Smudge's brake upgrade info

[smudge 1020]

So I've had a few people asking about exactly what setup I've gone for with my brake upgrade, so thought it was about time I made a separate thread with the details of part numbers and other useful bits

 

As with a few others on the forums, I opted for an OEM replacement from Subaru's extensive Brembo range off the Impreza's. Pretty much any setup from an 02-07 Impreza will fit the front of the GT86/BRZ. The only thing you have to remember is that the GT86/BRZ has a leading brake setup (caliper in front of the axle) and the Impreza has a trailing brake setup (caliper behind the axle):

 

GT86/BRZ (thanks Jay for the picture)

 

 

Impreza

 

 

 

So the front calipers need the bleed nipples swapping from top to bottom to allow you to mount the calipers properly given that the pistons inside are staggered. You can simply bolt them on upside down so that the bleed nipples are at the top, but this would cause uneven pad wear due to the different sized pistons

 

I went for a slightly bigger setup that the standard Brembo's on the Scooby. I decided to opt for an AP Racing kit which consists of 6 pot calipers with 362mm discs. Very similar if not the same kit as this:

 

http://shop.grahamgoode.com/ap-racing-big-brake-kit-362mm-6pot-subaru-impreza-gt-wrx-sti-ggs1364b-64786-p.asp

 

All in all, fairly simple for the front. I obviously had my calipers completely rebuilt and refurbished by the Brake Caliper Specialists up in Nottingham to make them stand out a bit and get some peace of mind that they are like brand new, even though they didn't really need doing upon inspection

 

The rears are a bit different. Subaru were obviously rummaging through their parts bin when they made the GT86/BRZ as you can't simply put a rear set of Brembo's from an 02-07 like you can on the front. The rears require the Brembo's off an 08+ hatchback style Impreza. Whilst they bolt straight onto the hub and there's no real faffing around in terms of fitment, they are quite hard to find!

 

However, if you are lucky enough to find a set, the only modification you need to make it to the dust/heat shields on the GT86/BRZ. They need trimming or bending back very slightly to allow for the larger caliper. But it's a very simple job.

 

The only headache with the rear setup is the discs. Subaru decided to make the rear PCD on the STi with the Brembo's 5x114.3 instead of the usual 5x100 that we all have. Thanks Subaru!

 

So, your options are:

 

- Use the rear discs off the 08+ setup that you would get with the calipers, and redrill to a 5x100 PCD

- Find some new discs that are 5x100 fitment (only the DBA2656-10 option for this as far as I know)

- Find some new discs which will be 5x114.3 and have them redrilled

 

After being given the wrong information and discs on a couple of occasions, I can now confirm the following part numbers for the rear discs:

 

DBA2656-10 or DBA42656SP - these are dual-drilled for both 5x100 and 5x114.3 PCD's but come at a price. The ONLY UK stock I can find is here - http://clarkmotorsport.co.uk/parts/4000-T3-Series-Brake-Disc---SLOTTED-%28Pair%29/Rear-Vented/DBA42656SP

 

EBC GD1511 - slightly cheaper option but will only come in 5x114.3 and need to be redrilled. Cheapest price for these can be found here - http://www.camskill.co.uk/m31b0s3145p80243/EBC_BRAKE_DISCS_EBC_TURBO_GROOVE_BRAKE_DISCS_-_GD1511_-_EBC_Turbo_Groove_Brake_Discs_

 

There are other options from the likes of Brembo and a few others, you just need to make sure that they are the following dimensions:

 

Diameter - 316mm

Thickness - 20mm

Height - 63.5mm (sometimes 63.4mm or 64mm on some websites)

 

There are some VERY similar sizes that will NOT fit, as they have a height of 67.5mm or 68mm which causes the disc to sit too far onto the hub. DO NOT ORDER THESE!!!

 

Front brakes are now on, rears are going on shortly seeing as I'm on my 3rd set of rear discs now!

[chillismoke 182]

Graham Goode is 5 minutes down the road for me

[smudge 1020]

Graham Goode is 5 minutes down the road for me

 

Great bunch of guys, very helpful and have put up with endless emails from me over the past 4 months or so

[chillismoke 182]

Pretty awesome display of a scooby engine cut in half in there showroom also.

