Under the skin of Jim Clark's Lotus 29

In the first of a new series, Keith Howard gets beneath the skin of the original Indy Lotus - with help from Chapman's chief designer, Len Terry

Jim Clark Lotus 29

Colin Chapman, Jim Clark and the Lotus boys at Indy '63 with the 29


When Colin Chapman was invited to the 1962 Indianapolis 500 by Dan Gurney, the Lotus founder surveyed the front-engined ‘dinosaurs’ on show there and famously remarked, “All you’ve got to do is to get an engine with half the power of these great lumps of junk, build a decent chassis and you’ve won the race.”

The Lotus 29, which competed at the Brickyard the following year, was the car charged with justifying this haughty dismissal of Indy tradition and it very nearly did.

Although Chapman himself laid out a scheme for the car in effect, a bigger version of the 25 which had made such an impact in Formula One in 1962 it fell to the newly appointed Lotus chief designer Len Terry to complete the design details and construct it.

Terry had worked for Lotus previously, before being sacked by Chapman in 1959 for building and selling cars in his off-duty hours. These two men, though they had similar philosophies of race-car design, had a barbed personal relationship – “He looked on me as a bolshie bastard,” recalls Terry. “And I was – I stuck up for my rights!” So to entice Terry back to fill the departing Mike Costin’s shoes, Chapman had to dangle some carrots. A big office and generous salary were a good start, but what really clinched the deal was the chance to work on an Indianapolis car; Terry had been attracted by the Indy scene since a very young age. He rejoined the payroll in September 1962.

(Original Caption) Indianapolis, IND: Dan Gurney, one of America's great racing drivers, is shown here in the prototype of a new Indianapolis car by Lotus Cars, Ltd. of England. The car is powered by a new Ford aluminum V-8 engine. The car, designed specifically for the

Gurney testing the prototype – codename ‘500’

Bettmann / Getty Images

Three cars were built for the 1963 campaign: one for Jim Clark, one for Gurney (his reward for the Ford introduction) and one as a test mule.

Cheshunt’s publicity was bullish about the 29’s prospects. Noting that it had a higher power-to-weight ratio 370bhp in a car weighing 1130lb than the awesome Mercedes and Auto Unions of the 1930s, Lotus predicted it to be capable of breaking “almost every lap record in the world”. Early testing at Snetterton, where it duly set a new lap record, confirmed those expectations.

The atmosphere at Indianapolis was not altogether sportsmanlike. Its establishment was riled, not only by Chapman’s irreverence, but by the fact that Gurney had introduced him to the Ford executives who would finance the project and provide it with a purpose-developed, light-alloy racing version of its pushrod Fairlane V8. When Firestone also weighed in with 15-inch tyres developed specially for the Lotus, the feeling of xenophobia intensified. The cocky foreign interlopers were backed by US dollars!

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Revenge was exacted in various ways. Jim Clark – whose one previous drive at Indy was a test session in a 25, an experience he described afterwards as “a bit dull really” despite a best lap of 143mph was compelled to take a humiliating rookie test. In the race itself Gurney started well but slipped back to seventh at the finish, whereas Clark, despite being robbed by yellow flags of much of the advantage of his fewer pitstops, looked set to win until Parnelli Jones’s leading roadster infamously began to leak oil onto the track. Furious complaints by Chapman failed to get Jones disqualified and Clark had to settle for second. A prize purse of over $55,000 helped soothe Lotus indignation. As did an emphatic win in the following Milwaukee race, where Clark led for all 200 miles.

Len Terry would exact his revenge in turn in 1965, when Clark triumphed in the third-generation Lotus Indy car, the 38, to become the first non-American to win the race since 1916. Still, that 1963 ‘robbery’ irks even today. “If they had stuck to their own rules we would have won the race,” says Terry for what must be the umpteenth time, “but I’m biased, of course.”

