A virtual magazine for a true passion!

Editor: Jaap Horst

Volume 3, Issue 1

Bugatti Seminars March 1998

Author: Ivan Dutton
Provided by: Jonathan Olnay

This is the text of the Ivan Dutton Bugatti Seminars of 21st and 22nd of March, 1998

Racing and Safety


Welcome to the first Ivan Dutton Ltd seminars dealing with matters Bugatti. I have spent my working life in the pursuit of performance, initially in the field of modern racing cars (historic now) and latterly the best part of fifteen years in the professional restoration of the cars from Molsheim. My experiences in Bugattis include much racing and many, many road miles. Through our restoration business we see many "restored" cars and I am continually amazed at the assembly mistakes repeated time and again. While I accept the importance of history and originality, this is the only knowledge generally shared. Little seeems to have been done to improve the general standard of mechanical understanding with respect to the operation of the cars.

These seminars are not intended as restoration schools, we will endeavour to cover the main areas of complaint and mistakes made about and on the cars. If the experience of how the cars should feel is widened then it will become plain when the cars are not assembled correctly. A common mistake we all make is to assume that the younger or less experienced owners know, if they are never told how will they ever learn.

Much of the assembly of the cars relies on good engineering practice and common sense, used every day in many situations remote from cars and certainly old cars. A considerable body of information is available from bookshops, it is the general approach and not the detail we can learn from. Every article printed on the subject of automotive engineering has the potential to be useful. Old Bugantics and the excellent books written by the late Hugh Conway contain much specific detail, studying these will save a lot of time and heartache. For the lucky few knowledge comes from meeting with the men who initially forged the reputation of Bugatti in the heady pre WW2 days of Brooklands. This seminar will be the first in a series that, by sharing and recording common experiences, will start to build an available and accessible body of knowledge for generations of owners to come.


In common with any machine, Bugattis require a service routine, safe and consistent running comes from conscientious maintenance. A great many Bugattis do not cover significant mileage and the service frequencies we use and recommend are generally time rather than mileage based. Checks on the oil and water are a pre-use or daily pre-requisite, especially bearing in mind the average Bugattis ability to keep its oil internal. It is worth noting the manner in which the water pump grease disappears during these initial checks; recharge when the plunger is fully compressed. Regular attention to this however is a sure sign that the water pum bush/shaft is looser than is desirable and may require attention. On type 57s the greasers lie in close proximity to the exhaust and the heating effect, thinning the grease, causes them to empty quickly even when the pump is in good condition. A worthwhile modification is the remote mounting of the greasers on the cooler bulkhead area. Picking up this problem early is important, as the grease leaking out into the water system clogs the radiator tubes, leading to overheating, an area we will cover at a later stage. Before the average week of use, common on most rallies, lubricate all the obvious grease points. Spring eyes, track rod ends etc. At this time the kingpins should also be attended to, we use a liquid grease EP140 in this application.

Yearly the car requires a proper inspection, a good time is obviously before its MOT. Check gearbox and rear axle oil, change oil and filter, remove hubs and dust down/adjust brakes. Lubricate and adjust clutch, lubricate brake chains and wheels (a really good lubricant is the penetrating chain lube delivered from an aerosol and commonly used on motorcycle chains), check condition of cables for fraying etc. Lubricate propshaft and check fabric couplings.
If the wiring on the car is in working order, check that the weatherproofing insulation is in place protecting the wiring from the elements, this will pay dividends over time as wiring failures are common on touring cars.
Battery condition suffers when a car is left for any length of time, however, often when a flat battery is suspected, it is dirty battery connections which are the problem causing voltage drops due to resistance. The Delco range of Freedom batteries are very suitable to the infrequent use we generally subject our vintage cars to as they have significally lower losses.
At a minimum clean and regap the spark plugs, pre war ignition systems are not as powerful as modern types and plug gaps stressing the windings are a problem they don't need. Similarly clean and gap the points, look out for signs of pitting and potential condenser trouble. The owner of cars fitted with a magneto should send it to be checked at least every two years to ensure good performance. Final area on the ignition plug lead, they do not last forever, heat causes them to embrittle and lose their insulation ability. Wit all the plug leads in a common tube (bad practice for ignition leads anyway) problems here are also common. Check the anti freeze 30% is about right giving good frost protection and also cutting corrosion problems in the system.