[Tweedbean 151]

Great idea getting the thread in place as I was going to start asking those exact questions as I am keeping an eye out for a pair of front calipers to come up on eBay or one of the many Subaru swap pages.

Any idea of a rough refurb/rebuild cost as a lot of the used calipers coming up are looking tired, so it would be good to know how much on top of the initial caliper cost someone may need to spend.

Thanks

[Tareim 343]

I take it you need 18s for the brake upgrade?

[smudge 1020]

Great idea getting the thread in place as I was going to start asking those exact questions as I am keeping an eye out for a pair of front calipers to come up on eBay or one of the many Subaru swap pages.

Any idea of a rough refurb/rebuild cost as a lot of the used calipers coming up are looking tired, so it would be good to know how much on top of the initial caliper cost someone may need to spend.

Thanks

 

If I'm honest, I can't remember what was rebuild and what was refurb costs. Best to get in contact with the Brake Caliper Specialists or another similar firm who can quote you best

 

I take it you need 18s for the brake upgrade?

 

For my front setup, yes. For the standard STi Brembo setup, no you can fit 17's

[Church 209]

I would advise against fitting aftermarket brakes just by arguments 'of big brand' and 'it fits/can be bolted on'.

Simply because it will change brake bias which will result in less reliable (in one of most important components in car) and sometimes even worse performing then stock brakes. It CAN work for most doing only daily driving, but problems surface easy if car is tracked and everything including brakes is fully used and margin of safety is less.

Each car has different optimal brake bias depending on weight distribution and weight transfer during braking to keep car stable and for shortest stopping distances. In addition to that some systems are tuned with expectations of it being within some range (eg. ABS, EDS and so on).

Taking brakes from different cars (with different optimum bias) or taking from different sets of part bins (unless it's designed for such combo, eg. APR Essex BBKs that designed to work with stock rear brakes) and looking on just for same PCD/if it will fit in wheel/if it can be bolted on may screw up brakes just for sake of having nice painted caliper with big brand name on it. For example - if you move bias to front, if fronts gets locked up even before ABS engage, if you move to back - fronts that are expected to do most of work, will be underused, resulting in longer stopping distance (and on hard braking again one axle can be locked befroe ABS proper engage on both axle brakes). In some bias change you can 'enjoy' on hard braking twitchy unstable car that may swing one rear end around in unexpected moment or make car understeer. Would one want to hit concrete wall on track corner or loose control when doing emergency braking to avoid hitting some obstacle on road just to have that 'brand' on caliper for less $$$?

Proper matching would ask to know what braking quoefficient brakes on each end have, and what have ones one tries to fit on. But it may depend on too many variables that often are not known (eg. what friction selected disks have, what is area of pads, what area of brake pistons, to pit it relative against other axle brake pistons and pad areas (preferably for brakes of same set/brand to not miss some other possible variables not known)), thus best to use kits designed for this car to keep bias at what it should be. And use same compound pads on both axles. Knowing just PCD/mounting bolt holes/wheel fitment is NOT enough for safe and reliable brakes.

[smudge 1020]

I can almost guarantee that this setup will stop me quicker than the OEM brakes would...but thanks for your concern

[Ade 517]

Church makes some important points. The Subaru impressa is front heavy and has alot more weight over the fron than back. Smudges setup does move brake bais forward about 16% (i've run the nubmers myself to confirm) which is undesirable but workable. With firmer springs on the front, you'll actually have less weight transfer to the front so really you want to move it back a bit over stock. That being said it wont stop any slower or faster (when cold) as both are capable of locking up the wheels. You will gain a whole lot of pedal feel though! and massive heat capacity, especally if you are going for mega power with a big twin screw SC

 

Also note our cars dont just have abs, we also have electonic brake force distribution which help sort out the slight shift forward with this setup.

 

There are cars in the states running down force (element tuning hydra) whereby the EBFD cant keep up and they had to develop a new brake setup using the wilwood calipers to move the bais back quite a bit.

