Resin

Resin (pronounced rez-in)

(1) Any of a group of non-volatile solid or semisolid organic substances & compounds (that consist of amorphous mixtures of carboxylic acids), obtained directly from certain plants as exudations of such as copal, rosin & amber (or prepared by polymerization of simple molecules) and used typically in pharmaceuticals, plastic production, lacquers, adhesives and varnishes.

(2) A substance of this type obtained from certain pine trees (also called rosin).

(3) To treat, rub or coat with resin.

(4) A precipitate formed by the addition of water to certain tinctures.

(5) Any of various artificial substances, such as polyurethane, that possess similar properties to natural resins and used in the production of plastics; any synthetic compound with similar properties.

1350–1400: From the Middle English resyn & resyne (hardened secretions of various plants), from the Old French resine (gum, resin), from the Latin rēsīna (resin), from the Ancient Greek rhētī́nē (resin of the pine tree), both probably from a non-Indo-European language.  In chemistry, the word came to be applied to synthetic products by after 1883.  The verb resinate (impregnate with resin) dated from 1756.  The adjective resinous (of the nature of, pertaining to, or obtained from resin) is documented since the 1640s, from the Latin resinosus; the earlier adjective was resiny (having a character or quality like resin), noted since the 1570s.  The related (and now rare) noun rosin (distillate of turpentine (especially when in a solid state and employed for ordinary purposes)) dates from the late thirteenth century and was from the Old French raisine & rousine, both variants of résine; it was used as a verb after the mid-fifteenth century.  The later adjectives resiniferous & resinless appear never to have been used except in chemistry or technical literature in relevant industries, the more common forms in general use being resin-like or resinous.  Because the word resin covers a wide field of substances, it usually appears in modified form (acaroid resin, acrylic resin, epoxy resin, phenolic resin, polyresin, polyvinyl resin et al).  The present participle is resining and the past participle resined.  Resin, resinousness & resinite are nouns, resinously is an adverb and resinify is a verb; the noun plural is resins.

Resin wheels

1972 Citroën SM with Michelin RR wheels. 

Although sometimes referred to as being made from “carbon fibre”, materials engineers insist the optional wheels offered on the Citroën SM must be described as “synthetic resin reinforced with long-strand carbon fibre”.  Notable as the first composite road wheel offered for public sale, they were developed by Michelin, the tyre-maker which since 1934 had been Citroën’s parent corporation and the innovation was an appropriate accessory for the SM which, upon release in 1971, was immediately recognized as among the most intricate and intriguing cars in the world.  A descendant of the DS which in 1955 had been even more of a sensation than the SM, it took Citroën not only up-market but into a niche the SM had created, nothing quite like it previously existing, the combination of a large (in European terms), front-wheel-drive (FWD) luxury coupé with hydro-pneumatic suspension, self-centreing (Vari-Power steering), high-pressure braking and a four-cam V6 engine, unique in the world.  The engine had been developed by Maserati, one of Citroën’s recent acquisitions and the name acknowledged the Italian debt, SM standing for Systemé Maserati.  Although, given the size and weight of the SM, the V6 was of modest displacement (initially 2.7 litres (163 cubic inch) and power was limited compared to the competition (181 HP (133 kW)), such was the slipperiness of the body that in terms of top speed, it was at least a match for most.

Michelin RR wheel.

However, lacking the high-performance pedigree enjoy by some of that competition, a rallying campaign had been planned as a promotional tool.  Although obviously unsuited to circuit racing, the big, heavy SM didn’t immediately commend itself as a rally car, early tests indicated some potential but there was a need radically to reduce weight.  One obvious candidate was the steel wheels but attempts to use lightweight aluminum units proved abortive, cracking encountered when tested under rally conditions.  Michelin immediately offered to develop glass-fibre reinforced resin wheels, the company familiar with the material which had proved durable when tested under extreme loads.  Called the Michelin RR (roues resin (resin wheel)), the new wheels were created as a one-piece mold, made entirely of resin except for some embedded steel reinforcements at the stud holes to distribute the stresses.  At around 9.4 lb (4¼ kg) apiece, they were less than half the weight of a steel wheel and in testing proved as strong and reliable as Michelin had promised.  Thus satisfied, Citroën went rallying.

Citroën SM, Morocco Rally, 1971.

The improbable rally car proved a success, winning first time out in the 1971 Morocco Rally and further success followed.  Strangely, the 1970s proved an era of heavy cruisers doing well in the sport, Mercedes-Benz winning events with their 450SLC 5.0 which was both the first V8 and the first car with an automatic transmission to win a European rally.  Stranger still, Ford in Australia re-purposed one of the Falcon GTHO Phase IV race cars which had become redundant when the programme was cancelled in 1972 and the thing proved surprisingly competitive during the brief periods it was mobile, the lack of suitable tyres meaning the sidewalls repeatedly failed.  However, the SM, GTHO & SLC proved a quixotic tilt and the sport went a different direction.  On the SM however, the resin wheels had proved their durability, not one failing during the whole campaign and encouraged by customer requests, Citroën in 1972 offered the wheels as a factory option although only in Europe; apparently the thought of asking the US federal safety regulators to approve plastic wheels (as they’d already been dubbed by the motoring press) seemed so absurd to the French they never bothered to submit an application.

Reproduction RR in aluminum. 

