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Old 09-14-2016, 07:13 PM   #1
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Fitted bigger disc on the S

I was looking into putting larger rotors on the base model. I also have a S model sitting in the shop. I scavenged the local Porsche dealer scrap bin and borrowed some rotors for measurements. I did find some 14" 350mm Cayenne disc in there as well as some other sizes.
These are very large(thick) and heavy. They will never fit in the calipers base or S model. You would have to use the cayenne calipers, which by the way are not radial mounted. They mount on the sides instead from the top like ours.

I searched and read every brake post on here. I also read other posts about boxster brake conversions for other car models. I wasn't aware how popular the base model calipers were with conversions. Many companies make kits which allow these calipers to work on other car brands and even mount them horizontal instead of radial using L shaped brackets.



One of the interesting post I found was a guy modifying the caliper to fit the thicker disc on his car. It was a VW model. He had to grind down the pad retainer pins.



So here are 4 rotors. From small to large: base, S model, Carrera S and cayenne.
The cayenne would require machining to open up the bore, plus it uses a different retaining setup vs our 2 screw retainers. Plus its extremely thick so it would require a caliper change. The Carrera S rotor shows major promise.









So the base calipers are too narrow. So I pulled off a S caliper and grinded down the retainer pins like I saw in another thread about modding them. I got them to fit the rotors.



Now I got find longer bolts and use washers to space out the caliper before I machine a spacer.

Help me identify that rotor please


Last edited by madmodz; 09-17-2016 at 09:02 AM.
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Old 09-15-2016, 01:35 AM   #2
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Hello madmodz,

the Porsche calipers are popular because they are Brembo monobloc calipers.

Concerning the rotor: what exact dimensions does it have? Is looks like a rotor made for a Porsche. Could you measure in mm please.

As far as i know all faster 996/997 models do have 330 or 350 mm brake disks in front. Most of them are 330x34 mm or 350x28 mm. Only the hub diameter differs.

The 986 has 5/130 diameter.

There are some 345 mm discs from other manufacturers. But a.f.a.i.k. only Porsche uses 5/130.

Regards, Markus
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Old 09-15-2016, 05:45 AM   #3
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If you're looking to sell your base brakes, I would suggest putting them on QuattroWorld. The Mk 1 TT folks (2000-2006) love to convert to base Boxster brakes.
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Old 09-16-2016, 03:34 PM   #4
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Well some good news. I found a hardware store that has long bolts, so I bought a few of them to test bolt length. Unfortunately they are not hex head. But those will come later down the line. So I put the rotors in my sandblaster to clean them up a bit and lo and behold some numbers appeared. 991.351.404.01 09 04 13
Not sure what the 09 04 13 mean but the other numbers link up to a 911 front rotor 340mm x 34mm. So I plan on spending some serious hours in the garage tonight because I have no life. The saga continues.....Can we fit bigger rotors on the S for cheap.

Thanks Markus and Husker for your help. Whats the going price for a set of base calipers

Last edited by madmodz; 09-16-2016 at 03:37 PM.
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Old 09-16-2016, 04:15 PM   #5
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Whats the going price for a set of base calipers
$300.

98-Boxster-Porsche-986-L-R-FRONT-Gray-BRAKE-CALIPERS

00 Boxster Porsche 986 L R Front Gray Brake Calipers
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Old 09-16-2016, 04:22 PM   #6
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I wasn't aware how popular the base model calipers were with conversions. Many companies make kits which allow these calipers to work on other car brands and even mount them horizontal instead of radial using L shaped brackets.
Yes, I have seen the same recommendations and kits to upgrade other cars to the Boxster brakes! The Boxster is nice bit of kit!
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Old 09-16-2016, 05:10 PM   #7
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Just curious, why do you want to mount discs that are so much larger than stock? From everything I've read and heard, the stock rotors are quite adequate for any foreseen use, including racing. Do you have some gigantic wheels that you want to fill up with rotor?

The reason the Cayenne rotors are so much larger are because it is a heavier vehicle that can be used for towing.
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Old 09-16-2016, 06:25 PM   #8
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Just curious, why do you want to mount discs that are so much larger than stock? From everything I've read and heard, the stock rotors are quite adequate for any foreseen use, including racing. Do you have some gigantic wheels that you want to fill up with rotor?

