posted on May 12, 2011 01:10
Making It Stop - Every Time
by Martin Gonzales & Steve Rockwood
Check out the rest of our Project Infiniti G20 Racecar build here!
Loud engines, big horsepower, gratuitous tire smoke, and high cornering speeds are why we love and watch motor sports. Most people, when they watch racing on TV, listen for the engines, stare at the gruesome crashes or marvel at the speeds drivers carry through the corners. However, much like the scrappy player on a basketball team that gets all the rebounds and never scores, brakes just don't get the attention they deserve. It seems that most people only pay attention to brakes when they're glowing red-hot during those late night endurance races, or when they don’t work. Newton's Third Law was 'for every action, there is an equal and opposite reaction,' and as it turns out, Newton was a pretty smart guy. A good braking system on a racecar is as necessary as a good engine.
|Unlike an ALMS racecar, our G20 simply does not have the weight or power to justify an extravegant brake set up.
Only about ten percent of each lap is spent braking, the other 90% is spent, to some extent, on the throttle. What this tells us is that while brakes are important, more effort should be spent on ensuring reliability and fade resistance rather than ultimate stopping power. Those massive manhole covers with 6 piston calipers may look dead sexy, but when you only have 225mm worth of tire and 2400lbs’ worth of vehicle to stop - motivated by only 170-ish-whp - you're not exactly justifying their existence or their premium price tag. Racing is expensive enough!
|Project G20 getting some race miles on her with NASA's SE-R Cup.
The goal of our braking system is to be simple, and have as little wallet-pulverizing potential as possible. While many feel that larger brakes are necessary, we were willing to attempt to use the stock brake set-up with upgraded pads and lines to see how well it works. We wanted to use OEM parts in as many places as possible because of reliability and ease of replacement. While multi-piston calipers and larger rotors are legal for the series, we wanted something, that if necessary, we could just run to the local parts store to pick up in an emergency. In addition, while most aftermarket calipers work great, they often need more attention to maintenance than their OEM cousins. Mom doesn’t notice something wrong with her brakes until they make horrible noises, or stop working altogether, so OEM engineers are paid to look out for Mom. We’re happy to report that in our car's current state of development, the stock system has performed well, and has withstood many race laps without noticeable fade or abnormal wear.
Friday, May 13, 2011 6:52 AM
Nice to see someone promoting OEM shelf parts instead of fancy billet stuff you really don't need. Nissan was one of the best at cookie cutter parts for multiple cars. Do you have any info for us one how much caliper/rotor you should have for a car's weight? Or something to that extent. I know this is kind of a black art like suspension tuning, but a ball-park figure would be nice to see.
Friday, May 13, 2011 7:25 AM
Nissan was good, but nowhere near as good as Honda ;)
We actually don't currently have that kind of brake sizing info, but that is definitely a good idea for future editorial. We used the ol' trial and error method, and so far no errors.
Friday, May 13, 2011 9:35 AM
That's a lot of math. Definitely need some time on that, and it'd probably have to be a future article with some new measurements made up (kind of like Monkey Power and the Dave Point).
Friday, May 13, 2011 9:54 AM
Martin, Steve - Excellent write up material. Nice to see a Harbor Freight tool last through a few uses! The caliper/rotor thought process would be a complex one for sure. In my limited experience, I could argue that on some cars you could go with a slightly smaller rotor with a higher grade caliper but then again I could argue that rotor size is more important for heat dissipation and larger rotors bring larger calipers (no matter the piston count). The one BIG point you guys hit home with is the ability to find replacement parts and the availability of said parts. A more fascinating article for me would be a "step up" one in which you guys (the Motoiq braking experts) lay out which steps to improve your braking, from the spirited street driver or weekend track warrior up to the purpose built racers. That would be an excellent guide, much like the ultimate suspension/handling guide has been!
Still waiting on project TDI notes/follow up Steve!?
Friday, May 13, 2011 10:07 AM
I know Sentra drivers love AD22VF, but 257mm just isn't big enough for the P10. When I first got a P11 I was impressed how much better their brakes are even though they are carrying an extra 300lbs over the P10. And since you are buying new pads and rotors anyway, why not use the chance to upgrade? The calipers are same, you just need new caliper brackets, or as Nissan calls them, torque members from a P11 or an Altima. My local junkyard sells brackets for $3.50 so for $7 + tax, you could have 280mm brakes that work great and fit under 15" wheels.
