38 replies to this topic

[MRA]

Ok thanks you guys lots of different opinions here, these were fitted opposite to to the photo by Green and White mini spares a few years back, I would have though they would certainly know which way to put them but ill get all the info from kad on Monday.

On saying this I have noticed the pads chipping away slightly but never really thought much of it!

Then what is the above statement meant to mean ?

[MIGLIACARS]

Yes on the very edges of the pads <not all the way around> there is some chipping but its very slight. I think I have some old pads some were I could photo and upload if it helps.

But why would I change a 7 year good thing. Plus pads do not last long anyway. Its not like you get 3000 miles from them.

[MRA]

Maybe you shouldn't...... However I was pretty sure racing was all about small improvements that allow youto win or get better positions anyway !

Ok ask yourself, if the chipping is not important then what is actually happening ? There is a sudden shock loading on the groove edge, now as small as that may be it is still not wanted and potentially dangerous, who's to say that 7 years and 7 days the disc isn't suddenly going to fracture ? It may not, however the type and mode of forces applied make it more likely to fail.

The bottom line is, w eare not talking about the difference between blue neons and green neon lights we are discussing safety, your first comment was about caliper distortion as you push the pedal.......

When we design a rotor the grooves are at a designated sweep angle to present a uniform slicing action, this is designed to minimise the shock loading on the disc brake assembly, the curve allows a change in angle presented that reduces vibration, a straight line in theory is a more uniform slicing angle but being constant induces and maintains a harmful harmonic into the equation.

[Wil_h]

As far as I can tell, grooves are a fashon item. Most are ground out purely for asthetics and have no testing data showing any advantage to having them.

so what you get is a fashionable brake disk, that is slightly lighter and has less surface area. Any benefits regarding cleaning the face are surely fanciful, the disk face and pad face have a prety severe time. What exactly is glazing that's always mentioned when talking about grooves? I tell you what it is, made up to sell you fancy disks.

The only clear thing that I could thing that groves could do is clear water quicker. Maybe useful for a rally car, but on a track?

P.S. I have 6 groove disks with the grooves facing forwards as instructed by the manufacturer, I notice no more 'chipping' on pads with these disks than any other. Pads chip, it is the nature of their construction and use.

[MRA]

No the grooves will remove water, but their primary role is to remove the thin layer of glaze that you get on the pads.

When you say facing forwards do you mean convex forwards ? As this is correct

[Wil_h]

No the grooves will remove water, but their primary role is to remove the thin layer of glaze that you get on the pads.

When you say facing forwards do you mean convex forwards ? As this is correct

I just don't buy the glaze issue. what is glaze? And how exactly does the groove get rid of it? Basically, a pad is being constantly wiped by the disk, which should be constantly wearing the pad, how a groove does anything extra to the pad to remove a specific layer is beyond me. It's BS.

The disks I have, have the groove further ahead at the outside edge of the disk.

The manufacturer of the disks also did a multiple groove disk (20+ grooves) theses were specified to run in the opposite direction.

[tiger99]

There is a mixture of good stuff, guesswork, supposition and utter nonsense here. One thing is CERTAIN, if you want the grooves to provide airflow at the disc/pad interface, the outer ends of the grooves MUST face backwards, i.e. the convex side of the curve is forwards. You cannot change the laws of physics, so that is how it must be. The same used to apply to the vented discs, they were handed, and it was very important that they were fitted correctly, as if they were wrong, the outer ends would be trying to scoop in air, in opposition to the air ejected by centrifugal force, so there would be hardly any airflow and probably serious overheating. They changed to straight vents to avoid the problem, and lost some small amount of air flow as a result, which is a better situiation to be in than having half of the cars fitted with discs that were useless due to being fitted backwards.

I would follow the same reasoning for the grooves, as they do need to eject dust and debris which will only happen effectively with the outer ends facing backwards. They will tend to clog if they are the other way round, because there will be little or no air flow.

[MIGLIACARS]

Ok I think I have opened a can of worms here.
I think we may be arguing the same point, maybe, so here is a photo of how my brake were and are know, as instructed by the manufacturer.

Edited by MIGLIACARS, 11 February 2013 - 07:42 PM.

[The Principal]

AP Racing used to have a good support section on their website explaining the difference between forward and backward facing grooves, unfortunately they have changed the site and this seeems to be the only reference -

Curved grooves,
(backward facing, running out on outside diameter to clear debris.
Only used on thick wall discs).
Digit specifies number of grooves per face.

source - http://www.apracing....9&ProductID=976