Possibly very stupid first post - Brakes

[bengie]

oh yes. they are greener than a green thing from greensville. And look HUGE! Parked next to a 106 gti on Sunday and wonder how the hell he ever stops! They are snug though had my wheels had a double thickness of balancing weights i don't think they would have gone on!

Pics and a freedom car thread to follow once it dries up and i can get some pics taken!

because they weigh about 4ton less

[bengie]

Oh, and BTW, in answer to a previous query regarding the need for calipers AND carriers, Ross's pictorial shows the reason clearly!

i can see the difference but i and a few others might not understand the implications of the difference.

[ap0gee1978]

i can see the difference but i and a few others might not understand the implications of the difference.

Hopefully this image will make things a little clearer, as the caliper and the carrier are different colours:

These calipers - in common with both the 288 and 312mm ones are of the 'floating' type, which means the piston(s) is/are only on one side, one end of which is/are attached to the inboard pad, and the other of which is/are attached to the outboard pad, by merit of the caliper (the grey part) reaching from one side of the disc to the other. (NB: both the 288 and 312mm VAG calipers are one-pot, and the picture's of a two-pot, but it makes no difference as regards the way they work - the picture did me nicely as the significant parts are different colours...)

So when you apply the brakes, what happens first of all is that the inboard pad (which is attached to the piston slider(s)) is pushed towards the disc. One it's in contact with the disc, it can't go anywhere, and so further pressure causes the piston to continue extending, but since the slider(s) can't extend anymore, the cylinder moves AWAY from the disc against one or more springs between it and the carrier (the gold part, which is attached to the hub and therefore the rest of the car). Since the cylinder(s) is/are attached to the outboard pad, this brings the outboard pad into contact with the disc, and from this point on, further pressure causes both pads to exert extra pressure on the disc. What this means, of course, is that the caliper needs to be free to move relative to the carrier, but must also be attached firmly, and so the caliper sits on rails in the carrier. Therefore, unless the caliper matches the carrier, the system won't work.

HTH

On a functional level, I have now got to grips with my (OEM discs and pads) 312s, and what I would say is that they probably don't offer any greater (initial) stopping than uprated pads on OEM 288mm discs, but being bigger they are practically fade-free. It took me two or three times as many hard stops to get them up to temperature as it did when I was bedding in my old brakes, and even then, they were braking positively and consistently. What was noticeable, in fact, was that the REARS were bedded-in before the fronts. So despite the fronts providing the lion's share of the braking effort, they weren't being working anything like as hard as the rears. This was what I hoped, as the Mintex Extremes I used to have ate through my discs like the Very Hungry Caterpillar, and I wanted better longevity without reducing the brake performance.

So in summary, I would say (subjectively!) that uprated 288mm pads will allow you to brake as hard as if you had 312mm, just not repeatedly!