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Introduction
| Fundamentals
| Pads
| Discs/Rotors
| Big Brake Kits
Brakes & Upgrades - Big Brake Kits |
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Background
OK so you've decided that uprated pads and standard discs aren't good enough for you. Such is true if you take your track days seriously. In such situations there is no substitute for a set of 4-piston calipers and huge brake discs up front. The upsides are great with a massive improvement in braking performance - arguably what the S2 should have had when it left the factory. Superb bite, shorter stopping distances and reduced fading. The downsides of cost are considerable however - Not just the price of the big brake kit itself, but that many will require 17" wheels and tyres to be fitted. Then you have to tell the insurance company :( WARNING - One factor which is rarely considered by vendors of big brake kits is their suitability for road use. Roadgoing calipers always have lots of dust caps and piston seals to prevent dirt entering the system. Many of the options below are really only for off-road/track use as the calipers do not have dust seals. Consequently they require significantly more care and maintenance to ensure the brakes stay in good condition. |
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Consider
the options
As with other sections of this part of the site, I have tried to capture the main points of each 'off-the-shelf' big brake kit for the S2 on the marketplace. All of the following use 4-piston calipers. WARNING - These kits generally include everything needed to perform a bolt-on conversion with brackets, bolts etc etc... In addition, many kits contain silicon based DOT5 fluid which is NOT suitable for the S2.
As for pricing the above
kits. The cheapest is approx GBP1000 and the most expensive around GBP1700.
Then add the price of 17" alloys and tyres and the wallet really starts
to hurt !
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Custom
Specials
Of course, if none of the above meets your needs or budget you can visit your friendly neighbourhood engineering machine shop and have custom components fabricated. There are two incarnations of a custom brake system for the S2 that I know of... 1. The BLT This is my unfinished idea to fit the bigger Lucas twin-pot (hence 'BLT') calipers and 314x30 discs from the UrS4/S6. My intent was to get a bigger front brake configuration from the Audi parts bin that was suitable for road use and gave an improvement on the standard setup without breaking the bank. It turns out I wasn't first to try this as someone in Scandinavia beat me to it and followed it all through. This setup is no substitute for a proper 4-pot conversion in terms of out and out performance but it is a helluva lot cheaper. This configuration DOES fit the 16" 6-spoke Avus rim, but does NOT fit the original S2 5-spoke alloy. This solution uses the 'BLT' calipers, discs and pads from the UrS4/S6. The Audi gurus in the audience will no doubt spot that the UrS4/S6 calipers are mounted on the opposite side of the disc than the S2. That isn't a problem as the two pistons in the caliper are the same size which allows the caliper to mounted on the 'wrong' side with the brake bleed nipples pointing the correct direction. In order to fit the S2, custom sized caliper mounting brackets need to be fabricated. As yet, the dimensions of these brackets are unknown for now. Photos to follow... Update - This 'BLT' conversion is a dead-end due to the cost of making custom carriers for such a weighty caliper that doesn't offer much in the way of improvement in comparison to a 4-pot system. 2. Modified Porsche System It is well known that the massive brakes of the RS2 are from the Porsche parts bin. This includes discs and hubs built for Porsche wheel-bolt spacing at 130mm instead of Audi's 112mm. Anybody wishing to fit the RS2 brakes and hubs onto their S2 is in for a shock when they see the parts bill, but there is a cunning alternative derived by Mike Dewar who must be credited for his work on this one. Basically the system takes the front calipers from a Porsche 968CS (as did the RS2) and mounts them onto the S2 hub carrier with the standard RS2 caliper carriers (part numbers pending). Using custom fabricated two-piece discs (304x32 from memory) instead of the Porsche hubbed RS2 items, the 112mm PCD is retained. This route provides all the 4-pot braking performance that one would expect at a fraction of the cost of an off-the-shelf kit. The only downside is needing 17" alloys to accomodate the big discs. Another factor that needs to be considered is having to get custom discs fabricated for replacement items, but any decent machine shop with brake component expertise should be able to replicate them - as long as Mike kept the drawings :) 3. Porsche 996 / Audi RS2 / Audi A8 Kit This configuration has been tried and tested by many members of the S2 Forum. In truth this upgrade has been around a few years before I got time to write about here at S2 Central. This link (hosted by one of the forums many devoted and talented people) takes you to a site explaining the modification in great detail. I can't remember if Greg invented the upgrade kit by himself - sometimes this kind of magic development happens in parallel by accident. The essence of this conversion is as follows (with part numbers to be added when I get time) -
Basically it all bolts up a treat to the front of the S2 with a few minor tweaks -
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What
about the rear ?
