Drilled Discs - 3.2

[ClubSport 911]

I note with interest that Zimmerman (OEM for Porsche) are now selling drilled discs for the 911 3.2- a snip at £60 each, and I'm wondering if anyone out there has had the courage to fit them and perhaps could report back on the effectiveness ?

Best advise is variable to say the least from: "Drilled discs crack" ...(so why fitted to RS's, GT3, Ferrari 360 etc) and "slotted = best" or "Go for Grooved rotors" - but from where ?, and finally - "standard is best"

I'm looking to replace the rear discs first, and would ideally like a mild upgrade in "bite" - EBC greens fitted, brakes well bled etc...

Gentlemen - start your opinons

THANKS

 

[Guest]

Eurocarparts sell both the standard and the drilled Zimmerman disks, front and rear.
As you say the drilled are about 68+VAT, which is approx twice as much as the standard disks.
Are there other options? - I can see that EBC disks are available but only upto MY77. What about TAROX, I have heard good things about them on rice/Japanese cars.

Also, would there be a problem in just improving the braking on one axle, as it might introduce brake imbalance - rears locking up before the front gets loaded, etc?

 

[ClubSport 911]

Hi Chappie

I did try to find Tarox, although frankly not that hard - perhaps they are available, but at a (high) price

Of course, I would need to be aware, that if the brakes were so much better on the back then these might lock up, but of all the brake balance issues I can recall with the 911 3.2, it was the fronts that locked up first, hence the reason for me to change the rears first (and the fact that the inner radius is reasonably scored.)

I suppose I'm hoping that someone out there has already been through this particular pain barrier ??

The other discs I did see (at Cornbury house) were the EBC "dimpled" versions...but Josh S informed me that they are not yet made for our cars.

 

[Guest]

Hi Steve,
I have just replaced my front discs with Zimmerman from design911 (because they were cracked) and scimmed the rears (because they were not) and fitted Pagaid fast roads all round. Breat bit and retardation and much less dust[]

 

[Guest]

I can't see how the rears would lock up in any case, as they are lightly loaded under braking, so improving them as an experiment seems the wrong way round - OK, I know the rears need replacing first, in your case.

The only thing that I have heard about drilled discs is that they can get clogged up with brake dust, so need to be cleaned regularly.

 

[Guest]

All I can is add is that I put standard Porsche items on when I swapped mine. Dont remember the price, but not too expensive, although the backs are more due to the handbrake assembly living in them I guess.

Was there a non-adjustable bias valve on the 3.2 or am I mistaken?

Do you do a lot of track work? I have never had any problems on the road, despite not standing more than about 5 laps on track (must learn how to brake!!!).

 

[ClubSport 911]

Freely admit that I'm asking the Q more out of curiosity than a specific need.

If drilled discs are as low cost as they are, then why have not more people fitted them? And, if as many people say:- "the holes get clogged up" then why-o-why do they (drilled discs) come as std fitment to a whole bunch of cars. ?

Like many people, I'm just at the point of replacement, and am wondering if there is any merit in the option ...

Thanks for all the thoughts, but has anybody actually got real world experience ?

Rgds

Steve

 

[Alan_Armstrong]

The purpose of cross drilled discs, is to dissipate heat, although the originals may be vented...are they?...I have'nt looked.....the more heat you generate with a larger pad or
a pad made of a material with less fade. can cause discs to warp or crack.
Grooved discs are to provide an exit for brake dust off the disc.

I uprated the from discs on my daily drive BM 323 coupe to vented, crossdrilled and grooved...with excellent results, and cured the the warped disc scenario I was expereincing perviously. Whilst this sort of upgrade is suitable for the fronts of most cars, especially if you intend to run a hotter pad, uprating the discs on the rears may provide additional cooling and could cause the brakes to be lacking as not getting hot enough.

If you want to have crossdrilled discs on the rear, just so you can see them through the wheel spokes...I would suggest upgrade the pads to compensate for the cooler discs!

 

[tim court]

and cured the the warped disc scenario I was expereincing perviously.

Sounds like you need a cold shower you dirty boy.

