Stef

I have heard various opinions on these, and wanted to hear what some of you think.
I seem to remember someone or somewhere saying they had 'no place on a high performance car' (old Scoobysport website?), but looking through lot's of recent motoring mags I can see countless cars with cross-drilled discs as standard (Porsche Turbo, tuned Jag XKR to name a couple).
I intend to upgrade to Brembos next year, but as I do so much driving I will get through another set of discs before this upgrade comes.
Does anyone have cross-drilled at the moment?
What are the main benefits over grooved?
What about drilled and grooved?
Thanks in advance for your comments.

Stef.

AlexM

Stef,

I think the cross drilling serves two purposes - to remove outgassing from the pads (same as a groove), and also to reduce the weight of the disk. The main problem is that the drilling helps to promote cracking due to concentration of stress around the holes as the material expands.

People also think it looks funky, which is probably the main reason! There are some performance cars that have them, but plenty of racers dont.

If you plan to replace the disks, don't blow loads of money on them. Their fade resistance is dictated by the size of the air gap inside the disks, so fade resistance wouldn't be improved too much anyway.

Cheers,

A.

JohnS

iTrader: (1)

I'm not sure if they will stand up to lots of track abuse, but at least one owner has just fitted a set of Black Diamond cross drilled discs and Mintex 1155 pads which he bought from Falkland Performance Centre. I think the cost was £190+VAT for everything, which is probably cheaper than a standard set of discs.

His initial feedback was very positive, being a big improvement over the standard setup he had before, though these were past their sell by date.

Did

"no place on a high performance car"- True Grip a couple of issues ago.

I frowned when I read that as it did seem to be an opinion rather than a balanced viewpoint.

I have used drilled discs previously on a heavily modified Peugeot 205 Gti and was quite pleased with their performance. They are noisy and mine ate pads but their fade resistance was very good (much lighter car than an Impreza though)

One of the benefits of grooved over drilled is that they clean the face of the pad much better. This is particularly useful if you are using a sports compound as glazing can be a problem before they get warm.

I guess you need to weigh up the potential benefits of the disk change pre- Brembos. As John S rightly says though, you are likely to pay less than for standard discs so why not give it a try.

Did

firefox

Hi guys..

Drilling in the correct pattern/manour...can release stresses.... its a technique used for strain gauging material...

Drilling can help braking...by allowing heat loss....deglazing the pads...weight reduction...

I was once told that a certain make of brake didnt need to be groved because they were perfect already..and grooving wouldnt increase the efficiency.... guess what... their brakes are now grooved...*shrugs*

Grooving/drilling is used on most high performance cars.... even the WRCs use the technique...

Have you consider Alcon brakes ? Prodrive fit them as standard on their Group N cars.... They are meant to be superb... and good value for money.

J.

ps - Steph... Brakes dont work going sidewards...

AlexM

Mike,

I don't think it is fair to personalise the argument - do bear in mind that the best part for a Track or Rally car isn't always the best for a road car. Horses for courses etc. One must consider the application before considering the validity of someone's argument.

If a set of competition carbon metallic pads and ultra light grooved and drilled disks squeaked like a bagfull of mice and needed to be replaced every 500 miles, then IMHO they would disqualify themselves from road car fitment however good their braking performance was. If PC stated that a particular Pad/disk combination didn't benefit from grooving as the pads were self cleaning, then that would be fine. If the pad specification were changed so that grooves were beneficial, would that make his previous statement incorrect? I think not.

Scoobysport's Brembo kit is obviously developed with roadability in mind, and uses the standard Subaru booster, master cylinder, and ABS modules to contain costs. Apart from group N, I think any competition car is going to start by ripping out the factory system, and are usually 'cost no object' projects.

I've gone off topic, but my point is that it is possible for PC to be correct for one application, and J to be right for another. Seeing as most people use their scoobys on the road 99% of the time, I personally think it would be a mistake to modify the car in such a way that the car is great in 1% of situations, and a pain in the A**e most of the rest of the time.

I think people look for consistant and broadly applicable advice i.e. grooves/drilling is always best, but you can't consider one factor in isolation and claim to know the whole story.

All of this is just my opinion - feel free to disagree or correct me.

Cheers,

A.

Benny Boy

Hi Stef

There are a few good brake kits out there, one of them being the brembo kit another AP Racing.

To put things in perspective Stef, I went around Cadwell with Neil Scott who has Colin Tinto's old 22B brakes and braided hoses. He has a 98MY and drives like a complete looney around the track and would keep up with you. It should be noted that Neil suffered hardly any perceptable brake fade.

Food for thought.

Ben

[This message has been edited by Benny Boy (edited 26-10-1999).]

Pete Croney

Sorry for ranting on Stef.

My comments are also retracted.

[This message has been edited by Pete Croney (edited 27-10-1999).]

