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While cleaning my garage yesterday I stumbled on a copy of the bedding instructions, and re-read them... and they do call for a cooling period after each set of near-stops. I missed that the first time around (but tend to do it anyway just as a side-effect of finding opportunities to do hard near-stops).
So now I wonder what's supposed to be going on inside the pad during that cooling phase.
While cleaning my garage yesterday I stumbled on a copy of the bedding instructions, and re-read them... and they do call for a cooling period after each set of near-stops. I missed that the first time around (but tend to do it anyway just as a side-effect of finding opportunities to do hard near-stops).
So now I wonder what's supposed to be going on inside the pad during that cooling phase.
What is the consensus on reusing hardware for two-piece floating rotors? DBA 5000s, Hawk DTC-60 F+R, 2017 GS with iron brakes & PSS tires & stage 2 aero. Car does go to the track.
DBA forgot to include the replacement nuts (going to call on Monday about that), but are the bolts and anti-rattle springs reusable? It doesn't seem like there's any way to get new ones short of ordering the laughably expensive ones from Racing Brake at $10/bolt * 10 per hub.
The instructions came with Stoptech's BBK, though I don't recall if they were packaged with the included street pads or were just part of the kit generally.
I used (and bedded) Carbotech 1521s, and I will be switching to Carbotech XP-12 / XP-8 for the track. So the rotors should be ready to go, and I wonder if I should heat-cycle the pads on the street before I use them on the track.
I had a 2015 Camaro 1LE, put a new set of Hawk DTC-60 in the fronts/30 on rears with oem brembo brakes, literally at the end of a track day at Watkins they were gone to the backing plates and burned the calipers from red to Brick brown, with titanium heat backing plates. Maybe the car was too heavy, the track is hard on brakes having to slow down from 100+ 4 or 5 times/lap. I moved to Raybestos and really enjoy them. I know others use them, I think it depends on the tracks and speed that you expect to use them on. I have a C6 Z06 now, put a set of Raybestos ST47 front and 43 rear (i wanted 45 on front but were back ordered), I had to slow from 153mph to 35 in about 400 feet every lap. I learned I used too aggressive of a front pad, the initial bite was so high that it impacted my driving style of wanting to move weight during the start of the braking zone, and I experienced the ice mode because I think I had too much pad. See what others are using at the events you plan to run with. Be aware, when you move away from street oriented pads, your car will look like it came from a coal mine and will sound like a dump truck at stop lights, your rotors will crack w/o proper cooling and the wear like I mentioned can insane when you put out near $500 for pads alone. It is a terrible habit.
Yep, I know the calipers can be bolted on and would need to change to a larger rotor.... the key question is will it clear the wheels. Sorry I should have formulated my question better.
What would cause angled pad wear on the front outside pads on a C7Z caliper? I have the iron brakes running stock rotors. This weekend after a two day track weekend using ST43 pads, I noticed the wear on the outboard front pads is greater towards the outside edge (towards the retainer pins) and is still quite thick nearest the hat. First I saw it on the outside pad on the driver's side. Figured the pad had an issue or there was a caliper issue. Then I went to the passenger side and the outboard pad had the same problem. Inside pads on either side looked fine and wore evenly. This is my third set of pads and the first two didn't do this. Ideas?
*after finding more info, it appears I have radial taper impacting only the outside pads of both front calipers. This is the first track event I've ever seen this happen on this car/setup and its probably seen 10-15 days of events. I don't feel like I changed my braking habits at all since prior events. The fact it's equal on both front calipers seems to argue against an isolated equipment issue. Whatever is happening is affecting both calipers.
Alex,
You’re always going to have some taper, and several millimeters of taper is actually completely normal. Sometimes it has to do with the track layout (you may see taper on only one side of the car), your driving style on that track (if you're doing a lot of trail-braking in certain turns), how the car is being loaded up going into those turns (the spindle to which the caliper is attached can flex).
