What's the real purpose of brake dust shields?
05-12-2011, 09:04 AM
#46
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I've always thought that explanation sounded the most logical ... but .. as the air is pushed in that general direction only, and not directed through a sealed duct to that point, I wonder if there would be any practical difference in air 'pumping' by the rotor ... with and without the shield.
Maybe the shield stops that side of the rotor from being cooled more than the outside, which doesn't get the same airflow towards it, and ensures that cooling is predominantly from air pumped through the rotor vanes, and therefore you get inner and outer disc temps more even (less chance of warping and cracking).
I might give my GTS a good flogging and take some IR images to see what happens to the inside and outside of rotors thermally. When I get my 82 with S4 brakes (no shields) on the road again I'll do the same.
Maybe the shield stops that side of the rotor from being cooled more than the outside, which doesn't get the same airflow towards it, and ensures that cooling is predominantly from air pumped through the rotor vanes, and therefore you get inner and outer disc temps more even (less chance of warping and cracking).
I might give my GTS a good flogging and take some IR images to see what happens to the inside and outside of rotors thermally. When I get my 82 with S4 brakes (no shields) on the road again I'll do the same.
I suspect there is more danger in the "gotta get out of the car quick and IR the front rotors quick" operation than there is in getting the rotors hot in the first instance.
I've been driving my 88SE without front disk shields for about 7 years - the brakes are still better than the 90GT brakes with shields. I don't think I've ever got them hot enough to actually test my theory, and I'm unlikely to do so until I get either car on a track as my last brush with vaguely having to test the brakes cost me 700AUD in fines and 1000 AUD in solicitors fees to avoid loosing my licence.
With hindsight I should have really tested the brakes as I could have sued the NSW police for whiplash injuries had I braked to stop when confronted with blue flashing lights behind me. It was only the knowledge that new S4 rear PUs are no longer available that prevented a rapid stop.
05-12-2011, 10:27 AM
#49
Rennlist Member
Dave
I suspect there is more danger in the "gotta get out of the car quick and IR the front rotors quick" operation than there is in getting the rotors hot in the first instance.
I've been driving my 88SE without front disk shields for about 7 years - the brakes are still better than the 90GT brakes with shields. I don't think I've ever got them hot enough to actually test my theory, and I'm unlikely to do so until I get either car on a track as my last brush with vaguely having to test the brakes cost me 700AUD in fines and 1000 AUD in solicitors fees to avoid loosing my licence.
With hindsight I should have really tested the brakes as I could have sued the NSW police for whiplash injuries had I braked to stop when confronted with blue flashing lights behind me. It was only the knowledge that new S4 rear PUs are no longer available that prevented a rapid stop.
I suspect there is more danger in the "gotta get out of the car quick and IR the front rotors quick" operation than there is in getting the rotors hot in the first instance.
I've been driving my 88SE without front disk shields for about 7 years - the brakes are still better than the 90GT brakes with shields. I don't think I've ever got them hot enough to actually test my theory, and I'm unlikely to do so until I get either car on a track as my last brush with vaguely having to test the brakes cost me 700AUD in fines and 1000 AUD in solicitors fees to avoid loosing my licence.
With hindsight I should have really tested the brakes as I could have sued the NSW police for whiplash injuries had I braked to stop when confronted with blue flashing lights behind me. It was only the knowledge that new S4 rear PUs are no longer available that prevented a rapid stop.
... would have been worth it to hit the anchors just to see the 
expressions on their faces in the rear vision mirror ... and to hear their explanation as to why they couldn't stop in time.I had a similar experience a very long time ago. Blue flashing lights on my tail ... knew I could become airborne over a railway crossing and do a perfect four wheel touchdown ... knew they couldn't ... maintained speed ... they both hit the roof and sparks flew on touch down. Got booked ... but I'll always remember the water leaking from the front of their car, the indignant look on their faces, and the synchronised head rubbing when they got out to book me ... which made it almost but not quite worth it.
05-12-2011, 11:01 AM
#51
Rennlist Member
05-12-2011, 11:25 AM
#52
Rennlist Member
