Theme : Wheels – Citroën’s Plastic Wonder

From a time when Citroën led the way – and, of course, nobody followed

I know which I’d choose

The standard wheels for the Citroen SM were heavy steel items, clad with hubcaps. These are made from stamped stainless steel, held firmly to the wheel by a centre bolt. The centre section is painted satin black and the sections between the outer fins are painted in satin silver-grey. There are holes in the hubcaps that allow the actual wheel bolts to show.

Although that might not have been the intent, there is the distinct feeling that they were trying to ape the fancy US wheels fitted to any US muscle car of the period. As such, I have never found these hubcaps entirely convincing and, although time has made me more tolerant of them, at the time I even found them a bit tacky. As I know, they are also a pain to restore, since paint never likes sticking to stainless steel.

The original SM wheel and hubcap.
The original SM wheel and hubcap.

But there was an alternative, that looked much better. The Michelin RR wheel, clad of course with a Michelin XWX tyre, is the holy grail of many Citroen SM owners. When I bought my SM in 1996, I toyed with the idea of finding a set of RRs, and there was talk of unused wheels being available for under £1,000 a set. This seemed an unjustifiable indulgence. Now, you will pay well over £1,000 for a single, used wheel.

SM RR Wheel

Like the SM name itself, there are at least two interpretations of the initials, either “roues en résine” or “résine renforcée”. Either way, these were developed by Citroen’s then owners, Michelin, with the intention that they would provide a lightweight wheel for the SM to go rallying with, which they did with some success.

Apparently derived from a NASA patent (used on moon buggy wheels) the wheel is a one piece, technologically advanced, reinforced resin casting, being almost 1/3 of the weight of the equivalent steel wheel and much stronger. Since carbon plays a part in the reinforcement, you will come across rash claims that RR wheels are, in fact, carbonfibre. That has some justification, but only if you believe that scrambled eggs are a souflée. Nevertheless, the wheels seemed to be of great technical merit and Michelin proposed them to various carmakers. In the early 70s, Lincoln even tested them on a Continental.

Rallye du Maroc SM
Rallye du Maroc victor

Why they didn’t go further is probably due to the industry’s conservatism, rather than an inherent flaw. The RR wheels come from a time when Citroen were truly innovative, and time has shown Michelin’s manufacturing process to be excellent, considerably more high-tech than that of kit car body laminate and, unlike, say, 60s Minilite alloys, there are no horror stories of drastic degradation.

But nothing lasts forever and there are maybe legitimate concerns about relying on a 45 year old composite for your contact with the road. Or maybe I’m just writing that to justify my still having those iffy hubcaps, now in need of yet another renovation, on my car.

There is, however, now a third alternative. SM tuning legend, Regembeau, have released a set of RR lookalike alloys. Damn.

A Regembeau SM with its own re-manufactured RR style wheels

17 thoughts on “Theme : Wheels – Citroën’s Plastic Wonder”

  1. If you still consider RR wheels, there is a set for sale for, as you state it, “well over £1,000 for a single, used wheel”:
    This recently turned up on the German Citroën forum as “the most expensive set of wheels ever seen” – at least in the Citroën world.

    The Regembeau wheels are a very convincing alternative, but the whole look of this car is greatly ruined by the pseudo-grille. Why would someone do that?

    1. Simon. Those are certainly the most expensive I’ve seen to date. Although SM prices have risen relatively recently (like everything else) that really risks the situation where the wheels are worth more than the rest of the car.

      As for the Regembeau, I agree it loses the purity of the original, but I have always assumed that it was dictated by cooling issues. SM’s will overheat and, since Regembeau claimed to have squeezed as much as 300 bhp from one of his conversions, I imagine the overheating problem would have been exacerbated.

      Georges Regembeau is dead now, but I believe his son runs the company. A few years ago I enquired about having my own engine rebuilt to a more ‘interesting’ specification. I got no reply. It was probably my dire French – I should have asked Laurent to check the spelling!

