{{Short description|Radial car tire introduced in 1975}} The '''Michelin TRX, '''(and the related TDX), is a [[Radial tire|radial]] [[tire]] introduced by the [[Michelin]] Group in 1975. It is one of the first volume-produced low-profile tires. Although technologically advanced, and reasonably successful, the tire's requirement for a non-standard [[Rim (wheel)|rim]] ultimately condemned it to a relatively short commercial life. It has thus been called the "[[Betamax]] of the tire industry.<ref name=":0">{{cite web |url=http://jpowell.tripod.com/saab-wheels/trx/ |title=SAAB TRX Wheels|last1= |first1= |last2= |first2= |date= |website= |publisher= |accessdate=27 February 2014 |archiveurl=https://web.archive.org/web/20060530035844/http://jpowell.tripod.com/saab-wheels/trx/ |archivedate=2006-05-30}}</ref>"
==Background and development== As passenger car performance increased during the 1970s, the need arose for improved tire capability. One of the possibilities was to reduce sidewall height, low sidewalls being common at the time on crossply racing tires, but not usual for the better-performing radial tire.<ref>[[Pirelli]] 1975 Pirelli created a wide tyre with a reduced sidewall height like a slick, but with a radial structure.</ref> The problem was that reducing sidewall height compromised tire comfort, in part due to the roadwheel rim profile used.
Michelin therefore decided to introduce the world's first tire and roadwheel system, where the two were designed together.<ref>For the first time, the tyre and its rim complemented one another perfectly, working as a single unit. The rim underwent a fundamental transformation, the essential characteristic of which was a flatter, lower flange. This new design of the rim and tyre bead resulted in a gradual curvature of the casing, without the "5" shaped flexing inherent in traditional designs.</ref> This would enable both lower sidewall height, (for better roadholding) whilst retaining comfort due to better stress distribution within the tire, enabled by the redesigned wheel rim and tire bead.
The "TR" was for "tension répartie", since tire stresses were better balanced in the new design, whilst the "X" was a reference to previous Michelin products such as the famous "X" radial.
TRX tires thus require the use of wheels that were specially designed for them; standard tires do not fit TRX wheels and vice versa.
To avoid potentially dangerous confusion, Michelin used metric sizes for TRX roadwheels instead of the standard imperial wheel size (normally stated in inches).
==Usage== [[File:Alpine A 310 V6, Bj. 1982 (2015-09-12 3736 b).JPG|thumb|Renault [[Alpine A310]] V6 with TRX tires]] [[File:1995 BMW 525i Sport, UK (rear) (22286662269).jpg|thumb|1995 BMW 525i Sport with TRX tires]] TRX tires were available either as standard or optional equipment on certain models of European makes such as [[BMW]], [[Audi]], [[Mercedes-Benz]], [[Citroën]], [[Peugeot]], [[Ford Motor Company|Ford]], [[Ferrari]], [[Alfa Romeo]], [[Renault]], and [[Saab Automobile|SAAB]]. They were also available on certain models of the [[Ford Mustang]], Ford Thunderbird, [[Mercury Capri]], Mercury Cougar, and [[Mercury Lynx]] during the 1980s.
Although most TRX tires were produced by Michelin, a few sizes were made by Avon, Continental, Goodyear (mainly for the American market<ref name=reinventing>{{cite web |url=http://www.curbsideclassic.com/automotive-histories/automotive-history-michelins-trx-tire-reinventing-the-radial-tire-didnt-work-as-well-as-inventing-it/ |title=Automotive History: Michelin's TRX Tire–Reinventing The Radial Tire Didn't Work Quite As Well As Inventing It |last1= |first1= |last2= |first2= |date= |website= |publisher= |accessdate=27 February 2014 |archiveurl=https://web.archive.org/web/20131018232542/http://www.curbsideclassic.com/automotive-histories/automotive-history-michelins-trx-tire-reinventing-the-radial-tire-didnt-work-as-well-as-inventing-it/ |archivedate=2013-10-18}}</ref>) and Dunlop. Dunlop fitted their version of the TRX tire as standard equipment on Austin Montegos and Austin Mini Metros.
