Drilled/Slotted Rotors

[ChevyBrad1500]

Has anyone replaced their rotors with the drilled/slotted type? Do they improve over oem? What brand did you buy? What brake pads? I think I will be needing brakes soon. Approaching 40,000 miles, had front rotors turned due to shaking about 10,000 miles ago. Now they are getting a little shaky again.

[Waaazooo]

I would recommend one or the other. Slotted or drilled, I believe the use of both the way aftermarket produces them is too much loss of surface area. The rotor is pretty much the same material as long you're not buying $25 rotors. Your biggest changes in braking feel is going to be in the pads and stainless steel brake lines.

 

 

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[NemesisC5]

The holes and slots allow for off-gassing of pads in racing applications. Brake torque is influenced mostly by pad material and to a lesser degree by rotor diameter. A set of good brake pads with a higher friction coefficient will yield the most improvement per dollar and work with stock rotors and calipers. If you want to spend more you can purchase a kit with brackets that will allow you to position your stock calipers further away from wheel center and accommodate larger diameter rotors but you'll still need pads with a higher friction coefficient for your calipers to experience a noteworthy improvement. Pads are the component to begin with, always.

[Bobber]

Sorry ChevyBrad, I'm finding that I wrote a novel... but you asked and others responded, which made me feel like I should qualify some of their answers in addition to sharing my answer with you.

 

What did I do?

I purchased the Power Stop K2069 / K2083 sets (drilled and slotted rotors with carbon fiber/ceramic pads) back in May since I was over 100k miles with my OE brakes at that time and knew I'd be replacing everything before very long. I still haven't done the swap, but probably will in the next few weeks, so as yet, I can't tell you anything firsthand about these. Yes, I (now) have 103k miles and still am on my OE brakes! But, I do a lot of highway driving... I haven't looked at my engine hours recently, but I know I've been (based on the last time I did look/calculated it against total miles) somewhere near a 45mph average (lifetime of truck); so I'm guessing that I'm in the 22-2300hr range. I can confirm this later if need be.

 

The Surface Area debate:

I disagree with others' thoughts regarding total surface area loss on combo drilled/slotted rotors... if you look at a drilled rotor and at a slotted rotor, and then look at a combo rotor, you'll find that many of the makers alternate between holes and slots in the same total pattern (1/2 holes & 1/2 slots, vs the same number of positions occupied by only slots or only holes). So if you go with only slots you actually have less surface area due to a continuous groove at every position than if you had only holes at every position; with the surface area of a combo rotor (with holes and slots) being somewhere in-between. That's just from a crude evaluation perspective.. you'd actually have to look at the surface area in contact under the pad at all given instances of rotor position relative to pad to know if there is really any "loss" in surface area from all slots vs all holes or combinations. All of life is a compromise... so the bigger question is are the gains in other aspects (by either or both slots and holes) worth the minimally reduced surface area.

 

Off-Gassing (is it only applicable in racing use?):

Slots and holes do provide an opportunity for off-gassing at super-heated temps on the track... but, in the same way, they also provide a place for any water (that makes it under the pad) to go (is it raining?). If you can avoid creating trapped steam, the rotor and pad will run cooler; and the exiting water takes heat with it. Slots or holes will provide this ability... Slots also create a wiping action that helps keep the pad clean. I'm expecting some folks to debate/challenge this... but, I've seen the extreme situations (mudding, bogging, etc, that prove that slots or holes clean rotors/pads when compared to solid surface rotors. And, the addition of the holes (with the airflow created by the standard ventilated brake rotor) carries with it an opportunity to further cool the pad/rotor surfaces.

 

Pad materials reign supreme:

Softer/Stickier pads are like stickier tires... they will certainly improve braking distance, but won't last as long; and sometimes will overheat the rotors if the pads and rotors are not matched well (in terms of materials). I don't need or want stickier pads... they won't last, usually create more dust, and I'm not racing for a paycheck... But, be careful about using "sport" or "performance" pads with stock (OE/aftermarket) or cheaper rotors. The higher heat created by those pads has to go somewhere!

 

I went with the sets listed above because of the following:

- GM Replacement Parts pads and rotors are extremely overpriced - but if I could guarantee that I would get the same life from them as I did from the true OE (assembly line) parts, then I'd spend it. Unfortunately, having been in the Automotive supplier business (including to GM) in my past, I know that the OE Service (OES) parts are not necessarily the same as the OE parts since the GM Parts organization shops around and doesn't just automatically use the same parts provided to the OE assembly line - especially on wear items like brake pads, rotors, bulbs, suspension components, gaskets, etc. Those parts don't even have to meet the same life and performance requirements that the OE parts do... "Nobody measures performance of a 3 year old vehicle like they do one that is fresh on the new car lot... so who cares whether they are as good or not?"

- The Power Stop sets I chose are not "track" or "sport" pads so they should last longer than than those labelled/marketed as such.

- Reviews written by purchasers of these items have indicated that brake dusting is not a significant issue with these.... (there is nothing I hate worse than blackened wheels from brake dust). Didn't have to worry about it with the OE pads and I don't want to now either.

