Cheese Man Chris
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Registered: 25th Sep 07
Location: Leeds Drives:1.2 Merit
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Grooved or Drilled disc's usually represent preformance cars i.e Porsche
I belive the idea behind them is to create a higher surface area to transfer heat to the air around them.
HOWEVER, the alternative argument:
Solid (//Vented) discs have a greater volume allowing them to absorb more heat into the metal and also they have more metal in contact with the pad consiquently giving better stopping power.
What are peoples personal thoughts on this? Which is better?
Any body know any articles or books on the issue?
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BarnshaW
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Registered: 25th Oct 06
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if drilled or grooved were not as good they would not have them on cars such as M3's , mercedes AMG's. porsches, RS audi's etc.
drilled is supposed to disperse heat better and grooves to disperse water better
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alan-g-w
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Registered: 9th Nov 07
Location: Glasgow
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Where are you getting your facts?
As in - how do drilled or grooved discs have a larger surface area? They have less surface area that the pad comes into contact with, a sacrafice for better cooling I thought.
And you don't need to 'absorb more heat' into the metal for the solid/ vented ones to make them work better. If anything they'll overheat and fade before grooved/drilled.
Stick to cheese my man.
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gez bay
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Registered: 14th Feb 08
Location: South Wales drives: Vxr
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i like just drilled disks, solid disks warp after so much abuse, the drills and grooves catch the air cooling the surface down
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Cheese Man Chris
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Registered: 25th Sep 07
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@ alan-g-w
I meant what you said on both acounts.
Imagin having a small stone (drilled disc) and a larger stone (Solid disc) that represents the mass of each disc. And you stick them in the oven (to simulate braking) for about a minuite. The small stone will be hotter then the larger stone BUT the smaller stone will also loose its heat quicker(which is a good thing) but the larger stone will not be as hot as the small stone in the first place becuase it takes longer to heat up.
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gez bay
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Registered: 14th Feb 08
Location: South Wales drives: Vxr
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so the drilled disk is better
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Cheese Man Chris
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Registered: 25th Sep 07
Location: Leeds Drives:1.2 Merit
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A few Subaru owners i've spoke to are the reason behind this logic by the way. I can see why it could be true but does it work in real life situation thats what im asking...
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SportBoy
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Registered: 5th Oct 01
Location: Retford, Nottinghamshire
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quote:
Originally posted by Cheese Man Chris
A few Subaru owners i've spoke to are the reason behind this logic by the way.
says it all 
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Cheese Man Chris
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Registered: 25th Sep 07
Location: Leeds Drives:1.2 Merit
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quote:
Originally posted by BarnshaW
grooves to disperse water better
But is it worth loosing all that surface area (in contact with pad) to disperse water, when if you had been doing any hard braking any water that touches the disk would evaporate straight away anyway.
[Edited on 12-07-2009 by Cheese Man Chris]
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SportBoy
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Registered: 5th Oct 01
Location: Retford, Nottinghamshire
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afaik its the rid of the gasses that build up between the pad and disc when it gets hot .. not water
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Cheese Man Chris
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Registered: 25th Sep 07
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quote:
Originally posted by SportBoy
afaik its the rid of the gasses that build up between the pad and disc when it gets hot .. not water
What gass? Any where did it come from?
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flybikeslee
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Registered: 2nd Jan 07
Location: Liverpool
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my grooved discs where shite, many people i know have cracked drilled ones, i run blanks, don't look gay either
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Cheese Man Chris
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Registered: 25th Sep 07
Location: Leeds Drives:1.2 Merit
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quote:
Originally posted by flybikeslee
my grooved discs where shite, many people i know have cracked drilled ones, i run blanks, don't look gay either
Another good point, Surly if you drill lots of holes in the disc its weaker....
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SportBoy
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Registered: 5th Oct 01
Location: Retford, Nottinghamshire
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fvck knows just from what ive read in the internetz at some point .... could be wround but im 99% sure it aint water the discs never really gets wet when driving anyway. unless your in a landrover up to your neck in mud.
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SportBoy
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Registered: 5th Oct 01
Location: Retford, Nottinghamshire
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just been looking on the google the grooves are there mainly to stop the pads glazeing which happens when they get hot.
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Cheese Man Chris
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Registered: 25th Sep 07
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Another point here.
If if a drilled disc looses its heat quicker, and it heats up quicker. That rapid heating and cooling will surly make the disc brittle after 100/1000's of fast heating and cooling.
