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Cross Drilled Verses Slotted

Global_Warmer
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Global_Warmer Proficient

Global_Warmer

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I am after some new brake rotors for my 260RS Stagea. I want to do track days but I am worried about cross drilled brakes being "weaker" than slotted rotors and therefore warping under extreme heat conditions.

Am I being to worried and under informed here?

I can only get cross drilled (apparently) for the front so will have to run slotted on the rears. Will this be an issue?

Also can someone clear up... does this car have an R33 or R34 drivetrain.

Thanks!

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GTR-N1 Grand Master

GTR-N1

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I can only get cross drilled (apparently) for the front so will have to run slotted on the rears. Will this be an issue?

Thanks!

How come you can only get cross drilled for the front?

There's no problem tho' to run cross drilled at the front and slots at the rear.

Cons:

Under heat, cross drilled can form blue heat patches and then a bit of cracking.

Even slots that go right up to the edge of the rotor can crack too. DBA found this out soon enough

Pros:

Slots that stay within the edges are desirable whether they be straight or fish-hook

Dimpled rotors are fine (as in RDA)

Curved vanes within the ventilation space are desirable

MrStabby Grand Master

MrStabby

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The cross drilled that came on my car cracked at the track, as did DBA4000s with the retarded slot design....

Very surprised you cant get slotted for the fronts - I would have guessed that your RS would have had GTR brakes or similar. The 33 and 34 GTRs had the same sized rotors. Do you have brembo calipers?

MrStabby Grand Master

MrStabby

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Even slots that go right up to the edge of the rotor can crack too. DBA found this out soon enough

My guess is that its more that the slot is almost perpendicular to the edge, rather that the fact that it runs right to the edge (but agreed that is also undesirable)

The RDA dimpled/slotted/gold ones run the slot all the way to the edge, but the slot is the conventional 45 degrees or so to the edge. They've been ok for me, unlike the DBA4000s.

Global_Warmer Proficient

Global_Warmer

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The cross drilled that came on my car cracked at the track, as did DBA4000s with the retarded slot design....

Very surprised you cant get slotted for the fronts - I would have guessed that your RS would have had GTR brakes or similar. The 33 and 34 GTRs had the same sized rotors. Do you have brembo calipers?

You can get slotted alround. But can not get cross drilled for the rears, only the fronts.

the vehicle has Brembo brakes alround.

R32.GTR Collaborator

R32.GTR

Posted
Posted
My guess is that its more that the slot is almost perpendicular to the edge, rather that the fact that it runs right to the edge (but agreed that is also undesirable)

The RDA dimpled/slotted/gold ones run the slot all the way to the edge, but the slot is the conventional 45 degrees or so to the edge. They've been ok for me, unlike the DBA4000s.

shit.. just bought slotted DBA4000s

are they really that bad?

GTR-N1 Grand Master

GTR-N1

Posted
Posted

^^^ If the ends of the slots are away from the perimeter of the rotor, it's all ok.

If your slots do meet the edge of the rotor at something like a 45 degree angle, you just need to watch them.

But there have been some batches of DBA 4000s with 5-10mm length slots meeting with the edge and perpendicular to the edge that have been notorious for cracking (via high heat > expansion > contraction).

When I cut glass (in leadlighting), I must start the cut right from the edge/perimeter > the glass is much more easy to break.

Another example is that medicinal tablets are meant to be 'scored' right up to the edges, to facilitate breaking cleanly - otherwise they're hard to snap.

Therefore, heat-cracking on cross drilled rotors starts at the extreme edge of the hole - which is the weakest point.

MrStabby Grand Master

MrStabby

Posted
Posted
shit.. just bought slotted DBA4000s

are they really that bad?

They were pretty bad - Here is the thread. The bottom of the third page shows my ones, they don't have the slot all the way to the edge (it stops just short). I dont know if they've updated the design since then. If you're not tracking it it will be fine.

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