 

There really is no perfect setup for our cars. Different track conditions, tyres, suspension, diff settings, corners all have slightly different ideal settings. F1 drivers actively change brake bais, diff setings ect as they lap a track.

 

To kep close to stock brake bais, perhaps the brembo or Ap racing setup is optimal, but at £4.5K+ this is a much more cost effective way to get more heat capacity for track.

 

You can put a more aggressive compound on the back to move the bais rearward a bit.

[smudge 1020]

Church makes some important points. The Subaru impressa is front heavy and has alot more weight over the fron than back. Smudges setup does move brake bais forward about 16% (i've run the nubmers myself to confirm) which is undesirable but workable. With firmer springs on the front, you'll actually have less weight transfer to the front so really you want to move it back a bit over stock. That being said it wont stop any slower or faster (when cold) as both are capable of locking up the wheels. You will gain a whole lot of pedal feel though! and massive heat capacity, especally if you are going for mega power with a big twin screw SC

 

Also note our cars dont just have abs, we also have electonic brake force distribution which help sort out the slight shift forward with this setup.

 

There are cars in the states running down force (element tuning hydra) whereby the EBFD cant keep up and they had to develop a new brake setup using the wilwood calipers to move the bais back quite a bit.

 

There really is no perfect setup for our cars. Different track conditions, tyres, suspension, diff settings, corners all have slightly different ideal settings. F1 drivers actively change brake bais, diff setings ect as they lap a track.

 

To kep close to stock brake bais, perhaps the brembo or Ap racing setup is optimal, but at £4.5K+ this is a much more cost effective way to get more heat capacity for track.

 

You can put a more aggressive compound on the back to move the bais rearward a bit.

 

I knew that this setup would move it all forward a fair bit, but until I've tried it all out on the track then I can't really comment

 

I've got the DS2500's on the rear and AP pads on the front, so that will certainly help to shift it back a little more. But as you said, no setup is optimal given the amount of choice we have over suspension, roll bars, tyres etc

 

Until I've tried it out for myself, I'll hold judgement. It's a bit of an experiment if I'm honest!

[GT86Jay 202]

I've run the Brembo STI caliper on the front of my car now for a fair while. Over a year. And can say it has no problems. 

 

It does move bias forward a little bite, bit I like that. On track around Snetterton the car definitely stops quicker! Pedal feel is fantastic. And the car isn't dangerous at all.

 

Wheels look up equally and there's no nose diving on my car. I run Z-rated pads on the front and Cosworth Pads on the rear. Car is very well balanced. There are cars in the TSS and in the US winning races with these setups. 

 

It does seem to work very well. I've had someone back to back test my car against their own car with big AP brakes for the GT86 and they've said it doesn't feel any difference really. Tyres are my limiting factor now anyway. Even on Eagle F1s. 

 

I still run stock caliper on the back and have heard running the STI rear caliper is worse and moves it even more forward. But I wonder how many people have tried it? 

[Ade 517]

The STI rear caliper piston has 2mm smaller diamater (36mm vs 38mm stock caliper) which when combined with the slightly larger diameterdisc, brake torque is more or less the same within a few %, but yes it moves it forware ever so slightly.

 

I cannot stress more that bigger brakes over OE (which is more than capable of locking the wheels) will absolutely NOT reduce stopping distances. They serve to give better heat capacity, nicer pedal feel and aesthetics.

 

Back to back test are so massively subjective. We are talking about fractions of seconds here. I've tried a car with the sti brembos just on the front, and because of the larger piston diameter you do get more pedal travel, which for me was offputting.

 

Im not knocking these setups chaps (I have an ebay saved searches for the STI calipers , I just want to make sure everyone knows the facts and can make an informed decision.

 

At the end of the day, you can move the bais back with different pad compunds. This is a very common way to do this and works well as long as you stay within the operating temperature of the pads.

[Ade 517]

Are the gold brembos the same as the 08+ STI calipers?

[smudge 1020]

Are the gold brembos the same as the 08+ STI calipers?

 

Not that I'm aware of. The 08+ STi calipers are black with different mounting holes compared to the gold Brembo's from 02-07

[GT86Jay 202]

Not that I'm aware of. The 08+ STi calipers are black with different mounting holes compared to the gold Brembo's from 02-07

 

Fronts their identical. Rear their different. 