Back to the post.... If you are driving a bit vigorously and your brakes are getting a tad too warm and you want to upgrade them then the upgrade should ideally be to all four corners.

Apart from grandad's sierra how many performance cars have different materials front to rear?

Any required bias is dialed in by Porsche by different disc diameters and bias valves in the brake lines. That is unless you have the facilities of a race team for on-track braking analysis.

 

[Guest]

Just a couple of quick points to note about brakes:

1. You are talking about drilled holes not cast holes a la factory 996 etc

2. Even factory discs with cast holes crack - ask someone who races

3. Discs with drilled holes crack faster than cast holes - but for road use this is basically irrelevant

4. Why do discs warp? 99 out of 100 it is because the car is parked with hot pads next to just one spot on the disc (or the handbrake is on). Solution is to roll the car a half metre or so every minute for a few minutes so heat transfers to multiple spots - and leave the handbrake off

5. Discs do not warp when the car is in motion as there is no unequal rate of expansion

6. All 911s have vented discs.

7. All serious race cars run grooved discs now - to vent gases principally but I guess dust also

8. Drilled discs look cool

9. A solid disc provides you with a bigger heat sink - a drilled disc may cool *slightly* quicker

10. Cool air ducted to the centre of the hub will do much more than a few holes in the discs for cooling

11. Slotted discs cost a fortune and may not be available for our cars anyway (although a call to Demon Tweeks would net a quick answer as they carry all major brands)

12. EBC Green pads are not an "upgrade". Put your hand in your pocket and get some decent pads like Pagid Blue or Porterfield (or even Mintex 1144s) []

13. Replacing just the rear discs will have no major effect - feel free to experiment.

14. Do not replace just the rear pads []

15. Brake bias is mainly a function of the piston size in the calipers. In the 3.2, the pistons are the same size front and rear but a proportioning valve operates over a certain pressure level to reduce the rear brake pressure and avert rear end lock up (maybe 33psi?). The aim of this is to even up front/rear wear in normal driving. It is unfortunately the worst bias of any 911 - until the proportioning valve kicks in.

16. If your 3.2 brakes wear evenly front/rear, then you are not braking hard enough []

17. You can heat up your brakes by applying them with the middle pedal. This works for drilled or non-drilled [] Your cross drilled will not stay sooo cool that heating up is a problem

I could go on but that is enough for now. Feel free to raise specific questions.

RB

 

[Guest]

Why do discs warp? 99 out of 100 it is because the car is parked with hot pads next to just one spot on the disc (or the handbrake is on).

Now, I thought that the handbrake mechanism is a seperate drum system ('tis on 3.2), so how would the h/b affect the heat of the discs ? H/b using the disc pads apparently don't work so well.

 

[Guest]

Now, I thought that the handbrake mechanism is a seperate drum system ('tis on 3.2), so how would the h/b affect the heat of the discs ? H/b using the disc pads apparently don't work so well.

Sorry, incorrect. The drum is a part of the disc on all 911s - it is not separate. If you replace your rear discs it will be very clear. In fact, next time you have a rear wheel off and are changing brake pads, just unbolt the caliper and undo the two screws that hold the disc on and slide it off. The handbrake mechanism will be right in front of you as it sits kind of inside the disc (or more correctly the part of the disc that forms the drum).

RB

 

[tim court]

I have often wondered about this one.

The drum although technically still part of the casting which includes the disc has handbrake shoes which when operated, touch virtually the whole circumference and thus acts as a continuous heat sink, away from the disc itself.

So how can discs be warped by handbrake operation?? More likely the heat is prevented from escaping from the patch of disc covered by the pad faces, which will be stopping air flow and heat escaping from a very small part of the disc surface.

Still the proof is in the proverbial.... leave handbrake off - no warping - handbrake on... warped discs.

 

[Guest]

So how can discs be warped by handbrake operation??

Good point Tim. I have seen a handbrake that ended up "stuck on" after a race but have no personal experience with the warping cause and effect. Steve Kevlin always mentions it in the track day briefings, so I guess I heard it so many times I just accepted it.

RB

 

[Alan_Armstrong]

The last few posts seem to have strayed into track days and racing, where the original question, I thought, was for general application,aren't Pagid Blue and Porterfield for competition use?, I know that Mintex 1144's are...

