posted on November 23, 2011 00:00
Project Honda Civic EJ: Fast Brakes Big Brake Kit
By Chuck Johnson
Photos by Joe Lu
In the past few months, we've completely revamped Project Civic's suspension with a plethora of Skunk2 components; and then most recently, equipped it with a new pair of running shoes in the form of Enkei PF-01 rims and Nitto NT01 tires. Combine the results of these modifications with our goals of producing 200 plus horsepower and we should see some serious reduction in lap times. To truly realize Project Civic's full potential though, it's obvious that we need to balance our modifications and address its brake system.
During our baseline testing at Buttonwillow Raceway, Project Civic's brakes turned out to be one of its biggest shortcomings. (Asides from the head gasket of course.) Our resident shoe, Annie Sam, couldn't even make a full hot lap without battling brake fade. (See Annie's baseline lap at Buttonwillow here.)
Knowing that the front brakes do the majority of the work on a front wheel drive car, we decided to start out our brake modifications by retiring the 260,000-mile, OE front brakes in favor of a Fast Brakes big brake kit.
The Fast Brakes big brake kit is centered around a well endowed 11.1" diameter rotor, which is vented in design and then drilled and slotted. The radial venting sandwiched between the rotors' two friction surfaces, helps dissipate the tremendous amount of heat created during braking by channeling cooler ambient air through the rotor. (Think about it in terms of a less-efficient turbo pump, shrouded impeller wheel or a turbocharger compressor wheel in its housing.) Without this feature, there would be a significant decline in braking capability.
The additional "cross drilled" holes on the Fast Brakes rotor also help dissipate heat, but their main function is evacuating friction material debris and hot gasses that form between the pad and the rotor during braking. Likewise, the slots on Fast Brakes rotor can serve this same function, but also increase the transient response at the same time. This improved feeling of brake bite is created when the brake pad comes in contact with the sharp edge of the rotors slots.
It's something of a misnomer that the primary advantage of a big brake kit is decreased stopping distances. Instead, the main advantage of Fast Brakes big brake kit is the larger rotors increased ability to absorb thermal energy (heat). See, the true test of a brake system is not its ability to stop once in a short distance, but rather its ability to decelerate a vehicle reliably again and again and again in rapid succession. It becomes very tricky to do this without creating a larger heat sink to absorb and dissipate the massive amounts of heat caused in scenarios like road racing.
|A Fluke Thermal Imager depicts perfectly how a brake rotor acts as a gigantic heat sink which absorbs the thermal energy caused from the friction of braking.
Wednesday, November 23, 2011 3:46 AM
Whoa is that an Apexi Dunk cat back exhaust?
Wednesday, November 23, 2011 6:11 AM
How noisy are these brakes? I just put EBC Greenstuff pads and EBC slotted rotors on my CRV (that's not a typo I do mean my tiny SUV) and they whir and groan when I stop from about 40 mph. I've only put on about 50 miles, will this go away or is it a product of the slotted rotors?
Wednesday, November 23, 2011 7:41 AM
Slotted rotors in an of themselves shouldn't be any louder than a blank rotor. Are the pads installed correctly? Did you ensure the caliper pins were sliding smoothly?
Wednesday, November 23, 2011 11:38 AM
Man, this project is on fire. Can't wait to read the next episodes. Stay tuned, folks!
Wednesday, November 23, 2011 12:00 PM
As much as I love rear-wheel-drive sports cars, there's something awesome about taking what used to be a front-wheel-drive econobox and turning it into a track terror!
Wednesday, November 23, 2011 1:49 PM
Rotor cross-drilling is mainly done to lighten rotors, as well as give them a racy look. Modern racing/track day pad composition does not lead to outgassing and the holes reduce heat sink mass while reducing swept area.
GRM has said it, Baer has said it, PF has said it, Wilwood and Stoptech have said it... there just isn't a point to cross-drilled rotors on a production car in a track setting.
Not trying to be a know-it-all, just correcting some common misconceptions about modern braking technology.
