Road test - The BMW 635CSi

A return to Munich’s old sporting coupé recipe. Good handling, fast and flexible performance, but a high price.

“Near perfection” is how W. B. described the BMW 633CSi in his August, 1977, road test report. But he did have reservations about some of the big coupe’s chassis behaviour, criticisms made even more pointedly by hard-driving European BMW customers; used to the taut, sporting appeal of the old 3.0CSL, they found the heavy, more softly sprung and slower 633 something of a let-down. The much loved coupe of old had lost some virility - almost an “old man’s car” in comparison - and sales figures were disappointing, especially on the home market. The new 635CSi is intended to put the gilt back on the sporting image and whilst sheer weight will prevent it achieving the racing cachet of the homologation-special CSL, which continues to reign supreme in the European Touring Car Championship, this BMW flagship is a very sporting car indeed.

With the coming of the 635 the 633 is officially designated as a “softer” car, for the four-speed manual gearbox option has been deleted in favour of standard automatic transmission. The 635 can only be bought with a five-speed Getrag manual gearbox. So you "pays yer money and takes yer choice", and in true BMW high-pricing tradition, never was a truer word spoken: the man who insists on a manual gearbox coupe is forced into paying £1,200 for the privilege to bridge the gap between 633 and 635. The 635CSi costs £17,199, and that is just for starters. The test car’s electric sunshine roof added another £560, its headlamp wash/wipe system a further £161, an electrically-operated door mirror for the passenger side £60 (the driver’s comes as standard), a stereo radio/cassette player with electric aerial £300, while air-conditioning, not fitted to the test car although the example used for photography was so-equipped, would be a colossal £1,050. So the quieter, faster, smoother, air-conditioned, stereo-equipped, though less sporting in feel, Jaguar XJ-S begins to look very cheap indeed at £15,149.

This bad news disposed of, on to happier matters. The 635 shares the same body shell, cockpit layout and general mechanical arrangement as the 633 described in 1977, but with some very obvious differences. W. B.’s description of that straider two-door, four-seater coupe’s appearance as “unobtrusive” is no longer true, this latest 15’ 7" long, very capaciously "booted" CSi taking on a much more aggressive demeanour from the addition of a deep front spoiler and a large rubber tail spoiler on the boot lid. These are not merely cosmetic appendages: they reduce lift at high speed by 15 per cent, an essential consideration on a car capable of 140 m.p.h. on the unrestricted autobahns of its homeland. The spoilers are neatly absorbed into the overall lines, unlike the strange growths which sprouted form that splendid 3.0 CSL "Batmobile". "Go-faster" stripes are tidily laid along the waistline and an increase in rim width to 6½" from the 633’s 6" enhances the squatter look on the road. The BBS web-spoked alloy wheels carry the same 195/70VR 14” Michelin XDX tyres as the 633, but the extra rim width gives better tread utilisation and stiffer side walls. I liked the appearance of this surprisingly big coupe, but that might reveal a subconscious boy-racer streak within me!

Those familiar with BMW-type numbering won’t need telling that the new model designation denotes an increase in engine capacity. This isn’t a simple case of boring or stroking the 633’s 3,210 c.c. engine to 3,455 c.c.: the 635 uses a different cylinder block, the M90, pioneered as the M49 type in the all-conquering 3½-litre racing CSLs and now being produced in M88 form for the low-volume production M1 mid-engined coupe. Within this different casting, the oversquare 635 engine houses a larger bore and shorter stroke than the 633 engine, at 93.4 mm. x 84. Unlike the 24-valve M1’s cast-iron block, that of the 635 carries an aluminium cylinder head bearing 12 valves, operated by the familiar chain-driven single overhead camshaft. This seven-main bearing, in-line, six-cylinder engine runs a 9.3:1 compression ratio, is fed its fuel/air mixture by Bosch L-Jetronic injection and is parked by an electronic, contact-breakerless ignition system. The twin exhaust pipes has been increased in size from 42 mm. to 50 mm. thus equipped, the 635 boasts an extra 18 b.h.p. at 300 r.p.m. less than the 633, producing 218 b.h.p. at 5,200 r.p.m. Equally significant is an increase in torque from 210 lb. ft. at 4,250 r.p.m. to 224 lb. ft. at 4,000 r.p.m.

This has allowed the final drive ratio to be increased from 3.25:1 to 3.07:1, but at the same time it has to take care of an extra cwt. over and above the 633. The 635 weighs in at approximately 30 cwt.

Criticisms of the 633’s suspension have been countered on the 635 by uprating shock absorbers, springs and anti-roll bars and adding anti-roll blocks to the front springs to stop the car keeling too much under hard cornering. The layout is otherwise as on the 633, with McPherson struts and coil springs at the front and semi-trailing arms with coil springs at the rear. When the 7-series saloons were introduced to us in Germany, BMW engineers intimated that the 6-series coupes would eventually inherit their new power-assisted rack and pinion steering and power-operated brakes, but this has yet to happen and the 635 retains ZF worm and roller power steering and conventional servo-assistance for the ATE 11” front and 10.9” rear ventilated disc brakes.

