UFO brakes again.

[JPL]

HiSpec Monster 4's arrived today, oohh shiny!!! Cheers Tom.

I've been looking at the 320mm Merc discs and there are 2 listed. There is a 320x30 standard vented disc and a 320x32 directionally vented disc and I don't know which one I need. Mihnea mentioned a directionally vented 320x30 but I can't find a part number for that, could it be the 32 Mihnea?. The kit from BIRA mentions a 320x30 as well but not directionally vented. Confused, I am.

Anybody have any info on which one will fit my UrS4 UFO equiped hubs??

Many thanks,

Graeme.

[gavs20v]

cant you use A8 discs?
Nice one
Gav

[JPL]

cant you use A8 discs?
Nice one
Gav

Honest answer, don't know. I've had lots of varying information but I don't think there are any Audi discs that fit the UFO hubs. I know the Merc ones will fit but don't know what the difference is to the Audi discs. The Merc one is listed in the BIRA UFO conversion and Mihnea has also said the Merc discs will fit. I just to make sure it's the right type, 320x30 standard vented or 320x32 directionally vented.

Cheers,

Graeme.

[gavs20v]

They used a conventional type caliper on the last of our shape s4's and the s6, these appear to be the same as a8 calipers, therefore the discs would fit (in theory) not sure if they changed the hubs when they went from UFO's to conventional twin pots with the 4-pads.
Nice one
Gav

[JPL]

They used a conventional type caliper on the last of our shape s4's and the s6, these appear to be the same as a8 calipers, therefore the discs would fit (in theory) not sure if they changed the hubs when they went from UFO's to conventional twin pots with the 4-pads.
Nice one
Gav

The hubs are totally different on UFO cars as the caliper is mounted inside the discs, a big single piston ATE job. The latter ones used the Girling G60 twin pot caliper round a conventional disc.

Graeme.

[gavs20v]

they were also fitted with the girling HP2 cailper which has different carrier mounting points to the g60.
Gav

[JPL]

they were also fitted with the girling HP2 cailper which has different carrier mounting points to the g60.
Gav

I never knew about the HP2 caliper, you learn something every day.

Back to the original question, 320x30 standard vents on 320/32 directionally vented? Any ideas?

Graeme.

[gavs20v]

Youre gonna get pissed off with me
These are the specs for some of the later vehicles, thought they might be of help,
2000 Audi S4 (321 x 30 mm discs)
2000 Audi A6 2.7T (321 x 30 mm discs)
2000 Audi A6 4.2 (321 x 30 mm discs)
2000 Audi A8 (as of calendar week 45/1999 production) (323 x 30 mm discs)
Tell me to bog off if youre definiteley going with merc discs and dont need any alternatives
Nice one
Gav

[JPL]

Youre gonna get pissed off with me
These are the specs for some of the later vehicles, thought they might be of help,
2000 Audi S4 (321 x 30 mm discs)
2000 Audi A6 2.7T (321 x 30 mm discs)
2000 Audi A6 4.2 (321 x 30 mm discs)
2000 Audi A8 (as of calendar week 45/1999 production) (323 x 30 mm discs)
Tell me to bog off if youre definiteley going with merc discs and dont need any alternatives
Nice one
Gav

Gav, are you an Audi disc salesman or what? I'm only going with the advice I've had and it's that normal Audi discs won't fit the hubs. The BIRA site only lists a Merc 320x30 disc for it's UFO conversion but lists lots of other discs from Audi for it's other conversions. This leads me to believe that if an Audi disc was suitable for UFO hubs they would have used it. This is backed up by what Mihnea has told me and also wrote earlier in this thread.

I don't know why other Audi discs don't fit but I know that the Merc discs do.
Can you see where I'm coming from?

Graeme.

[audiman]

Those calipers will only fit a 30mm wide disc

[JPL]

Those calipers will only fit a 30mm wide disc

Tom, did you specify 30mm when you bought them? The HiSpec site lists up to 32mm for these, a rough measurement shows 35mm between internal faces of the caliper.

Graeme.

[audiman]

Those calipers are designed for 30mm discs. The silver coloured block is the bit they change to make it for wider discs. These need to be changed by them.

[JPL]

Those calipers are designed for 30mm discs. The silver coloured block is the bit they change to make it for wider discs. These need to be changed by them.

Cheers Tom, decision made then, 320x30's it is.

Graeme.

[Mihnea]

OKay guys, the reason why A8 discs won't fit is simply the size of the wheel hub on the UFO'd S4. It is larger than the A8 disc's opening for it, thus it either has to be machined, or swapped for an A6/S2 (??) unit. Either way it's a wheel bearing job, not really what you want to be doing if yours are fine. Don't fix it if it ain't broke applies for this one and is fine for me.

The Merc discs are MUCH better than the A8 jobbies, simply because they're directionally vented, so a right hand disc will actually dissipate much more heat than the Audi discs will do. Watch out installing them the wrong way around, then they will just keep heat inside and warp after 2 hard brakings. Let them cool down and they're ok for 2 hard brakings again. and so on... BTDT in my friend's S4 (360+HP RS2 spec) on the Nürburgring, it's fn scary to know you have no more brakes in turn 2 out of 100-odd turns...

Hope this helps,

Cheers,

Mihnea

[Mihnea]

HP2 is the caliper used on S4 avants after 1993 (I think), 100 S4 4.2 V8 280HP, A6 S6 4.2 V8 290HP, 2.7T S4 and so on. They use 2 pistons and 4 tiny pads. They're pretty much ok for a 100 S4 sedan, however on the avant they're not that great, and they plain suck on the track. They require changing the front struts or at least the wheel hubs (ouch). IMHO not a great upgrade, and the discs aren't that great either.

HTH,

Mihnea

I never knew about the HP2 caliper, you learn something every day.

Back to the original question, 320x30 standard vents on 320/32 directionally vented? Any ideas?

Graeme.