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 AP Racing 410mm Kit - A Review View next topic
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Car: C6 RS6 Avant
Power: 907hp
Torque: 830ft/lbs

Joined: 01 Jan 2014
Posts: 361

Location: Nr Maidstone, Kent

PostPosted: Fri Oct 07, 2016 5:19 pm  Reply with quoteBack to top

Hi all,

I'd originally wanted to get at least 1 track day under my belt before posting this but a billion different things have conspired to prevent that so I thought I'd finally post up my review before the weather changes for winters lovely fun!

I thought I'd break this review down into several sections to help keep me on track as I write it but first a little bit of history (actual review near the bottom) -

The twisted route to 410mm - I was looking for a better alternative to the OEM steel setup as I do a few trackdays a year and I wanted to stick with steel discs. Now the OEM Brembo caliper is actually very good but the OEM 390mm discs let them down badly so, initially, I swapped to AP Racing 390mm discs which are perfect for a stage 2 road car but started to show a few limitations when used repeatedly on the track (they cracked to buggery after the 4th track day).

So I started looking around at the various options available and was joined by TomRS who had a 400mm Tarox T16 setup up which he was also looking to improve upon. After a few weeks of checking out the various 405mm Disc kits (MTM/Brembo GT etc) or 400mm Alcon complete kit I had a "flash of inspiration"! I knew the calipers were also used on the 2012 GTR so I looked at what they were using and found that AP Racing had already developed a 410mm kit using their latest Radi-Cal tech in the caliper (lighter/stronger).

So now I knew that a 410mm kit was available, and that it'd fit behind the GTR's 20in wheel, I took a leap of faith that it would also fit the C6. The next step was getting in touch with AP Racing for more info and they sent me to BG Developments who carry out AP Racings custom work as the C6 setup would need a 2 piece disc with a custom Bell and some custom brackets for the Callipers.

At this point I handed over to Tom to take over as he was going to be ready to fit a set months before I would be. He sent an upright to BG so they could mock-up the brackets and get the bell measurements sorted and shortly afterwards he was sporting the first set which, being first, had a few initial teething issues to sort. With those issues subsequently fixed he has since done a few trackdays and his feedback was extremely positive.

Fast Forward nearly 3-4 months and now it was my turn so my car was hurriedly dropped into my local garage for the work to be carried out so that I could attend a charity track-day by the end of the week. Sadly it was at this point that I realised I'd been an utter moron! In my haste to get them fitted in time for the trackday, I'd made a few basic errors - I'd assumed my existing HEL braided brake lines to the OEM Calliper would fit, that 1L of brake fluid would be enough to bleed them and that everything would just "work" first time. I was wrong.

The existing HEL braided lines were a direct fit to the OEM callipers but the AP's needed banjo bolt lines. To fully bleed the brakes it's about 2.5L of fluid, not 1L but worst was that, in trying to remove the heavily corroded braided lines, it was obvious that the brake line would snap. So we came up with a plan to cut the OEM brake pipe back and replace the section with a new piece of copper pipe which the new braided lines could attach too, only my garage didn't have the right bits to do this in-situ due to the lack of space. So I moved the car to another garage to finish off the work which meant I'd miss the track-day.

That was 2 months ago and in that time I've put about 2500+ miles through them since without issue.

The Review

What do you get in the kit - 2x Discs, 2x calipers, brackets & mounting bolts and 4x AP DS25 pads with fitting kit (Ferodo DS2500 compound on AP backing plate)

What else do I need - Fluid (I used Castrol SRF, Tom used AP Racing R4), 20in alloys (incase anyone is using 19in winter wheels) and new custom brake lines. I got mine from HEL for £60, details below -

What do I do with the old Audi kit - After a solid day of cleaning I sold mine on eBay after a few days for £900, meaning the AP kit which is usually £2500 only cost £1600, which is an absolute bargain!

How good are they -  Brilliant! I find my MPSS tyres are reaching their grip limits much more quickly than with my OEM calliper/AP 390mm disc/Ferodo DS2500 setup. Now the pad compound is the same (same Mu factor) and the disc composition is the same (same Mu) so the "extra" work over my previous setup must be being done by the caliper. As a reference, after being bedded in I can hit the the tyres grip limit at low triple figure speeds.

What is pedal "feel" like - The pedal now has a very "2-stage" feel with a soft 1st stage being adequate for day to day and a much harder 2nd stage when you really want to slow down quickly. The 1st stage feels like the OEM calliper did but the 2nd stage is a much firmer pedal feel compared to the OEM feel. It's caught me out a few times as my muscle memory is still adjusting so I found myself over-braking quite a bit for a few weeks.

What was the Bedding process - The initial bedding in was 15 full force stops (just above ABS activation) from 80mph to 10mph with 10-15 seconds of acceleration back to 70mph before braking again. To be fair this was pretty scary due to the new AP DS25 pads gassing off massively and giving little braking force at low speed after the first 5-6 80mph-10mph stops, where it would brake to 40mph and then there was almost nothing, just a solid pedal and hardly any brakes. However once through that, by 8-9 stops, the gassing off was complete and the brakes were utterly amazing! One thing I have noticed, just like the OEM 390mm kit, these are "race" discs so they require a good bit of abuse once a week to keep peak performance.

How dusty are the pads/what pads are available - AP call the pad a "CP7555D70" and sell either a Ferodo DS2500 (AP DS25) or a DS3000 (AP DS30) based compound for these calipers priced under £200. However Radi-Cal callipers aren't very common in the UK so you'd have to look to the USA for more compounds. The AP DS25 pads are *extremely* dusty for the first 1000 miles or so (see pics) but settle down by 2000 miles to OEM levels.

Are they worth the money - I'm obviously biased about this but for £1600 with new discs, calipers, pads etc it's much better value for money than MTM/Brembo GT/Tarox/Alcon etc. However, for everything up to and including a Stage 2 car which *ONLY* stays on the road then it's probably a bit excessive even though I would definitely say they are better than OEM steel and a good compromise if Ceramic discs are out of your price range. For Stage 3 cars and track work (Tom has has now done a few with these) they are a huge step over the OEM steels and I'm more than happy to give passenger rides to anyone if you see me so you can judge for yourself.

Where do I get the kit from and how much is it - Alex at BG Developments is the point of contact for both myself and Tom so far - the website doesn't have much info but the FB page is pretty good - and the kit cost £2500 inc VAT without fluid or hoses.


Brand New -

After 2500+ miles

New copper brake line (so much surface rust )


Lovely and clean again!!!!!!!!!!!!

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Old - Daytona C5 RS6 Avant - 500hp & 550ft/lbs - MRC'd

New - Daytona C6 RS6 Avant - 907HP & 830ft/lbs - MRC'd
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