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RS4 front brakes

Discussion in 'A4/S4 forum(B5 Chassis)' started by andybnwc, Jan 26, 2009.

  1. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    #1
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  3. Siena
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    Siena Active Member

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    [Jan 26, 2009]
    Link? Pictures??
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  4. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    sorry was editing hope that works now
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  5. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    the part number match up but still look a bit small
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  6. Siena
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    Siena Active Member

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    [Jan 26, 2009]
    They look correct.
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  7. Blue_Thunder
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    Blue_Thunder Active Member

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    [Jan 26, 2009]
    B5 RS4 calipers aren't very big. They look about right.
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  8. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    good good , it says comes with carriers , i have braided hoses all round already , can these be adapted?

    Are there any after market discs and pads available
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  9. Siena
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    Siena Active Member

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    [Jan 26, 2009]
    You'll need RS4 hoses - they're longer.

    Either stock RS4 discs (pricey) will be good.

    Or aftermarket version, there are a few options out there.
    Or seperate custom aluminium bells with seperate discs (my choice).
    #8
  10. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    who makes the seprates , i pressume they are really expensive
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  11. docurley
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    docurley Moderator Staff Member Moderator

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    [Jan 26, 2009]
    RS4 lines are braided but have a rubber coating so you will be good with them.
    #10
  12. jcb
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    jcb Active Member VCDS Map User

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    [Jan 26, 2009]
    you can get the bells machined up by a decent engineer, or buy them new, pricey.
    alternatively get some Phaeton discs. check on rs246 but a few of the rs4 guys are running cheaper discs and raping them with a decent set of pads.
    Pads are cheap compared to discs

    personally I would keep an eye out for some OEM ones on eBay or Rs246/srs forums,

    few there just recently.
    I got pads, discs and calipers all round from a B5 RS4 for £300. rear discs had less than 3000miles on them

    to fit them you will either have to:
    a) swap struts (hub carrier uprights) for the S/RS4 version, which enables the caliper to bolt on, you can also use your dust plates as well.
    this involves swapping the outer CV for the S/RS version to fit the hub carrier. you will need RS4 hoses unless your braided ones are currently too long.

    b) get some adapter plates made up. I have just sold mine otherwise you could have had those. slight offset and extension plate, any engineer could knock you a pair up once you have your discs to test fit.

    good deal for £45
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  13. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    ill think ill look for the disks then sort out some adaptors and hoses, ill have a look at these phaeton ones too , thanks for the info
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  14. jcb
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    jcb Active Member VCDS Map User

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    [Jan 26, 2009]
    Grizz is breaking a fire damaged B5 RS4, get all the bits you need for bolt on stuff
    email : sales-unit20@btconnect.com

    better option than adapters, not necessarily cheaper.
    I paid about £130 for two struts and two drive shafts, could get cheaper but that is pretty average.
    stuck new bearing in, more expense. blah blah

    but, I have a whole brake system that is OEM and I can sell for a lot more than a adapted unit should that time come.
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  15. andybnwc
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    andybnwc Member

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    [Jan 26, 2009]
    ill get in touch with him , that was gonna be my next step thanks again tho, theres a w12 4 motion phaeton breaking on ebay ive emailed about them
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  16. jcb
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    jcb Active Member VCDS Map User

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    [Jan 27, 2009]
    dsics will fit the stud pattern and diameter, not sure about offset, but with adapters that won't matter and even with the right struts people are using RS6 discs/calipers with RS4 bits and just spacing the calipers out to fit

    good luck
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  17. jcb
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    jcb Active Member VCDS Map User

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    [Jan 27, 2009]
    are you getting the W12 to go with it!?
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  18. Fraser
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    Fraser Member

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    [Jan 27, 2009]
    believe the phaeton discs are quite cheap in comparison approx £100 per disc

    i have a front set of RS4 calipers, discs, pads, carriers and hoses - currently deciding whether to fit them or get a bit more serious
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  19. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 27, 2009]
    More serious? You do realise that its the tyres that stop the car, and even the stock brakes can exceed the tyres limits of grip (ie lock up the wheels)...

    The ONLY advantage of fitting larger brakes such as the RS4 items, is to increase fade resistance.

    The stock car is probably slightly front biased for safety reasons, so you might marginally improve the stopping distance by slightly uprating the rears with respect to the fronts (the B5 RS4 runs slightly less front bias than an S4 for this reason)

    If you were to only fit the fronts, you would actually increase the cars stopping distance, as you would move the bias forward, meaning that instead of all four tyres reaching their limits of grip near the same time, and maximising the braking torque, your fronts will reach their grip limit (at the same torque level as before) and the rears wont be anywhere near because the fronts are now much more powerful in comparison, reducing the actual torque applied to the road, and therefore taking longer to stop.
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  20. andybnwc
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    andybnwc Member

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    [Jan 28, 2009]
    I will be getting rears as well when i find some and prob fit them all at the same time . Any other suggestions then apart from rs4 rears?
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  21. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 28, 2009]
    the "more serious" comment was aimed at fraser, but ye you really want to be doing all four at once, otherwise you'll actually lose braking performance.