Everybody raves on about huge big discs for the front of the S2, but you hardly ever hear how to upgrade the rear discs - a feeble 245x10 configuration. Sure enough the fronts take much more of a pounding than the rear, but the S2 was very unlucky in that it did not receive vented rear discs. The RR quattro, UrS4/S6 and 200TQ Avant all have vented rears however so it appears the S2 got a raw deal by Audi's chassis engineers. I took it upon myself to try and fit the rear vented discs (269x20), larger calipers (447 615 423 & 4) and carriers (447 615 425 ) from a wrecked S6 onto my S2. Well there's good news and bad news. The good news is that the calipers and carriers bolt straight on with no problems. The bad news is that by some horrible twist of fate, the rear discs on the S2 are a unique size. The hat-height is different on the S2 and so the S6 discs are much too deep to fit the S2. It turns out that the UrS4/S6 and RR share the same rear discs (857 615 601). The 200TQ Avant also used a 269x20 rear vented disc but with a smaller hat-height than the RR/S4/S6. I personally have not verified this, but the 200TQ discs can be fitted to the rear of the S2 with the help of a 6mm wheel spacer. The rationale for fitting the 6mm spacer underneath the 200TQ disc is as follows. The S2 rear disc has a hat-height (measured from wheel mounting surface to inboard side of disc) of 40mm, whereas the 200TQ is 46mm. For the record, the RR/S4/S6 rear disc has a hat-height of 59mm so the use of a spacer is way out of the question. Even with 6mm spacers at the rear of the S2 it could significantly alter the geometry and handling of the car. On the positive side the extra 12mm of rear track may be a bonus but there may be significant downsides in addition to increased loading on the rear bearings. An alternate solution (as yet unexplored) would be to fit rear hubs from the 200TQ, RR or S4/S6 to avoid use of a wheel spacer but the geometry would still be altered on account of the disc offset. UPDATE An even better alternative for the S2 rear is described below... I devised this conversion when I discovered that the part number for the rear disc on the S2 had been changed to one with an '8E0' prefix. That is to say that some infamous parts bin engineering had been going on at Ingolstadt (or a fantastic fluke) when they designed the rear brakes for the neu S4 (circa 2004). That car has a whopping 300x22mm disc at the rear with a single pot Lucas/TRW caliper using a modernised version of the S2's handrake mechanism. Coupe Variant - Disc 8E0 615 601R has correct bolt pattern (5x112) and centre hole size for S2 (56.1mm) The disc needs to be machined down to 280mm diameter for the Coupe application. S8 caliper carrier W4D0 615 425C (each side) - this is the variant for the 280x22 option on the S8 43mm pistoned calipers from the RR quattro or S4/S6 rear (447 615 423 & 447 615 424) or the alloy versions from the A8/S8 (W4D0 615 423 E & W4D0 615 424 E). Note the A8/S8 calipers need to have the handbrake cable location widened slightly for the S2 Coupe handbrake. More importantly, the hydraulic connection on the A8/S8 rear caliper does NOT work with the stock S2 rear hose - you will need to get a custom hose made. These problems do not occur with the RR/S4/S6 rear calipers that I have used. Pads for the 280mm version of the S8 (#) On account of this configuration on the Coupe, with different dimensions than as the original applications, a ~4mm spacer is needed between the mounting face of the S8 carrier and the strut. This positions the carrier centrally for the reduced 8E0 disc. I successfully used a handful of steel washers for this. To accomodate the spacers, longer carrier bolts are mandatory fitment. These 50mm ones from the S2 Avant (#) are long enough and can be trimmed down to size (~35mm) for the purpose. This upgrade is fitted to my own S2 Coupe and I am completely happy with it. In the fitting process I of course had to remove the backplates (splash shields) which are too small for the 280mm disc. It would be nice to source suitably sized alternatives that could be shaped to fit. Avant / Sedan Variant - On the Avant or Sedan models, due to the different handbrake mechanism, it is possible to use the full sized 300mm disc from the 8E0 chassis (listed above) along with the intended NeuS4 calipers (8E0 615 423/424 C) , carriers (8E0 615 425B ) and pads (4B3 698 451). These can only be used on the Coupe if there is a solution to the handbrake cable problem - hydraulically they fit up perfectly. One important point on the NeuS4 caliper is that a funky hydraulic hose is required ( 8E0 611 775H) - fortuitously it has the same sized fitting where it joins the hard brake lines. It doesn't hurt to replace the union clips at this stage (4D0 611 715B). Minor modification of the hole that locates the handbrake cable on the neu caliper is required for the avant/sedan cable - just needs enlarged a little. This upgrade has been successfully performed by a few members on the S2forum. |
Last Updated 29th June 2007