Nissan S15 Brakes
The S15 came out with two brake specifications. The turbo has the 280mm discs with 4-pot cast iron calipers. The Autech NA version also uses these brakes. This is the same 5 stud setup as used by the R32 Skyline M-Spec as well as the turbo 300ZX.
The non turbo S15 also has a 280mm disc except it has the more typical single pot sliding style caliper. The brake pad area and disc thickness is also less than the turbo. The non turbo also uses a 4 stud hub.
On both the turbo and non turbo S15 the rear brakes are the same. They are a 258mm non ventilated disc using a single pot sliding caliper.
The best way to upgrade braking performance is just to use some performance race orientated brake pads and flush the old brake fluid with a high quality Dot 4 or 5.1 brake fluid. Unless you're a serious track racer you will be unlikely to require anything more than that.
The only problem is that these days 280mm rotors look small especially if you have 17" or 18" rims. Many hot hatches and sedans are coming out with 300mm plus rotors as factory.
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Brake Options
While arguably the standard (4-pot) brakes are fine, there are some interesting options to look at for possible brake upgrades. There is the full after market brake setup with big discs and after market calipers. This will cost a lot and some after market kits are not that suitable for every day road use, often lacking the dust seals and generally a lot noisier than factory. Then there are the other Nissan OEM brakes used on the Skyline models. These are generally bigger and can be a direct bolt on replacement.
Only the front R33/R32/Z32 or R32/33 GT-R brakes are a straight swap for the S15. Calipers and discs must go together unless you go with an after market caliper mounting bracket.
All calipers mount to the knuckle spindles in the same way. That means all calliper's bolt holes will line up with the knuckle spindle mounting holes. The bolt will pass through the knuckle spindle bolt holes and will screw into the calliper. Unfortunately with the R34 Nissan changed the thread size which means you can't just bolt on an R34 calliper.
R32 and R33 GTR Brembo brakes should be a straight swap however prices of second hand Brembos tend to be quite expensive and probably not worth the money.
Rear brake swaps are some what more complex and will at least require some custom brake cable modifications to make them work. The Skyline R32 to R34 all use the same rear brake setup. Using the Skyline 2 piston calipers on the S15 will require everything that bolts onto the rear knuckle. This includes the brake cables coming out of the rear hubs. Unlike the S15 the Skyline uses a drum brake for the handbrake which is why you need all the parts. You will also need to make up a small braket to hold the brake cables properly.
Brake Disc Specs
Front Discs:
| Model | Diameter | Thickness | Center hole | height |
| S15 SR20DET | 280mm | 30mm | 68mm | 54mm |
| R32 M-Spec | 280mm | 30mm | 68mm | 54mm |
| 300zx Turbo | 280mm | 30mm | 68mm | 54mm |
| R33 GTST | 296mm | 30mm | 68mm | 53.75mm |
| R34 GTT | 310mm | 30mm | 68mm | 53.75 |
| R32 GTR - non V-Spec | 296mm | 32mm | 68mm | 54mm |
| R33-R34 GTR - Brembo | 324mm | 30mm | 68mm | 53.75mm |
As can be seen all discs all have similar dimensions apart from difference in diameter. All will fit onto the S15 hubs
Rear Discs:
| Model | Diameter | Thickness | Center hole | height |
| S15 SR20DE/DET | 258mm | 9mm | 68mm | 47mm |
| Skyline R32-R34 | 297mm | 18mm | 68mm | 63mm |
The S15 discs are non ventilated while the Skyline rear discs are. The rear discs are quite different and Skyline rear discs will not fit without swapping over most of the rear Skyline hub parts.
Caliper Specs
Front Caliper Specs:
weights per caliper and do not include pads and bolts| Model | Weight | Material | Thread | Pad | Piston area |
| S15 SR20DET | 4.8kg | Cast Iron | 12mm | DB1170 | 40.4mm x 4 |
| R32 M-Spec | 3.3kg | Alloy | 12mm | DB1170 | 40.4mm x 4 |
| 300zx Turbo* | 3.3kg | Alloy | 12mm | DB1170 | 40.4mm x 4 |
| R33 GTST | 3.3kg | Alloy | 12mm | DB1170 | 40.4mm x 4 |
| R34 GTT | 3.3kg | Alloy | 14mm | DB1170 | 40.4mm x 4 |
| R32 GTR | ? | Cast Iron | 12mm | DB1170 | 40.4mm x 4 |
| R32/33 Brembo | ? | Alloy | 12mm | DB1520 | 44+38mm x 2 |
| R34 Brembo | ? | Alloy | 14mm | DB1520 | 44+38mm x 2 |
Rear Caliper Specs:
weight per caliper and includes brake pads and bolts| Model | Weight | Material | Thread | Pad | Piston area |
| S15 SR20DE/DET | ?kg | Cast Iron | 12mm | DB325 | 38mm x 1 |
| Skyline R32-R34 | 2.1kg | Alloy | 12mm | DB1220 | 38mm x 2 |
As you can see all of the front calipers share a common piston size. This means that swapping any of the front over should not mean having to change the brake master cylinder on the S15. The Brembo calipers have a slightly larger leading edge piston compared to the trailing edge however overall piston are is the same.