JohnS

iTrader: (1)

Hi Benny,

I'm sure Neil would have some words with about the accusation that he drives likes a "looney"

Cadwell Park wasn't too bad for brake fade, as there are long straights between many of the hard braking points, giving the brakes a lot more cooling air at high speed than is encountered on other tracks.

At Knockhill recently, Neil was experiencing brake fade (as we all were, unless running on aftermarket brakes), and actually warped one of the discs. He has chosen to fit the drilled discs and Mintex pads, as they are a cost effective solution, and he's unlikely to be doing much (if any) track work over the next 5 months or so. With wet roads and cold temperatures, brakes on the road aren't going to be stressed to the same level as hot dry summer days. Having said this, many people experienced brake fade on last years Tour D'Ecosse! Can't wait until next week now

I think Neil will be looking at better braking options for next years track season

Aaron Payne

RalliArt had Tommi's Evo VI at the Motorshow in San Remo Livery and Tarmac Spec. The brakes were huge and were grooved not cross drilled.

Stef

J.
Do you know how much Alcon discs are?
Where would I get them from?
I'd like to change them before Donington if poss', for obvious reasons!

Stef.

Pete Croney

Stef...

Discs used to be drilled to allow the pads to de-gas. Since pad manufacturers stopped using asbestos, pad gas ceased to be a problem. Modern pads do not produce gas.

Cars such as Porsche do still use drilled discs, but it is for cosmetic reasons only. Brembo make the OE stuff for Porsche and had to over design the discs, to allow for the loss of strength that the holes created.

With regard to rally/race cars, you have to remember that they only need pads to last between services, or for one 30 lap race... and the drivers want fresh pad material at every brake application. You can cut your finger on the grooves these guys use.

David Higgins uses the Alcon group N discs, but there are some questions on their group N legality, as the vents are spiralled and not as the OE units. I think Alcon only make these in 292mm and not 274mm as your 98 two pot brake set up. Duckworth, Gwynne and Becton use the same 292mm group N discs that we supply. These teams, and Higgins, all use Pagid RS4-2 and RS1-4 with these discs.

J... we went to grooves in the new Brembo discs, so we could also use Pagid RS4-2's with this set up. This is a hard competition pad and likes a bit of cleaning to maintain full efficiency, when used for road use.

The new grooves are very wide, so they do not clog and become ineffective, but are profiled to have a negligable effect of pad life. A groove of less than 2mm will have little or no effect on modern, performance pads.

Mike Tuckwood

Comments intentionally retracted as a sign of good faith.

Mike

[This message has been edited by Mike Tuckwood (edited 27-10-1999).]

Stef

Interesting points Mike.

I agree that articles like the one in True Grip should be unbiased, as unless I'm wrong, the SIDC and Scoobysport are not commercialy linked.
However, nobody can deny the amount of effort Pete puts into the club, and it's not for me to say whether using his position as editor/author of True Grip to subtley promote Scoobysports products is right or wrong. I guess it's a perk that comes with the job!
The article certainly had me convinced that drilled were useless and four pots were the way to go, hence the reason I looked at Brembos (surprisingly!).
What convinced me more though, was actually going out with Pete round Cadwell Park. Whatever he wrote in True Grip could never do an actual demo justice, and it was on the strength of this that I decided to get Brembos.

Stef.
PS Pete.
I've only just read your post (after writing mine). Thanks for the info.
If the main reason you went to grooves was solely because you wanted to use the Pagids, does that mean that drilled were more suitable for a different pad?
And Porsche really use them for looks alone? That surprises me. Are the brakes not performing at their potential maximum then, because of this?

S.



[This message has been edited by Stephan (edited 26-10-1999).]

Benny Boy

I think Bob Rawle would have a more informed opinion on remapping. Not only that but it will be unbiased and he won't have any satisfied/unsatisfied customers to appease.

just a thought

Ben

Mike Tuckwood

Comments intentionally retracted as a sign of good faith.

Mike.

[This message has been edited by Mike Tuckwood (edited 27-10-1999).]

robski

"The truth" is out there........

..it just depends which version of the truth you want.

Robski

Pete Croney

Comments retracted.

Pete

[This message has been edited by Pete Croney (edited 27-10-1999).]

Stef

Come on you guys!

I only wanted to know about bloody cross-drilling!!!!
As it is, I think I'll get some drilled / grooved / drilled & grooved / grilled & drooved / whatever, discs and fast pads for Donington and see how I go.
There was really never any doubt in my mind about the Brembos.
But if someone has any better ideas......
No, no, don't start again, only kidding.

Stef.

Mr Leigh

No comment to retract You dont want any pads that are to noisey as this would get you out of the comfort zone

stv555

Whether you choose to use X-drilled or grooved discs, the main factor one must consider is the material that the disc is made of.