Lotus 29 1

Clark finished second on his first Indy attempt, before winning the next championship race at Milwaukee


Construction of the 29 was on the ‘bathtub’ principle first used in the 25. To maximise its fuel capacity and so capitalise on the decision to use pump fuel, the chassis ‘sills’ were taller and wider and a saddle tank was added above the driver’s legs, bringing the total capacity, including the small tank behind the driver’s back, to an impressive 42 gallons. Unlike the 25, the tanks were interconnected using a system of non-return valves of Terry’s devising which allowed fuel to flow into the left-hand sill tank but not out of it — other than to the engine! — thereby ensuring that the weight of the fuel load remained evenly distributed through lndy’s succession of left-hand corners.

Ford’s pushrod Fairlane V8 must have seemed pretty crude to Lotus eyes compared to the Coventry-Climax FWMV used in the 25, and its 370bhp from 4195cc (just 88bhp/litre) compared very poorly with the 130bhp/litre achieved by the Coventry unit the same year.

But Ford tests had shown that, even using methanol fuel, the Offenhauser four-cylinder engines favoured in the traditional Indianapolis roadsters only just topped 400bhp, and they were significantly more thirsty; hence the decision to run the 29 on pump fuel, despite the power shortfall. Its lower frontal area helped reduce the Lotus’s speed disadvantage on the straights, and it proved significantly quicker round the corners, enabling it to capitalise on its fewer pitstops.

Angled exhaust stubs identify this as an early incarnation of the 29, before Ford had developed a proper tuned header/collector system for the V8. By the time the 29s appeared at Indy the exhaust tubes had been twisted to the rear of the engine where they were combined via two 4-into-1 collectors, terminating in a pair of flared outlet pipes that exited almost horizontally from beneath the engine cowling.

Suspension was lifted from the 25, albeit beefed up and complicated by the 29’s body offset. To keep the rear suspension geometry as near as possible the same on both sides of the car (it wasn’t quite because the radius arms were shorter on the left than the right), the upper transverse arm and lower wishbone were identical either side. This simplified the car’s manufacture and reduced the spares inventory.

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One consequence was the unexpected kink in the front tube of the lower wishbone, which required an extra tube to be added to triangulate it — a distinctly un-Lotus feature. On the right side of the car this arrangement appears perverse, but the reason for it becomes obvious on the opposite side. Here the inboard pivot of the lower link has to be located further inboard to accommodate the body’s offset, with the result that the wishbone would foul the rear bulkhead hoop if it didn’t incorporate that kink.

A Colotti Type 37 transaxle replaced the ZF unit used in the 25 to accommodate the much higher engine torque. Only two of the four available ratios i were used — one low enough to start the car from a standstill and the other for normal lappery.

The 25’s inner Metalastik ‘doughnut’ UJs, which would have wilted under the Fairlane’s torque, were replaced by a Hooke joint-and-roller spline assembly, supplied by American firm Saginaw. Terry recalls that the driveshafts may have been derived from truck units, which would explain why they look so unfeasibly large for a racing car.

Jim Clark of Scotland sits aboard the #92 Team Lotus Lotus 29/3 Ford during practice for the 47th running of the Indianapolis 500 on 25th May 1963 at Indianapolis Motor Speedway in Indianapolis,Indiana, United States. (Photo by Bob D'Olivo/The Enthusiast Network via Getty Images/Getty Images)Bob D'Olivo/The Enthusiast Network via Getty Images/Getty Images

Clark would go on to win the 500 in 1965

Bob D’Olivo/The Enthusiast Network via Getty Images/Getty Images

Offsetting the 29’s body 2.625in to the left was done principally to even up tyre wear — essential if the 29 was to run fewer pitstops. Originally the car was fitted with Dunlop rims, but when Firestone agreed to manufacture 15-inch tyres for the Lotus, it understandably wasn’t too happy at the prospect of these being carried on a competitor’s wheels. So Lotus substituted American-made Halibrand knock-off rims. Ironically, Lotus switched, against Ford’s advice, to Dunlops for the Type 34 in 1964, only for tyre failure to bring the Lotus-Ford challenge of that year to a premature and ignominious end.

Despite the high average speeds on US ovals the braking requirements were relatively light so, although provision was made for increasing the disc diameter if necessary, the 29 ran with precisely the same 10.5in Girling discs and calipers used on the 25 in Formula One