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cross drilled slotted discs

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vnunnally Van Nunnally
Richmond, Virginia, USA   USA
1972 triumph spitfire. i just installed a new set of cross drilled slotted rotors on my car . am i going to have any issues with the new rotors . i am reading horror stories yet many autos use them. thanks Van

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SpitMan Avatar
SpitMan Doug Walls
Brandywine, Maryland, USA   USA
1970 Triumph Spitfire MkIII "70 Spit"
1998 Chevrolet Corvette "Silver Fox"
2007 Chevrolet Silverado
2013 Chevrolet Malibu "Pearl Baby"
Yes, you will get a lot of pro and con on the slotted discs. I put them on mine but the car has not seen any serious use yet........still restoring the car.

In my humble opinion and from research I've done:
I drive somewhat spiritedly sometimes and believe that with the slotted rotors to reduce heat (and thereby reduce brake fade), very good brake pads, SS brake hoses, and everything in good working order; you will not have any problems. The next step would be to go to the larger brake mods but this is not the subject of which you are asking.

R/ Doug/SpitMan

clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1495092 by vnunnally 1972 triumph spitfire. i just installed a new set of cross drilled slotted rotors on my car . am i going to have any issues with the new rotors . i am reading horror stories yet many autos use them. thanks Van

Depends on how you use them, many folks report cracks developing around the holes, and even broken rotors.
The whole reason for cross drilling is to extend the thermal capability under extreme usage, ie racing, hard street driving, etc.
For racing where maintenance and inspection is very frequent and part replacement is routine, that's no problem.
Avoid that kind of extreme usage, they will not get hot, and the problems will not develop, at least not as quickly.

But if you are not going to use them for the purpose they were developed for, then what's the point of fitting them?

Automotive Bling?

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quikrx Ralph Hansen
Antioch, Illinois, USA   USA
1962 Triumph Herald 1200
1969 Triumph Spitfire MkIII "Gloria"
1987 Mazda RX-7 "Mistress"
2003 Toyota Celica GT-S "Natasha"    & more
Doug, you may have missed the "drilled" part of Van's post - in the real world slots are slightly beneficial, they help remove pad gases from between the rotor and pad allowing the pad to keep more consistent contact, the gases tend to push the pads away, the drilled part does basically nothing, it does reduce the heat sink of the rotor and does make the rotor much more prone to cracking, even on the street

SpitMan Avatar
SpitMan Doug Walls
Brandywine, Maryland, USA   USA
1970 Triumph Spitfire MkIII "70 Spit"
1998 Chevrolet Corvette "Silver Fox"
2007 Chevrolet Silverado
2013 Chevrolet Malibu "Pearl Baby"
No, I did not miss the drilled portion. However, does not the slots together with the drilled holes allow the gases to excape??? In other words; if gases develop; heat is dissipated somewhat via the holes; but the slots allow the gases to move out from under the pad area.

I knew this discussion would come to this old debate!

In reply to # 1495110 by quikrx Doug, you may have missed the "drilled" part of Van's post - in the real world slots are slightly beneficial, they help remove pad gases from between the rotor and pad allowing the pad to keep more consistent contact, the gases tend to push the pads away, the drilled part does basically nothing, it does reduce the heat sink of the rotor and does make the rotor much more prone to cracking, even on the street

tmpass Avatar
tmpass Tim P
Medway, MA, USA   USA
1970 Triumph GT6+ (MkII) "Capo"
1970 Triumph GT6+ (MkII) "Blue Oxide"
In reply to # 1495117 by SpitMan
I knew this discussion would come to this old debate!

The whole point of the original post was to start this discussion.

I agree with carter that for a spitfire street driven car, its for looks only and unless there are Wilwood or Brembo calipers to go with them, it's only halfway done.
Without the high temps of racing use, I don't see the point of them.

Andy-Sherry Avatar
Andy-Sherry Gold Member Andy Martin
Portland, OR, USA   USA
Waste of money unless you race



Andy&Sherry
1974 Spit 1500 Carmine Red
1977 Spit 1500 Pink Panther Pink

Always learning something

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
So drilled discs "allow the gasses to escape", do they? What 'gases'? Brake pad material is non-volatile.
And where to? When the brakes are applied both ends of the drilling are closed by brake pads. Maybe the tiny cavity is enough???

Slots? maybe gases escape from the ends, if they are longer than the pads are wide - but the pads should be barely narrower than the discs, else you are wasting disc space.
Their edges keep scraping the pads clean? Of what? The 'merde' that those who sell them dish out.