57 owners should check the operation of the thermostatically controlled radiator blinds. This goes wrong periodically, it can however be refilled with special wax. This is a service we can provide, however, due to the nature of the rod seal we do not feel that it is a permanent solution and are looking into a better-engineerded answer using sealed wax cartridges. A useful addition to any touring car is a fuel filter, preferably one that includes a water trap as dirty petrol, and the problems of sticking needle valves and blocked jets are all too common.

To sum up:

Daily routine prior to use

Monthly routine or prior to a rally

Yearly routine, prior to MOT


Most Bugatti designs use the Bugatti toggle clutch, the mechanisms varying in detail design from model to model. The more widespread design of coil sprung pressure plate fitted to the type 57 the only common exception that comes to mind. As it is the most common method of actuation, and the most troublesome to adjust and maintain, we will begin with the Bugatti mechanism.

This clutch is frequently badly adjusted, the clamping force is designed to be developed not by the return springs, but by the centrifugal force and overcentre action of the mechanism, a point that is often not fully grasped.
Shown here with the clutch engaged, it can be seen that the linkage moves fully home, causing the links "1" to lock overcentre. The return spring pulling the carrier "3" forward assisted by the centrifugal force throwing out the links "4". This develops significant pressure without the necessity of an overly heavy clutch return spring. Very useful in the GP car where space limits the pedal ratio available. Adjustment is accomplished by turning the ring "5". Viewed from the rear, clockwise rotation increases clutch clamping pressure. This reaches a maximum when, if the foot is sharply released from the pedal, the mechanism justsnaps overcentre. If the pedal pressure is removed slowly it will not snap overcentre, centrifugal force bringing it in when running. When the clutch is withdrawn (right) the arms sit at an angle. In order toensure good release characteristics the actuating pins "6" must not jam in the cover. The length of these pins also sets the start point for the clutch mechanism. With a new clutch there should be at leasr 8mm between the cover and the brass pivot block "7". With the use of dry clutches lubrication of the mechanism is much more important as with no oil leaking from the clutch things get pretty dry. Which brings us to the subject fo clutch types, there are two types of clutch with four variations. The metal to metal clutch of the original Bugatti design used cast iron and steel plates running in oil. This clutch properly set up and clean works very well, however, due to large surface area there is considerable drag when disengaged and therefore a distinct effort is required to select first gear. A variation on this theme is the sinter bronze clutch that we produce. This clutch, which follows the original metal on metal concept, runs dry large nickel steel driven plates act as effective heat sinks keeping the assembly relatively cool. The clutch requires little maintenance, when fitted it can become slightly abrupt in operation after initially bedding in, this can be cured by a squirt of WD40 or similar into the clutch. Due to the lower surface area it frees exceptionally well and, as it can handle all the torque of a methanol burning 35B or 51, it is well up to the job for any touring car output. A third variation on the metal to metal theme is the cerrami-metallic clutch. This recent development has been designed to allow for limited slipping, it has a gentler action and is more suited to a toruing car than the previous sinter design. The other type of clutch commonly used, a departure from the original concept, is the organic lined clutch. Here ordinary clutch material is bonded on to the discs. There are several disadvantages apparent, the intermediate plates are thin and run very hot when slipped to any degree, this leads to buckled plates and jamming. The dust thrown out gums up the mechanism and with heat the clutch begins to slip.

These are the main points when setting up a clutch and assumes that the alignment with the engine and the operation of the linkages are correct.

