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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,447
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'79 930 - Brake refresh in progress
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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Registered User
Join Date: Sep 2002
Location: Johns Creek, GA
Posts: 1,358
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timely post for me as i may be doing the same thing soon. regarding the pad wear, i had the same thing on another car a while ago. the caliper/piston looked fine so i just stroked it a few times, cleaned everything well and made sure the pads were seated properly. the new rotors yo uare puitting, on,arethey ready to install out of the box orr ned some >prework"?
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Charles 79 930 #632 88 911 Cab 74 TR6 88 CRX Si |
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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,447
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Charles,
The VCI rotors will bolt up to the "floater rings" just like the factory ones.
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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Smart quod bastardus
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Typically when a rotor is resurfaced they remove from 0.010-0.020 inches per side to clean up the surface and insure flatness again. It really depends upon how badly the surface was gouged and warped. Assuming they removed 0.010 inch per side then you reduced thickness by 0.5mm or 0.020inches which puts you pretty close to the wear limit on the front rotors.
Plus you need to check to see how bad the cracking is between the vent holes in the stock rotors. Once they connect between adjacent holes or especially to the outside rotor diameter surface they are finished. This did mine in before they wore too thin. I asked for it with all the track days I was doing, not looking for excuses. The VCI are nice. Slotted is a better approach to longevity. And I reused my lock tabs....seen no reason not too if they still bent around the nuts. What are you using to lube the mounting tabs on the floating hub when you reattach the rotor? Uneven pad wear is hard to avoid, but theoretically should not happen, cycling the pistons will definitely help things. Do you know if they sell rebuild kits for the 930 calipers (ie seals and what would be a dust boot)? I have not seen it on Pelican.
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max ---"When you're racing it's life! Anything else either before or after, is just waiting" Last edited by fredmeister; 03-14-2011 at 11:41 AM.. |
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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,447
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Are you supposed to lube? I would think putting lube there would be a bad idea...it could get on the rotors. Also it would attract a lot of dust/dirt to build up so that eventually they would stop floating properly, no?
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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Smart quod bastardus
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Quote:
Also make sure to remove the dust shields while you are in there. They prevent cooling air from getting to the rotors and if you do any DE or track events removing these makes a big difference in cooling the rotors. Do you know if they sell rebuild kits for the 930 calipers (ie seals and what would be a dust boot)? I have not seen it on Pelican.
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max ---"When you're racing it's life! Anything else either before or after, is just waiting" |
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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,447
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I don't know. You could call if you can't find it on the website...I'm sure you can order the individual parts.
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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Registered User
Join Date: Mar 2006
Location: Metro DC
Posts: 5,394
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Available through the dealer network.. that's where I've bought them in the past.
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RGruppe #180 So many cars.. so little time!! |
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Smart quod bastardus
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thanks for the info.
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max ---"When you're racing it's life! Anything else either before or after, is just waiting" |
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PorscheMoparLiterbike
Join Date: May 2010
Location: up and down the east coast
Posts: 133
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Reading the thread reminded me of some good technical white paper/articles on the Stoptech website.
No affiliation. StopTech : Balanced Brake Upgrades
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88 930 BnB Kinesis tial 1bar k27/29, MSD Turbokraft IC,sc cams, KEP |
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Tinkering Pays!!
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I got mine from auto atlanta
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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,447
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update - mission accomplished
In typical fashion, the job took a few twists and turns but its done and the car is stopping with greater authority than it accelerates.
First off, I went to mount up the VCI rotors and found that they were just a little too thick in the center section where they bolt up to the hats. Just thick enough that they would not float properly. VCI offered to have them machined to correct the issue, but I decided to return them (VCI refunded my $ and were very good to deal with). The guy at VCI also provided me with some very important info about these 917 style floating rotors which I haven't seen anywhere else (wanted to acknowledge this, good service). I was able to source OEM Zimmermans for $249 a side, which is a very good price. ![]() The important info I learned is this. When you assemble the hats and rotors, the lip side on the ring (see photo below) should be facing up (not against the rotor) ![]() The bevel side of the ring should be face-down (against the rotor) ![]() It almost looks backwards (and mine were assembled lip side down when I pulled them apart). Apparently with the lip side down, the rotors will not float. According to Doug at VCI, this 'feature' allows you to fix the rotors for turning on a lathe, or just if you don't want them to float. Anyhow, once properly assembled on the hub, the rotors do float noticeably and make a racket when you spin them. ![]() Fresh rotors on the rear ![]() All back together now and the brakes are sweet!
