Anyone used AmD for "on hub" brake disk skim?

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To be fair, te rs4 discs are semi floating and not full floating discs.
Full floating disc you can grab and shake the rotor easily!
Semi floating are usually (no idea with the rs4) fixed with some kind of spring/retainer mechanism to hold ten in place but still allow a degree of movement under expansion.

So I guess in theory if you used the smallest amount of pressure so as not to disturb the rotor you *could* do it but it wouldn't be easy and there is room for error.

Personally I'd prefer to have it done on the bench but that's just me.

[P_G]

What I differed on was that you implied having to further take the rotor off the hat to skim with the disc was off the car which isn't the case. I've had fronts skimmed off the car with the rotor hat in place on 3 separate occassons with zero issues.

Whether the disc is on the car or off the car the float is between the bell and rotor.

If you mount the rotor in the lathe with the bell then by design the rotor has radial and axial float, if it's not floating due to corrosion or contamination with pad material then it may not move when being machined....it isn't right however.

What then happens is the rotor expands under load displacing the corrosion and dust and you end up having to get the discs skimmed a second or evidently a third time. At a useable thickness of 1.6mm and £600 per pair every time you have a swipe at them with the lathe and take 250 microns a side it's just cost you £200 onto the machine shop floor plus machine time

Same happens on S55 discs which share the same crap design, they put the float in the bell but then don't allow you to buy bobbin kits or replacement rotors or service them properly

See and that is where you have presumed wrong because whilst I have had fronts skimmed on 3 occassions one set is currently my spare set (bought used high sposts caused by pad deposition by OEM Pagids) and the other set I had skimmed twice when I still used OEM Pagid's and pad deposition was the issue, upon skimming on the second time I kept these as a spare set and then eventually sold them and the person I sold them to has had no issues.

The usable thinkness you have quoted is low and your skimmer appears to be taking chunks out of the discs if you say you lose a 3rd of the disc every time. I only post on such issues when I speak from personal experience, it can be done and done effectively.

[Dave_M]

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I know what you're saying about people (me included) saying they're light on the brakes. Unfortunately a lot of the driving I do, it's hard to do anything else. To do so would either result in the numpty behind driving into the back of me in a queue of traffic, or passengers complaining about being thrown around.

It does get some stick occasionally, but it's probably only 5% of the time...... Maybe I've got the wrong car for what I need, but it remains the car I want to have!

Dave

[DaveB1970]

There is a bit of lack of understanding here....

Doesnt matter whether you've skimmed them intact once/twice/three times. Fact is min thickness is 32.4 (says so on the side of the disc), another fact is your trying to machine square something that is moving!

Semi Floating Discs dont exist its like being a little pregnant, you control float in 2 axis by design, you put the float in the bell or float in the rotor, you picks your bobbins and takes your chances.

RS4/S55/GT Kit Disc Assemblies have about 0.3mm design axial float, with the best will in the world the best machinist is going to take a 1/4mm per side off maybe less if they belonged to him, the racing assemblies that have been described here as rattling above ^^^^ are racing assemblys and invariably have the float in the rotor which expands with heat directly so the design float needs to be bigger to get them back to 0.2 -0.3mm under load.

If you put the float in the bell like the RS4 discs then its possible when not mass producing to get the float to 0.2mm. The bobbin springs are not there to keep them quiet, the bobbin springs are there to prevent bell wear (as well as the slide plates on the RS4 which are the main culprit in the whole design getting bunged up)

To skim them without dissasembling them just doesnt make any sense from an engineering point of view, you'll be removing the same material as much as they would move as soon as you touched them. And if you do aspire to remove as little material as poss then they need to be bolted directly

Ideally one side should be machined square to the mounting and then they wold be ground and turned over and ground again, but thats for high end stuff which the RS4 rotors are not.

Simply dissasemble them have a mandrel made on the mounting pcd of the rotor (mine has multiple PCD's machined into it for many different rotors Ive done previously , 5 bolts to hold them in position - check them for runout as indeed deposits are sometimes the problem and then have a swipe, soak everything or send them away for replating like so



.....and put them back together for peace of mind that theyve been done properly

Regardless.... with the weight of them and the fact that their not even directional they shouldnt have got any where near an RS4 in the bloody first place, horrible casting , they'd have better of using the same design as the R8 - thats not much better but at least they'll do a track day or two and theyre £150 quid cheaper

[Ben @ AmD Essex]

Afternoon All,

Sorry, this isn't something we have the equipment to do here. Not sure why that is still showing on the site, I shall have to get that removed!

Ben

[sakimano]

re-bed the pads, most of the time the issue is deposits

I would do this first...google brake bedding and stop tech and you'll have a good guide

60 mph then hard on the brakes
Hard enough to pull your eyeballs out, but not hard enough to induce ABS
take it down to about 10mph (BUT DO NOT STOP)
get back to 60 mph, then repeat

do 4-5 of those, then do one from 80-85, then just cruise for 5-10 minutes to cool everything down ENSURING YOU DO NOT STOP AT ANY POINT. The rotors may glow red at this point or just about so the cool down is key. Coming to a full stop will roast your pads.

Obviously you need to be on a highway, or a rural highway to do this.

[Dave_M]

Ben

Thanks for confirming - I ordered some new pads last night and am on the lookout for new disks at a sensible price (best I've seen at the moment is £589 on fleabay - is that a good price?).

Sakimano - I'll give that a try - I've got nothing to lose! Finding somewhere where I don't have to stop for the cool down phase could be interesting though.....

Cheers
Dave

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I tend to look for motorway junctions that feed onto dual carriageways. Some places are ideal in that you drop onto a dual carriage way that has a slip road/road about very close.
Added bonus is that any downhill slope (like a slip road) is a great way of getting heat into the brakes (which is all you're trying to do with the first lot of stops). Youll know when you're getting there as the brakes will feel better and better as they get near the ideal temperature.

[Ben @ AmD Essex]

Ben

Thanks for confirming - I ordered some new pads last night and am on the lookout for new disks at a sensible price (best I've seen at the moment is £589 on fleabay - is that a good price?).

Sakimano - I'll give that a try - I've got nothing to lose! Finding somewhere where I don't have to stop for the cool down phase could be interesting though.....

Cheers
Dave

Retail is £795.89! So I would say £589 is a good price!

Ben

[klauster]

I can get you some cheaper than that

I should be reselling these and making £50.00 a pair....

http://www.stokeaudi-parts.co.uk/produc ... R-PRICE%29

[Ben @ AmD Essex]

I can get you some cheaper than that

I should be reselling these and making £50.00 a pair....

http://www.stokeaudi-parts.co.uk/produc ... R-PRICE%29

I feel a bulk order is needed at that price!!

[Dave_M]

Just ordered a pair of front disks. I was tempted to get a set of rears as well as mine have a noticeable lip after 56k miles, but I don't think my wallet could take another £400 this month......!

Thanks for the pointer Klauster.

Dave