TRX (A tire History)

October 05, 2012, 11:42:52 AM

I thought this was interesting:

Michelin TRX history (source: FAQs about Tires)

A brief history of radial tires... and the offbeat TRX system.

For those of us old enough to remember them, the dominant type of tire construction during the first 70 years of this century was the "bias-ply tire," a tire built up from a carcass of fabric which was then bonded with vulcanized rubber. To give the tire strength, the tire carcass was built up from alternate layers of fabric (the plys) oriented in different directions. Such a tire would have a sidewall as stiff as its tread... and in the case of most bias-ply tires, they were optimized for a smooth ride with 24psi inflation pressures (n.b. the low-pressure bias ply tire was introduced shortly after WW-II).

Beginning in 1955, with the Citroen DS, the radial tire began its use in automotive applications. The radial tire is made up of a carcass of fabric (with the fabric grain oriented in a uniform direction) topped (only under the actual tread) with a number of cirspoogeferential belts. The goal of such a design was to build a tire with a much stiffer tread foundation and a much softer sidewall. The stiff tread reduces rolling resistance and improves the geometry of the tread under cornering and braking loads. The flexible sidewall allows for a smooth ride.

(as an aside, many of todays high-performance radial tires have unusually stiff sidewalls, leading to a very harsh ride. many mid-price radials have very flaccid construction, only 3 tread plys, obviating the advantage of radial tire construction. Many racers continue to race on special racing bias-ply tires).

During the 1970's, tire design began to move towards lower profile designs (where the rim is larger and the tire sidewall shorter). Pirelli became famous for it's P7 and P6 tires, both unusually low-profile for its day. At the same time, Goodyear and Michelin began research into lower profile tires with good riding characteristics. The resulting design utilized a rim with a very different tire bead profile... to prevent these new tires from being used on older rims (and vice-versa) a new family of rims was introduced. Michelin called the system "TR" and Goodyear "NCT" - for Neutral-stress Contour Tire. And a family of new, metric rims sizes was introduced : 365mm, 390mm and 415mm.

The TRX tires are of excellent quality, and are only made in select, low-profile, high-performance sizes. The vendors of TRX tires included Goodyear (the departed "Wingfoot"), Sears (via. Michelin), Michelin (the "TRX" and "TRX M+S") and Avon (the CR28). TRX rims were adopted by a number of manufacturers : Saab (390mm TRX on the early 900s), BMW (390mm TRX on the 533i, 633i and 733i), Ford (optional on the Thunderbird, Cougar, Granada, Tempos, Topazes, Escort GTs and standard equipment on early Mustang GTs), Ferrari used the 415mm style on a number of production cars. The French were enamored of the TRX, many Renaults, Citroens and Peugeots (the 604SL and 505GTX among them) came with TRXes.

Unfortunately, the premium-high-performance TRX never caught on in the replacement market. Second owners of 25th Anniversary T-Birds would swap worn 220/55VR390 TRX whitewalls (yes!) on beautiful alloy rims for Fairmont steel wheels, 195/75R14 whitewalls and wire wheel covers rather than pay $150/ea. for a new TRX. Same goes for many Mustang GT owners (since the later GTs came with 225/60VR15 Goodyear Gatorbacks, much wider than the slim 190/65HR390's originally fitted).

Today, the TRX is a limited production speciality tire. Some places, like the Tire-Rack, carry them still. Current TRX manufacture is limited to Michelin and Avon. Sizes offered include :

180/65-390
190/65-390
200/60-390
220/55-390

TRX (A tire History)

Reply #1 – October 05, 2012, 12:14:53 PM

I remember seeing an '83 Mustang GT convertible with original whitewall Goodyear TRX's back in 1990 or so.
Bad times...LOL

About a year ago, my brother needed to get some window glass for his Firebird. We happen to have an all F-Body junkyard in the area, so we stopped in and starting rummaging through everything. We found what he needed, we paid the owner, and afterwards we were BSing with the owner outside in the parking lot. I glanced over at a tire on the ground...a random, non-descript thing for most people. Then I asked him, "Who brought a Mustang here?" He said, "My friend...wait, how did you know that?" I just grinned an pointed at the tire. I can sniff out a TRX tread pattern anywhere. He was amazed but my brother just said, "Yeah, that's a Ford guy for ya." LOLz

TRX (A tire History)

Reply #2 – October 05, 2012, 01:48:37 PM

Interesting!

TRX (A tire History)

Reply #3 – October 05, 2012, 04:24:05 PM

I have a set of Michelin TRX's that are whitewalls stored for my Silver Anniversary Bird, car has same on it now only blackwalls as they are a bit cheaper than the whitewalls

TRX (A tire History)

Reply #4 – October 05, 2012, 05:08:27 PM

Funny how history repeats itself, isn't it?

http://en.wikipedia.org/wiki/Michelin_PAX_System