As with most BMWs, this striking-looking coupe is an easy car to live with. In the exceptionally cold weather of the test period the test car required a few seconds’ churning on the starter to fire the engine after nights in the open, but once fired it could be driven away immediately without a trace of hesitancy. The test car had dark grey, velour trim to the seats (leather upholstery, as in the car shown on these pages, is a no-cost option), which picked up fluff and dust worse than any trim I have experienced, so BMW’s car cleaner should be thankful that the Motoring Dog was not involved in this test.

That aside, the bucket seats were most comfortable, less unforgiving and better locating than other BMW seats, their back rests adjustable for rake, their squabs with height adjustment and a tilt facility. The steering column telescopes but doesn’t tilt, the nice leather-rimmed, four-spoke, four horn-push steering wheel being mounted rather high. The man-sized pedals are well-positioned. The layout of instruments and switchgear on current BMWs is hard to beat. What the facia panel lacks in quantity of instruments it makes up for in clarity. Three big Vdo instruments are cowled behind a single glass pane in a binnacle in front of the driver, the larger 160 m.p.h. speedo flanked on the left by a dial showing contents of the 15.4 gallon tank and water temperature, on the right by a 7,000 r.p.m. tachometer, its bold red segment starting at 6,350 r.p.m., beyond which the needle’s potentially disastrous swing is prevented by an ignition cut-out. A row of warning lights runs above the instruments. The centre segment of the facia is angled towards the driver and contains a clock, its bezel doubling as the heater fan speed control, and heater/ventilation knobs and slide controls.

Although the water valve controlled heater warmed up quickly on those cold mornings its heat delivery was badly inconsistent. I had no cause to use the ventilation system, but this is unchanged from that which W. B. criticised on the 633 in the summer of ’77. On the right of the facia is the by-now familiar BMW check panel, which gives visual reassurance at the touch of a button that all the systems are working. The Porsche 928’s automatic warning system is more sophisticated than this BMW arrangement, which I tended to forget.

To those familiar with the old manual 633CSi, the most immediately noticeable difference once behind the wheel will be in the operation of that gaitered gearlever with an extra “leg” in the gate. This Getrag five-speed ‘box has first gear set over and down to the left, like the 928, which will no doubt upset some owners until they get their brains into gear. Reverse is opposite first, while the other four forward gears lie in H pattern. I had been warned that the gearbox wasn’t very pleasant, but ended up quite liking it. The secret is not to be too ham-fisted with it: the more gently the lever is stirred, the less notchy it becomes. Some force is required to overcome the strong spring protection against the first and reverse plane, however. It is best to let the bias into the 2nd and 3rd plane line up the lever for those gears. I found it a much pleasanter, easier to use ‘box, with shorter movements across the gate than the ZF unit in the 928. Some drivers might find its forward positions a bit of a long stretch. The clutch is heavy and needs to be fully depressed for clean changes.

I’ve often criticised BMW’s for being undergeared as well as having inadequate ratios. The 635CSi is the first BMW with, to my mind, ideal gearing, certainly for British roads, yet I note that other writers have criticised this swift coupe as being undergeared too. BMW have had Getrag make them a proper, close ratio ‘box with a direct fifth gear offering 23.555 m.p.h. per 1,000 r.p.m. Ratios are: 1st, 3,717:1; 2nd, 2.403:1; 3rd, 1.766:1; 4th, 1,263:1; 5th, 1.0:1; reverse, 4.234:1. The lower ratios offer speeds of 40, 62, 84 and 118 m.p.h, at the 6,350 r.p.m. red line, “long” enough gears surely for most use? The claimed 140 m.p.h. fifth gear maximum is reached at 5,900 r.p.m., well above the peak of the power curve, but not many owners are likely to reach that speed or wish to maintain it. The engine is right on song at just over 120 m.p.h., which is a more likely autobahn cruising speed, and packs tremendous punch through most of this range, which wouldn’t have been so good had fifth been made an overdrive. Indeed it feels long legged enough well into the three-figure bracket (100 m.p.h. equals 4,250 r.p.m.), much less fussed than the lower-geared manual 633 CSi of old. Gearing is not the only contribution to reduced fussiness: the Getrag box has killed the annoying, characteristic whine of the old four-speeder.

The gate arrangement of the gearbox does slow down the first to second change a little, but it doesn’t stop this 1½-ton, 3½-litre car accelerating from 0-60 m.p.h. in about 7½ sec. and 100 m.p.h. in about 20 secs. Several rivals can beat these times, but few 635 owners are likely to complain too much about performance.

