(first posted 1/10/2013) Michelin invented the steel-belted radial tire, which it introduced in 1946. That turned out rather well for them. In the early seventies, anticipating the trend to ever lower-profile tires, Michelin made a bold gamble to reinvent the genre, with a proprietary metric wheel-tire combination that was not interchangeable with conventional wheels and tires. Although it made considerable inroads for a few years, including a lot of American Fords, in the end the TRX concept went flat.
Michelin’s ideas behind the TRX tire were very valid. As tires moved to lower profiles, their smaller sidewalls naturally resulted in substantially stiffer rides. Michelin, being based in France and so associated with the smooth-riding French cars, looked for a compromise, to gain the performance benefits of a low aspect ratio tire and maintain good ride quality.
The solution was the TRX flange and tire (the TDX was a similar design but also included limited run-flat capability). The wheel flange is angled outward, and not so deep. That allows a more gradual transition from the tire bead to the sidewall, maximizing its ability to flex, even with a limited sidewall height.
The TRX was made in three wheel diameters: 365 mm (14.37″), 390 mm (15.35″) and 415 mm (16.3386″). They generally replaced 70-series tires more than one inch smaller in diameter. In the case of the Mustang and Thunderbird Turbo Coupe, their 220/55 390 TRXs replaced the standard 205/70 R14 tires. That was a big jump in diameter size and aspect ratio, but the TRXs did the job admirably, in terms of no noticeable reduction in ride harshness.
TRX tires were used by a number of European manufacturers, including BMW, Audi, Citroen, Peugeot, Ferrari, Alfa Romeo, Renault, Saab and possibly others. Ford of course, adopted them not only in Europe, but made a major push with them in the US, during the late seventies and early eighties.
In addition to Michelin, Avon and even Goodyear made TRX tires; but not for long (in the case of Goodyear). As tire technology improved with conventional rims and radials, the advantages of the proprietary TRX system soon became insignificant, and the TRX system petered out as OEM tires in the mid eighties or so. Most owners with TRX tires have switched to modern conventional wheels and tires, as replacement TRX tires became ever more expensive. At some point, Michelin started marketing the TRX through Coker, who continues to sell them for purists, at a price.
But in 1983, the distinctive graceful large wheels and thin TRX tires were not only desirable from an aesthetic viewpoint, they also functioned superbly. All things must pass, except perhaps for conventional inch-size wheel rims, it seems.
Something else I never knew about. Over $2K for a set of tires would certainly hurt.
I remember my ’82 Escort GT had the option. Replacement tyres were something like 20% more expensive than equivalent tyres, and the only other retail outlet who made the tyres were Sears. Fortunately, they were a bit cheaper than the Michelin’s.
Michelin was a Sears supplier at the time, and undoubtedly made them with Sears branding.
79 Mustang, silver with orange graphics and TRX tires. One of the many Revell or Testor 1/18 scale models I built.
Mine always had excess glue and fingerprints on them as my handiwork got sloppier and sloppier due to the glue high I invariably got.
I always liked the Mustang’s TRX wheels, but not enough to pay 500 bucks a tire to keep them on the car. Yikes.
Agreed. I loved Ford’s 6 spoke copies of the Lancia Scorpion’s 4 spokes, but the TRX diameter means that the vast majority of them are long gone. Michelin and various OEMs did it to their customers again when runflats became common, this time under the PAX brand name. Sadly for ignorant customers, the result is going to be the same. Tire technology keeps marching forward, and buying tires for metric wheels keeps freezing people in time, expensively.
But look at how much the tires cost on today’s equivalent cars. My dad has a Taurus SHO with the optional 20″ wheels. Very short tire life + expensive tires.
at the Tire Rack, the OE 20 inch Goodyears are $164 a tire and the highly rated Continental DWS is $264 a piece. The tires aren’t cheap, but you have options. The only option for TRX and PAX victims involves buying new wheels.
I’m just laughing that the tires at $500 a piece have almost 2000 likes on Facebook!
Likes are free.
I think the early BMW 6 series also used TRX tires.