The reason the Cayenne rotors are so much larger are because it is a heavier vehicle that can be used for towing.
Yep, I have 20" fronts on the base model and they look puny. So I'm going to S calipers and the bigger rotors.
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Old 09-16-2016, 07:29 PM   #9
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Originally Posted by madmodz View Post
Well some good news. I found a hardware store that has long bolts, so I bought a few of them to test bolt length. Unfortunately they are not hex head. But those will come later down the line. So I put the rotors in my sandblaster to clean them up a bit and lo and behold some numbers appeared. 991.351.404.01 09 04 13
Not sure what the 09 04 13 mean but the other numbers link up to a 911 front rotor 340mm x 34mm. So I plan on spending some serious hours in the garage tonight because I have no life. The saga continues.....Can we fit bigger rotors on the S for cheap.

Thanks Markus and Husker for your help. Whats the going price for a set of base calipers
These as you know are very important bolts...make sure they are of the right grade
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Old 09-16-2016, 07:59 PM   #10
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Brake Caliper Stud Kit

Brake

http://www.girodisc.com/Rotors_c_1036.html
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Old 09-16-2016, 08:32 PM   #11
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Hello madmodz.

seems to be 991 brake discs.

991 Carrera S and 991 Carrera 4S do have 340 x 34 mm in front and 330 x 28 mm in the back.

They use a 6 piston monobloc caliper in front and a 4 piston monobloc caliper in the back.

Only thing i'm not shure of is the hole pattern.

Regards, Markus

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Old 09-17-2016, 04:40 AM   #12
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So help my simple mind on an early Sat morning...

If you've ground off the pad retaining pins, how do you plan to keep the pads in place?
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Old 09-17-2016, 08:42 AM   #13
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Thank you Radium,
I read an old post that I think you linked the going superfast.com link to. I was amazed at the brains and the machining they did to cut off the horizontal mounts on the cayenne and then drill the caliper for radial mounts. Bloody amazing!

The Girodisc conversion is basically what I am doing on the cheap. The Girodisc are beautiful though.
Looks like Porsche increased the rotor size from 330mm to 340mm on the Carrera S and 4S.
The girodisc is 340mm. They must be running thinner disc then the Carrera since no retainer pin modification is needed.

Thanks for the brake caliper stud kit. 4 different lengths too. I will go this route down the future.
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Hello madmodz.

seems to be 991 brake discs.

991 Carrera S and 991 Carrera 4S do have 340 x 34 mm in front and 330 x 28 mm in the back.

They use a 6 piston monobloc caliper in front and a 4 piston monobloc caliper in the back.

Only thing i'm not shure of is the hole pattern.

Regards, Markus
Thanks Markus,
Bolts right up with the hole pattern.

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So help my simple mind on an early Sat morning...

If you've ground off the pad retaining pins, how do you plan to keep the pads in place?
I was reading a caliper conversion on the vw forum I think or audi forum. The guy had masking tape around the ends of the pins and it said cut off in the pic. I said to myself how the hell is he going to hold the pads in too lol. Let me post a pic of the retaining pins Im talking about. I don't want to confuse the pad guide pins to with the pad retaining pin and clip on top. These are four retaining pins that look pressed into the caliper.



I was hoping to steer the conversation this way today. So I ask, are there replacement pins? If there are, that means they are replaceable and a way to remove them. Using a press?? One of my rear calipers seems to have this pin pressed in a little more so its not flush with the body. I don't have a press in the shop. If they are pressed it would be easier to lathe them down and repress them in the caliper as they are difficult to cut. Somebody could even offer shorter pins.

The article of the vw modification said file these four pins down. I would suggest that you cover the pistons in masking tape to keep any shavings out of there if you go this route. These pins did not file easily at all and my dremel didn't make a dent on them. They have to be stainless. I used a grinding disc which worked.

