last couple of years in this direction, and the Coven­try Climax engines, with their lower rpm range, are better off if you're stuck with a high low gear.

It may sound silly that one can be stuck with a `high low gear', and you might well say, `Then why don't you do something about it?'. But with very high-revving engines and relatively big tyres you get certain mechanical limitations. There is only a certain physical size to which you can reduce the pinions in the gearbox, and that limits your low gear ratio.

Spa

John Bulmer - There could hardly be a more violent contrast to Monaco than the ultra-fast sweeps of Spa. By comparison. this circuit is almost kind on transmissions, but the prolonged use of near-maximum revs cer­tainly shows up any weakness in an engine. Under the 1.5 litre formula, every horse­power counts, and as at Reims and Monza. Spa is just the place to capitalise on a little extra power.

Racing for two hours on such a fast and exacting course (the lap record should be knocking on 140 mph by the end of this year) must be a tremendous strain on the driver, and above all he must hope for a car which is directionally very stable at high speed, and which in these conditions is not likely to suddenly alter its cornering characteristics. This suggests a certain amount of understeer, but not so much that it will noticeably cut down a car's exit speed from the fast bends. There is only one really slow point on the course. and here the requirement seems to be not so much cornering power as really sure brakes, followed by a good. clean engine pick-up for the downhill exit.

Bruce McLaren - Spa couldn't be more different than Monaco, and yet on the other hand this is the nonsense of it all, because a car which is good at Monaco will often still be good at Spa. I've heard Americans say, 'A driver, is a driver, is a driver', meaning that he's still good, whatever the conditions. And the same applies to cars, `A good car, is a good car, is a good car'. I have the '62 Cooper in mind, which won Monaco, and then was awfully fast at Spa before it broke, and also won on another fast circuit – Reims - that year. All we changed on the chassis between races were the anti-roll bars - those quick and trusty chassis-tuning devices!

Just getting off the track a bit, it's interesting to note that one of the best GP drivers used to like great big strong roll bars. He is now using much more conventional sizes, presumably getting a lot more chassis roll and going just as fast. But here's the point: He's probably changed the overall roll stiffness of his car by a factor of 50 per cent or more, so don't let anyone ever tell you what's black and what's white, or what's right and what's wrong, or for that matter quote exact figures of what's needed in the way of torsional rigidity, spring rates, roll stiffness or roll centre heights. Grey is a perfectly good colour for a lot of occasions, anyway.

The first thing you really want to do at Spa, particularly if you were able to get around the hairpin at Monaco without shifting your hands on the steering wheel, is to lower the steering ratio, because getting through the fast `S' in the middle of the straight is more a question of almost shifting your weight in the cockpit rather than shifting the steering wheel. You might move the steering wheel an inch or so, I Suppose, but it's all very quick, so first off you don't want high-ratio steering.

Secondly, you want a very neutral car. In actual fact, you don't want the understeer that I think John has suggested because this is just going to scrub off speed. What you do want is a car that you can put into an attitude at the start of a corner, and which will hold that attitude. If you have a car that's twitchy entering a corner, and won't settle into an attitude, you're going to have yourself a bit of a struggle, particularly through those fast uphill right-handers.

The other thing I think is a help at Spa is a gearbox which does not need to be taken right through the gears when you want to get from top down to second or low. When you arrive at the top of the hill for La Source hairpin you can stop in a ridiculously short distance, first because the surface is good, and second because it's still slightly uphill. You can stop a lot quicker than it takes you to get down through six gears, so the thing to do is what Clark does - go straight from sixth or fifth, down to second or low. This allows you to concentrate more on the braking (Ah for automatic transmission!).

Zandvoort

John Bulmer - The problem of pick-up rarely seems to give more trouble than at Zandvoort, at the banked Hunzerug left-hander behind the pits. As it is followed by a steep in­cline, the speed through this bend, and in particular out of it, is all-important. Opinions seem to differ as to the correct way to tackle the Hunzerug, but the actual line through it appears to be of secondary im­portance to the question of getting the power on good and early without tail­sliding off to the right.

Yet driving skill shows up most of all through the curves around the back of the circuit, and as considerable time can be saved here by getting everything just right. the car should, surely, be set-up with this in mind, in the hope that it will also handle reasonably through the Tarzan and Hunzerug corners.

Zandvoort is a very windy place, being on the North Sea coast. and this can play havoc with gearing calculations. But wind apart, it seems quite a difficult circuit for which to gear ideally-notice how often drivers have to change in the middle of a corner. The circuit is also quite bumpy in places, and this, combined with the problem of sudden gusts of wind-usually during the second half of the lap-which can quickly move a car off line, make Zandvoort quite a tricky circuit - is not the tyre torturer it used to be, nor does it seem to pose any fuel consumption problems-in marked con­trast to Spa, where the 1964 GP proved how close to the limit most cars were run­ning.

Bruce McLaren - Now Zandvoort. John suggested that the car be set up to be stable on the fast corners at the back of the circuit. Now in fact those corners are flat-out anyway, so you can cope with too much understeer by throwing the car into the corner, or too much oversteer by just sort of easing your way through in an over­steering attitude. So I have found that it helps to concentrate very much on the Tarzan Loop and the corner leading into the straight, and endeavour to get the car so that it will oversteer gently through these corners by itself, without too much driver effort, and this certainly has paid off in terms of lap times. The whole point of this business is to really adjust the handling of the car to suit the particular circuit. Perhaps I should elaborate a bit on this. First of all, most cars will understeer, or tend to plough straight on, at low speeds, become neutral at some point as the speed increases, and then give oversteer at a higher speed still, that is to say for a given amount of steering lock. If you don't believe me, try full lock at 10 mph, and then at 100 mph!

Now each circuit has its average corner speed, for which you try to set the car up, or a most important corner, lap time-wise. What you are trying to do is to try to make the car so that it will find its own way around the corner or corners which you regard as the most important, in other words, hold an attitude that will take you comfortably round the corner.

This situation then leaves the driver free to go in a little bit faster, and try a little bit harder. When you see a driver in a good car waggling the steering wheel about, what he is doing is correcting and holding the instant slides and drifts which are starting because lie is going just over the limit. In other words, the car is understeering or oversteering too much for that particular corner at that par­ticular speed. So don't go assuming that a car doesn't handle well just because the driver is working hard at the wheel. If he slowed down a couple of tenths it might look easy.

We are only talking here about relatively small differences, and you can cope with a car that doesn't do things quite right simply by making allowances. Remember that when Clark's rear roll bar came off at Monaco it didn't slow him down much on lap times, but it probably made him work quite a bit harder and he was probably having to throw the car into the oversteer he needed at the hairpins, for instance.

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