E36 M3 Porsche 996 front caliper conversion

[das borgen]

I decided to do this mod on my current M3 that I did on my old one



I sourced 2x front Porsche 996 Carrera calipers, same as front 986S and 987S (and used on the rears of some other Porsches I believe)


Then I went to a machine shop to have them shave down the mounting boss by 12mm (not my photo here)



then I got the front caliper brackets from Rallyroad, as well as the brake lines



Rotors are stock E46 M3 non-ZCP/CSL (ie: 325mm). If I hadn't shaved down the calipers by 12mm, I would have have been able to use the ZCP/CSL 345mm rotors, but that requires going to a 18" wheel, and I wanted to keep my stock 17"x8.5" Style 24s




this will give better pedal feel and fade resistance. It'll push the brake bias a bit forward (by around 10%) but that can be band-aided substantially by using a stronger rear pad

[CblockM3]

Awesome!

[ThreeD]

Good stuff. I was under the impression the 996 conversion actually pushes the brake balance back a bit, not forward

[das borgen]

Unless my calculations were wrong

[SamGrant951]

Looks good - Its a great conversion IMHO - especially because pads will wear evenly and pad changes take seconds once the wheel is off. Had the full set F+R on my M Coupe- will likely do the sedan as well at some point.

[Crustashio]

Good stuff. I was under the impression the 996 conversion actually pushes the brake balance back a bit, not forward

They definitely do. Stock is a 60mm piston (2827mm^2), these calipers are 40mm+36mm (2273mm^2). It gets even more rear biased if the 996 rear calipers are used.

[das borgen]

They definitely do. Stock is a 60mm piston (2827mm^2), these calipers are 40mm+36mm (2273mm^2). It gets even more rear biased if the 996 rear calipers are used.

On a stock caliper, there's only piston for a 2827mm^2 surface, yes...but you're only counting the total surface of a single side of pistons the Porsche caliper in your calculation.... There are 2x40mm and 2x36mm pistons per Brembo caliper. Each caliper has actually 4546mm^2 of piston surface to consider in calculations, which is way more than the stock caliper.

Or am I wrong here?

[Crustashio]

Or am I wrong here?

Yes. You aren't correctly accounting for the floating caliper - the clamping force from that is effectively a 2 piston caliper (equal and opposite reactions), so if you take into account all 4 of the fixed caliper pistons you need to count the stock caliper twice. So in that case it would be 2*pi*(30^2) = 5654mm^2.

[das borgen]

Yes. You aren't correctly accounting for the floating caliper - the clamping force from that is effectively a 2 piston caliper (equal and opposite reactions), so if you take into account all 4 of the fixed caliper pistons you need to count the stock caliper twice. So in that case it would be 2*pi*(30^2) = 5654mm^2.

No, that's wrong. In a hydraulic calculation, you don't consider reaction force outside the system from other surfaces.

By your logic, even on a 4 piston caliper, you'd have to consider the reaction force area against each piston by the rotor.

I doubted myself, but I checked with a couple of different brake engineers

[Crustashio]

It's not wrong.

By your logic, even on a 4 piston caliper, you'd have to consider the reaction force area against each piston by the rotor.

For braking torque calculations, yes. Each fixed piston applies a force of (line pressure) x (piston area). So say line pressure is 1 MPa to make this easy (1 MPa * 1 mm^2 works out to 1 newton) . In the case of the 996 calipers:

FPiston(40mm) = 1 MPa * (pi*(40/2)^2) = 1256N
Fpiston(36mm) = 1 MPa * (pi*(36/2)^2) = 1017N

Ftotal = 2*Fpiston(40) + 2*Fpiston(36) = 4546N (or 2273N per pad)

But the trick of sliding calipers is the caliper itself isn't fixed to the mount. So as the inner pad (piston side) applies a force of Fpiston(60mm), it pushes the caliper away from the rotor. But when the outer pad contacts it has to resist with a an equal force as it is what prevents the caliper from sliding further. So:

Fpiston(60mm) = 1 Mpa * (pi*(60/2)^2) = 2827N.

Ftotal = 2*Fpiston(60mm) = 5654N (or 2827N per pad!)

[aeronaut]

Very interesting. Subscribed.

[1000hp]

So....how much better do they feel, and how much better does the car stop?

[RobertFontaine]

Now if only it didn't say Perch on the caliper. It needs a decal that say Corvette.

[RauchenReifen]

Yes. You aren't correctly accounting for the floating caliper - the clamping force from that is effectively a 2 piston caliper (equal and opposite reactions), so if you take into account all 4 of the fixed caliper pistons you need to count the stock caliper twice. So in that case it would be 2*pi*(30^2) = 5654mm^2.