==TRX sizes== TRX wheels existed in diameters from {{convert|315|mm}} to {{convert|415|mm}}<ref name=sizes />
Some common TRX sizes and vehicles:<ref>{{cite web|url=http://www.forum-auto.com/automobiles-mythiques-exception/section5/sujet141356-35.htm|title=List found on this forum|accessdate=27 February 2014|url-status=dead|archiveurl=https://web.archive.org/web/20131013124051/http://www.forum-auto.com/automobiles-mythiques-exception/section5/sujet141356-35.htm|archivedate=13 October 2013}}</ref>
<nowiki> Size Application </nowiki> * 160/65 R 315 TRX [[Innocenti Mini#Minitre|Innocenti Turbo De Tomaso (1984-1989)]], [[Austin Metro]] * 160/65 SR 340 TRX [[Citroën Visa|Citroën Visa GT]] * 165/70 R 365 TRX Ford Escort GT, EXP, Mercury Lynx RS * 170/65 R 365 TRX [[Citroën BX]], [[Peugeot 305]] * 180/65 HR 390 TRX [[Saab 900|SAAB 900 S]] and [[Saab 900|Turbo]] (1980/81)<ref name=":0" /> * 190/65 HR 390 TRX [[Citroën CX]], [[Ford Granada (Europe)|Ford Granada]], Mercedes 200, 220, 240, [[Peugeot 504|Peugeot 504 Coupé]], [[Peugeot 505]], [[Peugeot 604]], [[Renault 20/30|Renault 30TX]] * 190/55 VR 340 TRX [[Renault Alpine|Alpine A310 V6]] (AV), [[Renault 5 Turbo]] (AV), [[Alfa Romeo Alfasud|Alfasud Ti]] * 210/65 VR 365 TRX [[Talbot Tagora|Talbot Tagora SX]] * 220/55 VR 365 TRX [[Renault Alpine|Alpine A310 V6]] (AR), [[Renault 5 Turbo]] (AR) * 200/60 VR 390 TRX BMW 518, 520, 525, 528, 728, Mercedes 200, 220, 240, 300 * 210/55 VR 390 TRX [[Citroën CX|Citroën CX 25 GTI Turbo]] * 220/55 VR 390 TRX BMW 525, 528, 533i, 535, M535I, 635 Csi, 728, 735i. [[Ford Fairlane (Australia)#ZK / FD (1982–1984)|Ford LTD]]<ref>{{cite web|url=http://www.boostedfalcon.net/falconfacts/fairlaneltd/zkfd.html|title=Falcon Facts: ZK Fairlane / FD LTD|accessdate=29 August 2018|archiveurl=https://web.archive.org/web/20160806223659/http://www.boostedfalcon.net/falconfacts/fairlaneltd/zkfd.html|archivedate=6 August 2016}}</ref> Ford Mustang, Thunderbird. Mercury Capri, Cougar. Ferrari 208, 308, [[Ferrari Mondial|Mondial 3, 2]] (AV) * 240/55 VR 390 TRX [[Ferrari Mondial|Ferrari Mondial 8]] & [[Ferrari Mondial|Cabriolet]], [[Ferrari Mondial|Mondial 3, 2]] (AR) * 240/55 VR 415 TRX [[Ferrari 400|Ferrari 400 i]], 512 B, [[Ferrari 400|412 i]] * 240/45 ZR 415 TRX [[BMW M635CSi|BMW M635 CSi]], Ferrari 512 BB (AV), [[Ferrari Testarossa|Testarossa]] (AV) * 280/45 VR 415 TRX Ferrari 512 BB (AR), [[Ferrari Testarossa|Testarossa]] (AR)
Note: AV='front', AR='rear'. Does not include North American vehicles.
Other sizes were available, for instance 160/65 R 315, in TDX version.<ref name=sizes>{{cite web |url=http://www.drtheo.nl/CX/TRX-history.htm |title=Michelin TRX-radials tubeless |last1= |first1= |last2= |first2= |date= |website= |publisher= |accessdate=27 February 2014 |archiveurl=https://web.archive.org/web/20120615102011/http://www.drtheo.nl/CX/TRX-history.htm |archivedate=2012-06-15}}</ref>
==Decline== Although the tire performed well and, as noted above, gained favour with some OEMs, its non-standard dimensions proved problematic in the aftermarket. It was also notoriously difficult to remove using basic tools, a consequence of the deliberately designed strong fit between the tire bead and rim.
Rival manufacturers, such as Dunlop, produced replacement wheels and tires for popular cars, specifically targeting high-performance or winter conditions.
Over time, advances in tire technology caught up with the TRX line, enabling similar performance and greater convenience at a lower cost. TRX tires are now produced only as replacements for vehicles originally fitted with them. As of 2024, Michelin Classic is producing these tires as part of its catalogue.<ref>{{cite web |url=https://classic.michelin.com/en/Classic-Tyre-range/TRX |title=TRX {{!}} Michelin Classic |website= Michelin Classic |accessdate=4 February 2022}}</ref>
==References== '''Citations''' {{reflist|34em}}
==External links== *[https://web.archive.org/web/20070430085728/http://www.michelin-passion.com/passion/front/templates/affich.jsp?codeRubrique=43&lang=EN TRX page from Michelin Group website]. * [http://www.curbsideclassic.com/automotive-histories/automotive-history-michelins-trx-tire-reinventing-the-radial-tire-didnt-work-as-well-as-inventing-it/ Independent history and review of the TRX tire.] * [http://jpowell.tripod.com/saab-wheels/trx/ Article on TRX tires for SAAB automobiles.] {{Michelin Corporation|state=autocollapse}} {{primary sources|date=June 2007}}
[[Category:Michelin brands]] [[Category:Tires]]