DBA Rotor Comparison

Dan · Postby **Dan** » Thu Sep 03, 2015 5:19 pm

That's interesting. Anouther reason not to run slotted rotors

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Hellmun · Postby **Hellmun** » Thu Sep 03, 2015 9:11 pm

Yeah I ran DBA's from the moment my stock rotors gave up and they were always the slotted 4000's. Looking through my logs I ran 1 set of XP10, 4 sets of XP12, Hawk Blue, Hawk HP+, Ferodo DS2500*3, DS3000*2 over 6 years and 3 sets of those rotors. That includes every club day, most all supersprints , mx5 challenge and 3 Wakefield 300's. Before I started logs I think I killed the stock rotors while running a set of pagid's but that was before I started on the ferodo's. Never had any vibration issues ever...I literally only replaced the rotors when they cracked which was usually from a slot but after a lot of abuse. That said maybe DBA changed the formula...or maybe there is another factor. Something like improper warm-up of the brakes etc.

StillIC · Postby **StillIC** » Thu Sep 03, 2015 11:41 pm

So, to summarise, those who are not against slotted rotors include:
Hellmun
Manga Blue
Madjak
StillIC (who copied Hellmun, on Hellmun's advice, a few years ago!)

Those against slotted rotors include:
Everyone else?

Please respond to correct me, in case I have just "verballed" anyone.

madjak · Postby **madjak** » Thu Sep 03, 2015 11:55 pm

I'm not for or against slotted... I think they are unnecessary and accelerate pad wear. But if you have them I wouldn't stop using them. If you dont mind going through pads quicker they may be marginnally better for very high performance. *

* based on my experience

Tony · Postby **Tony** » Fri Sep 04, 2015 12:02 am

I really don't want to get drawn into this, so here's a simple explanation:

1. To cut manufacturing costs DBA introduced the T2 and T3 design rotor which could be used on either side of the car. You no longer needed a separate LHS and RHS slotted rotors.
2. The design of the T3 slots act like sweeper arms, bringing pad material into the centre of the rotor face, rather than working it towards the outer edge of the rotor as with a traditional radial slot design.
3. The hot XP10 pad material seems really sticky and begins to accumulate in a "windrow" around the centre of the rotor face - see arrows on photos below.
4.This accumulated pad material eventually clumps into high spots around the centre of the rotor face - see circled areas on photos below. This causes severe pulsing of the brake pedal.
5. This windrow eventually builds up enough height such that it becomes the only point of contact between the rotor and the pad face. The brake pedal goes very "wooden" and you have no retardation. Needless to say, this ring of material around the centre of the rotor then gets excessively hot which glazes a stripe across the middle of the pad and also cracks the rotor. Game over.

I've had somewhat similar results with other pads, however the XP10 are by far and away the worst. I've subsequently changed to a different rotor design and pad material, and have had no problems since. YMMV.

Dan · Postby **Dan** » Fri Sep 04, 2015 12:39 am

[quote="StillIC wrote:Those against slotted rotors include:
Everyone else?

Please respond to correct me, in case I have just "verballed" anyone.

I'm not 'against' them, I'm the same as madjak and think they are unnecessary.

Hellmun · Postby **Hellmun** » Fri Sep 04, 2015 2:07 am

Well I wouldn't run slots if I had the option either but I certainly never found them to be a hindrance. I won't be trying the DBA T2/T3 pattern for some time though myself. The rotors I have are the old style DBA5000's and I just picked up a set of spares from V-sport because they're on clearance.

StillIC · Postby **StillIC** » Fri Sep 04, 2015 2:18 pm

Tony wrote:I really don't want to get drawn into this, so here's a simple explanation:

Well Tony, it seems like you have been drawn into this and I am all the happier for it! I love your work, as your explanation seems to be really useful, and a good lead as to why some of us (e.g. me) haven't experienced the same issues as you and others have. It appears that slots aint slots! Ahem.

I run the old style "handed" (left rotor must go on left side etc.) straight slots with the dust being drawn out radially. I had a look at my rotors this morning to find that I have a bit of a dark band (windrow, did you call it?) around the outer periphery of my rotors, exactly where I would expect it to be based on your logic. Well, well, well, three holes in the ground. I have just bought a newer pair of rotors with the slots patterned like yours, Tony, and I don't want to put them on now....especially since I was planning to go from Carbotech XP8 to XP10s!!