    2. If the grille serves a technical purpose, I’m OK with it, although I still don’t find it nice to look at.

    3. Beyond comprehension. The under-the-bumper grille is more than adequate for the A/C and motor cooling radiators and the motor oil cooler. The center glass covers the registration plate mounting for jurisdictions that require a front plate. I intended to mount driving lights in there as I lived in a state that did not require a front plate. Alas, all of my SMs were stolen, probably by a scrapper.
      1 driver that had the 5 speed gearbox out for refreshing
      1 under restoration
      1 non-USA fire damaged parts car, no motor or trans
      1 complete bodyshell-frame in perfect undamaged, unrusted condition
      Many new parts, almost all stolen by drug heads.

  2. It’s stories like these that make me appreciate why the resident Citroenistes get so melancholy about the current range. It also makes me appreciate Michelin more.

    In terms of the wheel dilemma I would buy a set of Regembeau alloys, get the current wheel trims refurbished, then put the wheel covers into storage. That way if you ever decide to either enter a car show or (heaven forbid) sell it, you have ‘stock wheels’ along with the set of acceptable aftermarket alloys for daily use.

  3. Underlying this story is the possibility that alloy wheels as we know them are getting stale. I seldom see a set I like and the ones I like tend to be quite simple. That said, the alloys on my XM are far from simple and even feature painted inserts.
    Here they are:
    But isn´t this attractive?:

    1. 100% agree with Mark. These are both original XM items from Day 1, and still the ones that fit the car best. I also liked the wheel covers for the very, very simple versions (without rear spoiler!), as seen here:

      (Very nice “vert amandier” colour, by the way)

      Later XM wheels were horrible in comparison. The “wavy” alloys from around 1994 were still quite OK, but the later “Exclusive” 10-spoke wheels were horrid, and totally unbefitting the car.

    2. Richard writes: “the ones I like tend to be quite simple”
      Quite true – and hard to find. I’m still looking for an adequate wheel to replace the original alloys on the C6, but all I see are thin spokes or asymmetric designs in thousands of variations. No plane, closed aftermarket wheels to be had…

  4. Incidentally, the metallic brown US spec SM that I used to illustrate the steel wheels is not an ideal example really . The outer area has been completely polished, getting rid of the satin infills. This is quite common and makes the trims look even more gaudy.

    It was surprisingly difficult to find a decent close-up of a hubcap. I intended to photograph mine (which I took the trouble to restore more accurately) but it was too dark by the time I got home.

    1. I actually like the hubcaps better. But then again, I don’t mind my XJ’s pepperpot alloys, either. And my favourite Bond is On Her Majesty’s Secret Service.
      Am I being leftfield or just plain daft?

    2. Kris. I agree with you on the pepperpots, and actually OHMSS is near the top of my Bond list (though, of course, Octopussy comes top). But you won’t convince me about the hubcaps. They just seem to have an identity crisis.

    3. Vented wheels are totally unnecessary with inboard front brakes mounted on the transaxle bellhousing. Their location ahead of the mid-motor allows plenty of cooling airflow. The tiny rear wheel brakes on the SM don’t do very much especially in hard braking, so don’t need any vents in the wheels for cooling.
      The CX and later cars have outboard mounted brakes. Cross-mounted power units don’t leave enough room for inboard mounted brakes.

  5. Simon: the spoilerless XMs are a curiosity. For the entire design process up until testing in the US, the car had no spoiler. Some seemed to have been sold in the EU but not the UK. Odd.

    1. As far as I know, the spoilerless one was the 2L carburettor version (and maybe the naturally aspirated diesel). I don’t know if it was ever officially sold in Switzerland, but we don’t buy base spec here. I actually like the pure rear shape of the XM, and the spoiler is the only point where I see an improvement of the 1994 facelift.
      The one about the US testing is an interesting story. I’ve never heard of it. Was it actually planned to sell the car there?

  6. I have a set of 4 RR Michelin wheels in very good condition with center caps I found stored in an airport aircraft hangar for the last 35 years if anyone is interest I can be reached here Pierre

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