Not buying it, let's consider a simplified example. We have sliding caliper #1 with a single piston with a face surface area of 1", and fixed caliper #2 with two pistons (of the same diameter as #1) for a total opposing piston face surface area of 2". Assume we can turn on a line pressure of 50psi. Put your hand between the pads on caliper #1 and activate the line pressure, and enjoy a snug 50 lbs of clamping force on your fingers. Put your hand between the pads in caliper #2 and activate the same pressure for a painful 100 lbs of clamping force. How can anyone suggest sliding caliper #1 will have the same clamping force as fixed caliper #2? It's all about piston surface area, and more piston surface area equals more clamping force for a given line pressure.

[FastFabM3]

Not buying it, let's consider a simplified example. We have sliding caliper #1 with a single piston with a face surface area of 1", and fixed caliper #2 with two pistons (of the same diameter as #1) for a total opposing piston face surface area of 2". Assume we can turn on a line pressure of 50psi. Put your hand between the pads on caliper #1 and activate the line pressure, and enjoy a snug 50 lbs of clamping force on your fingers. Put your hand between the pads in caliper #2 and activate the same pressure for a painful 100 lbs of clamping force. How can anyone suggest sliding caliper #1 will have the same clamping force as fixed caliper #2? It's all about piston surface area, and more piston surface area equals more clamping force for a given line pressure.

In a single piston sliding caliper, the bore bottom is the "second piston", so in effect, a single piston sliding caliper with a 1" bore would equal a two piston (with 1" bores) fixed caliper.

So to further clarify, if you had a 1 square inch piston area, the bore bottom also equals 1" square and operates the opposite side, so you end up with 2 square inches of piston area.

The fixed caliper in your example also has a 1" square area at the bottom of each bore, but since the caliper is fixed, that pressure is simply null and void as it can only be used to try and pull apart the caliper (which shouldn't happen if it's built strongly enough).

Maybe that simplifies it?

[KnudsonsM3]

BBK'k on our cars are pointless. I have PFC pads front and rear and even with 255 RE11's, the car still has more brake than the car needs.

Das, have you ever tried stock set up with the best pads or did you go right to the bbk?

[aeronaut]

BBK'k on our cars are pointless. I have PFC pads front and rear and even with 255 RE11's, the car still has more brake than the car needs.

Das, have you ever tried stock set up with the best pads or did you go right to the bbk?

More absolute braking force than needed using OEM calipers/rotors and PFC pads, sure. But what about pedal feel? I'm about to do this same mod (Porsche calipers on front), and am hoping to improve braking feel at least at and near limit. Several folks over in the track section have adamantly stated these calipers improve pedal feel. They're also much easier to swap pads.

[KnudsonsM3]

More absolute braking force than needed using OEM calipers/rotors and PFC pads, sure. But what about pedal feel? I'm about to do this same mod (Porsche calipers on front), and am hoping to improve braking feel at least at and near limit. Several folks over in the track section have adamantly stated these calipers improve pedal feel. They're also much easier to swap pads.

Just like most mods, this is all subjective. A lot of guys suggest them so it goes both ways. I would suggest stock calipers, rotors and a set of PFC pads front and rear. The pedal feel is fine. If youre going to be tracking the car, I wouldnt go without an endurance pad.

I cooked a set rear Porterfield R4S pads after one day at the ridge here in Washington and had a lot of fade throughout the day, it was not pleasant. With the PFC pads I was able to brake much later and have ZERO fade. Not to mention theyll last me a long time.

I am full NA, schrick cams, sub 3k pounds with a roll bar and TCkline DA's and these pads are all that are needed. Save your money.

Here s a video of where I went.

https://www.youtube.com/watch?v=SImdJm1STAg

[aeronaut]

Yes, I have OEM system in very good working order with PFC 08 pads. Brake feel leaves something to be desired. And yes, on track. And agree, the PFC pads are very very good.

[KnudsonsM3]

Yes, I have OEM system in very good working order with PFC 08 pads. Brake feel leaves something to be desired. And yes, on track. And agree, the PFC pads are very very good.

I hope you find what youre looking for

If the brake feel is worth the money for you then do it.

[aeronaut]

Are we really going to talk about mods that are 'worth the money'?

[ThreeD]

BBK'k on our cars are pointless. I have PFC pads front and rear and even with 255 RE11's, the car still has more brake than the car needs.

Das, have you ever tried stock set up with the best pads or did you go right to the bbk?

LOL. Get out of here.

[KnudsonsM3]

LOL. Get out of here.

Surely you have more to add than that...

[ThreeD]

Surely you have more to add than that...

Sure, if you'd like, but nothing I'm going to say is new.

Is decreased unsprung weight pointless? Increased heat capacity of the pads and rotors? Increased stiffness of the caliper and corresponding improvement in brake feel and consistency? Improvement in brake bias?

You and I are running PFC race pads on our stock calipers, and yes, we get what we need out of the brakes. They don't fade and provide enough braking force without breaking the bank. Is a BBK the best way to spend a couple grand? Depends. My pedal feel is certainly lackluster and I'd like a BBK in the future when I have more money to throw around. While a BBK may not make sense from a cost-benefit analysis to you and I, you can't say that they are pointless.

[aeronaut]

What he ˆ said. And...rumor is significantly less pad knock-back.