roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Backwards Brake Rotors ?
Seems many TV wonder build car programs, (Chip Foose/etc), and the installation stickers, left/right, (Full Stop brand brakes), have the vented, cross drilled and slotted rotors on "backwards" ? This seems to be in conflict as to what I was taught in college. The vented rotor should work similar to a centrifugal fan. Air or water is drawn in near the center and pumped outward with centrifugal force. Seems to me the angular slots on rotors should have a squegee effect , to shear water outward, with aid of centrifugal force. Comments ? roverman.
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Backwards Brake Rotors ?
This is generally true but if you look at squirrel cage blowers (and some water pump impellers oddly enough) you will sometimes see the reverse practice. Why, I don't know. Noise maybe?
Jim |
avbates Tony Bates San Jose California (25 posts) Registered: 03/22/2008 12:16PM Main British Car: 74 MGB roadster 4.2 litre Rover |
Re: Backwards Brake Rotors ?
When I have install slotted rotors I have always installed them so they "draw" the air in towards the middle
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Backwards Brake Rotors ?
I'm not sure that makes sense Tony. Centrifugal force will always push any spinning element to the outside so you are attempting to fight centrifugal force. Brake ducting always goes to the center of the rotor and flow is from the center out. Pump flow is always from the center out, fan flow is also always from the center out.
Granted the rotors aren't turning that fast, but even a few hundred rpm is enough to move some air. I suspect that the centrifugal force is greater than can be overcome by the angle of the vanes (I've seen vaccum cleaner blowers with the vanes facing the "wrong" way.) but it would seem to me like the vanes should be angled to assist rather than retard the air movement. Jim |
roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Re: Backwards Brake Rotors ?
Jim and clan, In contrast to sound theory, my Huffaker GT 1 TR8, has the front rotors installed "backwards". The rotor diameter is relatively small, and there wasn't enough room , to get adequate air flow into the center of the rotor. To counter this , Huffaker put a large supply box around the outside of the rotor, with the curved vanes attemting to scoop air from it. Who am I to argue with Huffaker ? Onward, roverman.
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Backwards Brake Rotors ?
Do a test. Chuck the rotor up in a lathe and spin it both ways. See which way the wind blows. I think that will tell you what you want to know.
Jim |
302GT Larry Shimp (240 posts) Registered: 11/17/2007 01:13PM Main British Car: 1968 MGB GT Ford 302 crate engine |
Re: Backwards Brake Rotors ?
I have slotted rotors on my car and the arrows that were stamped on the rotors make the slots draw air into the center. I originally installed the rotors the other way around but after some use the arrows showed up very clearly so I reversed the rotors to avoid potentially embarrassing questions.
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MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: Backwards Brake Rotors ?
IMO, it is not critical which way the slots are. The most important issue for left/right is if using directional/curved/angled vanes. They should be oriented so that they seem to "lean" toward the back of the car.
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88v8 Ivor Duarte Gloucestershire UK (1041 posts) Registered: 02/11/2010 04:29AM Main British Car: 1974 Land Rover Lightweight V8 |
Re: Backwards Brake Rotors ?
Just to air my ignorance now discussion has ended, I thought the slots or dots or drillings were there primarily to break the gas cushion?
Ivor |
Orange Alpine Bill Blue (45 posts) Registered: 12/20/2010 07:36AM Main British Car: 1967 Sunbeam Alpine 2.5 Ford Duratec |
Re: Backwards Brake Rotors ?
The shape and orientation of vanes is done to fine tune air movement. IIRC, a "backward" vane will develop higher pressure, but lower volume, that a "forward" vane.
Bill |