October 2020 Fastrack - The Brake Rules...

The cheap rotors are usually pretty accurate when using sliding calipers. You could invest in Brembo blanks, but they are usually made in China as well, so I don't think there is a huge benefit in paying for the premium. If they are cheap enough, throw them away every weekend. Thats what most guys running in IT did with Miata, Honda, etc rotors. They were $12-20/rotor not a huge loss if they don't hold up.
 
We tend to use off-the-shelf Centric 125-series rotors for everything we have (EP, STL, STU, HP). They're cost-effective enough to where we keep several spares in the trailer and consider them as consumable as lug nuts and brake pads.
 
Many years ago I use to run cheap ~$20/rotor "whatever is decent at O'AdvancedZone", but eventually those cheap Chinesium rotors just couldn't handle it. After just one weekend, they'd be all grooved and full of micro-cracks. I then was using Brembo blanks, until they got moved to China too several years ago, and I didn't think their performance/life any longer justified their ~$50/rotor cost. I then started using Meyle rotors for ~$65/rotor, which are still made in Germany, and I've had good experience with, but they weren't super easy to get ahold of, and were still only good for maybe 3-4 events. I still always carried a spare set in the trailer as "consumables".


Don't have to worry about this as much in 2021 though, when a pad & rotor change will happen less frequently and cost half as much.
 
Greg Amy":rx3ttk9j said:
We tend to use off-the-shelf Centric 125-series rotors for everything we have (EP, STL, STU, HP). They're cost-effective enough to where we keep several spares in the trailer and consider them as consumable as lug nuts and brake pads.
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So looking at Centric's catalog for 1984 Rabbit GTI, the bottom end rotor is 121.xxx "C-TEK Standard Disc Preferred". Then 126.xxx "StopTech Sport Slotted Cryo Disc" and etc. I don't think that I want slots or holes in the friction surface. Anyone disagree?

Looking at their listing for a mid 90s Integra (for instance) I see 125.xxx listed as having "high carbon" plus other alloys. So it sounds like a premium metallurgy that is not available for semi antique VWs.

Is the base Centric stuff junk? My philosophy wrt "Chinese" is that Chinese per se isn't bad, China makes semiconductors, pharmaceuticals and spacecraft. But "China" is also quite willing to sell and ship absolute junk if they think no one is looking. So name brand Chinese CAN be world class, off-brand Chinese is USUALLY junk.
 
The previously allowed 2-pc Coleman rotor (OE size) on my RX7 lasts multiple seasons- depending on hours and track of course. but I'd get 20+hours out of a set using DTC-70 pads which are known to be hard on rotors. I replace them when the tiny cracks can catch my thumbnail, and keep a set in the trailer as emergency spares.

The problem with the brakes on that car are the 40yr old OE calipers and pad taper. so much slop in the sliders on all of the reman units that short of machining out the pin bore and using a larger pin/ installing a sleeve, the calipers will get crooked on the pins and cause excessive pad taper. Even if I flip the pads at the end of a weekend, the pads wear into a triangle and then start flexing around the peak in the center. Thus pads must be flipped each race day. I get 2, maybe 3 weekends on a set of front pads and 2 in the rear if I'm lucky. Sad part is the tiny rear pads are limited in compounds and cost as much or more than the front pads (it's been a while since I've looked at prices since I stockpiled a bunch off Hawk & Summit contingencies).

Since the inner and outer pads are different shapes on the rear caliper, you can't flip them and *always* wear out one pad quicker than the other. this of course means I have a box of one pad and none of the other. urgh. Maybe Hawk will sell me a box of one pad shape? ;)
 
Al Seim":fmwgnf5b said:
So looking at Centric's catalog for 1984 Rabbit GTI, the bottom end rotor is 121.xxx "C-TEK Standard Disc Preferred". Then 126.xxx "StopTech Sport Slotted Cryo Disc" and etc. I don't think that I want slots or holes in the friction surface. Anyone disagree?

Looking at their listing for a mid 90s Integra (for instance) I see 125.xxx listed as having "high carbon" plus other alloys. So it sounds like a premium metallurgy that is not available for semi antique VWs.

Is the base Centric stuff junk? My philosophy wrt "Chinese" is that Chinese per se isn't bad, China makes semiconductors, pharmaceuticals and spacecraft. But "China" is also quite willing to sell and ship absolute junk if they think no one is looking. So name brand Chinese CAN be world class, off-brand Chinese is USUALLY junk.
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Agree on all counts. slots are OK on rotors as long as they come from factory and don't go all the way to rotor edge. it's the cheap ones that go all the way to the edge that cause the rotors to crack. FWIW, most of the Stoptech track-worthy brake kits come with slotted rotors and they don't seem to be an issue given the metallurgy of the rotors.
 