Brake discs are invariably made of cast iron but not all cast iron is the same. For example, Brembo make replacement discs for for all makes of car, the material is different from the the grey nodular cast iron that they use for the X-drilled range they sell and which is supplied as OE to Porsche, Ferrari and likes of Suzuki and Yamaha.

This fact is unknown by a lot of people who buy modified discs which start life as a standard vented disc and which are modified by grooving or drilling and then given a pretty cosmetic coating. Such discs are as much use good as having no brakes at all. I have witnessed such a disc shear off the hub section !!!

Even Porsche discs when used in vengeance will start to crack, but the dealers service schedule will have a built-in 'lifing' scheme i.e. they will be replaced as part of the service schedule at pre-defined time or milieage intervals.If you own a 911 you need the funds to run it properly.

To reduce weight mounting the disc on an alloy or titanium hub is the way to go not X-drilling/grooving. Such modifications used in conjunction with carefully selected pad material will help to bring the pad up to temperature much quicker than with a solid disc.

Additionally the number one cause of brake fade is the generation of gas from the pad material due the inefficient removal of heat from the disc into the air or surrounding materials.

Personally I would not trust any modified disc unless it came from the likes of AP, Brembo, Wilwood....as they say you pays your money and takes your choice...what price would you place on your car or better still your life. !!!!!

mark245

very good point about disc material. I dont think anyone would argue that the subaru 4-pots are not as fade resistant as a set of up-graded brakes from the likes of AP, Tarox or Brembo. However, when we talk of the merits of these against the Subaru brakes on the track, we are not really comparing like with like. These makes already mentioned use quality grey cast discs, competion type pads, and generally braided hoses. a long way from the spec on a standard set of subaru brakes. The 4-pots, or in fact any type of braking systen can be greatly improved by group N discs, braided hoses and a competion pad. They wont be as fade resistant [on the track] as the big brakes , but the gap will certainly be smaller.

Andrew Dixon

It might be of interest to note that the 'drilled' discs used by Porsche are actually cast with the holes in, rather than having them drilled out of a solid disc.

Or so I'm told!

Andrew

stv555

I don't think so ....!!!!

All discs are cast as blanks and then the friction zone is machined to tolerance. It is impossible to machine a disc accurately when it already has holes or grooves in it. Also the cutting tool would last 30secs. or less.

The disc on the likes of Porsche are designed with the X-drilling in mind at the design stage rather than as an enhancement at a later stage.

Pulsar

Guys.
Couldn't help but see this and I hope you don't mind our comments. We are having a very similar discussion on GTiR and a similar heated discussion is raging. see

mrlegacy69

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by Stephan:
<B>I have heard various opinions on these, and wanted to hear what some of you think.
I seem to remember someone or somewhere saying they had 'no place on a high performance car' (old Scoobysport website?), but looking through lot's of recent motoring mags I can see countless cars with cross-drilled discs as standard (Porsche Turbo, tuned Jag XKR to name a couple).
I intend to upgrade to Brembos next year, but as I do so much driving I will get through another set of discs before this upgrade comes.
Does anyone have cross-drilled at the moment?
What are the main benefits over grooved?
What about drilled and grooved?
Thanks in advance for your comments.

Stef.[/quote]

mrlegacy69

forget my previous post i am up late after studying. I would have to say that when i changed from std discs on my twin turbo legy to slotted , cross drilled discs that it made a bloody great difference in stopping power but the thing i appreciate the most is the discs resistance to fade, which i have been told will be mostly due to the cross drilling rather than anything else. The brand i bought were DBA which i picked because a:reasonable price b:good quality made in aussie. check out there web site as they sell heaps to all the WRX owners in aussie. the site is

jamesa

FWIW

Although not on a Subaru I have used both grooved and cross drilled items with various pads.

Black Diamond Grooved with Mintex 1144`s - excellent feel, wear and fade characteristics - road use only.

Black Diamond Drilled with Pagids ( forget the type no. ) - again good feel, wear and fade rate - road and competition use.

When deciding which way to go, I researched the supplying company more than the product -choosing people who built, competed and had the practical experience of the application I required - it works !!

Now fortunate to have a P1 with Alcons and looking forward to life after running in.

I have nowt against any of the other opinions expressed; am impressed by people`s investigative talents / knowledge etc... but the above works .... for me !

Cheers

...and again - all the best for tomorrow SdB and co.

jwhitton

I cracked my cross drilled Cossie 2wd (282mm) disks at Castle Combe on my RS Turbo. Having taken them off and examined them more carefully they are a death trap. I think the disks were OEM disk which had been drilled. I have now gone back to standard undrilled disks with M1155 pads.

I melted a set of M1144's last year and am now a convert of M1155's. As for dust I do not really care I just want top track braking efficiency. So far the non-drilled disks are looking good.

After the above experience I would never again us cross drilled.

jon