Michelin ceased to make the RR when SM production ended in 1975 but did provide another batch for sale in the mid 1980s and this was said to be a new production run rather than unsold stock.  A cult accessory for a cult car, perfect examples now sell for around US$2000 each which does sound expensive but, given what it can cost to restore (or even maintain) a SM, it’s not a significant sum and, unlike much of the rest of the machine, the RRs are at least trouble-free.  Michelin are not said to be contemplating resuming production but another company has produced visually identical wheels made from aluminum; these only slightly heavier.  Despite the success and the fifty-year history of robustness, Citroën didn’t persist and the rest of the industry never adopted the resin wheel.  The reason was two-fold: (1) Even if economies of scale operated to lower the unit cost, the technology was always going to be more expensive than using aluminum and advances in alloys meant the metal units can provide similar strength with only a slight weight penalty and (2) the resin was always susceptible to high temperatures, something not encountered on the SM which used inboard brakes.  Most cars however don’t use inboard brakes and as Ford found when testing resin wheels during Lincoln's downsizing programme in the mid-1970s, although the weight reduction was impressive, almost the same was possible with aluminum at much lower cost and the problems caused by heat-soak from the brakes were insoluble.  So it proved until the late 1980s when, with the development of new, heat-resistant materials, reinforced resin wheels were made available on the limited-production Dodge Shelby CSX (1989).

True carbon fibre wheels have had a little more success, although only at the top-end of the market, Koenigsegg in 2013 manufacturing carbon fibre single-piece wheels which it offered as a US$40,000 option; a number which needs to be considered in the context of the US$2 million price tag for one of their cars.  Porsche, Mercedes-Benz, Ferrari and Ford have all flirted with carbon fibre wheels and some manufactures are interested in the possibilities offered by hybrid designs which use aluminum for some components and carbon fibre for others, an idea familiar from earlier steel/aluminum combinations.  Regulatory authorities are apparently still pondering things.

The SM V8

1974 prototype Citroën SM with 4.0 V8.

Ambitious as it was, circumstances combined in a curious way that might have made the SM more remarkable still.  By 1973, sales of the SM, after an encouraging start had for two years been in decline, a reputation for unreliability already tarnishing its reputation but the first oil shock dealt what appeared to be a fatal blow; from selling almost 5000 in 1971, by 1974 production numbered not even 300.  The market for fast, thirsty cars had shrunk and most of the trans-Atlantic hybrids (combining elegant European coachwork with large, powerful and cheap US V8s) which had for more than a decade done good business as alternative to the highly strung British and Italian thoroughbreds had been driven extinct.  Counter-intuitively, Citroën’s solution was to develop an even thirstier V8 SM.  It actually made some sense because, in an attempt to amortize costs, the SM’s platform had been used as the basis for the new Maserati Quattroporte but, bigger and heavier still, performance was sub-standard and the theory was a V8 version would transform both and appeal to the US market, then the hope of many struggling manufacturers.

Recreation of 1974 Citroën SM V8 prototype.

Citroën didn’t have a V8; Maserati did but it was big and heavy, a relic with origins in 1950s sports car racing and while its (never wholly tamed) raucous qualities suited the character of the sports cars and saloons Maserati offered in the 1960s, it couldn’t be used in something like the SM.  However, the SM’s V6 was a 90^o unit and thus inherently better suited to an eight-cylinder configuration.  In 1974 therefore, a four litre (244 cubic inch) V8 based on the V6 (by then 3.0 litres (181 cubic inch)) was quickly built and installed in an SM which was subjected to the usual battery of tests over a reported 20,000 km (12,000 miles) during which it was said to have performed faultlessly.  Bankruptcy (to which the SM, along with some of the company's other ventures, notably the Wankel programme, contributed) however was the death knell for both the SM and the V8, the prototype car scrapped while the unique engine was removed and stored, later used to create a replica of the 1974 test mule.

Citroën Traction Avant 22, Paris Motor Show 1934.

It was a shame because, despite being most associated with the US, it was the French engineer Léon Levavasseur (1863–1922) who in 1904 created the first V8 engine and at the 1934 Paris Motor Show, Citroën displayed their “22”, a variation of their Traction Avant model but fitted with a 3.8 litre (233 cubic inch) V8, created essentially by joining on a common crankcase two of their 1.9 litre (117 cubic inch) four-cylinder units.  When presented at the show, several models were displayed and the promotional material confirmed the 22 would be available with an extensive choice of coachwork including a saloon, an elongated limousine, a cabriolet and a coupé.  Bankruptcy however halted the project and Michelin, having just taken control, insisted the company concentrate on the best-selling, most profitable lines.  A reputed two dozen-odd 22s were built before the Michelin Man dropped his axe and although all passed into private hands, none appears to have survived the war although there have always been rumors one remains hidden somewhere in the Far-East, a survivor of the colonial presence in Indo-China.

1967 Cadillac Eldorado, which proved the big, FWD coupé could still be done.

Evidence does however suggest a V8 SM would likely have been a failure, just compounding the existing error on an even grander scale.  It’s true that Oldsmobile and Cadillac had offered big FWD coupés with great success since the mid 1960s (the Cadillac at one point fitted with a 500 cubic inch (8.2 litre) V8 rated at 400 HP (300 kW)) but they were very different machines to the SM and appealed to a different market.  Probably the first car to explore what demand might have existed for a V8 SM was the hardly successful 1986 Lancia Thema 8·32 which used the Ferrari 2.9 litre (179 cubic inch) V8 in a FWD platform.  It was about a daft an idea as it sounds.  Even had the V8 SM been all-wheel-drive (AWD) it would probably still have been a failure but it would now be remembered as a revolution ahead of its time.  As it is, the whole SM story is just another cul-de-sac, albeit one which has become a (mostly) fondly-regarded cult.

Lindsay Lohan in Tsubi Scooter Jeans, Andrea Brueckner Saddle Bag, L.A.M.B. Lambstooth Sweater, Manolo Blahnik Butterfly Sandals & Louis Vuitton Inclusion Resin Bangles, Los Angeles, April 2005.