UFO Brakes, How Bad Could They Be?

"Urambo Tauro" (urambotauro) 03/06/2019 at 21:30 • Filed to: internal caliper brakes, ufo brakes, brakes, audi, wrenching

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This morning’s !!!error: Indecipherable SUB-paragraph formatting!!! reminded me that UFO brakes exist. Are they a dealbreaker?

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This has finally piqued my curiosity enough to ask. Changing them doesn’t seem all that bad, judging by the video above. I’m kind of curious what you’d do if you ever encountered a seized caliper, though. Looks like you really need that wiggle room just to get the rotor out of the way.

Worst-case scenario, is there any chance that a seized caliper could be unbolted and removed together with the rotor as one piece? Not sure if there’s room for that, as the caliper’s mounting ears appear to be inboard of the steering knuckle, and there might not be enough room to rotate the assembly to clear those mounting ears either.

And then of course there’s the whole thing about parts availability and pricing. Wherever I tried to look up parts, the vendor would only display conventional discs, not the UFO rotors. Audi’s nomenclature is a little weird, so maybe I’m just not selecting the right car for parts lookup?

I’ll be honest: this is really starting to reach the limits of the amount of research I’m willing to do just to satisfy my curiosity over a car that I have no intention of buying. Fortunately, a fellow !!!error: Indecipherable SUB-paragraph formatting!!! managed to dig up !!!error: Indecipherable SUB-paragraph formatting!!! , which quotes $988.80 for a pair of rotors. Oof. Well, it’s nice to know that they’re out there, I guess. Not sure how long the supply will last for owners of these cars, though.

At any rate, swapping to a conventional disc setup is apparently a thing that some owners do, but I’m still curious about how they go about that. The whole point of these internal caliper brakes was to maximize the size of the brakes that could fit within a 15" wheel. So it seems to me that converting to conventional discs would mean one of two things: Either you’re downgrading to a smaller rotor to fit the wheels, and missing out on some braking performance... or you’re forcing yourself to invest in a new set of wheels/tires to fit having calipers on the outside of the rotors.

Anybody familiar with this swap, or interested enough to pick up where I left off researching? Where do you stand on these oddball brakes, and how far would you go to preserve the original design (or overhaul it to something easier to maintain)? Would you be willing to sacrifice braking power for an easy-to-maintain design that was small enough to let you keep using the original 15" wheels?

Future Heap Owner > Urambo Tauro 03/06/2019 at 21:43

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These things are wild! I’d never heard of this before . Thanks for doing some research on them.

Given the price to replace those rotors , I think I’d replace everything and change wheels at the first sign of trouble. But I’d probably never end up owning a car with them, for various reasons.

Spamfeller Loves Nazi Clicks > Urambo Tauro 03/06/2019 at 21:43

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I love when people tell me “you can’t fit big brakes under small wheels.”

https://www.apracing.com/product_details/race_car/brake_calipers/formula_car_range/radial_4_piston-budget_calipers-cp7606_and_cp7613.aspx

“Budget Formula Cars” (295mm/11.6" or 265mm/10.4"   rotors)

Easily fits under even tall center 15" wheels.

Daily Drives a Dragon - One Last Lap > Urambo Tauro 03/06/2019 at 21:58

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I’m not sure I even understand the point of these? How is it any more efficient than a disk of the same size? Is it so you can maximize space with the braking surface on the outside of the caliper? For heat reasons? I’m confused as to why it’s worth the trouble. 

themanwithsauce - has as many vehicles as job titles > Urambo Tauro 03/06/2019 at 21:58

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I had a 200 20v. It had the Girling disc conversion. It was one of the few parts on the car I didn’t have a problem with. 

Urambo Tauro > Spamfeller Loves Nazi Clicks 03/06/2019 at 22:14

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I’m not sure how the math works out for clamping power and pad surface area for a true apples-to-apples comparison, but you bring up another good point: Couldn’t Audi have used multi-piston calipers instead of adopting such a wild design? I’m sure it was relatively easy to build calipers with mounting points for internal placement, but what did it take to produce those UFO rotors? Did it all come down to cost?Did they determine that this wacky design was cheaper than multi-piston calipers, conventionally mounted?

Urambo Tauro > Daily Drives a Dragon - One Last Lap 03/06/2019 at 22:19

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Yeah, i t allows for bigger rotors, whereas on conventional setups, the caliper prevents the rotor from getting that close to the wheel . Heat dissipation is probably somewhere between conventional discs and drums, I’d imagine .

Urambo Tauro > themanwithsauce - has as many vehicles as job titles 03/06/2019 at 22:22

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W hat is “ the Girling disc conversion”? I recognize the Girling brand name, but i s there one particular package that is favored among owners as being the most direct swap ?

Spamfeller Loves Nazi Clicks > Urambo Tauro 03/06/2019 at 23:02

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Oh, there’s a fuckton of solutions. Chrysler, when faced with a similar problem, called up Kelsey-Hayes and had them build what may be the largest single piston caliper to fit under a 15" wheel ever at 48mm. And those wheels had FAR less clearance than the Audi’s. Seriously - it’s like 1mm. To the face.

