arter

Very good thought.

The iron calipers get hot enough to change the color of the paint. It should melt either foam or RTV to a brown smunge.....

///M3THOD

I don't think foam is really the best solution. Im not sure its going to stop and redirect rocks away, instead possibly having them impact and stick in the foam, completely scraping the inside of your wheels.

The tmeperature concern of brake operating temps proabably also has to be considered, both on a melting point and becoming sticky. The foam, once hot, may actually become sticky and hold debris in place.

I think some kind of custom made metal deflector would work the best .

flickroll

Today I pulled the wheel in question. As an aside I am becoming quite a pro at removing and replacing centerlocks! So I followed arter’s lead about letting the wheel ‘sand’ the piece of foam which then allows a custom fit. I lined the wheel barrel with 2” blue painters tape, and then slapped on a piece of sandpaper with adhesive on the back. I drove the car about 2 miles and voila, I had a custom shaped piece of foam. Pictures at the end of my post. A couple of observations. One, to get clearance between the foam and the wheel, you need to build up more tape than what you think you need, otherwise the wheel squishes the foam a little and you’ll wind up with no gap at all. The second observation is this won’t fix the problem. No matter what gap you wind up creating with foam, there will always be road debris that come along that is slightly larger than the gap. That debris is likely to enter the gap and then get stuck, and at that point it will become sandpaper and destroy the finish of the wheel barrel. So my takeaway from this experiment is, unless you fabricate something solid like a piece of aluminum, you’re always going to have road debris wear. So not sure what to do at this point other than chalk it up to life in the PCCB fast lane. Opinions and other ideas welcome!

flickroll

Hurricane

If it was me, I would just drive it and enjoy it and not worry about it. (But I am not as handy and creative as you are, though!)

I am interested in hearing more about your tips and techniques for the center wheel locks as you gain experience doing it - I might want to try it myself with a winter tire set next season.

flickroll

Thanks Hurricane! I am at the stage of living with it or getting a different wheel set that has more clearance. BC Forged is sending a full scale drawing of their wheel. After I print it using stiff paper I'll cut it out and have a look at the additional clearance. Their pricing is really good, $4250 delivered for 4, and machined for Porsche centerlock. I am not familiar with the company so need to do some research. Another option is to go with 21" wheels which I am not thrilled about. Last option is to do as you said and just enjoy the car. I absolutely love it, the car is truly amazing.

For the centerlocks I follow Porsche's guide to the letter, just be very sure the center locking device is fully engaged after reapplying the nut. For the fronts, the brakes need to be applied so I do what most everyone else does and use a modified Irwin 18" bar clamp. I do a variation though. Most folks seem to be applying the clamp to the pedal and the seat. I took a different approach and apply the clamp between the pedal and the right hand seat positioning jackscrew endpoint nut and mounting tab. You have to remove a piece of plastic trim which is very easy to do, and also use a slightly oversized socked and extension against the jackscrew nut and bar clamp. You're not applying much force so there is zero risk of damaging trim. Works great. Other things you'll need is Castrol aluminum lubricant, proper capacity torque wrench (I have the Precision instruments and like it), breaker bar (Precision Instruments for me here as well) and a large jar of elbow grease

RacingBrake

I will only present the fact and data so you can make your own judgement.
997 Caliper on Left; 991 Caliper on Right:




997 caliper has leveled body



997 Caliper Installed - Even surface & clearance across the wheel barrel
Due to this caliper has an even surface (ie even clearance) it will only "admit" (& pass the rock through), or "reject" the rock. In other words it's very unlikely to let the rock "roll" between the caliper and wheel barrel.



991 caliper has two-way tapered body
Height were measured from surface plate with digitized Coordination Measurement Machine (CMM)



991 Caliper Installed - Uneven clearance (Large on outboard, tight on inboard)
This tapered body will create an uneven clearance, once a rock is trapped (on lower side-wider clearance) it will roll towards inboard (high side-tight clearance) and get pinched between the caliper and wheel barrel causing damage.

RacingBrake

We have a shop car MB CLS550 with 394/390 CCM rotors with 6 pot front and 4 pot rear calipers. RB calipers are made with same body as 997 (leveled body) and this set up has been running for more than one year now without any issue.

RB 394mm CCM rotor kit fits under 19" Mercedes (CLS550) OE wheel



Wheel clearance observed



Actual clearance (4mm) checked with a feeler gage



Have you heard any 997TT owner ever encountered with the same "Wheel Clearance" issue as 991?

flickroll

RacingBrake

This 993TT 19" wheel clears RB 394/390 CCB kit.
https://rennlist.com/forums/993-turb...l#post14320784

Basal Skull

Hey, that's pics of my car! Never knew this was a problem with porsche pccb's. FWIW I haven't noticed any marks on the callipers or wheels. 70% track, 30% street use. Happy to share more pics. Looks like I probably have more clearance, depending on where you measure. I can use the flat wheel weights and they don't get knocked off. The wheels are Fikse Profil 5s, also run Profil 5's.

RacingBrake

This RB 6 pot caliper is built for track abuse with a bolt on installation to Porsche 911 upright (Direct to 991 & with adaptor/spacer for 997/996).

Learn how RB reduced bias rear calipers help Viper track racer eliminates the wiggling under high speed hard braking.

Racing Brakes Rear Bias Kit Evaluation

Hurricane

mmuller

How do you stop the caliper from flexing across the bridge in the RacingBrake caliper? This one reason for the move away from open back calipers to closed bridge calipers in modern Porsche’s. Also, how does the piston sizes in the RB caliper compare to OEM? Lastly, what pad type does the RB caliper use and how many manufacturer alternatives and compound alternatives are available?

RacingBrake

Rigidity: This illustration should help you understand why RB caliper is stronger and more rigid based on objective data (design, material, and construction) comparing to OE. If you still have question I would be glad to reply.




OE caliper pistons are non-staggered:
Front: 30x30x30mm; 42.4 cm^2 (56.8%)
Rear: 32x32mm; 32.2 cm^2 (43.2%)
Total Area: 74.6 cm^2

RB caliper pistons are staggered:
Front: RB6A1 30x34x36mm; 52.7 cm^2 (60.6%)
Rear: RB4L2 32x34mm; 34.2 cm^2 (39.4%)
Total Area: 86.9 cm^2

As illustrated above, RB calipers use standard FMSI pad shape, they are same as Corvette ZR1 / Camaro Z28 or GTR in front and rear, so they can provide you the widest choice in pad suppliers and compounds which means low cost too.

Front pad:
ChevyCorvette/Z28: D1395
Nissan GTR: D1382

Rear pad:
ChevyCorvette/Z28: D1165
Nissan GTR: D1383

Chevy and GTR pads are same length and compatible to our calipers, the difference is the pad depth: ZR1 is 88mm vs. GTR 65mm. But we prefer 78mm (GT3 is 74mm) which is similar to the late models for Viper G6, Mustang GT350, and Camaro G6 ZL1 etc.