Upgrading to HD rotors

[Reprise]

It looks like I managed to warp the front rotors on the Sierra while I had the trailer attached to it this past week. Curious as to the 'why', since I didn't really drive super long distances, or stomp on the pedal super hard. Only thing I can figure out is that perhaps the front wheels were doing too much of the braking (TBC out of adjustment?), and / or GM-spec rotors are prone to warpage (apparently common, especially on the 1/2-tons)

So I'm figuring that I won't be able to have the rotors turned; I don't know of any place nearby that still offers the service. So we'll shop for new (the ones that came on the truck had rotors / pads that were practically new, but I don't know who made them. And they worked well (or so I thought)).

Have been looking for 'cross-drilled without slots' (I remember Mooseman (?) saying the slots chewed up pads -?) But there doesn't seem to be much call for 'drilled-only'.
Raybestos makes a 'wavy' slotted option (and AC Delco uses it on their Gold / Advantage line). Here's a representative pic (they call it 'S-groove') Of course, this has no cross-drilling...



So my choices seem to be drilled *and* slotted, or maybe just the Raybestos ?
Suggestions? Leaning toward the PowerStop Z36 'extreme truck and tow' option; they're pricey, but I don't mind the spend, if they'll hold up. They're drilled / slotted, and I don't see that they carry a 'drilled-only' option.

 

[Mooseman]

I am dead set against drilled or slotted brake rotors. They're BS. Check this post by @Chickenhawk :

Warped rotors again.... AC Delco slotted rotors?

Hey everyone. So I had these brakes replaced all around about 3 years ago and I believe the front rotors are warped again so I am in the market for a new set of rotors and pads as I am getting pulsation and vibration hitting the brakes from higher speeds. Would like to stick with AC Delco so I...

gmtnation.com

Do you know which brand was on there last?

 

[Chickenhawk]

LOL. I have been spending weekends the last few summers course marshaling on the road race track. If drilled rotors had the slightest benefit, they would be used on the full-cage race cars or the serious Time Attack cars. They aren't.

In fact, the only cross-drilled rotors we see at the track are the street cars who use them while hot lapping. They are strictly for looks. Don't misunderstand; I have nothing against good drilled rotors. They are better than cheap solid rotors. They just provide no appreciable benefit. The mass that is removed means it lessens brake performance instead of improves it, but for most of us, the disadvantage is negligible.

Lest anyone misunderstand how much full out race cars and the fastest Time Attack cars use their brakes, my corner is usually turn three. The long straight (taken at full throttle all the way) leads to a long sweeping 45-degree turn one, followed by a slight kink at turn two (also taken full out) and then my corner, which is a tight 180-degree hairpin. The track record was set in the 1970s by a racer named Gilles Villeneuve (yes, THAT Gilles Villeneuve, who went on to be World Champion) and we recently had a street car come within half a second of the track record. In a street car. (Chev Camaro) Solid rotors.

 

[Reprise]

Do you know which brand was on there last?

No idea. Guessing they were a budget / economy option, given prior ownership. They were fine until I hooked up the trailer. Of course, given the size of the pads, I'd expect them to stop an unloaded truck in pretty short order (they're like two Accord front pads, laid end-end.)

@Chickenhawk -- noted. You were spot on on the NUCAP pads, as I attested to when I put them on my Voy. Will find a set of same for the Sierra, and go with the best solid rotors I can find.


In any event, it's gonna be a little while, as I've got the Envoy in the garage and it ain't coming out for at least the next couple of weeks. And my Accord's A/C has apparently sprung a leak, so it's next to go in, before the Sierra (which is still frosty, thank dog).

 

[Mooseman]

Probably anything in a higher end like ACDelco Pro or Gold in pads and rotors would be good but then you say that "GM-spec rotors are prone to warpage (apparently common, especially on the 1/2-tons)". I wonder if there's a heavier rotor available? Looking at RA, there's some with high carbon. Maybe those would be better?

 

[Reprise]

I wonder if there's a heavier rotor available? Looking at RA, there's some with high carbon. Maybe those would be better?

One thing I have noticed, as I spec out options, is that they're all the same nominal thickness... and all have the same discard spec thickness, which isn't that much from new. Here's a screencap of the ones for a 2500HD truck, same gen as mine (incidentally, there are two different part #s, and the ones for the 3/4 ton gasser are $20 more than for my 'heavy half-ton'. Yet they're exactly the same, except for the part #. Go figure... )



I saw the high carbon options, too, but hadn't really thought they'd be better for my application than the "truck / tow" category. Now that I do a quick search on their benefits, they're supposed to dissipate heat better and be more fade resistant. Some are even advertised as 'no warp'. I'll have to take a closer look at them (so, 'thanks' for bringing them up... LOL)

Napa now stocks the Sierra's pads in their 'Adaptive One' line, which was the NRS / NUCAP version when I bought them for the Envoy. So I've got those in a cart. Ironically, they're more expensive than the Powerstop Z36 top-of-the-line towing pads; Rock carries the Powerstop for $49 and change, while the NAPA pads are a full $30 higher. But I love the Adaptive One on the Envoy.

The front rotors for the Envoy were just midgrade NAPA stuff, IIRC. Pretty sure I didn't get spendy with them, and the rear pads / rotors were just the Raybestos 'R-Line' (OEM equivalent, what you'd get at your local brake / muffler franchise). We all know that the fronts do ~ 70% of the stopping, and the rears are just along for the ride.

If whatever I put on the Sierra works as well as the Envoy, braking shouldn't be a worry, going forward. Never had to worry when I was towing the 4300# trailer with the Envoy, even going down some fast (spiraling) descents in Glacier NP in Montana that would probably tax a lesser pad.

