Mate defiantly the bore size difference is considerable , But between the 2 pots and brembos as a whole are physically the same size including the gap for the pad area . So the difference you see in size here is relative.

Hense why Doug and alot of others dont run rear Brembos . They even weigh around the same . Fronts obviously no comparison but rears are close to same size and shape just piston diameters differ . Your welcome to come past and compare in the flesh . The measurements are piston size the exposed part of the piston is tapered as you say and still big differences.

Sent from under my Dok Dok

Cool. I mis read your previous post and measurements. So that previous reply i made, didnt make any sense, hence why i deleted it. You must have already read it when you typed up this post ive quoted.

I appreciate your measurements. Always good to have the data there.

Further to the discussion. Pad size/area makes absolutely zero difference to braking torque. (It does however make a difference to pad life and heat handling capabilities and weight)

And caliper size/length material and weight etc also makes bugger all difference to braking torque. It does however affect things like caliper rigidity, which influences pad wear characteristics. Aswell as heat handling, and also the weight.

With braking. The important factors that effect the effectiveness of the system are :

Pedal ratio (or lever ratio in the case of the hydro handbrake) this is the mechanical force multiplication to the master cylinder by way of the pedal (lever) mechanism.

Master cylinder bore. The area of the master cylinder coupled with the force applied to it will result in the hydraulic pressure generated. Pressure = force / area. Hence SMALLER master cylinders generate MORE pressure for a same given force input. But the trade off is longer pedal travel and worse pedal feel because they move less volume.

Brake caliper piston area. The LARGER the pistons, the GREATER the braking force, because a larger piston has more area for the hydraulic pressure to act on. Its interesting to note that opposed piston calipers dont make any more braking force than sliding calipers with half as many pistons, given the same piston size. But opposed piston calipers do usually give better rigidity and weight savings, dont have the same issues with sliding mechanism, And look way better too.

Radius that the brake caliper/pads are acting on. This is effectively the disc diameter. Bigger diameter means more braking torque. More importantly with racing, it gives better heat handling due to bigger/heavier disc and more surface area to dissipate the heat away. With the trade off being more rotating mass.

And lastly. Brake pad friction co-efficient. Also called 'mu'. This is effectively how grippy the pads are. This gets pretty complex with various pad compounds and is greatly effected by heat etc.


In my quest to do a wicked skid in a Subaru. Ive tried playing with the lever ratio. With both the first twin cylinder arrangement i had, and also on the STi tandem cylinder.

Ive tried changing the master cylinder bore. (By going from a twin side by side arangement with 0.625" bores, to a tandem arrangement with a slightly larger 0.7" bore.) Even though the STi tandem is bigger bore than the twins. Its inline design does not double its surface area like the twins do.

I havent tried changing the rear calipers yet. Its a fair bit of added expense due to probably changing pads, discs rotors, and lines at the same time. But its not something im inpartial to, if i cant fix it other ways. Im hoping that maybe the Nissan calipers discussed before would be a straight swap onto my existing rotors, lines and even maybe pads. (Fingers crossed) i dont paricularily want to change rotors as i currently have 3 piece Biot rear rotors. And they cost a pretty penny. And they are sexy as.

A cheaper alternative could be trying a more aggressive rear pad. I currently have Cosworth street pads.




Oh yeah. While we are talking about brakes. These came in the mail yesterday. 355mm front Wilwood rotors. Straight swap onto my existing rotor hats. (With new bolts for safety) Still waiting on the hardware to space the calipers mounts out to suit. i opted for the slotted Spec 37 instead of the wanky electro coated, SRP drilled and slotted rotors. The drilled rotors are for 'show' and are considered a bad choice for track work. Unlike the old days of racing. The drill holes are purely an aesthetic thing now with advances in pad compounds that do not require drill holes to help with out gassing.

Check out how big they are compared to a stock standard Forester rear disc. If they were a few MM bigger, i could fit the entire Forester rotor INSIDE the Wilwood rotor.

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Mate the Nissan calipers that Nauli was talking about are the same as the Subaru suitomo 2 pots . The nissan 4 pots are also identical to the subaru 4 pots just different name put on them . Yes they do use a slightly bigger disc but use exactly the same pads as Subaru .
So the rears you need are Subaru 2 pots which will bolt straight on . Or the Nissan ones . They cost the same I've researched it and thought about buying some Nissan rears and painting them a plain colour for use on Subarus If they were cheaper ,but they go for the same price so no point doing it .

So the Nissan and Subaru rear factory suitomo 2 pots have pistons that are identical . Yes they are bigger pistons then the brembos . Ive had the nissan and the Subaru ones apart and measured . But the nissans do use a slightly larger rear disc with that caliper compared to the Subarus .

