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x - drilled rotors
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ic932  



Joined: 11 Feb 2005
Posts: 1104
Location: UK

PostPosted: Fri Mar 18, 2005 9:19 pm    Post subject: x - drilled rotors Reply with quote

I'm converting to 951 suspention/brakes on my 931.To help offset the extra weight I'm using 951 forged alloys and thought x-drilled rotors might help.

Does anyone know how this extra weight will effect the handling of the car and if these rotors will make any difference?
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Raceboy  



Joined: 01 Mar 2004
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PostPosted: Fri Mar 18, 2005 10:07 pm    Post subject: Reply with quote

Yes, they do make difference, but not so much in daily use. Their advantages appear more on the track as cross-drilling helps to maintain better cooling and brakes don't fade so much. Not to mention the look of these
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Helstrm  



Joined: 05 Feb 2005
Posts: 198
Location: Columbia, SC

PostPosted: Fri Mar 18, 2005 11:15 pm    Post subject: Reply with quote

What he said, but for everyday use remember that drilled rotors go through pads much faster. If you are going to track your car or you are looking for some bling go for it.
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Fri Mar 18, 2005 11:20 pm    Post subject: Reply with quote

Not even worth a damn on the track. They increase noise and reduce durability. Leave em to the ricers. They also don't make a significant weight reduction, yet will actually reduce your braking effectiveness (due to the loss of surface area). I've tested them extensively, they're a joke. The only nice thing is initial brake feel in the wet, but slotted rotors will give you the same benefit without all the downsides - just not as pretty.
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emoore924  



Joined: 13 Apr 2004
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PostPosted: Sat Mar 19, 2005 4:11 am    Post subject: Reply with quote

ditto.

For the street: don't bother.

For the track:

Vented: worth it.
Cross drilled: not worth it.
Slotted: probably worth it (allows that "plasma" to escape allegedly)
Cryod: Haven't tried it, but probably worth it.

I'd probably add cooling to the "worth it" list -- some kind of fresh air scoop -n- hose thing that directs air to the center of the rotor.

X-drilled are also prone to cracking, and therefore to catastrophic failure.
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Sun Mar 20, 2005 12:31 am    Post subject: Reply with quote

Correction - the notion of gases escaping from pads during braking is an outdated concept; while this used to be the case, it no longer is. This common misconception applies to two areas: break-in (aka bedding-in) and slotted or drilled rotors.

It was thought that the break-in period allowed "out-gassing" or "off-gassing" of organic volatile compounds in the pads. Modern pads don't have this, since they're baked before they leave the plant anyway. The bedding-in period (which should be followed) is to allow transfer of pad material from the pad to the rotor and back, establishing the optimal friction surface. As an aside, the simplest way to do this on a street car is to drive them real easy for the first 100-200 miles - no hard braking unless an emergency. After this initial period, make 3 hard stops (as hard as you can without locking wheels) from 60mph to zero, to get the pads up to temp good and hard. After completing those 3 stops, continue to drive to allow the pads and rotors to cool off - maybe 2-3 miles highway driving. Obviously you'll need to find a place where you can do this safely.

Break-in for racecars, obviously you don't have the same luxury on-track, but you can do your best. During a practice or qualifying session, you drive gentle on the brakes, braking lightly to get them up to temp - then hit them hard to bed them in, then allow them to cool at least one full lap of easy driving before pitting.

The benefits to following a proper break-in period is better brake wear (both pad and rotor) and better, more consistent braking.

For slotted or drilled rotors, obviously the same thought is erroneous for the same reasons. Slotted or drilled rotors would allow water to escape from between the pads and rotors, but there's no gas in there.

For background, I'll mention that in addition to all the wrenching and racing of these cars that I do, I'm also a Brake Engineer at Bosch; my regular responsibilities deal with vehicle dynamics more than details of brakes and how they work, but obviously a good working knowledge of brakes, chassis, and powertrains is a fundamental prerequisite for the work I do. So I've received quite a bit of training in this regard...
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emoore924  



Joined: 13 Apr 2004
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PostPosted: Tue Mar 22, 2005 7:56 am    Post subject: Reply with quote

ditto again.

operative word being "allegedly"
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ic932  



Joined: 11 Feb 2005
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PostPosted: Wed Mar 23, 2005 5:45 am    Post subject: Reply with quote

Well I'll forget about them in that case.The 4 pots and the club sport rims take care of the bling.LOL
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speedsta2003  



Joined: 12 Nov 2002
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Location: Lincoln, Nebraska

PostPosted: Thu Mar 24, 2005 7:53 am    Post subject: Reply with quote

I watched a recent show on braking systems in the past two years and they said that slotted/drilled/etc. rotors are a complete waste of money. They said that older brake pads created a gas barrier inbetween the pad and the rotor. But new pads will not create this gas, and thus slotted and drilled rotors are totally useless. They do not cool any better. The best thing for better braking is more surface area eg. having a larger diameter rotor and pad. As for saving weight, the most effective way is by finding a lighter material used for the rotor.
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maireeka  



Joined: 29 Aug 2004
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Location: North Alabama

PostPosted: Thu Mar 24, 2005 3:05 pm    Post subject: Reply with quote

This thread makes me sad, I just installed a pair of new brembo x-drilled rotors and was hoping my car would have supernatural braking power. I guess they DO look good, though.
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Ghostcloak  



Joined: 15 Mar 2005
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PostPosted: Fri Apr 15, 2005 6:03 pm    Post subject: Reply with quote

Well, This thread help me make my decision fairly quickly...

*crosses off "cross drilled rotors" from list of FUTURE MODS*

Thanks! I learned something here!

Wait... so just something I realized... The new Ford GT Has HUGE x-drilled rotors... No wonder Ford is crap .... Btw, I'm selling mine..
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Lizard  



Joined: 03 Nov 2002
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PostPosted: Sat Apr 16, 2005 10:02 am    Post subject: Reply with quote

Ghostcloak wrote:

... No wonder Ford is crap ....


hey they know exactly what is wrong they circled it didnt they.
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Ghostcloak  



Joined: 15 Mar 2005
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PostPosted: Mon Apr 18, 2005 2:27 pm    Post subject: Reply with quote

Lizard wrote:
Ghostcloak wrote:

... No wonder Ford is crap ....


hey they know exactly what is wrong they circled it didnt they.


Lol, I envy each and everyone one of you who own a 924/924s/931/944.... And I hate all of you that own more than one of the following previously listed.. STOP HOGGING THEM ALL

One day, I shall adopt myself into this wonderfully loving family of Porsche owners...
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Lizard  



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PostPosted: Mon Apr 18, 2005 3:58 pm    Post subject: Reply with quote

no we that own them will hog them all

are 928s in your list as well.
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Ghostcloak  



Joined: 15 Mar 2005
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PostPosted: Mon Apr 18, 2005 4:50 pm    Post subject: Reply with quote

Actually... I haven't even looked them up.. i've read up alot on the 924 and the 931... A little bit on the 924s and just a tad on the 944... But I don't know anything about the 928... What's the main difference between the 928 and a 931? Also... how would you rate a 944 compare to a 931? (I'm sorry for kinda stealing this thread )
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