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Old 04-25-2018, 04:14 AM   #1
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Base vs. S brake measurements

i am looking to replace the brake pads on my 97 with something lower dust and noise but i believe sometime in the past the brakes were upgraded to "S" model red calipers and rotors.

Are there measurements i can take to confirm before i order pads? the pads themselves had no visible markings on the backs so i can't go off the ones currently on the car.

Thanks in advance!
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Old 04-25-2018, 05:12 AM   #2
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Front Rotor Diameter: Boxster = 298mm / Boxster S = 318mm

that should get you started
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Old 04-25-2018, 02:55 PM   #3
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great, thanks!
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Old 04-25-2018, 05:50 PM   #4
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Lots of calipers get painted so you are certainly wise to measure first.
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Old 04-26-2018, 03:59 AM   #5
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even easier...do your pads have little circular weights on the top (1 on each side of the pad)? If so, those are S calipers. If not, you may have some aftermarket pads or you have the base units
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Old 04-26-2018, 04:09 AM   #6
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i dont recall little weights but i believe them to be aftermarket pads anyway. they squeak and squeal like crazy and a bonus i found SS lines when i checked out my brakes. I am leaning towards "S" brakes as a visual comparison they seem larger than base.

i am going to take the wheel off again and measure the fronts, second question though are the rear brakes the same from "S" to base? or are there different sizes/pads between both?
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Old 04-26-2018, 07:50 AM   #7
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i dont recall little weights but i believe them to be aftermarket pads anyway. they squeak and squeal like crazy and a bonus i found SS lines when i checked out my brakes. I am leaning towards "S" brakes as a visual comparison they seem larger than base.

i am going to take the wheel off again and measure the fronts, second question though are the rear brakes the same from "S" to base? or are there different sizes/pads between both?
S rear brakes will not fit on a base car without changing the hub carriers, which is quite a bit of work.
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Old 06-27-2018, 11:28 AM   #8
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Udpate - i have been doing a lot of work on the car and finally got it up on Jackstands with the wheels off. Was able to get part numbers off the rotors:

Front: 996 351 405 01
Rear: 986 352 403 01

When searching the part numbers they come back to Boxster S Rotors front and rear. So i know the fronts is a common upgrade, but how hard are the rears to do? it seems at some point before me the previous owner took the time to upgrade the rears as i dont believe you can simply put an "S" rotor on the rear with base calipers.

So strange, the only other mod on the car was SS brake lines, everything else is stock and the suspension part numbers match back to a base 97. It seems odd someone would go through the trouble of doing a brake upgrade like that but make no other mods to the car.

thoughts? Opinions on the brakes?
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Old 06-27-2018, 01:17 PM   #9
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Udpate - i have been doing a lot of work on the car and finally got it up on Jackstands with the wheels off. Was able to get part numbers off the rotors:

Front: 996 351 405 01
Rear: 986 352 403 01

When searching the part numbers they come back to Boxster S Rotors front and rear. So i know the fronts is a common upgrade, but how hard are the rears to do? it seems at some point before me the previous owner took the time to upgrade the rears as i dont believe you can simply put an "S" rotor on the rear with base calipers.

So strange, the only other mod on the car was SS brake lines, everything else is stock and the suspension part numbers match back to a base 97. It seems odd someone would go through the trouble of doing a brake upgrade like that but make no other mods to the car.

thoughts? Opinions on the brakes?
Maybe he felt like he needed more brakes!

Other than the HP increase 6 speed tranny the other really significant upgrade on the S was the brakes, probably easy mod to upgrade. Who knows what goes through different owners minds!
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Old 06-27-2018, 03:04 PM   #10
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The front brake upgrade makes total sense, it's the rears that do not. It is an involved install as you can't simply take the rotors and calipers and bolt them on, you need the whole knuckle from the S and the effort doesn't seem worth it for the small increase in the rear.

i'm just glad i checked before ordering any brake parts because nothing would have fit haha!
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Old 07-04-2018, 04:19 PM   #11
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ok, yet again another wrinkle in this story. After thoroughly cleaning the area around my rear calipers (the whole situation was just bothering me greatly) i noticed there are in fact spacers in between the caliper and where it bolts to the hub.

I searched but didnt find anything, did people do this to add "S" rotors on the rear of a base, is it possible? I cannot confirm if the caliper itself is stock Base parts but the rotor is definitely an "S" part and there are spacers for the caliper.

Can anyone shed light on this or heard of this type of "mod" to make S rotors fit a base rear setup? i am now concerned with this setup that it was hacked together. i took some pics but am having issues uploading, i'd be happy to text/email them to anyone curious to see.
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Old 07-05-2018, 02:19 AM   #12
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ok, yet again another wrinkle in this story. After thoroughly cleaning the area around my rear calipers (the whole situation was just bothering me greatly) i noticed there are in fact spacers in between the caliper and where it bolts to the hub.