Maybe try the Nissan project MU formula D spec pads on the rear if you get the subaru calipers as they will fit . Thats what Im using in my Subaru 2 pots with they Hydro setup

Nauli or Type25? Are you sure he was talking about the sumitomo 2 pots? Im sure he said brembos? Maybe he was reffering to Nissans that went from Sumitomo 2 pots to STi Brembos? Do you know if it would be possible to go to Nissan Brembos? They have an even bigger piston at 40mm. (4mm larger diameter than STi Brembos. And nearly 2mm more than Sumitomos?)
So your saying the base model GT Skyline and base model WRX Sumitomos are EXACTLY the same? Ie every aspect of the calipers, as far mounting, offset etc is the same? If they are identical and interchangeable in that reguard. Then it would mean the slightly different rotor sizes would be possible due to where the calipers mounts are on the knuckle/backing plate relative to the hub. And not different due to where the lug mounts are on the caliper side of the things? Can you confirm this point?

In going to the Sumitomo 2 pots, what do i do about discs? They would require the matching discs correct? But arent the WRX discs matched to a 170mm park brake? My car has STi hubs/backing plates with the 190mm park brake. I think maybe the 99/00 GC STi RAs had R180 rears with 190mm park brakes, but with those calipers? (Correct me if im wrong here) But then i also have 5x114.3 PCD. So i would need discs to suit those calipers, but with 190mm park brake and with 5x114.3 or have to re-drill 5x100s. Alot of dicking about for a relatively small caliper piston change. (Plus also a slightly smaller diameter disc aswell which is a downgrade in that reguard)

Yes ive considered getting the Pmu Drift pads (for the STi brembos). Pretty cheap aswell compared to the STi drum brake versions atleast.

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R32 gtr rear brembos will fit a subaru as 2005 sti brembos will fit 32 rears with out modding . The Nissan r32 GTst , GTR 2 and 4 pot suitomo will interchange as well. Not sure about r33, r34 as Ive only owned and played with an R32 GTR . But Ive had the subaru suitomos and nissan ones side by side on a bench and yes there exactly the same. I'm pretty sure the 300zx twin turbos are the same as well . I was reading somewhere years ago that FC RX7 fronts and rears are also the same suitomos. An option I have seen used on Subarus with an adapter are Porsche Brembos mate

Advice on Porsche calipers....Which to go for? - Subaru Enthusiast Forum - ScoobyNet.com

What about rotors? Rear GTR brembos have 300mm and rear STi Brembos have 316mm rotors? Thats means the GTR brembo caliper would be sitting 8mm in on the rotor, which equals fouling. Unless the bolt location on the backing plate on Nissan VS Subaru is equally different. If i bought a set of GTR rear Brembos, will they work with STi diameter rotors when bolted to the STi backing plate? This is crucial, as if not then its not really worth arse-ing about on small calipers like that.

If so, then i will keep an eye out on Yahoo auctions for a set. As said, ive already got a set of multi piece rotors in the rear brembo size. So a simply caliper swap up to calipers with 40mm pistons would be easy and make a good improvement for very little financial outlay. But im not even gonna bother if i have to then dick about with rotors fouling etc. And that is my only concern there.

If i was to have to do rotors aswell, then i wouldnt even bother with 2 pots. Id go straight to a small set of 4 pots. There are a few off the shelf kits with adapters and rotors. Like the APs etc. (But pricey)

Or get a set of radial mount calipers and make/machine adapters to suit. There are literally tons to choose from from brands like alcon ap stoptech wilwood etc etc.

For example, just now i am looking at the Stoptech STR-42 line up (smallest 4 pot calipers they do), they have a model that would even be a damn closr fit for diameter and width of STi rear rotors. And have them in multiple piston size too, so you could pick a really good match. All that would be needed is the adaters from STi backing plates to the radial mounting of the caliper. This would need to be custom. And possibly brake lines too. Being able to use the existing 3 piece rotors would be a positive.




Those are some sexy brakes you linked there. If i had my time again, id probably try for something like that. The Wilwood 6 pots are an economy brake package. Great bang for buck, (i got them a few yrs ago when the AUD was strong, cost about 1500 for full kit with multipiece rotors, pads, lines etc. I could not get a used brembo package with 2 piece rotors for that price) but they lose a little bit of the finer details of other brake kits.

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The bolt location on the backing plate make up the disc difference mate . I fitted 05 sti rear Brembos on my R32 they bolted straight on , The fronts required me to use a dogbone adapter . I used the subaru ones because at the time V spec Gtr ones were selling at much higher prices all I did was buy the Gtr brembo rear size disc and bolt on the sti Brembo caliper on the rear.

The other option is as I think you have tried to look at is mount another set of calipers and have them on their own circuit to the Hydraulic hand brake.


Yeah you scored with the Willwoods they are now up to 2600 landed for fronts due to our shit dollar

These are at a good price Import Monster | View Z33 Z R brembo K1995


But I dont know the specs of Z33 rears or weather they would fit . All the others ATM on Yahoo seem to be R33,R34,R35 and the Z33 Brembos

Awesome. Thanks for the info. Im surprised this isnt a 'thing' in the Subaru world. (Unless it already is, and i just havent heard of it yet)

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