[rob76turbo]

Well, it looks like the 968 will be staying in the stable. Not much of a market for the cars without giving them away....



So, on with the upgrades. The question is Cross Drilled vs Solid front rotors...

These will see heavy track use and I have heard pro and cons on both.

So what are you track guys running?

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[Cloud9...68]

The previous owner of my car installed Zimmerman cross-drilled rotors, and after a total of about 18 hours of track time in my hands (plus whatever the PO did), I'm very happy with them. My front pads are pretty much shot (I have a set of Porterfields on order), but the disks aren't grooved at all, nor are they glazed. I can't say how well they stop the car compared to the stock brakes, because as I said, my car came with the Zimmermans. I'd recommend them, based on my expereience.

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[xrad]

it's all about weight, heat loading , and mu k. Much research to do for racing ..and much has already been done on this forum. For street use, I am VERY satisfied with Zimmerman non-sport sized cross drilled front and rear and Porterfeld R4S pads all around. Much better than stock IMHO.



should be 'Porterfield'

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[S_Cal968]

I'm running slotted rotors with PBR Metalmaster pads and have been happy with them. I've also installed S/Steel braided lines and re-filled the system with Racing Blue brake fluid. I'm fairly hard on my brakes, but realize that doesn't compare to track use.

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[Big Dave]

Im running M030 callipers with SOLID 928S4 discs, no problems at all. And there a darn site cheaper than the drilled ones...

Personally im not a fan of the drilled discs, especially the Zimmerman ones.. I find they all crack after a while....



My car does get used hard on track, with Pagid Oranges , braided hoses + Castrol SRF fluid..KW V3 suspension + Dunlop D01J track tyres....The pads + discs both wear out at about the same time... usually 12-14 track days out of a set...BUT then it is a bit cooler over in the UK....

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[flash]

heat is the enemy here - there is a common misunderstanding about why manufacturers put larger brakes on the front - it is not because the front needs more braking - it is because they get hotter - the extra material handles the heat better - without it the fronts would fade



yes, more swept area means more braking, but that is not usually what is needed, and can actually make things worse - if you add too much front brake relative to the rear, the car "feels" like it's stopping better because the nose dives, but in reality all you get is less braking at the rear - that is bad



what is usually needed is more REAR brake - the fact that the fronts do most of the work is a necessary design flaw intended to provide for the average driver in normal situations - it is safer for them to have a heavy front bias - but, if you want your car to brake better, start by focusing on the rear, and add more cooling to the front - the trade-off of course is that you could lock up the rears more easily



as for cross drilled brakes versus slots - there is nothing wrong with cross drilled rotors as long as the pattern is such that it is not too close to the ribs, and that the holes are chamfered - again though, this is all really dependent on heat - if you cook them, they will crack - the key is to prevent them from cooking - slots don't generally crack, but are harder on pads and can be noisy



one way to do prevent cracking is to choose a pad that has a better heat transfer - semi-metallic pads are horrible - the pads are resilient, but the rotors take a beating - the oem organic pads are the reverse - a good kevlar compound is your best bet



the key to remember when doing ANYTHING with your brakes is to focus on balance - what you do to one end affects the other

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[rob76turbo]

That is why I will probably go with solid rotors. But I will also add the brake cooling ducts from Lindsey Racing. This will help keep the front brakes cooler, thereby increasing performance. I am running Hawk Blue pads, no issues with them although they seem a bit hard on the rotors...but they sure do stop the car!!

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[flash]

lol - it's always a trade-off isn't it?

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[Cloud9...68]

[quote name='rob76turbo' post='64958' date='Jan 2 2009, 11:59 AM']But I will also add the brake cooling ducts from Lindsey Racing. This will help keep the front brakes cooler, thereby increasing performance.[/quote]

Good thought on the brake cooling ducts. Do these replace the fog lights, though?

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[flash]

interestingly enough, i just had this conversation today, and am contemplating something along those lines

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[Cloud9...68]

[quote name='flash' post='64983' date='Jan 2 2009, 06:35 PM']interestingly enough, i just had this conversation today, and am contemplating something along those lines[/quote]

You mean along the lines of fabricating something that doesn't eliminate the fog lights?

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[Ryan]

Brakes work by converting motion into heat, therefore stopping us. If the fronts get hotter, than the fronts must be doing more work. I think it is because of weight transfer. This would push the front of the car down more than the rear making the rear lighter (like in real life).



I would say that the fronts need to be bigger because they do more of the work (get hotter).



