AP Racing vs VW Racing Brakes

[RedRobin]

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My 4-pot AP Racing front brakes incl everything weigh 10.5kg/side.

I didn't get them because of being lightweight though.

[fuscobal]

Wow, 20kgs per side as compared to 10-12kgs would mean 8-10kgs save per corner (and this counts more than the same static mass inside the car). Now, the question is how much improvement can I see over my current setup knowing I already have top pads suited only for semislicks + HEL lines + RBF660 fluid ? I can't really feel the extra weight either because of the power the car has but maybe it can bring some improvement on the track that can be measured in time gain. On the other hand, with the power/torque the car has, I might be spinning the wheels even more on corner exits with 8-10kgs less per wheel !

[RedRobin]

^^^^
20kg per side is still 2kg more than the total weight of my AP brake and OZ wheel! (excludes tyre weight).

My carbon bonnet will also save some frontal weight but I'm not prone to wheelspin as I'm only maxing 260bhp and also helped by the Quaife diff perhaps. It all supports how driveability is what's really important.

[fuscobal]

Robin, I have wheelspin now with the heavy brakes. I don't want to imagine how it would be with those !

[RedRobin]

Robin, I have wheelspin now with the heavy brakes. I don't want to imagine how it would be with those !

....And you are Revo Stage 3 with how many neddies at the front wheels? I'm not even Revo Stage 2+. There are other factors too why you may be prone to wheelspin including how you modulate your right foot.

[fuscobal]

Of course it's how you modulate your foot but I'd like the grip of a 4WD on corner exits. I've had some very nice runs with some Nissan GT-R and a Audi RS4 MTM at the last track day and the difference in grip on corner exits was noticeable. Now, with the Kumho V70a the wheelspin is much less than with my street tires but still there. I'm thinking, if I can feel the difference in weight between my summer and winter wheels (wich is only 2kg), the 10kg from the brakes should be like night and day for the steering (since the car has 380HP/475NM, the difference isn't felt on how the car pulls but on the steering response or wheelspin). That's why, before buying a BBK, I'm considering the following :

1) How much better can a BBK + a good track pad be than my R32 brakes + track pads + HEL lines + RBF660 fluid ? My brakes are already pretty good and I haven't had fade on Nurburgring at all but on Hungaroring the pedal softened a little bit on the end of the session (nothing to worry about though as the brake was still strong)
2) Buying a BBK also means taking into account a second pair of discs (one for the road and one for the track > Carbotech pads don't like to be used on the same discs after anothe pad) + I need to keep my 17" rims + winter tires & semislicks. Most brake kits recommended for a car having my weight use 340-360mm discs and have pretty large calipers wich mean 18"+ and spacers !
 

[tony_danza]

Wheelspin shouldn't even factor in your decision, it's unspring weight - it still has exactly the same amount of car pressing down on the tyres.

Even so, most of the weight saving comes from the centre of the disc being replaced with an aluminium bell, so its rotating mass effect isn't much at all. The caliper will be lighter too, but compared with the benefits, it honestly doesn't matter.

I used Carbotech XP8s on both road and track all year round, they worked from cold and never, ever faded on any track. That was on a 343mm Alcon kit, which a 17" wheel fitted over too. Because the brakes are better cooled and not heatsoaking one big lump of mass, and because you use them less because they're much more powerful, you can use a softer compound pad. Am I right in saying you have XP10s and got them to fade?

[rex]

Even so, most of the weight saving comes from the centre of the disc being replaced with an aluminium bell, so its rotating mass effect isn't much at all. The caliper will be lighter too, but compared with the benefits, it honestly doesn't matter.

One small correction... This is not what "moment of inertia" stands for. If there is some weight it is better to be near the point of rotation. Of course that having floating rotors will help, but it is not simple to calculate how much they actually help.
http://en.wikipedia.org/wiki/Moment_of_inertia

[ Invalid YouTube link ]

[fuscobal]

I had XP10 and the fade was barely noticeable at the end of session after I got out of the track to cool the brakes. I've now ordered the RP2 endurance pad (equivalent to XP12 but 2 times the lifetime). Ok Tony, can anyone write here all the kits using discs between 340 and 360mm with 30-34mm thickness that will fit under the OEM 17" denvers ? ( I don't mind putting some spacers if needed but not more than 10mm). Until now we have :

1)  343mm Alcon fits under 17"
2) From DaveB's recommendations another option would be the RS4 B5 4pot brake system wich uses 360x32mm discs. They are good for limiting rims but don't know what's the weight and how good they are compared to R32s or Alcon, Ap racing BBKs...(there seems to be 2 disc options for these, a one piece disc and a lighter 2-piece one made by audi-quattro). I also don't know the price for the 2 types of discs

PS : What I like about R32 brakes is that I can get OEM discs with less than 100 Euro !!!