I am seeing some similar thinking in rims made for tubeless bicycle tires where Stan’s Notubes isusing different shapes in the bead hook and spoke area to suit low pressure tubeless applcations.
A lot of ’80s BMWs had TRX rubber. It makes the prospect of owning one of those cars rather daunting because I imagine tire replacement is a hassle. I don’t know how available TRX tires are today, but I’m guessing they aren’t necessarily going to be stocked in your average rural tire shop.
Early BMW 6 Series used 14″ wheels, just like all other large BMWs of the ’70s. They got TRX wheels in the ’80s, which many of us still regret when we end up owning them because someone didn’t have the foresight to simply replace the wheels. Fortunately, there are many, many other wheels that fit just fine. One can usually pick up a set of used wheels – often with serviceable tires – for less than the cost of a single TRX tire.
I remember an 80’s Monte Carlo with 365 or 390 wheels, but darned if I can find anything about them now…
Never heard of GM using them.
They even came to Australia on the XE Falcon ESP (European Special Pack)
Also Jaguar had the horrible things to upto about 88 ;o)
And on the XE equivalent LTD?
The Fairmont Ghia ESP’s had 15×7″ rims, it was only on the 82-84 FD LTD’s that used the metric wheels. Just under 3500 produced.
True…a “flat disc” kind of alloy wheel, sporting/conservative look. My late father John had an FD 351 in charcoal black metallic (factory, my descriptive words on colour yes coloUr Americans !! 🙂 ) with light blue velour interior the big crazy stereo (Pioneer ?) and those wheels/tyres.
I’ve only just learned recently of the design aspect ie beading/safety feature.
The Betamax of tyres !! (He had 2 of those also ha, ha)
The local tip has some of the BMw factory BBS copy TRX rims currently and I can confirm their availability on early E32 (1986-1993) 7 series BMW’s.
Bit late to this post but I was looking up TRX tyres and came across this.
My Dad had a FD 351 as well in Hermitage with a cream interior. I remember that Pioneer stereo with all the little switches for fade/bass/treble etc….very advanced for 1982!
I loved those wheels, great quality and inside the slots they were painted white.
I was on my P’s when he had it and would take it out when he was away and drop one wheel burnouts on a regular basis, Those TRX’s were $200 bucks each to replace so he worked it out pretty quickly what I was doing and banned me from driving it….Damn you TRX’s!
Never realised those wheels were metric.
My first radials were a set of XZXs that replaced the worn-out Firestones on my Vega. It was an epiphinal moment.
I bought a Pinto time capsule back in 02 and it had all 5 of it’s Firestone Deluxe Champion bias ply’s. Unused spare. Cheap ass Ford, at retail Deluxe Champions were belted bias ply, but for Ford, Firestone made em plain ‘ol bias plys.
I had TRXs on my 79 Mustang 5.0L and they handled great. Looked great too.
The only thing I didn’t like was the premature wear on the fronts. The outer shoulders got worn away in no time due to the soft tire compound and nose-heavy layout of the car. The 5.0L (302) was cast iron back then. The rears looked like new.
A few months ago I saw a Ferrari Boxer at a local car show with aftermarket wheels. I asked the owner why he had those on the car and he said the stock wheels were TRX type. I said what’s wrong with that and he said something like there are no replacement tires available and wasn’t taking any chances!
302s were always cast iron.
The 1986 Peugeot 505 STI had a distinctive 6 spoke alloy rim that came in either a TRX or 15 inch version. Still causing problems years later as these rims are in demand for all varieties of Peugeots (and some Subarus), as long as its the 15 inch and not the TRX. They’re NOT interchangeable and given the lack of availability and price of TRX tires, the TRX rims are good only as paperweights. If you are still running TRX tires you, sir, are a purist of the highest order.
The Austin/MG Montego from the 1980s had metric alloy wheels and tyres on the up spec models. A common DIY car upgrade here (and I guess worldwide) is to buy a lower spec car and dress it up by swapping the tyres onto the wheels of the higher spec model. Second-hand factory alloy wheels aren’t expensive. One of my friends found that didn’t work on his low spec Montego, as the low spec cars wear conventional non-metric wheels and tyres, whereas when he went to upgrade to the factory alloys, they were cheap but new metric tyres were going to cost practically more than the car was worth.