- The Power Stop sets are not the bottom of the barrel (in price or performance selection), so I'm hoping that I'm getting better materials than the cheapest stuff if not some of the better rotor materials for the money (since they offer the same rotors with the more "performance oriented" pads as well). This makes me think that the rotor material has been selected to tolerate a lot more heat than I'll put into them. (Prior purchaser/owner reviews also provided this type of feedback about how these items seem to hold up).

- The Power Stop sets are "matched packages"... so they should work well together (pads and rotors).

 

Do I "need" slots and holes? No... my OE brakes prove that (never felt that I wasn't stopping fast enough, and who would complain about 100k miles!). I do haul a 7x16 enclosed trailer (7' door) with my Polaris Ranger or other items - so there are times when I'm working the brakes a little harder (yes, the trailer does have electric brakes, so maybe not a whole lot harder)... But remember, I don't use my brakes as often as most (based on my truck's higher lifetime avg speed) - so, when I do use them, I need to create more heat to get it stopped than an "in-towner" does. I just don't create the heat soak as often (stop, go, stop again before things have a chance to cool). So maybe - just maybe - those features make more sense for someone who does a lot of stop&go.

 

There is a break-in process put out by Power Stop - you should find it on Youtube so I won't have to scan/share the paperwork that I got with these parts

 

Quite honestly after reviewing their recommended procedure, I recognize that what they provide is actually a good reminder/primer on how everyone should operate (not the sequence, but the philosophy). In particular, not leaving your foot on the brake pedal any more/harder than necessary after a stop (quick way to heat soak one single spot on the rotors causing warpage or non-parallelism) - and roll a foot or two after you get stopped to move the hottest spot on the rotor away from the pad.

 

This is probably a part of why my OE brakes have lasted as long as they have... it is something that I have done all along (as well as not doing a lot of braking in the last 10-20' before the stop). I tend to back off on my braking effort in the final 10-20 feet so that I come to a smoother, more gradual stop - rather than feeling like I'm gonna plant my (or my passengers') nose(s) into the steering wheel (dash) in the last 10'. (Passengers have commented that I'm a smoother driver than most - but I'll freely admit to initiating braking later than many)... So I start my braking a little later and harder, then taper off, rather than have a long braking period (which can add a lot of heat; or braking hard all the way to the very end which can throw a lot of heat into the rotor with no place to go once stopped).

 

In closing...

Unless you are racing, braking performance is all about:

1- maximizing the moment arm of the pad (bigger rotors - limited by wheel size in many cases),

2 - increasing the force applied to the pad (multi-piston calipers - limited by wheel size and suspension/steering geometry) or

2a - increasing the pad area

3 - increasing the coefficient of friction between the pad and rotor. (rotor/pad materials)

4 - life (material selection of rotors and pads - rotors and pads just need to last the length of the race). -

Increasing #4 (life) usually means reducing #3 or spending cubic dollars on #3.

 

For the true daily driver most of these factors are predetermined except materials (pad and rotor) so the marketing departments of all aftermarket components suppliers try to convince you that you need something from the track so they can sell you something. Find quality materials, and use them wisely... it won't matter much in the long run about drilled or slotted. If you end up with either/both, it sure won't hurt anything.

[Bobber]

So... I finally got around to changing out the front brakes (will do the rear's tomorrow). The truck now has 107,000 miles and something just shy of 2500hrs (actually rolled the odometer past 107k as I was doing the brake bedding/break-in process that PowerStop recommends). I decided to do the brake change after hauling my trailer around this past weekend and encountering a fair amount of brake shudder.

 

In reality, I could have gone with brake rotor machining only; (but, having the truck down while having that done isn't an option for me):

 

The pads had anywhere from .124" to .25" of remaining material to the bottom of the groove - lowest pair of dims were on the right side: .124" and .134"; and the left side had .202" and .254" remaining. Quite honestly, I'm amazed! The dealership tech had commented (at my 97k oil change and tire rotation) that I should consider getting the brakes done as there was some rust scale growing on the rotors and since the pads were OE, they had to be getting near the end. (I don't know why anyone would think that rust scale growing on rotors in non-contact areas means anything significant at all!?!? I mean, I do live in WI - smack dab in the middle of the road-salt/rust belt!) They quoted me $1000 to do it - that was when I started looking for parts on my own.

 

At this point I might be able to leave the rears alone for a while... but I plan to swap them out just to have the Powerstops on both ends.

 

I'll be keeping my current rotors and getting them machined (for future use, if they aren't showing signs of heat-checking after machining). Just wish I could find a way to buy the exact same pads as were installed during production in 2013!

 

 

[Bobber]

Here are some pix of a quarter in the groove:

[truckguy82]

Aftermarket = go with solid rotors

 

Slotted and drilled on a truck = complete waste of money

 

A truck has heat cycles, it's not a race car that has to cope with continuous hot brakes.

 

You're completely wasting your money. Only thing that matters is the size of the rotor, the size of the caliper, the pad, and the fluid. Brembo blanks is the gold standard for affordable and high performing aftermarket rotor.