In racing situations we see as much as 10mm of taper, and the taper is not equal from pad to pad. Again, pad taper is completely unavoidable. We see it on every car, with every brake kit or type of brakes, from every manufacturer. We see it both radially (top to bottom) or longitudinally (end to end). We also almost always see slightly different wear characteristics on the left and right side of the car based on track configuration. We see it all levels of racing, including NASCAR Sprint Cup. Longitudinal taper (taper from the leading edge of the pad to the trailing edge) occurs because of uneven temperatures at the leading edge of the pad and the trailing end. The leading edge will always run hotter and wear faster than the trailing edge. The trailing edge floats a bit on pad material that is torn from the leading edge and pulled back towards the trailing edge. The longer the pad is, the more pronounced the taper tends be. If you look at a short four piston pad vs. a longer six piston pad, the six piston pad will always have more taper all else held equal. The pistons in our AP Racing calipers have differential bores (pistons are different sizes) designed to combat this phenomena. The piston on the leading edge is smaller to apply less pressure, while the trailing piston is larger to apply more pressure, to help even out the wear. Radial pad taper (The top edge of the pad wears near the disc's OD wears more than the bottom edge closest to the hub) is more a function of various components flexing. If you have a caliper that isn't terribly stiff, this is particular common. When the pistons extend, they push the two sides of the caliper away from each other. Since the two sides are connected on the top across the caliper bridge, they pivot around that point. In that case you can think of the caliper opening up like a clam shell. Over time and with enough abuse, calipers can fatigue, and start opening more and more.
One way to get more even wear out your pads is to occasionally flip the pads in the calipers from inner to outer and side-to-side, so that the edges that were leading last time are now trailing, and vice versa. Doing so also gives you a chance to inspect the pads and make sure they aren’t getting too low. Sometimes your inner will wear faster than your outer. Many people peek through the wheel and think, "My pads are good." Guess what, the inner may be on the backing plate. Heat can build up more on the inner and cause them to burn faster.
I used to mark the pad backing plates with a paint pen when I pulled them out and moved them around. I'd use abbreviations like DI (Driver Inner) or PO (Passenger Outer) so I knew where I pulled the pads from.
In summary, what you're seeing is normal, and I wouldn't have any concerns. If you flip the pads around as described above, you should be able to maximize their longevity. Hopefully that is helpful.
Is the bedding process for new pads strictly about treating the surface of the brake disc, or does it also result in a longer-lasting pad, similar to the way heat cycling helps tires last longer?
Thanks!
Pad and disc bedding benefits both the pads and discs in terms of longevity. As part of the manufacturing process, iron discs are typically heat treated to relieve stress. Racing pads are many times scorched in an oven at high temps to burn off some of the resins from the forming process. Some pad manufacturers call this pre-bedded. That is a bit misleading in our opinion. We consider the process of actually running in a set of pads on a disc as bedding or burnishing. We also believe that a true burnishing of the pads is far more effective than simply scorching them.
When you bed in a set of pads on a disc, the two faces mate up nicely with each other. The pads ride on the pad material that is deposited on the disc face. We burnish 10,000+ discs per year for racing teams and our big brake kit customers (we offer it to anyone who purchases one of our kits).
In this video you can see the difference between a raw iron disc vs. one that is burnished.
Here's a video on how to bed-in pads and discs on your car:
Here's one on swapping between street and track pads:
What is the consensus on reusing hardware for two-piece floating rotors? DBA 5000s, Hawk DTC-60 F+R, 2017 GS with iron brakes & PSS tires & stage 2 aero. Car does go to the track.
DBA forgot to include the replacement nuts (going to call on Monday about that), but are the bolts and anti-rattle springs reusable? It doesn't seem like there's any way to get new ones short of ordering the laughably expensive ones from Racing Brake at $10/bolt * 10 per hub.
It depends on the hardware DBA uses. If they are using a locking Jet Nut (also referred to frequently as a K Nut), they're not supposed to be reused. These nuts lock by using an elliptical offset on the unflanged end of the nut. What that means is that the threads on the end of the nut are not perfectly circular. When the bolt is threaded into the nut and reaches the deformed end, it stretches the threads back into a circle and locks the two together as it is torqued.
You may be able to get away with reusing them, but each time you reuse them the expectation would be that they would not lock as tightly.
With our Essex Designed AP Racing brake kits and discs, we use that type of hardware. We recommend a fresh set of nuts at every disc change. Below is a pic of our hardware stack for reference, and another view of what a Jet Nut looks like by itself. One way to check if it is a Jet Nut, or if yours are worn out, would be to flip it over and try threading it onto the bolt from the non-flanged side. Since that end of the nut is supposed to be deformed into an ellipse, it shouldn't thread easily onto the bolt (while it should thread easily onto the bolt on the flanged side). If the non-flanged side threads easily onto the bolt, that means that threads have been stretched back into a circle, and that it has lost its ability to effectively lock.
