Great stuff Bill, as always!

I had some belief in another reason for backing plates on road cars was to minimize water splash onto hot rotors.

Naturally the backing plates on the open wheel racecars are to control airflow, essentially directing airflow where you need it precisely. There is also a aero drag reduction component as well.

 

front top is the ABS sensor and wire, bottom is the ball joint, both are pretty close to the 800* rotor


rear, top 2 ball joints for the upper control arms, rear ABS sensor and wire, bottom A-arm ball joint


I've been running w/o them too, also w/o issue that I know of, but have been feeling increasingly uncomfortable w/ how close these components are to the very hot rotors, heat sink when parking after a session is the big concern, so I'm putting the backing plates back on.

 

Like this?

 

Apples and oranges, but I yanked all four backing plates off my old car when I was building it up to install cooling ducts in front and aid in cooling for the rear. In the rain on the street I thought I felt a slight braking 'lag' which I concluded were wet/damp rotors (non-slotted/drilled in the back). I somehow managed to never have a rainy track day over my 3 years with that car so I don't know if it would be different with hot pads/rotors, but I also wondered about water splashing on extremely hot rotors being something to worry about (cracking, a significant temperature delta between inboard and outboard, etc). It could have been all in my head, but..

 

Hadn't thought of that, looks like I have some work to do....

Thanks Bill and Cupcar for bringing this to light.

 

Every factory disc brake equipped road cars since 1965 has these rotor shields. They are there to prevent water splash from acting as a lubricant on your brake pads, and secondary as a stone guard. Remember that the manufacturers have to design a car to handle all sorts of conditions. Particularly in the area of braking safety, no corners are cut, usually.
Now I suppose a list of cars will form here that came without shields.

 

No problems after 137,000 miles without them.
Quit a few track days also.

Kevin

 

great info,

now I know a little more.

Thanks

 

The plates are definitely there to prevent heat soak to the uprights and ball joints (CV joints). They have nothing to do with water or stones.

We removed my front uprights after 20 years of abuse (last few years without the backing plates) to upgrade to RS uprights. The old ball joints were "welded" into place due to the heat. Interestingly there was not damage at that time to the abs sensors. I believe it also accelerated the failure of a rear drive shaft CV which ran dry of grease recently.

You benefit from cooler brakes and less fade. But on teh track when pushed hard you may find accelerated wear of other components. Its the usual trade off. Speed/reality/cost you can never get a tick in all three boxes!

 

Thank you Bill - Chapter & verse.

A 993 forum topic at it's finest; The car.