    The RS4 rears will best match the fronts in performance. the B7 items might work too, but i'd be guessing at that and i've no idea what the B7 rears are like.

    The B5 RS4 rears are basically exactly the same calipers as fitted to S4's, but spaced out enough to allow you to fit the huge 312mm disks under them. You may just be able to buy the carriers from audi and use your existing calipers (assuming they are the 256mm vented ones), but i'm not 100% sure on that.
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  22. Fraser
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    Fraser Member

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    [Jan 29, 2009]
    re the more serious comment thinking of going B7 RS4 all round... either that or match up with RS4 rears or S4 B6/7 rears or maybe the S8 rears :)
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  23. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 29, 2009]
    you defo want to do the rears as well, or you will lose braking performance.
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  24. docurley
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    docurley Moderator Staff Member Moderator

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    [Jan 29, 2009]
    b5 RS4 would do the trick
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  25. Blue_Thunder
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    Blue_Thunder Active Member

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    [Jan 29, 2009]
    Quite! I pretty much shat myself when I had to brake hard once when i'd just had my RS6 brakes fitted up front. I didn't have my RS4 rears fitted at the same time due to the discs needing skimmed, so still had stock S4 brakes at the back.

    The back end was trying very hard to overtake the front... and that was virtually in a straight line(although it was after showing my mate's Impreza Type-RA what a real car can do)!

    :thrashi:
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  26. Dan Gliballs
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    Dan Gliballs Active Member

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    [Feb 11, 2009]
    I have B5 RS4 fronts and rears on mine and the difference is amazing. The standard S4 brakes were hopeless.


    Check out 1min 30 onwards to give you an idea of the difference :)...

    http://www.youtube.com/watch?v=qVWL7SUb7ks
    #25
  27. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Feb 11, 2009]
    dan, the point it was trying to make is that if the S4 brakes are working correctly, they can easily lock all four wheels, which means the stopping distance is limited simply by the tyres grip.

    Two identical cars, one with RS4's all round and the other with the standard 288mm brakes, both stopping from 70mph, assuming same tyres and same brake pad compound, would stop in the same distance. The RS4's might be able to sustain that amount of stopping for longer, ie on a back road or track, but without changing the tyres your not going to stop any quicker.

    It may be that your S4 disks and pads were past it. Perhaps your pads were glased up or just a crappy compound, which would mean they'd overheat much quicker etc. But the ONLY advantage the larger disks are giving you, is better thermal capacity.
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  28. Dan Gliballs
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    Dan Gliballs Active Member

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    [Feb 11, 2009]
    S4 brakes are notoriously poor in ANY condition (just happen to be what, 321mm?).

    There's more to braking power than just disc size. The calipers/pistons/design/number of pads etc all give varying results.

    If size was of absolutely no consequence what so ever, then where does this rule cease to apply? Would a pair of 188mm brakes up front stop me just the same as my 360's?

    The S4 and RS4 in that video above are fairly similar weights, and I'll guess that they're both in tip top condition. Not exactly totally accurate laboratory conditions I know, but it seems to support the general rule that fitting the RS4 brakes in place of the crappy S4 ones is a smart move (from cold,........with heat in,.............whatever).
    #27
  29. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Feb 11, 2009]
    If you get in a standard 1.8 a4 with its 280mm disks and wind it up to 80mph then stand on the brake pedal as hard as you can, you will lock the wheels (and the ABS will take over)

    That means the brakes can generate more torque than the tyre can apply to the road surface...

    Fitting some 380mm floating disks with 8 pot brembos and do the same test, ok you'll lock the wheels with less foot pressure, because the brakes will be generating more torque, but the maximum torque you can apply is still the same, ie the point at which the tyre loses traction on the road surface...

    Fit some super sticky tyres to the 1.8 A4 on stock brakes and it will stop faster than an RS4 on plastic-fantastics, might only manage it once, before overheating the things, but it will stop faster.
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  30. Dan Gliballs
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    Dan Gliballs Active Member

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    [Feb 11, 2009]
    So assuming both cars were nearly new, Tiff had driven both from cold, neither car squealed tyres or locked up.............and the slightly heavier RS4 pulled up far earlier. Tiff was far more impressed with the RS4's brakes :- Is this purely down to tyres then?
    #29
  31. jcb
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    jcb Active Member VCDS Map User

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    [Feb 16, 2009]
    I know what you mean but it is not as simple as that.

    if you are making the ABS cut in the brakes are not working at their optimum. its the ability for the pad to scrub off as much speed as possible WITHOUT them locking up or having the ABS cut in that counts.
    you learn pretty quickly where the lock up point is and you avoid it for a reason.
    there is far more modulation in a larger rotor and you can get closer to the point where the wheel locks up and hold it there. the fact that the rotational energy is only turned into heat gives you only one exit for it, through the metal mass itself. increase the ability for the system to lose heat from braking and it is as significant in the single application of the brakes as it is in a track situation where you boil you fluid.