I was a fan of the 79 Fox bodied Mustang Cobra and thought the TRX rims were the perfect look for that new car design. I’d like to think it is a rim that has aged well and is an iconic design in it’s own right, right up there with Detroit’s best. Just a shame the metric tire that goes with it is made of almost-unobtanium! Many thanks for the indepth look at this wheel and tire. Stuff like this I can count on finding here at Curbside!
Funny how metric measuring works nearly everywhere, we went metric here in the 70s I have French Michelin steel rims on both my cars but in inch sizes 14s on my Citroen and 15inch Peugeot rims on my Minx
Metric system was part of Napoleon’s plan to rule the world along with the Napoleonic code. In the US we still fight against it, same as our resistance to Napoleonic Law. Common law and English system of measurements work just fine in the US. In a lot of ways Napoleon was more insidious than Hitler or Stalin.
Women certainly didn’t gain much from Code Civil.
I wouldn’t say we “fight” against metric, it’s more a matter of cultural inertia & political priorities. Other traditions have been cast aside easily when the desire is there.
I bet the Navy will get an exemption if the gov’t ever tries to enforce metric!
The English use imperial measurements the US has its own weird measuring system totally alien to anyone else on this planet.
One solution to the tire debacle…
http://forums.corral.net/forums/wheels-tires/977655-ford-thunderbird-cougar-trx-wheels-modified.html
WARNING: Clicking on that link brings about multiple redirects, and the screen is overtaken by a message that you’ve “won” something. You probably don’t want to click the “OK” button in the message.
I love the wheels on that T-Bird!! Don’t think I’ve ever seen them before… way cool.
I didn’t know you could actually still buy these anywhere, that’s pretty neat.
You can’t…he had a machine shop take the centers of the TRX wheels and put them in 16″ and 17″ hoops.
I have a few michelin trx tires sizes 165/70/365 about 6 of them and 8 200/65/365 if anyone is lookin to buy them
please give me the alternative size for this TRX 200/60 VR 390
I recall Michelin running ads in my Canadian newspaper offering alloy wheels to those willing to change up to these TRX tires.
This was about 1985 and I guess they were trying to clear stock.
I appreciate this article on automotive esoterica.
Three or four years ago I sold 4 Mustang TRX wheels for scrap…
Wahahah! When I sold my Thunderbird (see next post) the buyer wanted the ‘stock wheels’ I warned him what I’d paid for two tires but no he wanted them. So I got most of what I paid for the tires back and had the wheels hauled away for free!! ^_^
Dammit, I had to clean up just ’cause I had a mouthfull of coffee when I read “…they also functioned superbly” and spit it out all over.
I bought a Tbird virtually identical to the one in the last picture. At first I loved them, they cornered better and rode smoothly. It was only later I found out they also hydroplaned at the drop of a hat, got very skittery on slush and as far as snow goes, forget it! I ended up buying a set of steel wheels at a junkyard, um SALVAGE yard and putting snap-on wheel covers. A minus for looks but gigantic plus for all weather roadability!!
Just curious as to where you found the last picture….
I’m the photographer and the owner of the car in the photo is a friend…..
Via a google image search. I really should have given credit to the site where I found it, but I failed to note it. I’d be glad to do so after the fact.
Yeah, thanks 😉 Shoot me an e-mail at V8Demon@hotmail.com for my info.
You can see some of my other work here: https://secure.flickr.com/photos/v8demon
Enjoy!
As long as there are other follow up comments, I’d like to clarify my previous comment. The Thunderbird shown is a 1983 Heritage edition. I owned one of these first only with regular tires/wheels. I later owned an 1984 Elan edition with TRX radials so my ownership of a car with TRX was colored by years of ownership of virtually the same car with regular tires. As a point of interest, at a later, post TRX date, I got a set of lower profile tires for free which had 30-40% of the tread left and mounted them on the car and they quite easily outperformed the TRX in terms of handling AND, though not quite as good as standard tires in rain and snow, were orders of magnitude better than the TRX!