Nissan made some calipers from alloy and some from cast Iron. All are 2 piece calipers. I'm not 100% sure why there is a difference. Cast Iron would certainly be cheaper to manufacture and would be more rigid. Cast Iron is however quite a bit heavier! Looking at the R32/300ZX alloy calipers we see ribbing which must be to aid cooling. This would seem to indicate that Nissan used differet aluminium alloys with this caliper and that it needs to be kept cool to ensure it stays rigid. Later R33/R34 calipers do not have this ribbing which would indicate that the aluminum alloy could withstand heat better.
Just swapping the standard calipers for 300zx or R32 M-Spec calipers would reduce unsprung weight by 1.2kg per wheel!
The rear caliper swap is as mentioned earlier not quite so straight forward. Apart from the extra complexity of the swap it's also necessary to take into account the brake bias. Factory S15 rear brakes are single piston sliding caliper. The Skyline rear brakes are twin piston calipers and the discs are a lot larger in diameter. The Skyline caliper roughly doubles the piston area. The brake bias valve is built into the mater brake cylinder and can not be changed without changing the whole MC. Comparing 'split pint' and reducing ratios of the S15, R32 and Z32 the split point of the later are lower than the S15 and the reducing ratios are x 0.4. Interestingly the S14 has a higher split point of 569psi and a reducing ratio of x 0.4 even though the S15 is almost identical in weight distribution with the same brakes as the S15. While you may not need to swap over MC, braking distances could possibly end up being longer than for factory brakes.
All non Brembo calipers listed take the same pad, DB1170. The rear pads differ but are about the same size between S15 and the Skylines
Brake Weights
Looking at the DBA rotor catalogue we can see the difference in weight between the different discs. The OEM weights I have measured myself.
| Model Part # | Diameter | Weight |
| OEM S15 Spec R front rotor | 280mm | 6.7kg |
| DBA909 - factory replacement | 280mm | 6.9kg |
| DBA4907 - 4000 series | 280mm | 7kg |
| OEM R33 GTS-T front rotor | 296mm | 8.6kg |
| DBA4963 - 4000 series | 296mm | 7.7kg* |
| DB42304 - 4000 series | 310mm | 8.9kg |
| DBA906 S15 rear rotor | 258mm | 3.5kg |
| DB908 Skyline R32-34 rear rotor | 297mm | 7.0kg |
OEM R33 front rotors while only 16mm bigger have an extra 1.9kg in iron. Front brake pads and pins/plates add about 800g per wheel for all brake setups.
Factory brake weights for the S15 turbo is 4.8kg + 6.7kg = 11.5kg per wheel. Upgrading to R33 brakes using OEM rotors would take this to 3.3kg + 8.6kg = 11.9kg. If we belive the DBA rotor weight that's a reduction of 500g per wheel in unsprung weight with the added benefit of an increase in rotor diameter from 280 to 296mm.
The rear brake swap for the S15 will add quite a bit of extra weight over factory. First up the brake discs for the Skyline is a lot heaver and second of all the rear hubs from the Skyline weigh more as they have the drum handbrake setup. I would estimate that swapping to the Skyline rear brakes would add about 6-7kg extra weight per wheel. As for whether the additional braking power at the rear would help much I think it would be fair to say it wouldn't add much benefit. The Skyline brakes would however look a lot better with big rims though.
Brake Master Cylinder
Master brake cylinders also differ between models. The brake bias valve is built into the MC body and is not adjustable. Nissan have used both Tokico and Nabco master cylinders and according to my research the models used on various Skylines and Silvias are BM33, BM38, BM44, BM50 and BM57. Nissan used the BM50 Tokico made master cylinder for the S15 turbo. The factory master cylinder of the S15 turbo model should be fine for any of the upgrade options. Upgrading the rear brakes to Skyline 2 pot calipers will probably result in less braking force going to the rears under high brake pressures. The best option would therfore to swap the S15 MC for a BM50 from a 300zx or Skyline BM50. Just remember to get an ABS model MC as the non ABS has different outlets.
| Model | Type | Master Cylibnder Diameter |
| S15 Spec R | BM50 | 25.4mm |
| 300zx turbo | BM50/57 | 25.4 and 26.9mm used |
| R32 GT-T M-spec | BM50 | 25.4mm |
| R33 GTST | BM44 | 23.8mm |
| R32 GTR non Brembo | BM50 | 25.4mm |
| R34 GTT | ? | ? |
| R32/33/34 Brembo* | BM57 | 26.9mm |
Other options to consider
- Brake upgrades are all 5 stud so if you have a non turbo S15 you will also have to swap hubs
- Rear brake upgrades are possible but are more fiddly to do. Handbrake cabling will need to be fabricated
- Aftermarket adapter plates are available to allow you to use your standard calipers with 310mm and 324mm rotors. These however may not be legal without an engineering cert
- After market big brake kits with 4 plus piston calipers are common for the S15 if not expensive. Be careful to ensure they are suitable for every day road use