So the purpose of grinding down the 4 pins is to allow the thicker Carrera rotor to fit into the S caliper. The Carrera rotor is thicker so the pins block it from going in. In this pic there is a base rotor, a S rotor and the 340mm Carrera rotor I'm using. Look at the different thickness of the rotor.


\.
So Husker, your not really changing anything, great question. I wondered about it too. The Carrera rotor thickness makes up for the amount you cut down. Your taking mm from the pin but equaling the amount with the extra mm from the thicker rotor. The four pins act as a guide for the backing pad on the brake pad not the brake pad.

So two issues so far:
(1) If you modify your pins, your running Carrera disc for now on. No more S rotors. Unless someone can answer are those pins replaceable, there is no turning back. I don't really see this as an issue though, since you have thousands of conversions running these calipers. Let the next owner of the car know though.

(2) Since the rotor is thicker, I had to push the pads back into the piston to fit. My pads looked pretty thick. I was wondering how much room there is if the pads are brand new. I will look at that angle this afternoon.

Thank you all for your contribution. If all the vw and audi and countless other cars can do it, we can do it. 330 or 340 rotors on the S for whatever you find the price of the rotors. Sorry for the grammar.

Last edited by madmodz; 09-17-2016 at 09:31 AM.
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Old 09-17-2016, 09:10 AM   #14
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Girodisc will sell just the spacers and the longer bolts.
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Old 09-17-2016, 09:37 AM   #15
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Girodisc will sell just the spacers and the longer bolts.
That's great news. Saves me from machining a spacer. So since girodisc is 340mm
you would have to use S model Carrera or......the 330 and machine 10mm off the spacer.
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Old 09-20-2016, 08:51 AM   #16
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As I wait for the spacer, I picked up some uses rotors from porsche for the rear. These are pretty big at 330mm.

Questions for you guys:
(1) does the S rear disc and caliper fit on the base with no modification?

I though I read on planet9 that you need to transfer S parking brake parts. The thread gave on further info.

I want to try and get the 911 rotors on back of the S and space out the caliper.
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Old 09-20-2016, 08:58 AM   #17
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uncertain. I *have* read that base front calipers will fit on the rear of an S and give you more bite (bigger pistons).
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Old 09-20-2016, 09:20 AM   #18
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As I wait for the spacer, I picked up some uses rotors from porsche for the rear. These are pretty big at 330mm.

Questions for you guys:
(1) does the S rear disc and caliper fit on the base with no modification?

I though I read on planet9 that you need to transfer S parking brake parts. The thread gave on further info.

I want to try and get the 911 rotors on back of the S and space out the caliper.
You need the S upright/carrier/hub to fit S rotors and calipers on the rear of a base. The 986 S calipers and rotor are the same as a 996.
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Old 09-20-2016, 05:10 PM   #19
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uncertain. I *have* read that base front calipers will fit on the rear of an S and give you more bite (bigger pistons).
Thanks Radium, I read a thread on here about that. Lots of talk too about changing the braking bias.

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You need the S upright/carrier/hub to fit S rotors and calipers on the rear of a base. The 986 S calipers and rotor are the same as a 996.
Thanks Woody. Do you have both rear calipers loose? I'm curious if the insides are wider due to the thicker rotor. I read your informative article about the differences.

Has anybody actually done a base to S "rear" brake conversion? I know the front conversion is very common,


I haven't started on the rear calipers yet. These 330mm real rotors look so sexy! Nothing sexier then a big brake system on a Porsche.
I'm going to need the S parts Woody mentioned for the base . I will try and get the bigger rotors on both the S and non S to see if they even fit this weekend.

Here's a good link from JFP in PA:
http://www.renntech.org/forums/topic/49299-brake-swap-from-boxster-s-to-boxster-base-model/

Last edited by madmodz; 09-20-2016 at 05:55 PM.
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Old 09-22-2016, 07:56 AM   #20
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I can confirm that the base front calipers will fit on the back of a 996 carrier. It should fit the rear of a 986 S too. I can't say how well it will work though. The front base caliper does have much larger Pistons than the rear S caliper.

The rear base calipers won't fit over the S rotor because of the pins that hold the pads. Maybe if you ground the pins down, the base caliper would fit over the S rotor.

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