we must have had on of these threads before but i'm asking, people say that drilled discs crack,well i've got grooved and they've worn down, so what does it matter in real life everyday cossie use.......pro's n cons peeps....cheers Pete

 

my ap330mm are drilled and they are cracked like f**k round the holes....

More money i need to spend .....

Be putting grooved only ones on next...

 

Just grooved should see you alright mate.

PS FOR OTHERS GOING TO ADVISE!!!! Pete drives like a cunt every time he is in it.

 

They are likely to crack way before you would've worn grooves down.

 

They will crack, grooved are better for road use as they stop pad glaze. If you do use drilled discs, make sure you clean them out every couple of weeks or even more often, they crack due to heat and cooling cycles, and if the holes are full of brake dust, the discs cool down and the pad dust hardens to the point that as the disc contracts as it cools, it cannot compress the build up of dust in the hole anymore and is forced to crack!

 

as above if you look at any of the wrc cars you will see all discs are grooved

 

sound...........more grooved it is

 

they say drilled are better for racing but have no life as they crack, i run fishhook groves

 

Drilled ones should be counter sunk to prevent cracking. I've not had experience with them really so I don't know how much of a difference it makes.

Grooves are better for letting out the bad gasses and improving surface contact. Drilled are to improve cooling.

Fish-hook slots are the best I believe.

I can't say I've checked my wilwood drilled and grooved discs for cracks ever, but I'll have a look at them next time the wheels are off.

JAmes.

 

Drilled will crack,m but it's nothing to do with brake dust doing it, it is bcause of the different rates of expansion of different thickness metal, that's why the cracks always start at the thinnest part in the bottom of the hole, same as pads cracking is not a fault.
Mosty of the brake dust is resin used to bond the various mixes together on the pad plate, if it were hard enough to crack discs, do you really think you would simply wash it off when the wheels are dirty with brake dust.
Any surface that is not uniform and heated will develop weak spots, as some areas by defintion are not as strong as others.
As to how much cracking is acceptable is up to debate, I've had discs split on vented/solid drilled grooved etc before now, these are replaced, but cracks around the holes, usually means you would benefit from larger discs.
Porsch put shed loads of holes in their discs as do other performance cars, interestingly Porsche are NOT countersunk.
tabetha