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Registered
Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
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Blocking plate for front hub cooling duct
1)I am changing front rotors. For ducted air brake cooling (SCs need this if tracked), this involves installing blocking plates so the brake cooling air blown into the center of the rotor can't just escape past the spokes of the hub. Alas, my car is in the trailer sitting on the hatch which contains my spare hubs, and I can't get the rig home until mid-next-week. But I cut some plates, just to be ready. The dimension I don't have is the OD of the center of the hub. The plates have to have that circle cut out of them so they will fit over the hub.
 Does anyone have a hub sitting around, and could give me the measurement I need to cut out the center? Based on the Cool Brake kit I purchased in the late 1980s, I have always cut out holes for the five 13mm wrench bolt heads which hold the rotor to the hub, so none of this thin plate is involved with fastening the rotor to the hub. And pop riveted the thin aluminum plate to the rotor. But I can save some work if I install the plate like a washer, using the bolts to keep it in place. I am wondering if, despite proper torque, the thin aluminum over time might compress more, allowing the rotor to wobble, so to speak. I don't think it will. Anyone tried this? |
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07-05-2019, 10:00 PM
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Registered
Join Date: Feb 2009
Location: Park Hills, KY
Posts: 2,459
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I have the hubs off of my 78 SC. will check when at the shop today.
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Bob Cox 78 930 clone project car. 87 924S resurrect at some point. 84 928S, Ruby Red linen/brown interior - sold  86 944 turbo my new DE/track car - sold
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07-06-2019, 05:59 AM
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Join Date: Apr 2011
Location: behind the redwood curtain, (humboldt county) california
Posts: 1,433
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I am chasing a hub run out problem and have the plates off of my disc/hub.
Later today, when I get back from work, I will trace the pattern and drop it in the mail if you pm me your address. The hub projects beyond the inside mounting face of the disc, so it must cut to clear those bumps. I don't think a plate with a hole in the middle of it will fly. Drop the disc on the hub and you will see what I mean. Chris Last edited by chrismorse; 07-06-2019 at 07:30 AM.. |
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07-06-2019, 07:24 AM
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Caveman Hammer Mechanic
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Pretty sure using the aluminum as a washer will cause problems:
https://link.springer.com/article/10.1007/BF00648157 https://www.quora.com/What-is-the-maximum-temperature-the-disc-brake-can-reach
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1984 Carrera El Chupacabra 1974 Toyota FJ40 Turbo Diesel "Easy, easy, this car is just the right amount of chitty" "America is all about speed. Hot,nasty, bad ass speed." Eleanor Roosevelt, 1936 |
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07-06-2019, 07:34 AM
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I am my 911's PO
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1978 SC - original owner 1983 SC - D stock "rescue" track car DECEASED 2015 Cayenne Diesel (rear ended by distracted driver) 2017 Macan (happy wife...) 2016 Cayenne Turbo - tow vehicle and daily drive |
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07-06-2019, 07:56 AM
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Registered
Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
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Thanks, guys
I've been successful in installing these plates without sculpting them. They raise up some over the spokes, but covering the openings is all they need to do, and I am using pretty thin stock, which is malleable. Sometimes I have put some RTV (which didn't burn up) around the inner joint for a slightly better seal, though this isn't like keeping leaks away from the CIS intake or the like. I can see 78SC's were installed washer style, and from their appearance (used)nothing bad happened. SRP product? |
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07-06-2019, 12:33 PM
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I am my 911's PO
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Quote:
I had these on my '78 SC for 5 years running DEs up until I got a dedicated track car, and yes, no ill effects. I removed them as part of my campaign to restore the car to pure stock. Steve |
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07-06-2019, 12:58 PM
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street car
tow vehicle
track car