 

[tim court]

The last few posts seem to have strayed into track days and racing

Well I don't think so.... I can get brake fade driving to Sainsbury's. []

The original posts was asking for opinions on the use of drilled discs and a pad upgrade.

I have fitted Zimmerman discs to my old 944 with standard pads - no problems encountered with cracking or warping.

My 996 C4 (Silver caliper model) has drilled discs as standard and EBC do not appear to do upgraded pads for this model yet.

 

[Jamie Summers]

I'm currently running Porterfield RS4 pads on my car - they are absolutely fine for day to day use and obviously a heck of a lot better on track than OE. They squeal a bit under light braking which is a tad embarassing at times but not really worth worrying about given the overall improvement in performance. There are a lot of scare stories out there that 'racing' pads need to be operating at about a zillion degrees celsius before they will stop your car and if you try to brake from cold you will crash and die. In my admitedly limited experience they work fine for day to day use - you might need to stand on the pedal a little harder but I don't really notice it.

Getting back to the topic, other than for aesthetic reasons, before bothering with looking at drilled / slotted discs, in order to improve the braking on a 3.2 make sure that you are running good quality tyres, properly inflated and with the alignment set up correctly - makes a surprisingly big difference. Next think about upgrading to higher temp brake fluid. Replace old brake lines (over time the rubber hoses begin to deteriorate and swell under high temp / hard braking) - decent quality stainless steel braided hoses cost little more than straight replacement OE rubber hoses. Next look at pads - as far as I'm concerned Green Stuffs are little better than OE, you'd be better to go up to the Mintex 1144 which are a pretty reasonable compromise of price v performance. Porterfields / Pagids are great, but at a price. Think about cooling ie. a ducting kit and then if youare still not happy go for the drilled discs.

That's a rather roundabout way of saying that IMHO the money you would spend on the discs would be more effectively spent on other bits of the braking system. That said if your current discs are on the way out and the drilled discs not significantly more expensive then why not give them a go ? I wouldn't expect a dramatic increase in braking performance esp. in day to day use, but they certainly look pretty !!!

 

[Guest]

I have run Porterfields and Pagid Blues on the street (and track) and they are fine - particularly the Blues. The Mintex 1144 is a fast road pad. I have 1155s, a race pad, on the car now and they are also fine on the street.

On a previous car I had Pagid Orange compound, again a full race pad, on the street and no problems.

All race pads will take about a half second to bite when they are cold and work better when hot but this is nothing like the apocryphal stories of having no brakes at all when cold. Read Jamie's post.

RB

 

[ClubSport 911]

Appreciate all thefeedback, but still, no one has actually written in and said "yes, I tried the drilled discs on my 3.2 and......"- This is what I'm looking for - perhaps because they are so new ? - I do know from Rennlist and PCA that slotted discs are better but again, who in the UK has tried them ??

Also, I must be strange.... because I fitted the new V4 (as in Version 4) EBC green pads, and to my dismay and disgust have to report much better bite, more persistent braking, and a better pedal feel all round.

Perhaps I need to write a letter of complaint because it seems that EBC greens are supposed to be no better than std etc... Must be a faulty batch []

Seriously - I have no problems with these EBC pads, but then again, I don't track the car (the car was raced by Andy Rouse for 2 years from new so it's resting now) - I'd recommend them as a low cost upgrade.

 

[Jamie Summers]

Perhaps I should qualify my statement about the EBC Greenstuffs. I put a set on the front of my car to replace OE (leaving OE on the rear) and it was a really horrible set up. The balance was all wrong as the fronts kept locking up and then eventually faded to nothing (on a fairly aggressive trackday). This was, however, running crappy tyres and with boggo fluid. I have no doubt that if you took all of my own advice in my previous post and used Greenstuffs all round then I'm sure they would be better than OE. But frankly the Mintex 1144 are only a bit more expensive than the Greenstuffs and believe that they are rather better suited to the 3.2
Anyway, you pays yer money etc etc .......

Not really helping on the issue of real world experience of the drilled discs though !!!!!