Disk rotors

turbs · tinkerer Joined: 22 Apr 2002 Posts: 58

Has anyone used the dba sport X Drilled and sloted or disk rotors or even just the vented ones as advertised in the rare spares gemini shop? Worth the money?

WAY2LOWatwork · tinkerer Joined: 02 Apr 2002 Posts: 188

they should work well... ive got dba piazza turbo x drilled adn slotted rotors on my gem. never actually driven it though cause im still building it up but by the looks of it, it will REALLY a stop. a mate has the dba's on his commodore and he rekons they make a difference and they can take a lot more abuse than standard brakes.

Adam · Site Admin Joined: 04 Oct 2001 Posts: 682

I've got no problems with the slotteds but I'd avoid the cross-drilled rotors, cross-drilling in this instance is all about looks (yes, yes it is... if you want to argue, please go right ahead), and the reduction in mass from the removed metal actually undermines the basic design of a brake rotor (that is, to be a heatsink).

Even the best gemini brakes (dba slotted rotors, race pads, dot 5.1 fluid, everything in brand-new condition) can only stop as well as their design allows. The small, thin and solid rotors are just unable to disperse the heat generated in repeated hard stops.

WAY2LOWatwork · tinkerer Joined: 02 Apr 2002 Posts: 188

i thought the x drilling was for a reduction in heat and to aid cooling. also i thought the holes were put there for anti glazing of the pads???
neway would they really sell them if the x drilling was a undermining feature of the brakes?
oh well i guess ill find out, till i can get a volvo disc brake conversion ($1000 from just gemini spares Razz

)

Adam · Site Admin Joined: 04 Oct 2001 Posts: 682

Historically yes, but the deglazing and de-gassing is more the capably handled by the slots... You will note that DBA recommends the slotted only rotors for more intensive applications while the cross-drilled and slotted rotors are promoted for 'the look'.

WAY2LOW · tinkerer Joined: 07 Oct 2001 Posts: 176

ahhh.. fair enuff.......
they r just "tempory" brakes ne way. i need a volvo brake conversion Surprised

)
gotta stop the rotor ;o)

Racegem · backyard mechanic Joined: 30 Jan 2002 Posts: 987

I sort of agree with Adam on this one. The cross-drilling should actually help with a bit of heat dissipation due to the increased surface area, however, on a street car, where the brakes are getting hot, cold, hot, cold, this can lead to heat fractures developing between the cracks; I've seen it. Although some DBA rotors I've seen have the hole spacings further apart to help stop this happening.
The other reason for brake fade is that the quality of resin used to bond the brake pad material together varies with the price of the pads. Cheapie pads use cheaper resin, which has a lower boiling point. As the resin boils, it turns to a gas and the pads "aqua-plane" on the surface of the disc rotor. The better quality of pad, the higher the boiling point of the resin, the higher the temperature of the brakes before brake fade. The slotted rotors help wipe away this gas build-up resulting in a slightly higher temp. before fade.

Yonnee.

Gold TX Sleeper · backyard mechanic Joined: 05 Feb 2002 Posts: 509

Just some questions, do the slotted rotors have a noticeable increase in pad wear ? Do they chew them necessitating the need for a pad change more often - like once or twice a year ? How often are the change intervals on rotors like these ?
Or have the slots been shaped to help avoid this problem ?
In short, do they wear your pads alot quicker ? And how often is a pad change necessary with day to day driving & street racing on weekends ?
Jasyn...

Adam · Site Admin Joined: 04 Oct 2001 Posts: 682

The slotted rotors will wear out your pads faster... as for how long they will last, that is akin to asking "how long is a piece of string", the will last until they are worn out.

Racegem · backyard mechanic Joined: 30 Jan 2002 Posts: 987

...cause it all depends on the pads you buy in the first place. More expensive pads not only have better quality resin, but usually harder pad material. And then some compounds, ie; Bendix Metal Kings, will chew through rotors quick-as, but have a higher CWT (constant working temp.) than Bendix Standards. I'm going to try a set of EBC greenstuff pads. They're a Kevlar-copper compound that's not as harsh on rotors but have a CWT of 550deg.C. (BS's only 280C and BMK's mid to high 400's) BUT..... they're not cheap.

Yonnee.

Adam · Site Admin Joined: 04 Oct 2001 Posts: 682

Speaking of cheap brake rotors, was over playing racecars yesterday and we were 'taking stock' of the pads from rnd 2... 6, count them, 6! sets of pagid blue fronts at over $100 per pad... I'm in the wrong business I tell you.

Slug · tinkerer Joined: 06 Oct 2001 Posts: 196

Speaking of brake mass, DBA did a test on a stock commodore. the test involved a stop from 100km/h to a dead stop. they then machined 1 mm off the rotor(as you do when you overhaul your brakes) this added "4m" to the stopping distance, which is roughly the length of the car. If that isnt a wake up call then nothing is.... Michael

GasGem · backyard mechanic Joined: 05 Nov 2001 Posts: 755

what?????

by removing 1mm from the width of a commo rotor it added 4m to the stopping distance???? how why??

there is still the same surface area,

did the change in surface ie after machining affect the contact on the pads....

this just does not make sense

i'd be very interested in knowing more about this,

cheers
Eggy

Loz · backyard mechanic Joined: 05 Oct 2001 Posts: 943

Along the same lines. 85% of commodores brakes are not sufficient for them to pass present day aust standards. If you were to have them tested to the present day standards required for a car of its weight and power, they wouldnt pull up soon enough.

Fastgem · tinkerer Joined: 04 Oct 2001 Posts: 166

Same surface area but less disk to heat, therefore the disk heats up quicker and most people would be a wear that hot brakes = shit brakes.
I am assuming was an extra 4m after several runs which although quite crap is understandable. Dont tell me it was 4m on the first run.. that would be terrible.