Sorry, got to argue

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[flash]

that is only a part of the story - heat is a byproduct not a function of braking - reducing the heat increases braking effectiveness, by allowing the friction to be at maximum without causing the compounds to effectively melt

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[S_Cal968]

It's my understanding that front brakes are bigger because they are tasked with stopping most of the weight of the car as the CG shifts forward while braking. As a result, heat is a by-product. Brakes are designed primarily on stopping power - reducing heat is a secondary feature.



Also from what I've read drilled & slotted rotors reduce gas build-up between the pad and rotor there-by providing better contact. And, the sweeping action of the holes [or slots] keep the pad clean and reduce dust build-up. If they circulate more cooling air that's icing on the cake...

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[flash]

they aren't "tasked" by design to do most of the work - they end up doing that though - the key to better braking, is to balance it out more - you are trying to slow the wheels from turning without locking them up - this means providing as much friction as possible without the compounds failing - because of the physics involved, weight is transferred forward, and results in the front brakes needing to do more work than the rears - this means more heat produced up front - it is cheaper to make bigger rotors, which dissipate the heat better, than it is to use expensive compounds, add ducts, etc



however, by design in a street car, they leave some rear braking on the table - they aren't being used to their maximum - this does provide a safer car, as it is easier for the average driver to control a front brake lock up than it is a rear - if you want to test this, go out in an anti-lock car and see which wheels lock up



remember that this is all small amounts of change we are talking about - nobody is saying that a car won't brake better with bigger brakes - however, it needs to be balanced, and there is no way to do that with big reds up front only

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[Lim Yong]

Hi all,

so will replacing the back calipers with the fronts calipers balance and improve the car's braking?

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[flash]

i have heard of this idea before, but it is my understanding that they don't interchange for reasons of mounting or something

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[rob76turbo]

Cloud...



I am thinking of adding the 944 brake ducts that Paragon sells and placing them behind the mesh below the bumper. I have not worked it out just yet and I am not sure I will actually use those ducts, but that is the general idea. I will then add those brake cooling brackets from Lindsey and the 3" tubing. I have to figure the best way to route everything, but I think that cooler brakes mean better performance. I am not doing a "Big Black" or "Big Red" update at this time and will use my current braking system. I need new rotors anyway (that is why I was asking about cross drilled vs solid). It seems the racers in the group say solid is the way to go....

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[Big Dave]

[quote name='Lim Yong' post='65010' date='Jan 3 2009, 05:28 PM']Hi all,

so will replacing the back calipers with the fronts calipers balance and improve the car's braking?[/quote]



I have fitted the standard fronts to the rear with no problems regarding mounting, just bolts straight on.. BUT...

Im running the M030 front callipers, with the "original fronts" on the back, the car is VERY unstable under heavy braking, especially in the wet. There is TOO much braking at the rear , so much so, that the rear locks up before the fronts...

It feels GREAT in the dry, but its a real handfull in the wet. It just wants to swap ends all the time, especially if you dont brake in a straight line.... <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

Ive yet to try it with Big Reds fitted to the front, And im waiting to see if Pete [RS barn] has any comment on this.???

Although i think ill be re-fitting the original rears back on soon...





[quote name='rob76turbo' post='65018' date='Jan 3 2009, 06:53 PM']Cloud...



I am thinking of adding the 944 brake ducts that Paragon sells and placing them behind the mesh below the bumper. I have not worked it out just yet and I am not sure I will actually use those ducts, but that is the general idea. I will then add those brake cooling brackets from Lindsey and the 3" tubing. I have to figure the best way to route everything, but I think that cooler brakes mean better performance. I am not doing a "Big Black" or "Big Red" update at this time and will use my current braking system. I need new rotors anyway (that is why I was asking about cross drilled vs solid). It seems the racers in the group say solid is the way to go....[/quote]



Im not sure youl be able to do this. AS the oil cooler will be in the way...

I had fitted a set of the fog light replacements to an old car i had. I eventually managed to route the ducting through to the brakes, but it was DIFFICULT , theres not much room behind the oil cooler / power steering area to route the ducting...VERY convoluted. + not sure if it actually did anything when fitted...

Ill be fitting the cooling /fog light replacements to my current car, but just blanking them off. Just a cosmetic mod... <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

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[Jason Judd]

I've always been a fan of more brakes...You can never have too much braking power in my book! It was the first mod I did to my car.

I now use cross-drilled rotors, and have them "frozen"...My results indicate that it does help. I have fewer cracks coming off the holes than I did compared to last season.

That being said, I am seeing a <i>LOT </i>of people switching over to slotted rotors, for the track.

When I went over to one of the DP Porsches, before the ALMS race at Lime Rock a year or so ago, they all had slotted rotors!

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