Wednesday, November 23, 2011 1:54 PM
@Eric yeah that is an Apexi Dunk exhaust.
Wednesday, November 23, 2011 3:13 PM
What the frak is a "Dunk" exhaust?!
Wednesday, November 23, 2011 3:36 PM
Chuck - Great, detailed explanation! I'm interested in which direction you guys go with the rear brakes? I'll be excited to see how sharp these brakes and wheels look together :-)
Steve - I'm not going to get in a pissing match with you but Chuck's explanation of debri removal and outgassing with the cross drilled rotors is spot on. If your explanation of merely lightening the rotors and giving them a racy look, then guys who've been buying them for their FULLSIZE pickups for the last 15-20 years just wasted their money. Yeah, I've driven them, they work, they improve braking, especially when braking with a load! Granted they propagate cracks, which is why I like the trend toward dimpled rotors but slotted are great (I'd pick plain slotted for the money myself).
Wednesday, November 23, 2011 5:50 PM
@Der Bruce -
Not to continue the pissing war, but just because people have bought a product (cross-drilled rotors) doesn't mean that the product works as advertised, or is beneficial.
I'd love to see some back to back tests where we use blank rotors, slotted rotors, and then cross-drilled rotors to evaluate the claims made by proponents of each type. This article has too many changes to quantify the difference the cross-drilled rotor makes over another type. They changed the rotor size and type, caliper, brake pads, and the brake lines were changed. It would be impossible to draw any meaningful conclusions about any one of those upgrades without testing each change in isolation.
GRM did a brake pad test a few months back that I thought was a pretty solid test. They used a new set of wheels/tires for each pad, had the same driver, same bed-in procedure, and then ran the test again with the first pad in order to see if its performance was consistent with the runs earlier in the day. If someone wants to do a test like that with blank rotors, slotted rotors, and cross-drilled rotors then I'd be willing to take a look at the results and eat crow if I'm wrong about cross-drilled rotors. After all, none of us want to waste our hard-earned money on a part that doesn't work. And if a part does work well, we're all going to want to invest in it!
Braking performance aside, the other problem I have with cross-drilled rotors is their longevity. To me, anything that's going to increase the risk of a rotor cracking doesn't make sense to me, especially in a track application. However, if you could quantify the improvement of a cross-drilled rotor over a slotted rotor, I think it might have a place in something like a time-attack where longevity isn't as critical.
I enjoyed the article and the discussion!
Wednesday, November 23, 2011 6:03 PM
I notice that cross drilled rotors make a slight whirring noise. I think they are fine on street cars but I always crack them on race cars so I have gone to slotted or no surface feature rotors for race cars.
Wednesday, November 23, 2011 6:17 PM
Its a funky name for the grape fruit shooter ;-)
Wednesday, November 23, 2011 6:37 PM
That picture made me crack up!
Wednesday, November 23, 2011 8:46 PM
Brembo is actually a big proponent of cross drilled rotors and only shys away from them in the most extreme applications.
Wednesday, November 23, 2011 10:09 PM
Brembo is a big proponent of cross-drilled rotors because they charge an additional $44 for the pair of front rotors on an E36 M3 compared to the blanks (tirerack.com prices):
Also note the caveats from the notes for the cross-drilled rotors (from the same link above):
"(Front) Drilled vented rotors. Not recommended for track use. Do not use with race compound brake pads. Drilled rotors are not warranted against warping or cracking. "
Thursday, November 24, 2011 12:45 AM
Performance Friction dimples their rotors.
Thursday, November 24, 2011 1:41 AM
@dj06482, those are also direct replacement rotors for the stock rotors which are undersized for any track use on almost every vehicle sold.
If you look at their brake upgrade systems with upsized rotors and calipers, their high performance street kits come with the cross drilled rotors. Brembo does advise slotted for race use and their topend race setups only used slotted.
Look at their OEM Porsche, Lambo, Ferrari applications and they all come with cross drilled. Is cross drilled good for heavy track use, i.e. dedicated race car? I would say not. But for a high performance street car that sees occassional hard use, there are some benefits.
