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When you go from drive to reverse and hit the brakes, do you have a pretty noticeable pop from the front? I think it is just my pads shifting (I do have the retainers) but the first time it happened I thought I hit something. The pads are pretty grabby at low speeds so I don't think that helps.
I remembered this question when I was driving tonight and tested it out. I "thought" I heard it happen once. I went forward and reverse the length of my driveway 5 or 6 times and could never get it to happen. Pretty sure this setup isn't popping front or rear...
Hi Guys,
I'm glad you're all enjoying your Radi-CAL kits! Thanks so much again for your continued support. I love reading about how our kits improve our customers' days at the track. :cool
On the pad rattle issue, a few notes...
The Pro5000R calipers were designed to take a wide range of brake pads from a lengthy list of manufacturers. If you examine ten pads of the same 'shape' from ten different manufacturers, you'll likely find that none of them are exactly the same size. Some will be slightly longer, some slightly taller, etc. They vary by as much as 1.5mm or 2mm in some cases. One of the reasons for this is that different materials absorb heat and grow at different rates. For example, CL Brakes sintered metal pads tend to grow more than an organic compound would when heated to track temperatures. As such, they manufacture the pad a bit smaller so it has more room to grow. So when they're cold, CL pads move around in the caliper more.
Each manufacturer also has a tolerance range for their pads. That means if you pull ten sets of the same part number from a single manufacturer, you're going to find some variance in the size of those pads as well. That means one pad set is not going to fit the same as the next, even within the same part number from the same manufacturer.
With the AP calipers, there also is an acceptable tolerance range. While those tolerances are super tight, there will be a tiny bit of variance in how much room there is for pads among a given batch of calipers as well. In the worst tolerance stack scenario, you may have the smallest set of pads possible in the basic shape, mated to the biggest caliper pad opening, and the pads have enough room to move around a bit and make some noise.
When AP designs a caliper, they build that caliper to accommodate a list of pads from a long list of manufacturers. If they didn't, they would be like other caliper manufacturers who force their customers to use their proprietary pad shape and compounds. Since everyone likes different pad compounds, that severely limits choice and the utility of brake kit. In the case of the Pro5000R's, they use basic pad shapes that AP Racing created many years ago (and have been borrowed and leveraged by many other caliper manufacturers).
AP does not include any type of pad retention/spring clip/anti-rattle mechanism in their racing calipers, which is what the Pro5000R calipers are. The assumption is that these calipers are for race cars, used on track, etc. NVH is pretty low on their priority list relative to low weight, stiffness, cooling capacity, etc. Basically, a pad retention clip isn't going to make the car go faster, so it's not a major concern for them.
Therefore, it falls on our shoulders as AP Racing's implementation expert in the North American market to assess how our customers are using the parts, and make sure that the those customers are having the best experience possible with the product. We have lots of innovations in our kits, down to the packaging, that are implemented to make sure the unique needs of our market are met appropriately (calipers with custom piston bores, discs of unique sizes spec'd specifically for us, unique brackets and hats for all makes and models, etc.). We had several customers bring the rattle issue to our attention, so we addressed it ourselves. Our engineering director designed the pad tension blocks, and machine them out of billet aluminum, anodize them, and add the heat-treated spring on top. They are more costly to produce than one would expect, and we had to buy thousands of them to make them remotely affordable.
The pad tension blocks are not included in our kits however, because not everybody wants them. We could have made them standard, but we would have had to raise the price of our kits to accommodate them. We didn't think that was fair to all of our customers who don't want or need them (which is actually a large percentage). I view that situation as being similar to including pads in a brake kit. Many manufacturers throw a set of $7 junk pads in with their 'racing' brake kit, and then inflate the price of the kit, or cite it as a tremendous value because the pads are included. We don't go that route.
When to use the pad tension blocks? Our recommendation is to use the standard bridge that comes loaded in the calipers from the factory when on track. If you want rattle-free performance for AutoX, etc., then install the Essex pad tension bridge when you swap your pads over for that use.
As noted above, you do want the spring clips oriented to the outside when you install the pad tension blocks.
Pad Clunk
As pointed out by various users, pad 'clunk' is typically the pad shifting from one end of the caliper to the other when the car changes direction. You come to a stop, put the car in reverse, and start to back up. The pad is pulled from the abutment plate on one end of the caliper to the other, and clunks against the abutment plate on the far side making a clunking noise. That occurs for all of the same reasons above...pads of different size, tolerances, etc. Also as pointed out, that isn't by any means exclusive to our kits and can happen with many different fixed calipers, including OEM Brembo's, etc.
Hopefully all of the above makes sense. Thanks guys, and let me know if you have any other questions.
Thanks Jeff! I was a bit put off by the cost of the retainers, but given the nature of the kit and what apparently goes into manufacturing them...it makes a bit more sense. As always, your input/knowledge is appreciated.
Thanks Jeff! I was a bit put off by the cost of the retainers, but given the nature of the kit and what apparently goes into manufacturing them...it makes a bit more sense. As always, your input/knowledge is appreciated.
Thanks for understanding. It's not ideal, but it was either get our cost back out of them by offering them as an accessory, or include them automatically and raise the kit prices. Since many people don't need them, we chose the former rather than the latter. The big problem in manufacturing is the cost/volume relationship. To design and machine one part requires approximately the same amount of work as it does to create 500 or 1000 of them. The design has to be drawn in CAD, CNC mill still has to be programmed, the cutting tools and overall machine setup needs to be changed, etc. The same thing goes with anodizing...a batch of 500 is basically the same as one part. Obviously you need more raw materials to make more of them, but all of the other associated costs with the part are the same regardless of how many you make. That's unfortunately the nature of custom machined aluminum parts. Fortunately our engineering director is a whiz, and he was able to provide a solution for those who want it.
Had my first day on the track with the brakes, and also my first track day in this C5. Brakes were as amazing as advertised. This was a great track to start out on and feel things out, but not terribly agressive on brakes like Road America. This was during an open track day, so no sessions and only breaking for lunch. Ran the car 30min once to see how things went, no change. Pedal feel was always exactly the same and exactly where you left it, right at the top. Brakes were immediate. The only thing I noticed was that it seemed to get into ABS very easy. I worked on maintaining threshold, but it didn't take near the amount of pedal pressure I'm use to. I also tossed the keys to a couple buddies that are notoriously hard on cars and asked them to do their worst on the brakes. Again...no change. These brakes are wicked!
I'll be removing the wheels soon and taking a close inspection of everything. Will put a caliper on the front and rear pads and see how things are holding up and report the wear. There are 7 sessions of 20-30min each from that single track day. Car is a bone stock 2001 ZO6 with only Toyo R888R 295 square tires and brakes.
Here is a short reference video of my best lap for the day. There's a lot to work on, and I'm looking forward to giving it a workout again and hopefully at Road America yet this year. Car is a bone stock 01 ZO6 with just Toyo R888R 295 square tires and AP front brakes.
03-28-2017, 11:31 PM