    I doubt very much stock 1.8t brakes with same tyres would manage to pull up once faster than an RS4 on **** tyres unless they were so bad they were illegal.

    basing this on personal experience of 1.8t brakes vs RS4 brakes on the same car with same tyres. all weights and forces are pretty much exactly the same.

    hauling my 1.8t up from 90mph on stock brakes was a scary occurance. they regurlarly lost braking power on a single long application from high speed. I can think of one shorter than average motorway slip road exit with a roundabout at the top that sticks in my mind and my trousers, where from about half way through the pull up there is no way in hell the brakes would be able to lock up the wheels. they were barely doing anything!
    This was not brake fade due to heat build up from lots of use on a track day but from one press.

    same tyres, fitted temporarily to new wheels, running 8 pot brembos and EBC yellow pads not only was the ability to pull up improved dramatically but so was the lack of fade.
    now with new tyres they are night and day.
    I don't notice the ability to lock up the brakes more than before, I am not constantly slamming into the steering wheel as you obviously get used to the new set up.

    but they are without doubt better at pulling the same car up on the same tyres.
    #30
  32. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Feb 16, 2009]
    A lot of that fade will be down to pad glazing but yer i hear what your saying, ive been there myself. But i've also been in that situation (brakes faded completely on one application at speed) WITH uprated brakes. My old nova had 256mm vented disks from a astra GSi, uprated from its standard 236mm solids, and in a similar situation to you ive had them fade completely when braking hard from motorway speeds, and have no brakes by the time the cars slowed to 40. The very same brakes worked amazingly when first fitted and bedded in, but 10k of everyday non-aggressive commuting rendered the pads useless.

    I think whats most important here, is that the braking system needs to be kept balanced.

    If you fit RS4 fronts and keep the crappy rears, you will not be able to stop as quickly. As you pointed out maximum braking is when your modulating the pressure just before the point of ABS activation, but because the fronts are a lot larger, they reach that point waay before the rears, meaning the total torque your now applying to the road reduces.... The standard setup is slightly front biased for safety, but if you massively increase your front stopping power with respect to the rears, you will mean its even more front biased, and thats not a desirable thing to have.

    An interesting point, is that huge RS4 rotors will be more prone to glazing than small ones, as they're being used even less most of the time. It would be interesting to compare and RS4 setup thats been on the car for 10k and never driven in anger, with a similar stock setup, and see if you get the same levels of pad fade.
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  33. Siena
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    Siena Active Member

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    [Feb 17, 2009]
    Regardless, I'm fitting the B7 RS4 set-up, in conjunction with 370mm custom discs with seperate bells.
    #32
  34. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Feb 17, 2009]
    Theres nothing wrong with fitting B7 RS4 brakes, you will gain fade resistance, larger pad surface, more pistons etc. You just need to keep in mind your maximum braking force is limited by the tyres, not the rotors.

    Just make sure you keep them balanced. B7 RS4 fronts and stock rears isnt a good idea.
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  35. Siena
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    Siena Active Member

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    [Feb 17, 2009]
    Rears will be suitably upgraded too, with B5 RS4 carriers, calipers and rotors.
    #34
  36. Oranoco
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    Oranoco Well-Known Member

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    [Feb 17, 2009]
    My stock 1.8T brakes are a bit sucky if I'm honest. 285mm (or there abouts) really don't give much confidence as they fade out quite quickly. Will see how they fair on track but I'm guessing my first post on Sunday will be "Need new brakes"
    #35
  37. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Feb 17, 2009]
    i did the 312mm upgrade on ours becuase it needed new disks and pads anyway and the parts were pretty much the same price for 312 or 288, only extra spend was the carriers.

    Its running standard rears, and although i'd like to upgrade them too, i dont have the funds to do so.

    I've been looking thru the parts catalog and i suspect there are some A6 or Passat rear stub axles that can be fitted enabling the use of quattro style disks (ie just a plain disk, without the integrated hub. But i dont really have the cash to shell out on a pile of components to find out they dont work, and seen as its just the missus driving the car and its never driven in anger i'll probably just leave things as they are.

    If anyone fancies trying to upgrade the rears on a FWD i can dig out my research and give you the details.
    #36

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