The data picked the self-supporting run-flat in 1980. BMW made it standard 23 years later.
A run-flat tire keeps a car moving after a puncture. Two ways to do it competed. A support ring is a separate ring inside the tire, on a special wheel, that the flat tire rests on. A self-supporting tire carries the car on its own stiffened sidewalls. For each we measured how much better per dollar it got each year, using only the patents that existed at the time.
% better per dollar each year. Readings every two years from 1976. Improvement rate is read from patent citation networks across 180M+ patents.
In the 1970s the support ring was improving faster. From 1980 the self-supporting tire pulled ahead, and it has stayed ahead at every reading since. In 1997, the year the first support ring system was shown, self-supporting was getting about 15% better per dollar every year, the support ring about 10%.
The support ring needed an asymmetric wheel, a ring fitted with special machines, and tire shops able to service it. The self-supporting tire carries the load in the tire itself. Run-flats stayed a small share of tire sales, and the ring kept a niche in armoured cars, but on regular cars share moved to the sidewall.
Our data: self-supporting improving faster than support ring.
First self-supporting run-flat on sale: Goodyear EMT on the Corvette.
Michelin shows its support ring system, later named PAX.
First car fitted with PAX: the Renault Scenic.
BMW makes self-supporting run-flats standard on the 5 Series.
Michelin ends new PAX development: “no big market demand”.
It would not have said whether run-flats would replace the spare wheel: they stayed a small share of sales in Europe. It would have said the run-flat carmakers would fit is the one that carries the car on its own sidewalls, from 1980, years before a support ring system was shown.
Michelin was filing on both routes from the 1970s. The reading would have said which one to back.
Self-supporting still leads, and by more than in 1997. The same reading works for the race you lead now, such as airless tires.
TIR — the Technology Improvement Rate — measures how fast a technology gets better each year, computed from global patent data. Not who is filing, or how much: how fast the route is actually moving. Historically, the fastest-improving technology always wins.
Provenance. Every patent carries a filing date, so the record can be replayed: every improvement rate on this page uses only the patents that were public at the time. Chart data: GetFocus platform exports, October 2026.
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