Matt -

Re taper wear - I've read an SAE paper saying that higher pad surface temperature increases taper wear, so maybe some additional airflow would help. I presume that your pads are doing the typical pattern of more wear at the leading edge.

Re rears - can't you go side to side? That's what I do on the VW which also has different inner / outer pad shapes (on the front).
 
Re slots - I've heard some people say that slots cause a significant increase in pad wear. Anyone have experience here?

I've always viewed slots as a stopgap defense against pad fade - letting gas out from the pad/rotor interface. Am I wrong?
 
The slots were originally designed for that purpose, but modern pad compounds don't really have that issue like the old pads. We have come a long way from Velvatouch linings. HAHA. As to the increased wear, I can't comment I have them on my street car, but obviously has little to do with racing conditions.
 
A friend of mine that crews for a pro team told me that the brake engineers advised them that slotted , cross drilled, scalloped and floating rotors are a waste of time and resources. Consequently I will not use them when I upgrade my brakes.
Paul L
 
I have not measurably noticed increased pad wear with slotted rotors. today's pad compounds are so hard and uncompressible that they don't have the cheese-grater effect.
the only thing slots are really good for in today's cars is wiping away water on the surface if you get the rotors wet. hopefully you don't have that problem on track!!!
.. My old street car had StopTech ST40 brake kit on it, and I put 150,000 miles on one set of slotted rotors using Hawk HPS pads. I went through 3 sets of pads in that time I think. and as I suspect most of youz guys do as well, I regularly enjoyed my driving when there wasn't anyone around.

Al, re pad taper-- I have 3" ducts on the front, and use the highest temp pad I can reasonable find. At Hallett, I can cook RBF600 fluid in a day. To keep the car on track, I have to start the weekend with fresh seals and bleed the brakes after every session. if I don't, I'm pumping the brakes multiple times on every straight.

Next step up in pad compound would be going to a custom-cut Raybestos ST43 or ST47 "nascar short track" compound. Porterfield will do it for me, at a price.

Rear pads-- the inner and outer pads wear at different rates-- (I think) the inside wears about 50% faster than the outside pad. I cannot simply swap them left/right since it's not taper but uneven wear rates. the inside pad is still the inside pad regardless of side. Uneven wear like this is typical of uneven rotor temps. Maybe I could cut holes in the rear windows and install NACA ducts for the brakes? Not really in the cards for me since I'm trying to sell the car. I'll keep it running, but I'm not going to spend time or money on it at this point. I'm posting this info for the benefit of others to see the struggles of old cars with tiny brakes pushed beyond their design intents.
 
Now that there are multiple weight adders in Prod (trans and brakes), the PAC may wish to clarify in the regs that both percentage adders apply to base weight and are not sequential.

If they are intended to be sequential, then the order of application should be specified.

Example: EP car with 2450 base weight. Alternate trans (5%) and alternate brakes (2%.)
- Applied to the base weight, the resulting weight is 2450+(.02*2450)+(.05*2450) = 2621.5#, or 2622# minimum.
- Applied sequentially, it's (2450*1.02*1.05) = 2,623.95#, or 2624# minimum.

"Inconsequential difference" you may say? Not when "Weight is absolute minimum."
 
Brake rule says 2% of base weight.

The gearbox weight penalties are listed on each spec line.

I think we are good.

For me brakes add 50.2 lbs to each line.
 
Aaron Johnson":15kb4zh3 said:
Brake rule says 2% of base weight. The gearbox weight penalties are listed on each spec line.
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Fair point, I overlooked the redundancy of having the individual trans-related weights also listed in the charts.

However, brakes says 'percentage of base weight'...isn't base weight that listed in the chart? And if so, since that's dependent on trans installed, then would not the brake regs be a percentage adder over that, thus a sequential multipier?

Just me being a strict interpreter of the regs. 'Cause you know this will eventually come up...

I'd recommend removing the individual weights from the chart, showing only the "baseline" weight prior to trans decision, then specifying 'percentage of base weight' in E.2.n.5 on trans selection. Make it clear.

GA
 
Now you guys have all confused it up.

I assumed base weight was the lowest weight.

Brake penalty is 2% of that weight added to any of the trans combos. So my car with a dog box and brakes - 2686
 
Jesse Prather":yhpk78fa said:
Base weight is the first weight of the car with a stock transmission.
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Jesse, show me in the rules where it says that.

Don't underthink it. Or are you new to this SCCA thing...? ;)

- Greg
 
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