It’s just typical fucking Audi. “GENTLEMEN! Ve need to stop ze car vith all zis horsepover. Ja?” “BIGGER BRAKES!” “Nein, nein, we cannot put bigger v heels on it.” “Vhat?! Vhy not?!” “BBS already made them.” “Inboard brakes?” “Nein, zey vill not fit. But vait! I have had a stroke of geniuz! Vhat if ve made brakes ... zat vere inboard of ze ROTORS?!”

You know, nevermind that Lamborghini was putting 4 piston calipers under 14" wheels on the Countach in the 70's.

gogmorgo - rowing gears in a Grand Cherokee > Daily Drives a Dragon - One Last Lap 03/06/2019 at 23:04

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Putting the friction surface further out gives you more torque (think better leverage) on the rotor,  and therefore more braking force without having to increase brake pressure. 

gogmorgo - rowing gears in a Grand Cherokee > Urambo Tauro 03/06/2019 at 23:13

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I don’t think a seized caliper would be that tough to deal with. The only active piston return mechanism is the elasticity of the square seal around the piston , so i t doesn’t really take much to overcome that. That is to say, seized callipers aren’t typically all that seized. You can usually get a prybar in between the pad and rotor and push the piston back in, which should give you enough clearance to pull the rotor. If it’s seized bad enough you can’t make it budge, cut the rotor off around the cal liper cause it's probably hosed anyway, and go from there.   

RallyWrench > Urambo Tauro 03/06/2019 at 23:25

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Nothing wrong with them other than being a little harder to service. B ut 1 5" tire options are so bad now that almost nobody still runs them , and because of parts availability and cost most cars are upgraded to standard A6 or S4 brakes. I still see a V8 quattro with UFOs in sometimes , but have a 200 Turbo Avant in the shop now that’s disc swapped with B5 S4 wheels.

Shift24 > Urambo Tauro 03/06/2019 at 23:33

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L iterally the germans “how can we make disk breaks more complicated”

This is how

Daily Drives a Dragon - One Last Lap > gogmorgo - rowing gears in a Grand Cherokee 03/07/2019 at 00:22

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Th at’ s what I guessed but also I wonder why they wouldn't just go with a bigger tire. 

gogmorgo - rowing gears in a Grand Cherokee > Daily Drives a Dragon - One Last Lap 03/07/2019 at 01:14

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It’s 1990 and that's the wheels you get?

pip bip - choose Corrour > Urambo Tauro 03/07/2019 at 04:13

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German “ engineering” at it’s finest.

kanadanmajava1 > Urambo Tauro 03/07/2019 at 05:45

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My friend had these in his S4. This was also the first time when I saw someone purchasing used brake discs from eBay. Apparently €300 for an used pair was an acceptable price.

I think the idea beh ind the design is awesome.

bhtooefr > Urambo Tauro 03/07/2019 at 08:13

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It’s the dual piston brake setup from the 1992-1993 Audi V8 and 1992-1994 S4, which Audi officially retrofitted to older cars with the UFO brakes.

Urambo Tauro > bhtooefr 03/07/2019 at 12:53

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Ah, that makes sense. The part about Audi “ officially” retrofitting these to older cars sounded a little odd, b ut according to this page I found , it sounds like it was something more along the lines o f a TSB action than a recall situation:

After introduction, Audi would retrofit the G60 dual piston calipers and conventional rotors from the Audi S4, along with new strut assemblies on customers cars that complained about the shimmy problem.

And apparently despite the dual piston calipers, the conversion was indeed a downgrade performance-wise:

Unfortunately, the braking capability was reduced with the G60 brake setup... When they are working well, [the UFO brakes] do offer better braking with their 310mm (12.2 in) diameter rotors, versus the earlier G60 dual piston calipers with smaller 276mm (10.9 in) diameter rotors.

gmporschenut also a fan of hondas > RallyWrench 03/07/2019 at 18:12

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15” selection is terrible. Went to buy some for my parents 914 and pretty much vredstein or no- name Chinese brand

gmporschenut also a fan of hondas > RallyWrench 03/07/2019 at 18:13

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15” selection is terrible. Went to buy some for my parents 914 and pretty much vredstein or no- name Chinese brand

RallyWrench > gmporschenut also a fan of hondas 03/07/2019 at 18:25

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I’m looking for a set for the 911 now, the options are only Hoosier racing tires in the correct rear size, or BFG Rivals or Hankooks that are of the correct width but a full size too short on the aspect ratio (50 vs 60), so the back of the car is lower and the speedo is way off . The front size is probably the same as you found for the 914, a bunch of shit no-name brands or snow tires. Wish somebody would make 15" tires great again. 

Rusty Vandura - www.tinyurl.com/keepoppo > Urambo Tauro 03/08/2019 at 21:52

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The thought of owning that car scares the liver out of me.

jimz > Urambo Tauro 04/27/2019 at 09:57

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Ah, Audi. Reinventing things that have worked fine for decades.

if everything’s seized, it looks like unbolting the caliper from the knuckle would give enough “wiggle” room to force the whole thing out of there.

I have to believe in this day and age anyone doing a conventional disc conversion is also going to larger diameter wheels.  There’s no reason to limit yourself to 15s in 2019.