Same trick works for the rear as well. A32 Maximas have torque members that are 10mm taller, bumping the rear size from 258 to 278mm. Their rotors are 5 lug, but 4 lug b15 spec-v with brembos have rotors of the same dimension.
Friday, May 13, 2011 10:44 AM
Project TDI's follow up will come soon enough, just haven't completed all of the maintenance the car needs. Patience, young grasshoppah. :)
I assure you, 257mm seems to be plenty with Hawk Blues. The car is a featherweight now compared to most street cars (2450lbs WITH driver and a full tank), and SE-R racers get away with AD18s and Hawk Blues in SCCA ITA (or whatever class the SE-R is in now) with a higher race weight.
We will likely stay with 257mm rotors for a couple of reasons:
1. Easy to find, reasonably priced rotors.
2. Less unsprung weight.
3. Cheap replacements that can be had almost anywhere.
4. The F:R brake bias is perfect right now. Larger rotors would need us re-tune the bias selector.
5. Did I mention cheap and simple to locate?
6. No fade issues whatsoever, even at CA Speedway (~130mph down to ~45mph for T2, and ~100mph down to 45mph for the infield).
7. In case you didn't know this, replacements are extremely economical and available in most locations.
Friday, May 13, 2011 11:26 AM
I think this car has the unofficial lap record at Willow Springs for the fastest FWD Nissan. Anyway I can assure you that this car is fast with the stock brakes and good pads.
Friday, May 13, 2011 1:30 PM
BTW, I once had a P10 with an SR20VE (HS Gen VI header, SR16 cams, etc) for a daily driver, and ran it at Streets of Willow for a track event. Had some fade, but it was entirely manageable. This was with all stock rotors/calipers, Metal Masters up front, and OEM pads out back, Azenis, a 200lb passenger, and a 2 sub setup in the trunk.
BTW, the track was run in reverse, so over 100mph to ~45mph threshold braking into the skidpad, downhill. There was a picture somewhere of the car where you could see the rotors glowing in DAYLIGHT. Like I said, had some fade, but entirely manageable, and I didn't have to take any cool off laps.
And yes Mike, I don't think anyone's gone faster than a 1:35.9 at Willow Springs in a FWD Sneezan.
Friday, May 13, 2011 2:27 PM
I ran hawk blues in my full weight P10 and didn't have any fade issues with stock size calipers and rotors. Even with race tires, they held up fine.
This project makes me want to build another G20, but this time make it a full out track car.
Friday, May 13, 2011 5:58 PM
Excellent write up on doing this and it also brings back memories and the toils of doing your own brake lines while removing the ABS setup from the car.
Your article was right on with how you had to redo some of your lines because of leakage and what you had to do to get it right. I had similar situations with my car but the end results were well worth it.
Friday, May 13, 2011 8:19 PM
I always wondered if "big brake kits" were a waste of money for anyone other than a pro-level driver. Now I know they are.
Friday, May 13, 2011 10:42 PM
It really depends on the car. My Sentra needs big brakes and I just went even bigger. I have faded stock brakes with performance pads on a Z, G35 or a R32 GTR for instance in just a few laps. Most cars can benifit from a big brake upgrade.
Rock is beating me by one tenth of a second, damn.
Saturday, May 14, 2011 5:52 AM
So the reason for a big brake upgrade really isn't stopping power; it's brake fade?
Saturday, May 14, 2011 7:07 AM
@ Dusty: Yeah a lot of the time that's the case, bigger brakes let you deal with fade.
Steve and Martin took a bunch of energy out of the brake system by dropping the weight of the car and then put most of it back in by adding horsepower to the vehicle and enhancing their grip through tire and suspension work. For them the equation works out about right to run a fairly stock setup. I bet their stopping distances decreased too because they were making more effective use of their rear brakes then the stock proportioning did.
If on the other hand I was to add a 100 horsepower to something like my 240SX and still keep it at its full street weight I'd be well advised to at least upgrade my braking setup to Z32 300ZX brakes.
Saturday, May 14, 2011 8:29 AM
The key point to come away with here is that brake options should be based on APPLICATION.
The stock components in our car, IN ITS CURRENT STATE OF DEVELOPMENT, have held up well. This may not be the case if we were to significantly increase power and have a lot more forward momentum to deal with.