It depends on the hardware DBA uses. If they are using a locking Jet Nut (also referred to frequently as a K Nut), they're not supposed to be reused. These nuts lock by using an elliptical offset on the unflanged end of the nut. What that means is that the threads on the end of the nut are not perfectly circular. When the bolt is threaded into the nut and reaches the deformed end, it stretches the threads back into a circle and locks the two together as it is torqued.
You may be able to get away with reusing them, but each time you reuse them the expectation would be that they would not lock as tightly.
With our Essex Designed AP Racing brake kits and discs, we use that type of hardware. We recommend a fresh set of nuts at every disc change. Below is a pic of our hardware stack for reference, and another view of what a Jet Nut looks like by itself. One way to check if it is a Jet Nut, or if yours are worn out, would be to flip it over and try threading it onto the bolt from the non-flanged side. Since that end of the nut is supposed to be deformed into an ellipse, it shouldn't thread easily onto the bolt (while it should thread easily onto the bolt on the flanged side). If the non-flanged side threads easily onto the bolt, that means that threads have been stretched back into a circle, and that it has lost its ability to effectively lock.
Are all nuts that look like the picture "jet nuts" or are there some that have just copied the shape/look?
Any marking to verify real jet nuts?
There are flange nuts with a flange on them that don't have any type of locking mechanism, or they may have a serrated underside to stop them from spinning. That doesn't mean that they have the elliptical threads on them however.
In other words, you can't just look at a nut with a flange on it and assume that it is a jet nut.
Last edited by JRitt@essex; 05-24-2018 at 02:51 PM.
The rotor in the burnishing video has visible runout relative to the hat. Is this due to the floating hardware? How much runout is tolerable before the balance of the wheel/tire/brake assembly is affected?
Originally Posted by JRitt@essex
In this video, you can see the difference between a raw iron disc vs. one that is burnished.
Are all nuts that look like the picture "jet nuts" or are there some that have just copied the shape/look?
Any marking to verify real jet nuts?
Purchase them from a reputable dealer.
They are aerospace grade hardware and on a jet or rocket you would not reuse the nut or bolt. They lock by deforming.
NAS1291-C4 is the basic spec - there are other finish specs but that is the basic rotor nut that everyone uses and buys from Clarendon (previously Coast Fabrication)
You know they are real when you pay $2.50/each on low volume.
I have the GM/Brembo 2 piece hardware apart right now and what I found was interesting as it is not quite what I expected. Details after I get some pictures.
The rotor in the burnishing video has visible runout relative to the hat. Is this due to the floating hardware? How much runout is tolerable before the balance of the wheel/tire/brake assembly is affected?
The point of the vid was to show the pad transfer layer. I honestly have no idea what disc that was, where it came from, or how it was mounted. Over the years we've burnished discs from many sources. Most likely someone slapped a junk disc on the machine to use as a sample for the sake of the video.
In my 10 years at Essex, I have yet to see any issues with run-out on AP Racing discs. I literally don't recall a single instance.
FYI...we burnish discs for all of the top NASCAR Cup teams, as well as OEM vehicle manufactures, and even our competitors' discs. Our machine and process are both patented as well.
I sure wish someone would start a new thread and close this one. The OP hasn't even logged on the corvette forum since last September:
Last Activity: 09-19-2017 09:37 AM
I disagree. Why not use the one that's already there? The age of the thread and status of the OP are irrelveant to the valuable material in these pages. It should be stickied at the top of this forum forever as far as I'm concerned.
I must admit that threads this long make it tough to find info. Personally I'd rather have shorter more focused threads (i.e. a thread on rotor hardware and a thread on brake burnishing). Does anyone actually come in and read the entire thread from the beginning?
The one thing I like about this thread is that I know most of the people contributing will offer great info.
I must admit that threads this long make it tough to find info. Personally I'd rather have shorter more focused threads (i.e. a thread on rotor hardware and a thread on brake burnishing). Does anyone actually come in and read the entire thread from the beginning?
The one thing I like about this thread is that I know most of the people contributing will offer great info.
I'm still trying to decide what to do about a big brake kit. I've got 7 track days on the st-43 pads and they look good for Tuesday. I read yesterday that's about what you're getting on the 25mm pads you're running. My problem is the first set of rotors with those pads lasted less than 3 track days before I had a crack. I've got 3 track days on these and they still look pretty good so maybe they're going to last longer. I've had no discoloration on the yellow rotors and the car stops well. I just don't want to drop 10 grand and not see much of an improvement.
05-07-2018, 09:41 PM