No, the best mod is vented discs. Slots and drillings can do nothing to keep brakes cool, and over heating is what leads to brake fade.
Even then, unless you race or make a habit of pass storming, you will do well to get your brakes to fade, and even then, a set of 'hotter' pads will do as well.
I use Mintex 1155s, and Ford Capri venteds. And I'm the Last of the Late Brakers!

John

clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1495136 by tapkaJohnD So drilled discs "allow the gasses to escape", do they? What 'gases'? Brake pad material is non-volatile.
And where to? When the brakes are applied both ends of the drilling are closed by brake pads. Maybe the tiny cavity is enough???

Slots? maybe gases escape from the ends, if they are longer than the pads are wide - but the pads should be barely narrower than the discs, else you are wasting disc space.
Their edges keep scraping the pads clean? Of what? The 'merde' that those who sell them dish out.

No, the best mod is vented discs. Slots and drillings can do nothing to keep brakes cool, and over heating is what leads to brake fade.
Even then, unless you race or make a habit of pass storming, you will do well to get your brakes to fade, and even then, a set of 'hotter' pads will do as well.
I use Mintex 1155s, and Ford Capri venteds. And I'm the Last of the Late Brakers!

John

Done properly, the holes are drilled at an angle to the rotor surface.
This enables them to impart pumping action, creating airflow that helps with heat dissipation during the
90% of their rotation when not obscured by the pads.
That said, vented rotors are far more effective, having better ratio of surface area to mass, and more
effective pumping, although their greater mass increases rotational inertia and unsprung weight.
But greater mass also requires more heat energy to heat up to a given temperature.

From a practical standpoint, brakes are subject to a heating/cooling duty cycle in use that determines their
suitability for a given race course, or usage (mountains, large payloads, towing, etc.)

If the brakes you have perform properly for what you do with them, there is little reason to change.

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vnunnally Van Nunnally
Richmond, Virginia, USA   USA
yes many negative comments . i have steel braided lines (new ) and just got some regular brake pads from moss. i think they will be fine thanks :

clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1495155 by vnunnally yes many negative comments . i have steel braided lines (new ) and just got some regular brake pads from moss. i think they will be fine thanks :

They should be OK.
Just inspect them now and then.

tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
Not negative, constructive!
+1 for Carter, for properly set up OE brakes. Add 'hotter' pads if you need.

Drilled/slotted discs are a marketing dream!
John

Brad.Cogan Avatar
Brad.Cogan Bradley Cogan
RAF Cosford, Shropshire, UK   GBR
1977 Triumph Spitfire 1500 "Wray"
2007 Fiat Grande Punto "Pepper"
I've got them and love them.

I don't think you'll have any issues with cracking or anything since these are quite thick as they are not vented. But a regular check should be carried out (should be with regular discs too!)

I found that the biggest difference with these is in the wet. I think this is probably because the water escapes quickly through the grooves and holes instead of staying on the disc, making it 'slippy'. That's just my guess but there is a noticeable difference in the wet



Brad Cogan

1977 Triumph Spitfire 1500 'Wray'
2007 Fiat Grande Punto Active 1.2 'Pepper'

SpitMan Avatar
SpitMan Doug Walls
Brandywine, Maryland, USA   USA
1970 Triumph Spitfire MkIII "70 Spit"
1998 Chevrolet Corvette "Silver Fox"
2007 Chevrolet Silverado
2013 Chevrolet Malibu "Pearl Baby"
There you have it. Cruising and daily driver; go standard brakes. Hot foot and racing; go for the other stuff.

The high end cars use the drilled or drilled and slotted probably just for the Bling.........yes, no????

Anyway, when mine crack or warp; I'll eat crow! LOL.........good discussion, ending as I thought.

Best regards,

Doug/SpitMan

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
In reply to # 1495155 by vnunnally yes many negative comments . i have steel braided lines (new ) and just got some regular brake pads from moss. i think they will be fine thanks :

I think you are just getting opinions. Mostly from members that (I KNOW) have considerable experiance.

Personally I try not to be negative about something someone has already bought/installed, but if asked beforehand I will give an oppinion based either on my own experiance or what I have seen. If it is hearsay, I will say so.

Belive it or not, but the members here, collectivly, have Hundereds of years experience with our cars.

Not all of us are right all the time, and some of us are (legitimately) getting to be Grumpy old farts, but even so this site is a valuable resource. Use it asyou wish!

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