Your explanation perhaps gives good reason as to why Ford Australia put a single elliptical slot in some of the XR6 rotors some years ago. I can't find an image but they were a bit like the one in this link, but with only one orbit of the rotor, if you get my drift......
http://www.rapidrs.com.au/shop/?id=361

Slots must provide some benefit when companies such as Mugen describe the testing they do to optimise the angle and number of slots (swept back straight slots) on their rotors. I mean, they could be fibbing, but I doubt it. My seat of the pants testing makes me believe that slots provide a greater amount of retardation, but by how much, I don't know. Perhaps the answer is to have what the V8 Supercars have.....
http://farm3.static.flickr.com/2203/2266118521_1e7338378e.jpg
Or perhaps not.....
http://www.speedcafe.com/2013/02/16/v8-supercars-monitoring-brake-problems-at-sydney-test/

hks_kansei · Postby **hks_kansei** » Fri Sep 04, 2015 2:54 pm

My understanding was always that slotted rotors provided marginally less braking than plain ones since the slotted has less surface area for the pad to grab onto.

BUT, the slotted were less likely to fade since the slots allow and gases from overheated pads to vent out (rather than form a cushion)
As well as also letting out dust and crap.

In saying that I'm running 15 year old OEM rotors and $50 pads.

madjak · Postby **madjak** » Fri Sep 04, 2015 3:00 pm

If you look at all the high end racing series, they are all running slotted rotors so there must be a performance benefit either in braking consistency, driver feel or outright performance. If there wasn't a benefit they wouldn't run them... but remember they also running floating rotors and at least 6 pot calipers as well. These teams have budgets to replace rotors and pads far more often than us and the also have hours of testing getting the right combination of pad, ducting, brake biasing etc to get their rotors operating at an ideal temp. We don't get to do any of that other than basic guesswork.

I can't help but feel that the slots are being put on rotors more for looks than any tangible benefit. Similar to cross drilling. Make it look high performance like what the big guys run and it will sell. How can you sell a performance ford without slotted rotors?

Based on my limited experience, the slots are impacting on the life of the pads, and really aren't offering me better lap times that I can see or feel in the car. They increase the risk of brake failure (source Emilio) which is something I'm extremely conscious of as brake failure is one thing that can end it all in Motorsport. The Wilwood rotors have been reported to crack if the torque on the hat bolts isn't right has me checking the rotors between every event and even at half time.

If I had already purchased slotted rotors I'd still run them, but like the Wilwoods, I'd examine them before each event. At least running them will give us all some more information on how they work for you.

hks_kansei · Postby **hks_kansei** » Fri Sep 04, 2015 3:07 pm

madjak wrote:If you look at all the high end racing series, they are all running slotted rotors so there must be a performance benefit either in braking consistency, driver feel or outright performance. If there wasn't a benefit they wouldn't run them... but remember they also running floating rotors and at least 6 pot calipers as well. These teams have budgets to replace rotors and pads far more often than us and the also have hours of testing getting the right combination of pad, ducting, brake biasing etc to get their rotors operating at an ideal temp. We don't get to do any of that other than basic guesswork.

What I was more suggesting (granted, just from thought with no research) was that up to the point of pads getting hot enough to generate gas, the normal rotor may have a slight benefit (would likely depend on the pad size, slot size, and basically the surface area able to be utilised))

Once heat/dust/etc are generated the slotted would overtake in performance since it can deal with the effects of heat (gas/dust/stuff) more efficeiently.

Which would likely explain the usage on racecars etc, where there's a lot of heat to deal with, a lot of the time. So racecar brakes likely only spend an absolute miniscule amount of time at the temps that a normal rotor may have the edge. (maybe the first corner after the start? loading onto the truck at the end of the day?)

Tony · Postby **Tony** » Fri Sep 04, 2015 5:12 pm

StillIC wrote:I have just bought a newer pair of rotors with the slots patterned like yours, Tony, and I don't want to put them on now....especially since I was planning to go from Carbotech XP8 to XP10s!!

Run Forrest... run! :wink:

Knowing the laps times you're achieving Scott, I reckon you'd be a definite candidate to have the same, or at least a very similar problem. I'll be interested to see how you go.

I've always found that a couple of sessions running Hawk Blues cleans the rotors up nicely and gets rid of the build up. They get rid of those pesky slots too!!

marcusus · Postby **marcusus** » Fri Sep 04, 2015 8:41 pm

Lots of good info coming out now! Maybe I'll turf the slotted ones once they're truly done and dusted. I'm definitely not as aggressive on the track as many of you, so any benefit I would gain from slotted would be negligible.

But as madjak says, they definitely do look nice. I know that when I was looking in to getting slotted vs cross drilled, it seemed the cross drilled were definitely a more style oriented design, and were more prone to cracking. I'll see how the slotted rotors look in terms of thickness/wear once I get them back. Seems it's not worth going down the slotted/cross drilled path again though once these generic ones die.