Do slotted rotors really help on street trucks? This is not a judgemental question; I am working on a diesel swap, and I want to make sure it stops well. The current system works really well (I panic stopped a 6600# trailer in "only" an extra 20 feet). The current system is stock (3/4 ton, 2004 Silverado).
Regardless of vehicle type:
Brake pads squeezed against a spinning rotor give off a gas that mitigates pad-to-rotor pressure a bit.
Dimples, slots, and 'drill' holes give that gas an escape route to the central rotor vent.
(If the rotor is UNvented, the dimples / slots / drill holes are cosmetic. Hopefully the pad has a slot?)
Obviously they are most useful during longer emergency braking events, as well as intense autocross / pursuit driving where brake temps do not get a chance to come down under 'boring commute'.
Those who drive conservatively have little to no need for them (better to have more than you need).
In the rain, dimples / slots / 'drill' holes yield a pleasant surprise; water can't get between the rotor & the pad either!
So long as the rotor ALREADY has at least enough mass AND venting capability for what they are being asked to do AFTER the dimples / slots / 'drill' holes are taken into account, they are helpful.
No, "brake pads squeezed do not give off gas that mitigates pad to rotor pressure." - When brake pads get so hot the materials in them start to melt, then they give off gas. This does not happen every time you brake, or every time you drive.
Actually during "longer emergency braking events" is when slotted and drilled rotors hurt braking. They have less surface area which creates less friction. A blank rotor is going to stop in a shorter distance than slotted or drilled rotors.
My analogy is always, if you live in a city where people drive with a heavy foot on both pedals, like LA, New York, DC, Austin, you have no clue how to coast, and only push down on both pedals too hard, you MIGHT benefit from slotted rotors. If you live out in the country, or take long commutes, and your biggest braking concern is if an animal such as a deer were to jump in front of you, then you DEFINITELY WANT blank rotors, because they will create more friction, and will stop in a shorter distance.
Two caveats:
1. Most of TYF is already aware that more brake rotor mass is always a good thing, which explains and justifies upgrading the GMT800 front brake hardware for larger more modern rotors.
Normally the small amount of rotor mass lost to dimples / slots / 'drill' holes still leaves more than plenty of rotor mass, and enhances venting.
Some of you may know that GM's '90s B- & D- cars lacked enough front rotor mass for police pursuit duties, that officers complained of brake fade during MSP road course testing, and that GM spent the minimum possible to alter the front air damns to provide more rotor cooling by just enough to not need to make the J55 limo front brake upgrade ABS compatible for 9C1 duty (because of GM's plans to kill the B- & D- cars).
Most of the Impala SS Forum (ISSF) is well aware that a front rotor upgrade is (in their case) REQUIRED if the brakes need to withstand anything more intense than a once-every-blue-moon 60MpH-0MpH panic stop (Astrafari front brake rotors at a minimum).
2. Slots & dimples are generally preferred over 'drill' holes for two reasons:
a. Rotors that already lack enough mass to start, with lose even more to 'drill' holes.
Counterprodcutively, this could lead to excessive rotor temps during harder braking, softening of the pad / rotor, and/or brake fluid boiling.
b. Holes actually drilled into originally plain rotors are potential rotor fracture points.
This is why most 'drill' holes are actually pre-cast into the rotor.
In other words, ANY bigger front brake rotor upgrade for a GMT800 is a wise investment.
Slotted and drilled rotors are designed for
EXCESS gasses. The average person would never need them on the street, and you would earn at least one reckless driving ticket if you ever NEEDED slotted on the street. They are designed for a track, for repeated excessive braking, and no time to cool off between.
They use less material, companies can charge more for em, they wear out quicker, and people think they are the "cool thing to do", so yeah, companies are going to keep on selling them.
The reason we put larger rotors on is because they have more surface area so that we can use larger pads. Larger brake rotors are heavier, and have more rotating mass, which is a bad thing. If we could all spend $20K on carbon fiber brakes, we would. The mass is not a good thing, it's a trade off so that you can have larger pads.
"rotor mass loss because of drilled and slotted"? What are you talking about?
If drilled rotors are "stage 2", slotted and/or dimpled rotors would be considered "stage 1", but if you say it like that, its as cool as saying nos.
Drilled rotors will not have "excessive heat, due to loss of mass because of the drilled holes".