The short stroke "six" is delightfully smooth and responsive, a normal characteristic of these L-Jetronic injected BMW big sixes, which is even more marked in the 635’s case thanks to the flat torque curve. There is a no real need to use maximum revs for good performance in most circumstances, for the well-spaced gear ratios and good torque give swiftly progressive performance up the scale. Fourth is a particularly useful overtaking gear. More surprising that outright performance is the 635’s flexibility, for it will pull 800 r.p.m. in fifth without stalling, nearly 200 r.p.m. below tickover. This makes for a Jekyll and Hyde car, happy to be driven lazily around town or treated like the high performance sports coupe it is when conditions allow it. The heavy spring opposition against selecting first gear can be largely forgotten in most town traffic conditions: the 635 is quite happy to set off in second gear.

Engine noise rises from a distant burble, accompanied by the characteristic exhaust twitter, at tickover, to a health roar under hard acceleration, when this BMW either shows its true sporting colours or its lack of refinement against the likes of Jaguar and Mercedes, depending upon the driver’s mood at the time. Certainly it doesn’t compare with Jaguars for wind noise suppression (nor do Mercedes). The test car was quieter than other BMW models in this respect, but still far from hushed at speed.

The revised suspension settings have transformed the 635 compared with the 633. Gone is that "floating feeling over some surfaces" which W. B. described, gone is most off the diagonal pitching, roll and sogginess when cornered hard and it its place is new found tautness and obedience to the helm which make this a much more enjoyable car to drive quickly. Its handling is safely neutral, though the tail needs watching under slippery conditions and traction is helped by a limited slip differential. It’s road holding is not up to the exceptional standards of the P7-shod 928, of course, but in many conditions the balanced handling and direct and positive ZF steering make this BMW more interesting and enjoyable to drive quickly and more forgiving and communicative at its (lower) limit of adhesion. At the same time its bulk an weight don’t give it the lively, thoroughbred feel of a Porsche 911, but then, the latter is an out and out sports car, the 635 effectively a coupe derivative of a long line of saloons. The stiffer suspension has not removed the tendency for the semi-trailing arm rear suspension to squat heavily under hard acceleration nor the nose to dive under heavy braking. Bumps in mid corner can upset the 635’s equilibrium too. I wasn’t able to run this 635 to much more than 120 m.p.h., but the spoilers and associated “tweeks” seemed to have improved stability.

Stiffer suspension and the steel braced Michelins give rise to some bump thump and suspension noises, a few sympathetic body or trim rattles and a harsher low speed ride. It would be fairer to say that the ride is "taut" rather than "harsh", because "harsh" implies discomfort whereas the excellent seats prevent this from being so. The ride improves with speed, as might be expected and overall I rather liked the sporting compromise.

When the same car (CLX 181T) was borrowed from BMW by a Standard House colleague some months before my own test he complained bitterly about the brakes, which would only withstand a handful of stops from high speed before fading. I suspect that new pads had been fitted before the car came to me, because I had no such complaints, though my driving is usually more exuberant than his. Admittedly, the bad weather I experienced may have helped their survival. Come to think of it, slight fade did show up after one particular long, downhill “blind”, but on the whole the braking performance, feel and firmness of pedal was rather better than on earlier BMW coupes which have passed through my hands.

This elegant coupe is extremely well finished and generally well appointed, though I always cringe when a supposedly luxury car has a long list of very high cost "extras" offered on top of an already very high price. Useful standard equipment in addition to that already mentioned includes metallic paintwork electrically operated door windows and rear quarterlights (though the latter open only a short distance) and the usual comprehensive BMW toolkit in the bootlid. The optional headlamp washers/wipers were a boon in the filthy conditions which prevailed during most of the test, but the multiple headlights were dreadful on dipped beam. The electric sunshine roof was extraordinarily slow in its operation and I would have thought its operating switch would have been more conveniently placed on the centre console, with the window switches, instead of in the roof lining. However, when open the roof did not subject the occupants to the buffeting experienced in a 733i. The twin electric door mirrors have one adjustment knob with a change-over switch like that of the 928. One important standard fitment I had momentarily forgotten is efficient central locking, which includes the boot lid. Though ostensibly a four-seater, there is so little head and knee-room in the deeply-contoured rear seats that the 635 should be regarded more as a 2 plus occasional 2, although young children would no doubt be very comfortable therein. There is plenty of useful stowage space in spring-loaded door pockets, a lockable glovebox, in which is a rechargeable torch, in lidded wells behind the rear seat, headrests and in a cavernous well in the centre console, though this is filled in when air conditioning is fitted. I wonder if anybody at BMW has tried to read a London A-Z from the driver’s seat of a 635 by the dull light of the single interior lamp on the passengers’ side.

I am not certain that anybody who can afford to spend upwards of £17,000 on a motor car will be too concerned about fuel consumption, nor am I sure that foul weather and slow commuting will allow my figures for the 635 CSi to be considered representative. They showed a worst of 15 m.p.g. and best of 18.4 m.p.g., which I am sure could be improved upon in fairer circumstances.

In recent times I have lost some of my enthusiasm and respect for some BMW models. The 635CSi has done much to redress the balance, a return to the enjoyable, sporting high performance BMWs of old. But the price? - C. R.