As subject really. Is all this stuff about grooved discs actually true? Or just marketing bull?

Reason I ask.... discs for my tin-top project are £35 for an OEM set, or £135 for a 'performance' grooved set from EBC.

Is it actually worth spending the extra £100 or do they just look nice?

Chris

Yes, they wear down your brake pads quicker

I think the general consensus is that for a 7 they're not necessary.....

Cross-drilled are definately a bad idea as they just produce areas for cracks to appear....

Bit of both I reckon. They do perform better than standard equipment and you're also paying for the machining and labour costs. There is a premium to pay for the bling factor though.

There are alternatives cheaper than EBC. Try CRN performance on e-bay. They buy OEM stuff and machine the grooves themselves and are usually slightly cheaper than most.

Phil

[Edited on 6-5-08 by Hellfire]

Put one of each type on either side of the car and see if it pulls to one side under braking?

Mike

Clears the dust a bit easier....

TBH, unless the tintop is heavily modded (power-wise) I doubt very much that you will see a great deal of difference........IMHO of course!

Fozzie

BTW.....'we' (work-wise )would not go EBC.... (IOE) for owt..........

Has any manufacturer ever fitted them where they couldn't be seen?

you are probably better to invest in some pads which will stop you faster,say like the pagids.Run these on an elise 160 and its like hitting a wall braking from speed

Why are drilled disks a bad idea ?

Seems to be some bad press about drilled disks.

Drilled and grooved disks are made for a reason namely to help with cooling and to help stop the pads glazing ( which is why there eat pads )

Just interested in peoples views...

quote:

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Originally posted by short track 123
Why are drilled disks a bad idea ?

Seems to be some bad press about drilled disks.

Drilled and grooved disks are made for a reason namely to help with cooling and to help stop the pads glazing ( which is why there eat pads )

Just interested in peoples views...

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I don't know about the dust clearance, but the cooling effect of slots or holes must be virtually zero. There's no way there could be a cooling flow of air though a series of small holes, less through the slots, and the increase in surface area is negligible.

John

BTW, Chris, did you get my U2U?

I used to work in one of the major OEM's that made thousands of discs per day.
Drilled/cut discs need to be done professionally or they can be lethal. Do not buy from third parties who drill/cut discs without proper crack detection facilites. We used to use magnetic field and die penetrant, which show up cracks not visible with the naked eye. The machining stresses even from simple holes can set up microscopic cracks which can be disaster. DO NOT DIY !!!!

[Edited on 6/5/08 by clanger]

quote:

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Originally posted by short track 123
Drilled and grooved disks are made for a reason

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in my opinion, drilled and groved both reduce the surface area that is in contact with the pad, which would make them less effective.

This was backed up when a friend of mine changed the discs on his R21 Turbo from drilled and groved to plain. His brakes were drastically improved - ok, the new pads go some way to improve this.

I also think that the groves dont let the pads fully bed in as they are always being resurfaced.

mhh i cant totally agree..

you will need to compare more situations...
what happens when there is water between the pad and the disk????

or snow???

i think they look nice and they work better... saying that they are more expensive and eat pads...

bike discs are also drilled... there must be a reason for it.. i think its for antiglazing..

Tks

quote:

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Originally posted by tks

bike discs are also drilled... there must be a reason for it.. i think its for antiglazing..

Tks

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Cooling effect with drilled discs is not about the flow of cool air. It allows the air to expand into the pocket ( the drilled hole )

quote:

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(That was not meant to be an attack, im just pointing out that just because the manufacturers claim it, it doesn’t necessarily make it true)

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Drilled and or grooved discs are there to help with cooling the discs and indirectly caliper and deglazing of pads. they do not help the car to brake any better as they do have less surface area in which the pads use to apply the brake force.
They do however keep the brakes cooler under more extreme circumstance.

most supercars i.e porsche, ferrari, Lambo and nearly all race cars used some sort of drilled, grooved or otherwise discs for their cars so there has so be some merit in them.

if you are only planning on steady road use you will not need them in a seven type car. If you are planning to use for trackdays and racing then i would recommend you get them.

thats just my twopence worth!!

[Edited on 6/5/08 by skydivepaul]

quote:

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Originally posted by mr henderson2
I don't know about the dust clearance..........

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The holes are to reduce a gas build up between the pad and disc. Some of the new better ones dont drill all the way and others a chamfered to prevent cracks.
Grooves get rid of water and help de-glaze the pads.

My 2pence worth!

I work with very experience vehicle braking consultants who do work for major OEMs and I once asked whether such things actually did anything.... I think the response was laughter.

