fuego

Posting in the 997 forum for visibility.

I bought a used Cayman. It came with these big brakes in the front.



At first glance, I thought they were cannibalized Porsche brakes, but these don't have an OEM number nor the flat caliper face. They're definitely brembos; it's stamped on the back side.

My thought is that they're some sort of aftermarket upgrade kit, just painted yellow. Problem is, which one???

Another thing is I have a wicked freeway steering wheel shake. All signs point towards the rotors. How do I even begin to ID the rotor rings? There are no markings anywhere I've seen.

Any suggestions would be greatly appreciated.

captainbaker

They might be factory. Shake at speed or shake while braking. One is brakes and the other is wheel, tire out of balance etc.

Type_LT

I'm no expert on Cayenne's but the calipers look stock (just painted yellow) and the best guess I have for the two piece rotors is that they are Brembo.

https://www.etektuning.com/brembo-fr...s-a3-mkv-mkvi/

There are knock of rotors that look like that on eBay as well.

http://www.ebay.com/itm/Brembo-2P1-9...dXiFDd&vxp=mtr

OKB

you can put stickers on anything, those look a little long, probibly somebody diy

speedracerf4i

the brake hat is different than what I have. So the rotor is certainly aftermarket.

semicycler

The Brembo stamp on the caliper is a start. Brembo is an OEM supplier and many of the OEM calipers have Brembo's stamp on them. But the lack of a Porsche part number stamp is a very big clue. Check near the brake pads on top of the caliper, that's where the Porsche part number is on the 997.1 C2S.

Measure the diameter of the rotor rings. Pretty sure OEM are 330/350/380mm. The hats would be stamped with Porsche part numbers so they are most certainly aftermarket. They almost look like GiroDisc hats, but I don't think GiroDisc makes drilled rings.

And check if there is an adapter connecting the caliper to the knuckle, or if the caliper bolts right up. Many of the larger 6-piston aftermarket big brake kits need an adapter to get the caliper mounting holes to line up. Yours look like elongated 4-piston ones though.

If you do pull the caliper off, measure the size of the pistons too.

Dennis C

The entire thing looks aftermarket to me, including the calipers. Perhaps it is a Brembo upgraded brake kit with yellow calipers.

fuego

I've already chased down the simpler causes. Tires were rebalanced yesterday, tie rods replaced a few weeks ago. There is both a shake at speed (max amplitude around 70mph, 80mph+ not there at much surprisingly) and heavy under braking until 50mph or less. Then I can't feel it at all.


The vehicle is a Cayman, not Cayenne.

All the Porsche brakes I've seen of that generation have a flat outer face, eg





And based on the abuse I've put them through and their construction, I don't think they're fake.

I think they are elongated 4 pistons as well, I don't see the third pair. I think Girodiscs also have some color on them, where the hat meets the rotor ring. So you're most likely right on both counts. I will check the knuckles. Thanks for the advice.

What info will measuring the pistons give me?

Also, are rotor ring bolt patterns universal?

This is my guess too. They look very much like this BBK found here. Notice the parallel lines, bleeder nipple placement, etc.

Type_LT

Yes, Cayman != Cayenne, silly me! Sorry about that.

The Vividracing picture looks like a winner, although it's missing one of the rotor set screws.

semicycler

Knowing the rotor diameters, or more importantly know all the meaningful dimensions will let you verify with a vendor if it matches a setup they offer. Things like rotor ring ID, OD, thickness, hat diameter, offset, number of mounting points to the ring, caliper piston count, piston diameters, mounting spread, pad radius, etc. If some of the critical dimensions match OEM specs then finding replacment parts will be easier. Oddball ring diameter or piston size is a sure sign it's aftermarket narrows down the vendors tremendously.

I'm assuming you want to reuse most of the setup - find new rotor rings and perhaps new pads while keeping the calipers, hats, and hardware. Sure if you knew who made the setup it would be easier. Knowing the dimensions is an alternate way to crack this nut. Find replacement parts that match your dimensions. For example, there are 10 mounting points on those hats. Some brands have twelve. Search for two-piece rotors matching your diameters and mounting points to narrow down the possible vendor list.

And given the early evidence that it's a Brembo aftermarket kit, call them and ask for help. It might be a kit they offer through distributors rather than a kit put together by some unknown speed shop using off the shelf parts.

JW911

Porsche 993 caliper. Possibly from a turbo.

Petza914

Pretty sure that's not a Girodisc rotor, as I think they only offer solid or slotted, not drilled. I have Girodisc 993 TT rotors paired with 928 Big Black calipers on my 928 Spyder and they look like this. If I remember correctly, they're a 322mm diameter rotor



Disc Brakes Australia (dba) makes a two piece rotor in a C2S fitment that's 350mm diameter. We have the slotted versions of those on my wife's car, but there may be a disc option with them that's drilled. I don't have a good picture of those, but remember them as looking different from what you have.

Regarding the vibration, are your wheels OEM or do they have the correct 71.6mm center bore for the hub-centric flange to mate with on your wheel carrier. Is the flange on the carrier the correct 71.6mm also? Are the lug bolts the correct tye to make with the bolt seats on the wheels themselves, i.e. both ball/radius seat or both conical seat and not a mixed combination. The speed at which you describe the vibration occurring is right about where it would happen if you have the wheel held on by the wrong type of bolts or if your not married up correctly with the right hub-centric dimensions. Could be other things as well - tire or wheel runout, improperly balanced wheel, etc. If it's a problem on the front of the car it will usually shake the steering wheel. If it's a problem at the rear of the car, it will shake the whole car.

Let us know what you find.

Widsinator

That is almost certainly a Brembo Gran Turismo Big Brake kit. Likely a direct fit for the car, the cross drill on the rotors has the matching pattern for the brembo rotors. Someone likely just slapped a Porsche decal on in place of the Brembo logo for a more OEM feel.

fuego

The wheels are aftermarket but take the stock conical lug bolts. As for the hub, when putting the wheels on, they seat perfectly flush against the flange but I will double check again.

It's definitely coming from the front.

I'm beginning to suspect so as well. Weird thing is they look like the GT kit for older Porsches. The more recent kits don't have the parallel lines. Now I need to figure out the brakepads!

Wheel Dynamics

Well I hope this helps, this was a Cayman we had on our rack for brake caliper refinishing, I'm sure you can see the difference.