Re: E60 Brake caliper caping
Dude, it's not about the cost...
The covers are usually made of plastic, which tends to melt at high temperature.
Even during daily driving, brake components are subjected to a lot of heat stress, which is why none of the essential brake parts like calipers and discs are not made of plastic.
If the cover melts and fuse to your calipers, it might be messy when you need to need to change remove the calipers to change your brake pads.
In the worst case scenario, something hard (like a stone) gets wedged between the calipers and your rims when you are driving at speed, causing the plastic to 'explode' into little bits of shrapnel, slicing your brake line, causing catastrophic brake failure.
Not frightening you - it has happened before. Go google it...
The calipers also need to cool down quickly after heating up during braking (otherwise your brake fluid will start to heat up until it starts to boil - very bad news), so that it can work effectively the next time you need to slow down. How is it going to cool down if you cover it with a piece of plastic?
If you can't stretch your budget to aftermarket calipers, don't mess with your stock brakes.