They knew of only one situation where I think it was grooves were used on a production car for reasons other than aesthetics. Even then it was because it solved one very specific problem.

These guys have specified/designed/developed/tested enough brake systems that i wouldn't disagree with them.

Brake disks can be designed to be drilled, with extra metal around the holes to reduce stress concentration, but many of the cheap ones are standard disks with holes in them that will inevitably develop cracks.

AFAICT the silly grooves just make an annoying noise under braking, chew up pads and cost more. I'm certainly putting standard disks back on my tintop when the current grooved ones are worn out. Horrible things.

I wouldn't even CONSIDER using drilled or grooved discs that weren't OEM. If you find them cheap, they're most probably dangerous, or at least prone to early and catastrophic failure. OEM brakes, if grooved or cross drilled, are designed and manufactured to be that way, and all the engineering that goes into them can't be duplicated by somebody in Taiwan with a felt marker and a drill press (most probably how the cheap discs originate). There are many things to consider...the metallurgy, cooling/gas and water dissipation, hole/groove pattern effectiveness, etc. Stay away from anything not OEM!!

Where do OEM get there parts made ?

I have seen ( more that once ) OEM disc cracking and not just surface cracks.

Just think about the amount of recalls.

jason

Another Race Car part that simply is for looks on a street car.

Grooves and drilled holes are not there for additional cooling. They are there to help vent gasses that tend to outgas when pads are heated to extreme temps, such as when you are attempting to slow your car from 200mph at the end of the Mulsanne Straight or entering Turn 3 at Talledega.

These gasses can prevent full contact of the pad with the rotor just like air holds a hovercraft off the ground. The slots and/or drilled holes give the gasses a way to vent out.

But that situation rarely occurs on most cars. Probably almost never on a Locost. You'd be able to see the smoke from the pads and rotors.

holes in discs.

firstly this will reduce the mass (less unsprung weight is never bad) so the disc will run hotter.

It does increase surface area but I would say that discs cool by convection - heat transferred to air - rather than radiation.

When running at speed, I doubt a lot of air will be able to flow through the holes so they aren't adding much in way of additional cooling, in fact since the side surface area is smaller, they may in fact be worse.

Surely a disc with cross section like an I - so it presents a large front surface area, like a drum, would be more effective at cooling in the air stream?

quote:

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Originally posted by 02GF74

It does increase surface area

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Lucas Cymbran AFSAIK used to make Heavy Duty Braking Systems.

Holes in a single vain rotor - as they are known, is a safer bet and is provided for de-gassing therefore reducing the glazing effect. The same goes for grooves.

Vented rotors are a different game as the holes and grooves nneed to be aligned - you wouldn't want to drill or groove the actual joint pad.

Any modification of the rotor surface (by drilling/grooving) is actually focusing heat to the sharpest edge - the result is thermal cracking. This will reduce the life of the rotor and will require replacing more often.

95% of OEM brake disc's are now manufactured in China and India. They are bought; finished machined, for approximately £5 each - anything more than that and its all profit.

To increase braking power effectively you need to increase surface area. IIRC the Bently disc's (340mm diameter) and calipers to suit (from aluminium billet) are produced in Willenhall (Birmingham) and cost a bit more.

So to summarise - yes drilled holes/grooves do have an effect but it reduces life by 30-50% whilst the gains are minimal - it's mainly for aesthetics.

Steve

[Edited on 8-5-08 by Hellfire]

quote:

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[I]Originally posted by saigonij[/I]
I also think that the groves don’t let the pads fully bed in as they are always being resurfaced.

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Thanks for your replies so far everyone, and sorry for forgetting to come back and reply!

For info, this is for a tin-top project. It's running getting on for 2x standard horsepower, runs Wilwood Dynalite 4-pots on the front with 285mm discs, and Sierra rears on the back. Use is mainly what I call fast road - ie it gets taken out for a thrash and driven hard, not taken shopping or anything like that. It does get the odd bit of track time when I feel in the mood, but it's not a regular occurance.

Not sure if that changes anyone's opinion??

At the moment, I'm still thinking that I'll go for the grooved ones, but mainly as an aesthetic thing. Let's face it, I spent a fortune on fitting rear discs which do 2/3rds of nothing, so I should make the front look good too!


Chris

Both drilled and grooved disk have one advantage --- the improve the initial brake response in wet weather.

In for example very wet motorway running the disc picks up a coating of slime off the motorway. In these conditions on initial application of the brake it takes heart stopping a fraction of a second for the brake pads to bite.

If the discs are drilled the holes should be properly finished --- counter sunk to soften the edges and properly de-ragged.

Grooved discs are really dodgey an open invitation for the disc to fracture.