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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Registered Driver
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I have some replacement Zimmermans on the way and does anyone know the benfit of floating vs fixed (ie having the lip side up or down like Jacob mentioned.)
Does anyone know the torque value for the bolts and does anyone know if you can still buy the lock-tabs and what the part # is?
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Ben '85 930 - Black on Black '95 993 Turbo - Silver |
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Registered User
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Quote:
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John- I blame and thank the longhood boys of Austin -84 911 Carrera w/ 930 t/p,efi'd,dizzy free,HFS turbo, 78 930 RoW no option sunroof coupe, 64 Corvette roadster, 71 911T, 73 911E, 67 Bronco survivor. 71 FJ40, 95 M3 (for sale) "Illegitimi non carborundum" |
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Registered User
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does Zimmerman make gas slotted front floating rotors?
thanks
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"IGNITION LEFT OF STEERING" Alex |
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Registered User
Join Date: Jan 2012
Location: Colorado
Posts: 2,870
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I have 930 rotors and brakes on my 911S, very similar to your set up. Early on, I had significant problems with a pulsating brake feel, to the point there was significant fore/aft motion felt in the cockpit.
Had the rotors checked for runout, disassembled the whole thing a few times without material improvement. Finally one of the old mechanics at the Porsche dealer felt that I may be getting some pad build up on them as I was (typically) using the brakes lightly in traffic. He suggested serious and very hard braking in a set, enough to get everything good and hot and then let the pads do the cleaning as it were (I had tried different sets - Pagid to the current Mintex). Well, hallelujah, it worked....so whilst I would not suggest that is your problem, just for guys who have the cross drilled rotors, if you unexpectedly get pulsing - it may be resins bonding rather than a warp in the actual disc. This was supported by an article published by Stop Tech (not sure if they are around anymore) that gave detailed analysis of causes and remedies for pulsing brakes. Dennis |
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Registered User
Join Date: Oct 2009
Posts: 567
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is there not some who have an assembly drawing so we can see how the disc with lip must face, because I'm not sure that the lip facing away from the brake disc to be liquid.
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Registered User
Join Date: Jul 2006
Location: San Diego, CA
Posts: 94
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This is surprising. I had no idea that the ring is supposed to be mounted with the lip away from the rotor. Mine was originally mounted with the lip down against the rotor, and thats the way I have always assemled them too.
Is this worry about your thick center section, and clamping with lip towards the disk and thus making the disk non-floating a real problem? Isn't the forces involved, when the disk heats up and expand, great enough to overcome tha clamping force of the bolts? I had to replace the original hats with a hat and ring set with T-locks from VCI. Mine were badly corroded (steel bolts in alu hats provide a good ground for corrosion) , and some of the square tabs had fallen off. I went from quiet brakes to very noisy since these hats provide more float. I thought maybe I could grind down the T-locks a little bit to provide less play for the disk. As for lubing, I used copper spray to try and quiet them down, and reduce friction, but they are just as noisy. Maybe copper paste? ![]() ![]() ![]()
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Arnljot 1980 930 GT35R, TurboKraft IC, 965 P&C, 964 Cams, Tial WG, ported heads, BLWUR, RarlyL8 hdrs&mfflr, Zeitronix logger & wideband 1989 928GT 1972 BMW 3.0S |
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beancounter
Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,447
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I think that's a great question. I tend to agree that the rotor should probably still be able to expand and contract separate from the hat, despite the clamping force. Since the hat is aluminum, you'd expect it. I suppose it might be more of a "semi floating" with the lip side down, as opposed to "full floating" with the lip side up. Cast iron floating discs that were standard on some of the Ducati motorcycles I used to play with were noisy like these 930 set ups. Regardless, next time I am messing with my 930 rotors, I will be flipping the backing plate over to quiet them down...it's almost unbearably noisy going down the road.
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Jacob Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690 Past: 2009 997 Turbo Cab / 1979 930 |
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