 

[Mooseman]

If they're in there, check the weights. They will always have the same nominal thickness however cheap CCC rotors will have a wider gap between the inner rotors surfaces where the vanes are.

 

[Redbeard]

It looks like I managed to warp the front rotors on the Sierra while I had the trailer attached to it this past week. Curious as to the 'why', since I didn't really drive super long distances, or stomp on the pedal super hard.

I do have a theory about the rotors warping. Pressure from each pad must not be equal hence "pushing" the rotor more to the opposite side. If the pressure from both pads remain equal the rotors cannot warp. When pads seems to get worn down a bit (for me when less than about 1/3 of the pad is left) the pistons in the caliper are less guided by the cylinder (because they are pushed out) they are in (especially the plastic pistons) and more likely to bind up. When they get "bound up" a bit they cannot retract properly (and we are only talking a few thousands of an inch). During the stop the brake fluid pushes the piston out some more but the binding of the cylinder and piston keep it from retracting properly, hence generating more heat on the rotor making it more susceptible to warping when the pressure of the pads are not equal from both sides.

And to think of another reason not to have slotted or drilled rotors is think of a dragster. To keep the maximum amount of traction what kind of tire does he run? Slicks. Do they have slots in them?, no Do they have treads on them like we use on the street? No the tires don't. You need maximum surface to surface (tire to ground that is). The same is true for maximize stopping power of a pad pushing against a rotor. One needs the most surface of pads against the rotors for best stopping power. Just food for thought.

 

[Reprise]

Appreciate everyone's feedback / suggestions (I did ask for them, after all... )

As I mentioned, it'll be a couple of weeks before I can get the Sierra in the garage. But I ran across a post on another forum where the OP said he was able to cure the 'warpage' issue by re-bedding his pads (and his explanation of what happened rang true to my experience -- while I didn't have to do any panic stopping, I did press the brake pedal harder than usual a couple of times when I had the trailer on it. Not much, but 'some').

Anyway, I'm going to try and re-bed the pads this weekend and see if that helps. If nothing else, it'll buy me some time, if it works. Drove the truck a little yesterday and noticed that the pedal has more travel in it than I remembered (indicating that the pads may be worn further than I thought). But they're nowhere close to 'finished' (at least, from a thickness standpoint).

Will report back once I have some news. And the good thing is... I'm heeding advice and *not* springing for drilled / slotted rotors. Saved me some $$ (and frustration), you did!

 

[Blckshdw]

Have been looking for 'cross-drilled without slots' (I remember Mooseman (?) saying the slots chewed up pads -?)

FWIW, I bought some R1 Concepts slotted rotors and ceramic pads off Ebay in November 2016. I didn't have to replace the pads until this past February. I just wanted something with a different look, I don't tow at all, but had seen some people complain about their drilled rotors forming cracks at the holes, so opted for slotted only. Have only had a handful of panic stops over the last 6+ years, but never had any issues with braking.

I had also heard someone mention the slots ate up pads, but I figured if all the drilled options also had slots, then everybody should be suffering shortened pad life right? Seems like that would be bad for business.

 

[Reprise]

Seems like that would be bad for business.

The accounting and marketing teams figure that your belief in 'superior tech' will override your actual experience, and you'll repurchase their product.

"Yeah, they only lasted half as long, but they worked twice as good!"

 

[Blckshdw]

It's all relative I guess. The pads that were on my EXT when I bought it lasted me about 4 years from that date. No idea how new those were, but I wore them down to metal. Replaced them with some Raybestos rotors and pads after that, which also lasted about 4 years, and I did the same thing. The R1 concepts were next, and got 6 years (before I recognized the sound of the wear indicators this time). I imagine the introduction of a hybrid work schedule in recent years has a lot to do with that. So I call it even.

I'll have to look up the nominal/minimum rotor thickness, cuz these are definitely showing some edges where the pads stopped. It was probably time to replace those too.

 

[coveman]

My 1999 k1500 GMT400 Burb would warp the front rotors periodically, I tried a bunch of different pad compounds, new and resurfaced rotors without much difference and eventually did the gmt800 front brake swap with larger rear wheel cylinders which seemed to make a good difference in both stopping power and reduced warping. I think the OEM brakes were ridiculously undersized and were torching the front brakes.

On my 2013 k2500 burb I had some serious front shaking after some panic stops in Christmas traffic going south on 95 (if you’ve been in that mess you’ll know what I mean—no atheists in that crowd as traffic goes from 80 to zero and trucks whiz by you on the median). Not sure if there was a chicken and egg thing but when I got to Georgia and looked things over, my camber cams had moved and I had abnormal wear beginnings on my front tires. I swapped the cams with the drilled, not slotted parts and realigned it, made a good difference but I think my rotors had warped too.

When I got back home to Pennsylvania I did a complete brake job (those rears were a mess too and the parking brake inside the rotor hat was shamefully rusty gunky nasty so that got some love as well.

The fronts had maybe 30k on them and the pads were like new, which made me feel like the pads that should be designed to wear before the rotors may have been part of the problem.

I replaced the pads and rotors with the power stop drilled and slotted rotors after reading a bunch about warped rotors and improper pad bedding. My take away was that some hard stops (especially dead stops with hot brakes) can leave uneven pad material on the rotor surfaces which feels like warped rotors, and the slotted rotors can help shave down those lumpy build ups for smoother braking.

Its been about 6k miles and so far so good. I must say that this set up feels so much more responsive and stops so much more smoothly than the ones I replaced that I thought it worth sharing. Time will tell to see how they age and wear but for now I cant say I’m hating on the slotted rotors.