I searched but didnt find anything, did people do this to add "S" rotors on the rear of a base, is it possible? I cannot confirm if the caliper itself is stock Base parts but the rotor is definitely an "S" part and there are spacers for the caliper.

Can anyone shed light on this or heard of this type of "mod" to make S rotors fit a base rear setup? i am now concerned with this setup that it was hacked together. i took some pics but am having issues uploading, i'd be happy to text/email them to anyone curious to see.
Brembo used to make a kit that used spacers on the rear and specially machined rotors that were S diameter, but used the base e-brakes. None of this stuff has been available for many years.
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Old 07-05-2018, 03:37 AM   #13
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Jeff, thanks i saw there was a kit from brembo however the rotors are Porsche parts and stamped with Porsche part numbers. i was under the impression the Brembo kit would have used brembo rotors, was that not the case? did they actually take Porsche rotors and machine those to fit? if so it would make sense why the kit was so expensive

if it is the Brembo kit, am i to understand when these rotors are shot i am kind of screwed as they are no longer made? or is it as simple as unbolt the caliper, remove the spacers, put on stock base size rear rotors, rebolt the calipers without spacers and good to go? from what i read, the brembo kit was made not just to upgrade the rotor but to accept the S caliper as well. If that is the case and the rotors are no longer available i would need to switch back to base calipers to accept base rotors as well?

translation - a rear brake job is going to cost me a fortune if i need new rotors lol!

Last edited by dav9515; 07-05-2018 at 04:05 AM.
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Old 07-05-2018, 07:53 AM   #14
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Brembo made the rotors for this kit, but never made any replacements because the kit was not a big seller. The rear's are unique because they are internally machined to accept the base e-brake, which is totally different than the S car's. And before you ask, no, you cannot retrofit the S e-brakes to your base car without also swapping out the carrier hubs, etc.

I do not believe you can just remove the rear caliper spacers and use base rotors as a replacement, you would need to get base calipers as well.
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Old 07-05-2018, 07:46 PM   #15
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Thanks Jeff, that is what has me the most stumped about this rear setup as it has spacers much like the brembo kit but it has factory porsche rotors with "S" part numbers and the Porsche Part stamp not a brembo one. So, if the rotors arent brembo and spacers are still need to work, what the heck do i have on my car?

are there any identifiable markings on the calipers themselves that can be used to determine which ones are on there?
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Old 07-06-2018, 05:52 AM   #16
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If it is the Brembo kit, the rear rotors are Brembo's, just not any that you can buy as the e-brake area inside is machined differently to compensate for the base brakes. The calipers are stock S calipers, nothing more, with spacers to get them at the right distance from the axle centerline to obtain proper pad contact because you are using them on the wrong hub carriers for them to line up correctly.

And no, I have no idea where you can get replacement rotors. You can contact Brembo USA, but they would have to make them up for you, which (if they will actually do it) is not going to be cheap. Be sure to let the board know what you come up with, as I am sure you are not the only one facing this problem.
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Old 07-06-2018, 07:37 AM   #17
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Thanks for the responses, i am at a bit of a loss right now because i don't believe it is the Brembo kit and if the PO went through the trouble of switching the rear hubs to make the S brakes work, the spacers wouldn't be necessary.

I think when i have time the best next step is to remove the calipers and rotors for a closer look at the spacers and the inside of the rotor hub to see if that provides any answers.
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Old 07-06-2018, 10:46 AM   #18
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If you have spacers underneath the caliper mounting bolts, you have the five speed hubs; if you used spacers under S calipers on S hubs, only about 2/3 or the pads would contact the rotors and pads would have a rather large unused area as a lip.
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Old 07-06-2018, 11:44 AM   #19
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That is definitely not the case, the pads are making contact with the rotor without issues. i'll have to pull the rotor off and check it out when i have time. It is a porsche part so is it possible for someone with the skills and machinery to take a stock "S" Rotor and machine out the hub to fit over the 5-speed hub? i'm not sure how much metal there is to work with to make it possible.
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Old 07-06-2018, 01:08 PM   #20
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That is definitely not the case, the pads are making contact with the rotor without issues. i'll have to pull the rotor off and check it out when i have time. It is a porsche part so is it possible for someone with the skills and machinery to take a stock "S" Rotor and machine out the hub to fit over the 5-speed hub? i'm not sure how much metal there is to work with to make it possible.
Works the other way around, the five speed e-brake is smaller, not larger.
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