[rex]

3) Movit 342x34 should fit under 17 (not sure).

[laurent.d]

Fuscobal,

If you are looking for a cheap upgrade over OEM brakes and that you don't care of adding weight to your car (I don't think you do as you already added a 150kg system sound ) which fit under 17'' rims, then R32/S3/Leon Cupra OEM brakes with braides line and proper pads are the way to go. It will be a bargain and a good set up which would do the job. But the more efficient solutions are much more expensive and are called BREMBO, AP RACING, ALCON, VWR, MOV-IT, STOPTECH, TAROX, ETC...

[tony_danza]

Agreed, if they're working for you, you've got to decide if the extra 1500euros is worth the weight saving and extra braking power?

I had the Alcons on my Golf and I wouldn't have chosen anything different, they were perfect, small & light enough at 343x32 and with odd sized pistons to be easy to use on the road and powerful enough to use on track.

But a big brake kit (BBK) isn't the answer for everyone, I have a Clio RS200 now and it has 312mm solid discs and 4-pot Brembos, all I've done is swap the pads for Pagids and the fluid for RBF600 - they are absolutely fantastic, work all day on track and it is very cheap to replace parts, so a BBK for this car would be insane.

In an ideal world, I think the best compromise would be a custom radial mount 4-pot caliper on an R32 disc. Power combined with cheap spares.

[DaveB@Vagbremtechnic]

Errrr - isnt that what the NQSBBK was all about....

I got a NQSBBK with S3 Hubs and 315mm two piece AP discs to be saving nearly 60kg over stock, thats not just good for unsprung weight thats good for 1/4 mile times!!!!!!!

One of the down sides of two piece discs (There aren't many) is the fact that if you wanted to build a perfect Gyro then all the weight would be at the periphery, this aids another gryo term called rigidity which in effect helps the disc store more energy for longer. Gyro's dont like to change direction by nature, they are also suffering from precession which means that any force acting on a spinning Gyro acts 90 degrees further along the gyro (in essence a force left to right on a gyro causes an up down movement) this is why on F1 cars and the 996/997 GT3RS move the calipers around to the 10.30/01:30 position instead of the more common 3 oclock/9 oclock as it aids turn in.

I'd never reccomend the B5 RS4 setup for weight purposes but its a big powerful setup with MASSIVE pad choice, it also works for those with Works or BBS LM style rimmage

[RedRobin]

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Although I'm a big fanboy of VWR I would favour the AP's, not because of performance but because the VWR's are 1mm too big (416mm) to fit under OZ Alleggerita 18's and OZ don't do a 19". A very lightweight wheel and well proven aftermarket brake kit is in my opinion the best package as a whole.

Unless you do a serious amount of trackdays or actual racing, I can't help thinking that too many folks are OTT on their choice of big brake kits for the 2.0T FSI platform whether off the shelf, homemade, or expertly made up like DaveB's etc.

[DaveB@Vagbremtechnic]

I would agree with that, I really liked the 343mm Alcons on TD's GTI. I would consider that pretty much optimal, the problem as ever is the fact that they make you touch your toes and go in dry when its disc replacement time at Alcon & Brembo...AP less so.

Do you always need 100% of what a 2000GBP BBK will give you or will you be ok with 85% of that ultimate performace for 800GBP how much of that missing 15% can be made up by the less unsprung weight??

If I was running a NQSBBK I'd have 3 Pairs of discs - 1 running the DS2500 for on the road, I'd then have for track or enroute to track two J hooked or straight grooved discs both having been bedded with a carbon metallic pad of choice and have one as a spare in case you toast a pair. Never the twain shall meet.

That arrangement would still be less cost than a BBK and you would be driving around the outside of the guy with the vibrating VWR brakes cos he's just put the DS3000 in on 700 pound discs that have been bedded with DS2500.

It also breaks my heart to see KW V3's with S3/R32 brakes hanging off them......