Thread: Slotted rotors - Worth it?

I just had a look at their website and it looks like dba are now doing cross drilled for race spec. Interesting, and admittedly it was 3 years ago that I sat down with them. I wonder if the kangaroo paw rotor construction now makes cross drilling acceptable where traditional ventilating design didn't. Thats some good development in that case.

This said, if there are cracks I still would not run them. It's a bit like the Cooper rep that told me it was ok to drive on tyres that are missing lugs... until I asked about them being liable in the event of an accident.

Originally Posted by Slunnie

I just had a look at their website and it looks like dba are now doing cross drilled for race spec. Interesting, and admittedly it was 3 years ago that I sat down with them. I wonder if the kangaroo paw rotor construction now makes cross drilling acceptable where traditional ventilating design didn't. Thats some good development in that case.

This said, if there are cracks I still would not run them. It's a bit like the Cooper rep that told me it was ok to drive on tyres that are missing lugs... until I asked about them being liable in the event of an accident.

Would be nice to get an unbiased professional evaluation of these, because I am thinking of replacing the Defender ones soon.

Obviously, it's a question of driving style & location, but I've found that the LR rotors & pads work well for me.

While it isn't under extreme conditions, I've even had the "pink slip" (NSW) (RWC) inspector be impressed by the braking on my Disco 1.

The way that I look at it is: the D1 rotors aren't really designed to be machined, therefore I don't want to go to harder pads, thereby promoting disc wear.

On the other hand, if I go to different disc rotors, the selection of appropriate pads becomes a lottery.

I'm happy with LR's selection on this one.

The idea of slotted rotors, is to help release gases that form between the pad and rotor under extreme heat. The gasses come from the resin that bonds the pads together. This is what causes Fade.
Cross drilled(holes) or slotted rotors would actually have less surface area than non drilled/ slotted rotors.
Some pads come with slots in the surface as well for the same reason.
You don't realize how much braking quality you loose over time.
Machining the disc surface of old rotors can have an amazing effect at returning the brakes to there former glory. The same as if new rotors are fitted.
To get better brakes they have to be Bigger, with more surface area between pad and rotor +clamping pressure.
Braking power = friction = more heat. Greater surface area allows heat to escape. ie vented rotors.
Slots and cross drilling are really only needed on racing cars. You have to be really flogging your brakes to make the pads fad. Better quality pads would be my first option in this case.

Brake Handbook by Fred Puhn (HP Books) is excellent reading for any one seeking better understanding.

If my Defender was a dog I would say that it was suffering from Hard Pad. The last lot of Bearmach pads are so hard that they will last forever but don't have any stopping power. What do you guys reckon are the optimum brand of pads for stopping power?

IF you can get them, the EBC 2000 series are absolutely brilliant - I think I got the last 2000's for the Disco2 when I bought. Avoid the EBC 6000 series like the plague.

Originally Posted by Slunnie

Out of interest, I ran OE plain rotors with EBC 2000 series proper greenstuff pads and drove down through the pass towards Fitzroy Falls in NSW with a loaded tandem axle trailer that had failed brakes. The hotter my brakes got the better they worked and I was able to brake enough to hear the tyres squirm on the road on any/every corner - it was just sensational.

It's interesting that almost all accounts of using EBC greens on 4 wheel cars are positive. Because I've ridden mountainbikes with EBC and they were terrible. Didn't stop well and faded easily.
I do think that mountainbike rotors run much hotter than your average 4wd though.

I fitted the defender front calipers to my rangie with vented rotors and I highly recommend it to all. 25% more clamping force might not sound like much, but it's the difference between having 5% braking power in reserve and 30%.

Originally Posted by Dougal

It's interesting that almost all accounts of using EBC greens on 4 wheel cars are positive. Because I've ridden mountainbikes with EBC and they were terrible. Didn't stop well and faded easily.
I do think that mountainbike rotors run much hotter than your average 4wd though.

<snip>

talking to one of DBA's engineers a few years back he really, really disliked EBC pads as they were so inconsistent batch to batch. DBA do a lot of testing, both on the brake dyno and track and this is what they had found. At the time, he felt Ferodo were more on top of the asbestos free game than anyone else.