Type 57 Clutch:
This is a very different design being of a modern disc pattern, originaly utilising a coil spring pressure plate, this can now be effectively modified to use a diaphragm clutch. Early 57 clutches are quite heavy, the factory later adressed this with a linkage completely contained by the bellhousing, considerably easing pedal pressure.


The Bugatti designed steering arms and joints are common in principle to all Bugattis. The elegant tapered arm with integral ball fitting into machined slots in the stub axles, the slotted track rod ends with cups and springs. The design is common, as are the problems; oval balls require the whole arm to be replaced, incorrect assembly of the track ends causing oval balls.

Perhaps the place to start is with the balls, these should be round no more than 0.005" (0.12mm) ovality. Attempting to set properly the track ends with any more than this will end in failure. In order to obtain rotation there would necessarily be more than 0.005" of slack in the joint, enough to make the steering vague. Obviously any deep gouges or cracks also render the arms unusable. When the taper fitting the stub axle is filed to fit the end of the arm must be 3-5mm under the stub axles surface to avoid bottoming when tight, leaving the arm loose in its' stub axle.

The rod ends have their own series of considerations, the caps should be locked with a 5mm screw, this has the thread tapped through the cap and the end, the end is not merely countersunk. Now on to the major part of setting the steering ends, when properly assembl;ed it should be possible to leave the spring out of the end without impairing its function. That is the cups properly fitted should have no more than 0.002" of end float on them. The spring lightly tensions the cups to the ball to prevent any feel of play. If the spring is coil bound to set the end , very heavy wear of the ball will result. Altering the inner cup before setting up the outer cup sets the tracking; in most circumstances we use between 1/8" and 1/4" of toe in. On many occasions this requires the manufacture of a new track rod, no choice here I'm afraid. The standard Brooklands scrutineering test was to stand on the end and bounce to chech that it would not come off. Every part on the steering should be lockwired or split pinned, safety first.

The steering column taper pins should protrude both sides of the joint and be drilled so the wire through the nut circles the column, ensuring not only that the nut can't come undone, nut also the pin can't fall out should the thread break off.


The Bugatti braking system with its chain and bevel/fiddle bar compensating system produces a firm brake pedal and brakes which pull up evenly. The brakes are not only good by vintage standards but good full stop, that is when they are properly maintained. The biggest problem we see here is the adjustment of the brakes, using the cables to pull on the brakes slightly. To adjust the brakes properly you have to remove the brake drums, an easy task on an alloy wheel car, less so on the wire wheel set up. First problem is if the hubs are fitted on the rear axle properly you will need a hydraulic puller to get them off. the puller using a forcing srew won't work, if it does, the hub wasn't tight enough.

Inspect the brake shoes, if only one shoe is working or the pattern is uneven, then the pivot is probably out of position. If it is only slightly out, then adjusting tthe brakes with shims under the saddles, one shoe at a time, can work, otherwise the backplates need setting on the milling machine and the centres resetting and bushing. When the brakes are about right, the lever movement is 3-5mm, adjustment is required when it gets to 8-10mm. All the nuts on the brakes must be split pinned, all of them! This includes all the pulley wheel spindle bolts, and all the brackets where they attach to the chassis, the pedal shaft mounting nuts and the swivel over the kingpins. The spring links should be wired by first wrapping wire around the spring clip and it side of the chain link and then circling the whole link. The same compensating mechanism which makes the brakes so exceptional, also leaves you with nothing should any part fail! With this in mind we must be very conscious of the condition of our brake cables ends. When fitting new shoes pay careful attention to brake lead, this will prevent the brakes grabbing.

Racing and Safety

The mechanical operation and the general engineering approach to maintaining a racecar varies little from those used to maintain a Bugatti road car. However, as performance is our main aim we need to work at the cars to produce and maintain an optimum. Where we can live with a tight gear selector or a little slack in the steering of the average road car, we can not with a racecar. Where the penalty for overlooking the condition of your wheels on a road car is likely to be a walk to the phone box and a wait for the RAC, the penalty for the same oversight on a racecar can be far more serious. We therefore have two fundamental aims with any racecar, the first and most important is safety. The second is performance; we will be concentrating this time on the safety aspect.

