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Technical Curiosities: Audi’s UFO Brakes

October 21, 2011 by Matt

Audi V8 200 200q20v 20v ATE UFO Brake Brakes Calipers

I love weird engineering. As much as I might be cursing on any given Sunday afternoon leaning over the engine bay of a car featuring said weird engineering, shaking my fist at the gods as I ask why the automaker couldn’t have assembled the car the “normal” way, I’ll always admire manufacturers who march to the beat of their own drum. Whether it’s an all-encompassing philosophy or a random decision here or there, automakers who deviate from conventional wisdom will always command my attention.

Today we embark on a new series of posts highlighting technical esoterica, or unique solutions to engineering challenges in the automotive world. Sometimes there are plausible justifications for off-the-beaten-path decisions automotive engineers make, but sometimes it seems like automakers just want to do things their own way for the sake of being different. Either way, let’s dive in.

The year was 1989. Audi was introducing its top-of-the-line Mercedes- and BMW-fighter, its V8. Built on a stretched version of its 100/200 mid-size chassis, Audi stuffed a brand new, all-aluminum, 3.6l, DOHC 32-valve V8 (oddly enough) under the hood, paired it with its first automatic quattro drivetrain and decked the whole car out in appropriately luxurious trappings. In spite of the added bulk over the run-of-the-mill 100/200, the big V8 moved the car along as a respectable clip. Braking prowess, however, was another area Audi wanted its new luxury flagship to have sporting credentials. But instead of simply giving the V8 larger front brakes, they decided to do something a bit different.

Constrained by a maximum wheel size of 15 inches, Audi enlarged the swept area of the brakes, and thus their potential stopping power, by “flipping” the caliper inside the disc, creating their “UFO” brakes, so called because of the resemblance of the disc carrier and its heat-dissipating holes to a stereotypical alien spacecraft:

Audi V8 200 200q20v 20v ATE UFO Brake Brakes Calipers

This move allowed the diameter of the disc to fill the inside of the road wheel, without having to allow for a caliper positioned on the perimeter of the disc, as is the case with every other disc brake system.

Did it work? By all accounts, it did—when operating as designed, compared to “regular” disc brakes engineered to fit the same 15″ wheel diameter, the UFO brakes provided tremendous bite and resistance to fade. The system gave the V8 (and ’91 200 Turbo quattro, to which it was also fitted) braking capability commensurate with its accelerative abilities.

Did it have downsides? Most definitely. UFO brakes weren’t shared with any other automaker, and failed to benefit from economies of scale in manufacturing; replacement rotors and calipers are quite expensive. Improperly maintained, the rotors can warp; an often-prescribed “solution” involves multiple consecutive panic stops from highway speeds. Allegedly, this can straighten out the rotors and eliminate the shimmy. And perhaps the most significant bummer for those concerned about appearance, especially when exposed by thin-spoke aftermarket wheels, to the uninitiated UFO brakes have the decidedly downmarket appearance of steel wheels.

Regardless of its engineering justifications, disadvantages or even its benefits, Audi’s experiment with UFO brakes appeals for the simple reason that the automaker tried something different. Kudos to them.

Editor’s note: This post is part of an ongoing series spotlighting obscure automotive engineering solutions. Read the other installments here:

Filed under: Audi, Technical, Technical Curiosities

6 Comments

  1. Aaron says:

    What a post – interesting esoterica such as this is what makes Spannerhead worth reading

  2. John D says:

    Hear, hear.

    And seeing as how Matt is personae esoterica, I think it a fitting post. I love these kinds of things and am eagerly awaiting the next installment.

  3. areopagitica says:

    Matt is a writer with wit, brevity and style. Also apparently curiosity and technical savvy. I always wanted to know more about these brakes and had hoped to see them catch on. The first Taurus mistakenly made for 14 inch rims suffered fade, rapid pad wear and constant warpage roughness because of the inability to fit a decent sized rotor, as a lesson unlearnt from the notoriously under braked early eighties Mustang V8. Something less severe afflicted also the first Lexus 400LS. I think Matt might like to check out the rare final English HRG sports car of 1956 if he can find any of the six they built. It had what looked like artillery or truck wheels, onto which the rotor was attached. The intent was much as the recent Audi UFO. The idea probably goes further back even to aircraft and perhaps Bugatti’s drum cum wheel. To change a tire on that HRG without the caliper interfering, the rim unbolted from the wheel spider as on many trucks.

    • Matt says:

      Thank you sir. To paraphrase the old Avis Rent-a-Car corporate motto, I try harder. :)

      Interesting about the HRG. I’ll check that out; thanks!

  4. DANIEL says:

    I own two 1990 V8 Quattro’s. One with UFO’s. They run great and easy to replace pads. All replacement parts for these brakes are for the rich! Pain full. great design. My other V8 has the twin piston Girling conversion, which is more capable and cheaper to run. I like the write up! Love the cars.

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