Where as a solid disc may not cool down as much so less subject to less stress where rapid heating and cooling is concerned
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SportBoy
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Registered: 5th Oct 01
Location: Retford, Nottinghamshire
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good old wiki.!
Many higher performance brakes have holes drilled through them. This is known as cross-drilling and was originally done in the 1960s on racing cars. Brake pads will outgas and under use may create boundary layer of gas between the pad and the disc hurting braking performance. Cross-drilling was created to provide the gas someplace to escape. Although modern brake pads seldom suffer from outgassing problems, water residue may build up after a vehicle passes through a puddle and impede braking performance. For this reason, and for heat dissipation purposes, cross drilling is still used on some braking components, but is not favored for racing or other hard use as the holes are a source of stress cracks under severe conditions.
Discs may also be slotted, where shallow channels are machined into the disc to aid in removing dust and gas. Slotting is the preferred method in most racing environments to remove gas, water, and de-glaze brake pads. Some discs are both drilled and slotted. Slotted discs are generally not used on standard vehicles because they quickly wear down brake pads; however, this removal of material is beneficial to race vehicles since it keeps the pads soft and avoids vitrification of their surfaces.
A mountain bike disc brakeOn the road, drilled or slotted discs still have a positive effect in wet conditions because the holes or slots prevent a film of water building up between the disc and the pads. Crossdrilled discs will eventually crack at the holes due to metal fatigue. Cross-drilled brakes that are manufactured poorly or subjected to high stresses will crack much sooner and more severely.
must be some truth in it 
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Cheese Man Chris
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Registered: 25th Sep 07
Location: Leeds Drives:1.2 Merit
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Hummm see Porsche should have read Wiki pedia before sticking drilled discs on all their cars. Amatures!!! haha
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ed
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Registered: 10th Sep 03
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A friend of mine did analysis on this using different disk designs. The drilled ones gave better performance than the solid ones. He did some wavey ones which were also drilled, they were the best, but the design was considered too risky.
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dhdev
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Registered: 22nd Dec 05
Location: Midlands
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The problem with aftermarket drilled discs is that they are not subjected to the same level of post machining treatment as the OE spec Porsche (for example) drilled discs, thus your average geeza in his modded car will buy drilled discs for as cheap as possible then end up with cracked discs. The OP made a valid point that the mass of the disc does have a direct relationship to temperature, a larger mass of disc has a larger thermal capacity, combined with proficient venting, will result in cooler disc temperatures.However the reduction in mass from drilling will be negligible.
Apart from the outgassing from the pads being removed, the other benefit of drilled/grooved discs is to clean the pad face to ensure consistent braking.
The removal of disc surface area created by the grooves/drillings has no relationship to the torque capacity of the braking system, torque is a result of effective radius, force from piston and mu alone.
Hope this helps.
[Edited on 12-07-2009 by dhdev]
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Mobby
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Registered: 31st Dec 07
Location: Leicestershire
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Vented grooved Ftw
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Ian
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Registered: 28th Aug 99
Location: Liverpool
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Its worth noting that the choice of configuration is also based on your application.
Drilling and grooves both result in higher pad wear and make the disc inherently weaker. While if you're after outright performance in the short term may be a good idea for heat dissipation and avoiding glaze but it's not ideal for long term road miles.
Also do bear in mind that heat as such isn't a bad thing. Hot brakes if that is what your pads are designed for are more effective.
The trouble with a road car is you'll generally have pads which work well from cold, so the pads then won't tolerate heat as well and hot discs will damage them. Racing pads have no such requirement for use when cold so a bit of heat isn't such an issue.
[Edited on 12-07-2009 by Ian]
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Ste
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Registered: 5th Mar 03
Location: Taif, Saudi Arabia
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I'm about to upgrade my kit car brakes from vented to solid as I don't have sufficient mass in my car to get the disks up to temp to utilise the softer compound pads I use.
I would rather lose by a mile because i built my own car, than win by an inch because someone else built it for me.
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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Drilled = Lets brake pad gases out and makes the rotational mass lighter, not really for heat disipation.
Grooved = again lets gases out easier and also takes off grazing from the pads.
Solid = has more surface area but isn't as good because the gases build up and the pad isn't as "clamped" on the disk as it could be.
yo
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sand-eel
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Registered: 15th Mar 07
Location: carluke/braidwood--IRNBRULAND
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grazing = glazing BTW
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