As I have already stated, the requirements for makling a racecar mechanically safe are not very different from the requirements of any Bugatti. What we are constantly doing with a racecar is monitoring the condition of the parts we use. Probably the biggest incident that most people encounter with a Bugatti in a competitive environment is axle tramp. Generally minor tramp with the worst damage being a dented undertray, if you don't heed the warning there is the major tank slapper. Here most of the components of the front axle are bent, the front legs of the engine can be broken, and if you don't get it unbder control while still on the circuit, the lucky outcome would be gravel in every orifice, if you are unlucky an there is only a wall, it doesn't bear thinking about.
Myth number one, axle tramp is an uncurable part of having a Bugatti without resorting to tie rods or cables. Wrong, a properly assembled and maintained GP Bugatti with all the standard bits and driven properly doesn't tramp. This is increasingly true as breaking areas get smoother. We must have our cars set up right, the first area is no slack anywhere. No kingpin slack, no steering arm slack, no slack in the linkage to the shock absorbers, no slack in the spring bushes and no slack in the wheel bearings. The brakes must be properly set up and bedded in using brake linings with friction characteristics that suit the application. The shock absorbers must be lubricated with proper high-pressure grease and evenly set up.
Non supercharged cars should be modified to use the supercharged front springs for the benefit of axle control. As we mentioned the subject of leaving the circuit, lets look at personal safety, forget the aesthetics for a moment and concentrate on the practicalities. In their day the Grand Prix Bugatti was a cutting edge racing car driven by great drivers, admittedly on circuits with inferior safety precautions, they got caught out and some died. We now drive these cars, they are no slower, they don't handle or stop considerably better, we are surrounded on circuits by unconscious blind drivers in much slower cars. The cars are now seventy years old, they are not prepared with the budgets of a works racing team or, with a few exceptions, by works quality mechanics and how manyof us, hand on heart think we are as good as louis Chiron at the height of his powers. The fact is it can happen to us now just as easily as it did then, and if we don't use every means at our disposal to mitigate that risk we are stupid.
So full-face helmets, fireproof underwear, two but preferably three layer suits, fireproof gloves and boots. Fire is a real risk and not just methanol, oil gets real hot too. Methanol burns without visible flame, if we run methanol make sure the orange sticker is very prominent or the marshalls might just think you are a bad dancer. Water hoses are often overlooked, but sitting in a car at 100mph being sprayed with boiling water while you try to get the brakes on is no joke. Proper personal safety equipment can save your life. Methanol is a prblem ever if it isn';t burning, it is absorbed through the skin and the lining of the lung, it forms formaldehydes in the blood leading to blindness and insanity, perhaps it is the root of our illness. The effect is cumulative and we must be aware. Methanol vapour is heavier than air, so an open container in an enclosed space fills the floor with volatile fumes. Sparks and smoking are out.
Moving on, for the health of our cars Methanol is an effective degreaser and reacts with magnesium and aluminium. In the day after running it was common practice to run the cars briefly on petrol and redex, to clear the system and lubricate the bores. We drain the system and run the car on petrol lubricating the bores by spraying WD40 in the spark plug hole.
throttle return springs: Pay real attention to mounting them correctly, they are important and must not fall off. Throttle linkages in general must be in first class condition, properly lubricated and cared for, sticking or binding can get you killed.
I think the subject of wheels has been done to death, my opinion is that an old wheel is suspect, from the brake drum condition and material as well as rim strength. Original rim width means we are sticking our necks out any time we fit a tyre larger than 5.00" section. Wheel castings must be balanced prior to the fitment of the tyre and, where possible, the heavy spot of the wheel should be used to counter the heavy spot of the tyre. Tyre pressures are a function of performance in a racing situation.

Here endeth the lesson.

for more technicallities on Bugattis, see this Article: Detailing Details.
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