Grooved Brake Disc Orientation

Gaijin · 22 Oct 2007 at 22:28

Was thinking about these today whilst drifting about on the AP website ( http://www.apracing.com/roadcar/brakekit/identification.htm ), and came across this:

Now unless i'm being dappy (to be honest i dont think their explanation is brilliant), this suggests that the grooves in discs should rotate so that the outer point of the groove hits the pad first, before the inner part of the groove.

I.e. (See awesome diagram below)

From what I can tell - AP say that B is right? Is that right?

Luke · 22 Oct 2007 at 22:33

B is correct.

Gaijin · 22 Oct 2007 at 22:41

Thanks for your reply - could you explain why?

Jonnycoupe · 22 Oct 2007 at 23:00

Depends on the manufacturer- afterall the rotation of curved vanes is far more important than the grooves.

Check the direction of curved vanes (if they are) pump air from the centre of the disk outwards.

Gaijin · 22 Oct 2007 at 23:09

How would you check that?

Say the discs are similar to these?

Dogbreath · 22 Oct 2007 at 23:38

Look into the edge of the disk at the vanes between the two friction surfaces.

Gaijin · 22 Oct 2007 at 23:43

Ah I think i'm with you now, was thinking the grooves and vanes were one and the same. Now I know different.

Oh well, you don't ask - you don't learn

needmorespeed · 23 Oct 2007 at 11:46

Surely they will only fit one way it's not as if you can turn them around :confused:

Confused · 23 Oct 2007 at 11:49

needmorespeed said:
Surely they will only fit one way it's not as if you can turn them around

As they're handed - you'd have one of each - so yes, you could put both on the wrong sides, so they'd be the wrong way.

needmorespeed · 23 Oct 2007 at 11:55

ConfusedTA said:
As they're handed - you'd have one of each - so yes, you could put both on the wrong sides, so they'd be the wrong way.

yeah good point so how do tell which way round they go as mine just have straight vanes

Jonnycoupe · 23 Oct 2007 at 12:36

needmorespeed said:
yeah good point so how do tell which way round they go as mine just have straight vanes

Doesnt really matter a huge amount.

I'd just check for a LH or RH marking

Dogbreath · 23 Oct 2007 at 12:44

needmorespeed said:
yeah good point so how do tell which way round they go as mine just have straight vanes

It really makes very little difference. AP shows the outer end of the slots leading, EBC's website shows the outer end trailing. If the purpose of the slot is to expel gasses, pad dust and water etc. then IMO the outer end of the slot should be trailing to be most effective, just like the vanes.

needmorespeed · 23 Oct 2007 at 14:54

Dogbreath said:
It really makes very little difference. AP shows the outer end of the slots leading, EBC's website shows the outer end trailing. If the purpose of the slot is to expel gasses, pad dust and water etc. then IMO the outer end of the slot should be trailing to be most effective, just like the vanes.

cool thanks