Saturday, May 14, 2011 10:17 AM
In my opinion the driver's style also makes a difference. Some drivers are harsh on their brakes, and some other drivers are a little bit smoother on the brakes.
I would say that if you track your car, getting a big brake kit is a wise choice, but even more important are the oil, brake pads and even those bracket that bolt on onto the shock tower and are in contact with the master cylinder (those small brackets that prevent the firewall from flexing and generally give the driver more feedback on the braking). Replacing the brake oil (and keep an eye on it), as well as checking the rotors for small cracks are also a must.
Anyway, all these upgrades in my opinion are a lot more worth it than let say an exhaust upgrade or a highflow filter.
Saturday, May 14, 2011 11:17 AM
Driver's style definitely has a lot of impact. Also lacking the PV setup on my B13 this car has, I effectively downgrade my Max/Alty rear brake upgrade with less effective pads (OEM or OEM replacement). But that PV is on my to-do list, same setup there.
I know the Cup drivers use the 22's etc, but that's rule based as much as anything. I have nearly identical power and suspension setups on two 1991 B13's and the main difference in driving is one has Wilwood 11.0 fronts, both have MC upgrades. It's not the rotor size or ultimate braking power of the Wilwoods over the Nissan brakes I really love, it's the ease of modulation, the braking control it gives me on one car that is noticeably lessened on the other.
Both have comparable pads, SS lines, simiilar power, weight, CO's, tires, etc. It really comes down to the brakes where I get in one car and just go WOW compared to the other. I do swap in race pads (Ferodo) in front on track for the Wilwoods, but both are DD street cars NA, bolt-ons, JWT tune, etc. I wouldn't give up the improved feel and ability to brake later, more smoothly with the Wilwoods for 22's, no way.
But I need that PV to tame the overactive rears at times ;)
Saturday, May 14, 2011 11:24 AM
@Mike's comment - "I have faded stock brakes with performance pads on a Z, G35 or a R32 GTR for instance in just a few laps. Most cars can benifit from a big brake upgrade."
The stock Brembos at least on my cars have had shib for pads, more about low dust than good stopping power. So IDK what you mean by performance pads, but stock Brembo calipers, GSpec SS Lines, on my G with excellent rotors and pads, you'd have to abuse them to get fade in a few laps. IDK about the G37/370Z calipers but if Nissan is consistent the sport calipers probably also come with crap for pads despite a significant improvement in the actual brake calipers.
However, the stock Nissan floating calipers in the Z, G, first gen, IDC what pad however you put in there, there is nowhere near enough brake on a Z33 w/o at minimum a front caliper/rotor upgrade. I've seen more 350Z's boil their fluid, or lose their pads, etc at HPDE's, track days, etc. than I can count. Weight of course is also a factor in each car you mention, none of them are light by my standards at least. The 6MT G Coupe Brembo's with stock pads, same issue, enough brake, not enough pad by a long shot, and mushy pedal with OEM fluid that had too low of a BP.
Saturday, May 14, 2011 11:32 AM
@ Fly'n_Z - great point on the PV effect on the rears, my main issue was too much rear in the B13, to the point the fronts were smooth as silk and then I'd get lockup under heavy braking in the rear. The compromise of crappier pads rear is ok but for a full track car no way, and I will get to using this same PV setup eventually. I expect eventually the rears would tend to have heat problems, even with larger rotors and calipers on their now. I've run the car hard up to an hour on course no issues, but that was at NJMP Lightning, a track pretty easy on brakes. Tighter courses where I'd brake later and harder, not so much confidence the rear pads would handle the temps.
Saturday, May 14, 2011 11:33 AM
E-mail this guy if you want more info on Axxiss brake pads:
where # = @
Saturday, May 14, 2011 11:08 PM
Fadeds those OEM brakes drivng 7/10ths. They had some sort of performance pad and the normal street mods. Full race pads would sorta work but be totaly harsh on the rotors in street use.
The main reason why I like Willwoods on Sentras is not so much braking power or whatever over ADF22's its the fact that the pads are so much cheaper.
Going bigger so I can use a less agressive pad and have everything last longer, longer life for rotors and pads, less work for me. With the bigger Superlite caliper I can run a soft Hawk DTC30 pad no problem.