They can 'get away' with cross drilled on the upsized rotors as they have greater thermal capacity resulting in lower temperature swings and reduced stress with the end result being less likely to crack with the cross drilling. To take it to an extreme, if you size the rotor big enough then it doesn't matter how many holes are in it. If you size a solid rotor small enough, it'll still crack easily (like on S2000s and Vettes).
For a high performance street car that sees occassional track use (low number of duty cycles at high stress), the cross drilled rotors (I think actually cast in holes in the high end stuff which results in less stress) have advantages of being lighter weight and running cooler. So the compromise is getting the benefits of lighter weight where the car operates 99% of the time versus the occassional 1% of hard use where the drilled rotor has shorter fatigue life.
Thursday, November 24, 2011 10:42 AM
@spdracerut, cross-drilled rotors do not run cooler. There is a decrease in the mass of the rotor making it a less effective heat sink, which can actually raise temperatures.
@Der Bruce, this is no pissing contest. There was more noise than signal in the explanation and it needed clarification. Cross-drilled rotors on a front axle application don't make any sense for hard street or track driving; what little outgassing there is can be controlled with slots and the thermal argument will be disproved with brake dyno results. The common knowledge in this case is outdated; pad outgassing in the '70s and '80s was certainly a very real concern.
In addition, I would like to correct my comment saying "Modern racing/track day pad composition does not lead to outgassing." There is indeed a boundary layer of gasses produced but it is negligible and a slotted rotor would easily mitigate any problems.
Cross-drilled rotors do have a place, and that is on the autocross course or on the rear of lightweight cars.
Thursday, November 24, 2011 1:23 PM
The exotics runs cross drilled because the rotors are huge. The crossdrilling is to reduce unsprung weight and to cool the rotors by letting air through the vanes and out the holes which is why it does run cooler. Rotors are heat sinks but heat sinks are only good if they are passively cooled. A rotor is not passively cooled, it has vanes which let air travel through, the perforated holes are to let the air through to evacuate the heat.
For carbon ceramic brake rotors its the same thing, since carbon rotors are always oversized, they are drilled to reduce unsprung weight even though they are lighter then iron rotors.
For some side reading, theres an article called Pulp Friction by GRM, its online somewhere. I remember reading it years ago.
Thursday, November 24, 2011 9:07 PM
Nice article on the brake setup but I'm wondering why the rotors were a solid rotor instead of the two piece rotor with aluminum top hat.
This further lightens the assembly but I'm sure there's a reason for not using this two piece setup.
Some thoughts would be nice on this.
Thursday, November 24, 2011 11:35 PM
@RotaryKnight, cross-drilling does not run cooler. Ask the pros... heck, consult the very same article you cite.
"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses somewhere to go. It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads.
For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.
The one glaring exception here is in the rare situation where the rotors are so oversized that they need to be drilled like Swiss cheese. (Look at any performance motorcycle or lighter formula car, for an example.) While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember that nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life, at the expense of higher weight. It's all about tradeoffs."
... and that's all I'm gonna say about that.
Friday, November 25, 2011 2:11 AM
Misnblu, The fit is really tight so their was no room for a two piece rotor. We wanted it all to fit in a 15" wheel.
Friday, November 25, 2011 2:49 AM
Steve, according to a SAE 2006-01-0691 paper , at high speed with no brakes applied, temperature did decrease faster with drilled rotors then blanks. it depends on the situation. Drilled rotors do not provide any cooling during braking, but this SAE paper suggest that it does cool when at high speed and not braking. During braking, the biggest aid to cooling would be heat dissipation of the friction, which blanks are superior because of mass. But if people want to run drilled rotors, they will have to increase mass by going bigger, or by building a brake duct to provide cooler air to cool down the rotor while braking.
if anybody wants a copy of the SAE paper, I can link to a download copy of it.
Sunday, November 27, 2011 3:30 PM
Please post them!
Sunday, November 27, 2011 11:29 PM
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