One of the few ‘industry standards’ was tyre/rim sizes. 10-12-13, etc wheels.
Then Michelin had to ‘fix’ what wasn’t broken.
Ford Australia was gullible enough to fall for it, haven’t seen any of the Frods that used the TRX on the roads for a decade or so.
That was deliberate. They didn’t want people putting TRX tires on non-TRX rims and vice versa.
BTW, the TR in TRX stood for tension repartie–spread tension.
Brings back memories. I bought a set from a friend who had a 80 ‘ s mustang pace car. Put them on my 79 fairmont and transferred them to my 84 tbird when I upgraded. Who would have thought both of those cars as strange as they were would be so hard to find now. What a great car. Had a lot of fun. Had to put the factory icky urethane rims back on when the price got too high. Looking at 67/68 cougars now.
I worked in the auto parts business back when these tires first came out. Needless to say, the Ford sales folks failed to tell the buyers of their replacement costs. I saw a lot of shock and anger when I gave them the quote.
Sales folks never volunteer such information on anything, & I wouldn’t trust ’em if they did. This was why I phoned a Toyota dealer parts dept. about the Prius’s battery price before buying.
And I complain about $75 a tire! Maybe I’d better shut up.
Tire Rack lists my tires at $365 each.
What are they for?!?
They are run flat all season Pirelli 255/35 19 for a 2014 CTS. This seemed to be the only tire like it there, but Nokian does have a WRG3 that fits, but not run flat.
Recently, LMR has reproduced the Mustang TRX wheels in a more manageable 16×7 size.
https://lmr.com/item/WK-39067452/mustang-trx-wheel-kit-r390-style-16×7-7993-machined?year=1993&gclid=CPaAyu_4-9ACFUOewAod9C8L4g
Beat me to it; I ran across the LMR 16″ reproductions when I was shopping for toys for my Mustang the other day.
The really nice thing about these is that it appears that the original center caps work, and they got the offset and proportions right. Prior to this, a few guys tried cutting the centers out of the TRX rims and mount them in new, 16″ rings, which didn’t look quite right. Or worse, some tried simply milling a new bead on the TRX rims, which was taking a huge chance on them becoming dangerously thin in cross section. I’m glad that someone has stepped up and made these in conventional sizes.
That’s not a bad price for 4 new wheels. Cheaper than a lot of other aftermarket one’s.
Very nice, and offers someone wanting to keep their early Fox Mustang wheels with an OEM, yet still servicable/daily driver, appearance. The TRX wheels certainly ‘looked’ much better than the standard aluminum wheels that were offered on the Fox back then.
Gotta love the Mustang aftermarket. Makes me want to find a 79-84 just to buy those for
Well this clears up a mystery I had forgotton about.
Back in the late 80s I worked with a guy who bought a very nice early 80s Ford LTD (aussie) in white with beautiful factory alloy rims.
Then one day it appeared with the crappiest looking aftermarket rims, now I understand why.
He didn’t look after the car one bit, was a heavy smoker, the inside resembled a giant ashtray, a sad decline of a once beautiful car.
Parting out late ’70’s to early ’80’s BMW cars for 25 years… I cannot count the number of TRX-size aluminum rims I brought to the scrap metal yard for CASH. No one wanted those rims!
I did have many requests for used TRX tires from purists or people who didn’t want to invest in (or have the cash for) “normal” size replacement rims. No used tires were good enough to sell.
TRX rims & tires were nothing but a headache.
Whether a car had the damn things was a serious consideration when deciding on purchasing it or not during my days as an impecunious student in the early 90s. Nobody wanted them but if you knew your wheels you could always haggle the asking price down, buy the car and immediately proceed to junk the TRXs, replacing them with imperial size wheels.
The TR in TRX stood for tension repartie = spread tension.
