random_guy

Hi All,

Thank you in advance to anyone who can help. I am, unfortunately, going through a family member's estate and am categorizing the various car parts in their garage into recycle/toss, and salable. I am not familiar with Porsche things so I registered an account just to ask you guys these two questions :-)

There are two Porsche Cup rotors (991.351.106.8A and 991.351.105.8A) and I want to see if you guys can let me know if they're junk or not.

- I read the specs for the type of car they should be used on and thickness is listed at 32mm; is this just for when they are new or is that the minimum thickness to be allowed on the track? These are currently at 31.6mm.

- One of the rotors seems to be a little loose on the hat. I tightened down the bolts but it still wiggles just a tiny bit. Does this make it junk?

Thanks again.

skxf430

I believe these are the PFC front rotors and they are floating rotors if I am not mistaken.

Are there any visible cracks on them? Post some pictures of them.

random_guy

Yes, they are PFC. Here are some pictures.

Ed@Demonspeed

Good morning.

The rotor disks are used up. The axial cracks that you can see are common for the rotors as they wear and heat cycle. We run them with small signs of these cracks, but as they grow they become more likely to have an issue, so we change them out about when you have them there.

Thanks

Ed

random_guy

Thank you! Into the recycle can they go.

Phokaioglaukos

Hi Ed,

Please tell me more. I have tossed cross-drilled rotors when cracks connect two holes or reach the edge, but for slotted rotors I use until the slots are about gone. What is failure mode you see on slotted rotors before they are worn to the bottom of the slots. Also, for these rotors, don't the hats have some value?

Chris

Jas0nn

I wouldn't just toss them - someone may want those hats and hardware. Add a new brake ring, and voila - new rotors!

Ed@Demonspeed

The cracks that you can see in that face grow and connect with each other and eventually reach the outside of the rotor. When that happens bad things can happen. Our experience is that it goes from what you have there to bad faster than anticipated.

Also, our experience is that PFC does not sell a rotor ring (nor does motorsports) separately when they are made to a motorsports part number like these are. You can only buy them as a set from Motorsports. Unless someone has had different luck, but we have not been able to. If you call PFC they tell you to call motorsports.

Thanks

Ed

Skibum1963

Clark at Apex performance will sell the endurance version of the rotor without the hat. A lot cheaper but a little heavier.

Clark-ApexPerformance

Get them out of recycle bin.
The rotors in question are 32mm thick at the start so 31.6MM is well within acceptable tolerances. I am one of the largest PFC resellers to Porsches and can tell you the rotors you gave pictures of still have a lot of life left I would not throw them out.
Most of what look like cracks are heat fissures created by thermal expansion.

The rotors I am selling are 32MM front and 30MM rear thick the same as delivered on the 991 Cup car from the fcatory.
I have the front PFC 32MM replacement rotors in stock for $479.95 a rotor and also have the rear PFC rotors for $458.15 a piece. If you go to Motorsports they will sell you another hat that you don't need.
The correct PFC number for the replacement rotors are front 380.32.54.451/.461 and rears are 380.30.54.451/461. These are V3 design rotors but they fit the V2 Cup car hats perfectly. I have sold numerous sets to 991 Cup and GT4 Clubsport guys.

I have in stock Ferodo DS3.12 pads in the 991 Cup Car pad shape. These pads are 28MM thick front and 26MM thick rear. The 991 Cup car calipers are made to take pads this thick. The pads Porsche Motorsports is selling are 22mm thick front and 20MM thick rear. Call or email for pricing.

Ed@Demonspeed

What about the 997 rear rotors. Do you have disks for those.

Thanks

Ed

Clark-ApexPerformance

ED,
Do you need rotors with hats or just rotors. I have the one set of V3 Rotors with hats and 1 set of replacement rotors in stock.
Clark

Ed@Demonspeed

I need to look and see where we are at on rotors, but we have been buying the motorsports rears, which are the floating hats and rotors complete instead of just disks.

Thanks

Ed

Steve113

This is what happens

Skip Wolfe

I have to agree with Ed on this one - these are nearing the end of their useful lifespan. While heat checks are normal, you have to monitor them to see when they start to propagate and combine. They can go quickly from the heat fissures in the original poster pictures to the crack that @Steve113 just posted.

I spent time working in the performance and motorsport breaking industry, and showed the pictures to a long-time motorsports braking industry expert and his take that those are near the end and he would only use them for a test and tune and said that "there was no way he would let anyone start a serious race on those"

So definitely not salable - too risky.