Porsche 996 Brembo BBK Conversion Install

[HighOnLSB]

So I am following this DIY to install my 996 brakes finally over the last couple days and have run into this issue regarding pin clearance on one of my rear calipers as well.

I purchase a mismatched set of rears, but with correct part numbers for our application, and seem to have one carrera and one boxster caliper. The carrera caliper has perfect pin clearance on both sides of the rotor, however the boxster caliper does not.

When I originally mounted the caliper with p0lar brackets it was a tight fit but I thought it was nothing serious. Turns out the outboard pins were binding on the rotor and I never noticed. After a quick test drive I find out that the outer face of the rotor has been damaged. A new rotor and new RallyRoad brackets later and I am trying to tackle this issue properly this time now that I am aware of what’s going on.

Does anyone know what the minimum clearance needs to be? Even with the supplied washers from RallyRoad the outboard pins are very close to the surface of the new rotor, maybe only 1-2mm clearance. Is this enough clearance to be safe? Or do I need to continue to try to remove material from the pin?

[maupineda]

I took some measurements and I think the pins in the callipers are not really an issue. Please see the image below with some references I added.

A --> B = 61MM
A --> C = D --> B = 19mm
A --> E = F --> B = 19mm
C --> D = 23mm

Based on the above, the pins are centred in the rotor ditch of the calliper.




I still have tape on the pins as I have my clear coat pending, but I am for sure not 3mm off as I saw when mounted for fit test. at least not in my case. the pins' length is symmetric side to side so if I center my rotor between them, I am centring the rotor in relation to the calliper monoblock.

I hope this makes sense and is useful to others.

[Tbonem3]

Roll pins. Dowels go in between two mating faces.

This was an issue for a few people on m3forum. I would grind/file the pins down a hair.

[duracellttu]

So just to be clear, there is no way to press the pins back because of the dowels. The only way to get the pins centered are to offset with washers or use a dremel to shave them down?

[i_love_japan]

I believe Porsche uses the same part number for the Carerra and the Boxster, however the Boxster (non S) has a different offset on the rotor which can be seen looking at the face of the caliper. If the 2 pins are flush with the face, it will fit the M3 fine. If they are inset by about 2-3mm, they will not clear the rotor (just like the ones in your photos). Also, my RR brackets did not come with any washer as well.

[WOLFN8TR]

Yes they are held in place with dowel pins so that would have to be removed to move the pin. Makes sense there is a variance between different Porsche calipers, the washer is the easiest route. It's Gary btw...

[maupineda]

My Rally Road brackets did not come with those washers and my pin clearance was perfect. It looks like the pins are pushed inward too far on the face of the caliper. Most pins ( including mine ) are flush with the face of the caliper. If they were flush the front pin clearance would be the same as the rear pins.

Hi Json, that is a good point, I also checked how the pins are attached, and they seem to have a locating dowel pin (I assume so they don't come out), but without taking them apart, I don't know how much tolerance there is to push the pins more in than not, but in your photo is obvious your pins are flush, mine are not, and yes, I can tell the front pins (where the Porsche logo was) are not within the same location into the pockets as the backside. odd, however, both of my callipers are identical

What I will do is to measure the distance from the rotor face to the inner face of the calliper and see if their distance is consistent with the measurements I took using the pins.

when I collected the kit, Eric (Rally Road) did say I am giving you these washers if you need them to center the calliper in relation to the rotor. he mentioned variability, based on this it seems the variation may be in the calliper themselves if the pins are pushed-in differently from set to set.

[maupineda]

Are there threads in the knuckle for the bolt that holds the adapter? Or are the threads just in the adapter?

I’m wondering if adding a washer or two will cause issues if it reduces the threads on the adapter side.

threads are in the trailing arm, all things kept equal, 1.6mm are about 1.5 turns of the bolt, I don't think it matters, or... use a longer bolt but there is not much space between the other side of the knuckle and bearing. so it is no brainer. with heat expansion, I would be more concerned about the pins binding to the rotor.

[WOLFN8TR]

So far so good, but then I also checked how centred was the calliper in relationship to the rotor, and I found that is 3.2mm too car inboard. the bracket kit comes with 4 washers but they are just 0.8mm thick, so for the calliper to be centered I would need to use the 4 washers on one calliper, so I need to get some stainless washers from home depot.

See how the supporting pin of the outboard pad is contacting the rotor



Here you can see how much clearance is on the inboard side (that gap is 3.2 - 3.3mm), I measured it with feeler gauges. in this very picture, you can see where the bracket seats to the knuckle, there it is where the washers need to be placed, ideally 1.6mm thick to put it in the middle.

My Rally Road brackets did not come with those washers and my pin clearance was perfect. It looks like the pins are pushed inward too far on the face of the caliper. Most pins ( including mine ) are flush with the face of the caliper. If they were flush the front pin clearance would be the same as the rear pins.

[duracellttu]

Correct. Between the adapter and the trailing arm mounting points

Are there threads in the knuckle for the bolt that holds the adapter? Or are the threads just in the adapter?

I’m wondering if adding a washer or two will cause issues if it reduces the threads on the adapter side.

[xpme46m3]

I dont remember mine coming with washer either. I'll have to double check again. I'll update the POST with the pictures you have sometime this weekend. The more info out there the better!

[maupineda]

Thanks for sharing. I never got any washers in my kit from RR. Looks like I need to make a trip to HD.

Where exactly are you placing these? In between adapter and trailing arm I'm assuming?

Correct. Between the adapter and the trailing arm mounting points

[duracellttu]

Hi, these are the washers I was given. they are 20mm OD, 11 ID and 0.8mm thick. They don't seem to be inox, so I may just buy some from home depot. or ask Eric from RR to give me 4 more.

Thanks for sharing. I never got any washers in my kit from RR. Looks like I need to make a trip to HD.

Where exactly are you placing these? In between adapter and trailing arm I'm assuming?

[maupineda]

Hmmm my RR adapters didn’t come with washers, only the locking washers in the zinc bolts. Looks like I’ll need to grab some.

Hi, these are the washers I was given. they are 20mm OD, 11 ID and 0.8mm thick. They don't seem to be inox, so I may just buy some from home depot. or ask Eric from RR to give me 4 more.

[duracellttu]

Hmmm my RR adapters didn’t come with washers, only the locking washers in the zinc bolts. Looks like I’ll need to grab some.