[smudge 1020]

Fronts their identical. Rear their different. 

 

Yeah sorry I was on about the rears, assumed that's what he was asking about?

[Ade 517]

I should point out where these bigger brakes can improve stopping distances. Not really applicable to stock GT86s but some with track tyres and more power perhaps.

 

I'll give the example of a porsche GT3 that Colin Hoad likes to use as an example. Over about 150MPH the stock brakes of a porsche GT3 (dont ask me which model) cannot lock the wheels up no matter how hard you hit them. They will of course lock up once they slow down enough. This is actually intended by the engineers at porsche. ABS has a finite reaction time and slamming the brakes at 180MPH can make your starfish twitch.

 

In this case a bigger disc will allow you to lock the wheels up and potentially increase stopping distances from very high speeds.

 

I dont know what the limits of the stock brakes are on the GT86, but I'd expect a 300hp GT86 with grippy tyres to hit 150Mhp down bentley straight at snetterton.

[Ade 517]

Sorry yes rears. The old brembos, I think have smaller diameter pistons than the STI rears that smudge is fitting.

[smudge 1020]

I should point out where these bigger brakes can improve stopping distances. Not really applicable to stock GT86s but some with track tyres and more power perhaps.

 

I'll give the example of a porsche GT3 that Colin Hoad likes to use as an example. Over about 150MPH the stock brakes of a porsche GT3 (dont ask me which model) cannot lock the wheels up no matter how hard you hit them. They will of course lock up once they slow down enough. This is actually intended by the engineers at porsche. ABS has a finite reaction time and slamming the brakes at 180MPH can make your starfish twitch.

 

In this case a bigger disc will allow you to lock the wheels up and potentially increase stopping distances from very high speeds.

 

I dont know what the limits of the stock brakes are on the GT86, but I'd expect a 300hp GT86 with grippy tyres to hit 150Mhp down bentley straight at snetterton.

 

With mine getting the Sprintex 335 kit and a built engine in the next few weeks, bigger brakes were definitely the way to go  150mph isn't too hard to achieve with the 210 kit that I have now, so I have no idea what the 335 is going to be like!

[Ade 517]

Absolutely! That thing is going to be a beast!

 

Like I said you can fiddle the bais to your liking with different pads anyway   

 

I want a brake kit mainly to reduce comsumable costs. £150 worth of pads in two tracks days on the OE brakes

[smudge 1020]

Absolutely! That thing is going to be a beast!

 

Like I said you can fiddle the bais to your liking with different pads anyway 

 

I want a brake kit mainly to reduce comsumable costs. £150 worth of pads in two tracks days on the OE brakes

 

Ouch!

 

I went for more stopping power and the aesthetics side too, as you can probably tell with the colour I went for on the calipers!

 

Cost-wise, mine was considerably less than buying a new BBK front and rear even after the rebuild and colour change

[Church 209]

I can almost guarantee that this setup will stop me quicker than the OEM brakes would...but thanks for your concern

 

If brakes are at optimum bias, stopping distance will be same with ANY kit. Even on some AP Racing 12 pot custom made one. Stopping distance, or in other words 'stop me quicker' will change only from tyres with more grip. There are tests done that can be found if you'll search. Different brakes, same braking distance. Different tyres - different distance. Of course i count out cases where brakes are bad fit for car, and due eg. one axle wheels fully locking while another is underbraked, then distance can change from brakes too. Worsened that is.

Imho aftermarket BBKs are usually installed 65% to gain more heat capacity. Not stop quicker, just be able to not fade even after heavy track use of more then 10min session, for which stock brakes should be enough. 15% for BBK choice is lighter unsprung rotational weight. 5% for cheaper consumables. 15% left - for "bling" .

None from these top four reasons include "they will stop quicker", as they won't. Except if one believes myth of that by empirically expecting due placebo subjective feeling that they should.

[smudge 1020]

1st post edited to give correct rear disc information, finally!

[smudge 1020]

Some pictures of the fronts finally fitted