Contrary to what was stated in the post there was more ride harshness with the TRX tires as I experienced them on my 79 Mustang Cobra. However, they did last many kms and contributed to an excellent handling car.
Couldn’t you find a picture of an actual TRX tire and wheel? That lead photo is of a TRX center than has been fitted into a inch size rim and shod with a BF Goodrich tire. The groove where the two meet is a dead giveaway as that is not present in an unmolested wheel nor in the reproduction units that use inch size tires.
The original Fox body TRX tires were 190/65 and it wasn’t until later in their run that they moved to the 220/55.
Michelin did not sell the molds to Coker they still make them and still list them in their vintage catalog, but have updated them with modern rubber compounds, carcass materials and construction techniques.
Jeez; where were you when this was first posted? 🙂
I’ve changed the picture now and updated the text.
One of the few remaining international uses of inches versus metric. Tire and rim sizes.
It was the American tyre manufacturers who “rebelled” against going metric with wheels and tyres. I worked for Michelin during that time, the European vehicle makers were ready to go with metrication but the good old boys in USA said no way are we doing this, now 40 plus years later,we TRX users are paying for it.
I worked in the “Automotive” (repair) department of a major chain store, early in my career.
I can still remember would-be customers with ~five-year-old Fords coming in for new tires, and having to tell them that our chain had nothing in that size, they were oddball, non-industry-standard tires that were going to cost them a fortune IF they could find someone who had a set.
They looked at us like we had just stabbed their puppy. More than one asked us to just “stretch” a regular tire over the rim.
Another world-class Ford (and Michelin) idea, with typical world-class Ford/French results.
Great lighting and illustration in the lead pic. TRX marketing, really added an appealing European flavour, to the early Fox Mustang’s promotion/character.
Those wheels looked so modern for a domestic car, at the time.
In addition to the diameters mentioned here, a couple of rare Renaults came with 190/55 VR 340 TRX tires mounted on their front wheels. The small diameter tires are still available from Coker. It seems like the hardest ones to get are the narrow TRX tires for 365 mm rims meant for affordable cars like the Escort and EXP.
315 mm TRX tires were also fitted to the Innocenti Turbo De Tomaso and some version of the Austin Metro according to Wikipedia. I can’t find any evidence of Michelin running off a batch of replacement tires for them in the last decade. It seems like the cars which remained valuable through the years have the best TRX availability. It is likely that Ferrari owners never had to give up on their cars when tires were not acquirable.
I wish auto manufacturers would worry about ride quality again. You’d think the older and fatter population demographics would have an impact by now. These days, higher interior trims usually get you even less sidewall and an even harsher ride. I’d give up some 0-60 performance if their lawyers would allow softer springs and shocks. Why hasn’t technology solved this problem? I can’t be in the only city with washboard asphalt and badly located manholes.
Fully agree. I used to DD big old (60s) cars. The comfort they had is not matched in modern cars. Would be nice to have it as an option to the standard hard (“sport”) setting.
Yikes! 2100 bucks for 4 tires in 1983 would be about 5900 today!
I don’t recall them being quite that expensive in 1983. As I recall they were somewhere in the $100 to $150 range back then, which was still expensive for the time. As I recall, the regular Firestone 721 P175/75R14 tires on my 1989 Mustang were $60 or $70 each, installed. I remember this well, because I blew two of them hitting a curb on the way to band practice, and my parents made me pay for them. 😉
If you’re going from the ad in the fourth image, that’s from 2013. And when I checked the price today they’re actually less expensive than in 2013: $410 per tire, versus $514. Not sure why that’s the case.
Has this ever worked out well for anyone, even once? I think not. It surely didn’t end well for Firestone’s big, flashy LXX thing.
I have a set of these rims, waiting to go to the scrap yard. I bought a used set with decent tires, ran then on my 78 Futura, added fresh rubber and put them on my 84 T-Bird, when the Bird left I borrowed them to my nephew to finish then off on his 86 Mustang.
Had good luck with them. Time to throw them on craigslist to see if there is any takers or off to the scrap yard.
I do think they were one of the better looking OEM aluminum rims ever put on a car.