Sunday, May 15, 2011 11:18 AM
What is involved with adjusting the proportioning valve (aside from turning the knob)? How do you dial the bias in?
Monday, May 16, 2011 6:38 AM
Start with the valve completely backed off (on the wilwood proportioning valve like the one in this article, turn it all the way in direction labelled 'LESS BRAKE')
Find an appropriate road or track to test on, and do repeated braking runs, each time dialing in 'MORE BRAKE' until you feel the rears locking up before the front. At this point back it off just a bit so the bias shifts to the front again.
Ideal bias will change depending on tires, road surface, etc, so if you're right on the edge, you'll have to adjust periodically. Otherwise that's all there is to it.
Monday, May 16, 2011 7:24 AM
Those cheap flaring tools have a 45 degree SAE flare (think the plumbing going to your sink). AN/JIC fittings are 37 degree flares. These two are NOT compatible!!! You might be able to get it to sort of seal after overtorquing the nut, but it offers a huge stress riser and much reduced fatigue life. Not to mention they have a bad habit of vibrating loose given that you're loading the flare in such a small area that they tend to deform and loose torque over time.
The "ferrule" is called a tube nut, and you also need a tube sleeve.
I know somebody is going to say their 45 degree flare tool works fine for them on AN lines and has for the past 49 years, but the simple fact is AN fittings are really awesomely reliable when used correctly! When not used correctly in something critical like a braking system, well, bad things can happen.
I'd be more than happy to write an article on aerospace fittings for MotoIQ to clear up some confusion on the subject.
Monday, May 16, 2011 9:22 AM
@ Steve: Yeah, driver has a lot to do with how much brakes you need. I'm not incredibly hard on brakes, but I do know some people are. The car has been able to consistently out-brake even the Mother's Mazda RX-8s (factory supported team with ABS) going into T1 at Willow Springs.
We'll see how they perform at CA Speedway in 2 weeks, since we're about 20 or so HP stronger now than the last time we were there, with stickier tires.
@ Tony: Good response on setting up a proportioning valve. In our case, there's a missing step: getting the brakes up to temperature. Since we're running street pads out back, and race pads up front, the bias certainly changes once up to temp. This is one thing that has nearly bit me in the ass on more than one occasion: I forget/don't have time to get the brakes up to temp, and then dive into T1 hot, usually locking up the rears before the fronts. Luckily, this hasn't become critical until after I was able to safely get back on the throttle, but it's certainly a surprise when someone parks it in front of you in some overpowered drag racer come roadracer.
@ Def: Ferrule/tube sleeve, collar/tube nut, pot-ay-to, po-tah-to, IMO. And yes, you need a tube sleeve/ferrule, otherwise it'll piss fluid everywhere and we'd have major problems! :)
As for cheap flaring tools, as you say, it has worked well for us (but not for the past 45 years). We've had to take some stuff apart, and haven't noticed any damage to the seating surface. To be honest, I was not aware that AN and SAE flares were different, and that definitely good information to know. In the meantime, we'll monitor things closely. If we end up with a failure, we'll probable just switch to a 3/16" SAE T, since that will have the same taper as our Chinalloy HF tool, and will be easier to source in the event of a failure. Luckily, if this fails (a catastrophic event is unlikely with our constant "nut and bolt" inspections), it'll almost certainly be a slow leak, and we'll end up with a slightly mushy brake pedal, slow fluid loss, and a puddle somewhere. The fittings are in a place where we'll definitely notice a fluid leak as well (right next to the MC, and the other ones are above the shifter). Thanks for the tip!
Either way, the key thing here, as with anything in a vibration-prone racecar, is to make sure to check torque on ALL bolts/fittings/critical components often.
Monday, May 16, 2011 7:42 PM
In addition to the AN / SAE mis-match, brake lines should be double flared - in addition to the flaring tool you have, making a double flared brake line requires a die. A quick Google search shows the double flare method:
Monday, May 16, 2011 8:20 PM
My understanding is that flaring tool is only for mild steel not stainless, the ones for stainless cost more and are a little different. But you can get away with them for a little while with stainless (at least I have) they just aren't the "proper tool".
Tuesday, May 17, 2011 1:05 PM
All good responses, and are perfect examples of doing things exactly by the book. However, we were able to cobble these lines together for somewhere around $50 (including tools) and have had a reliable brake setup for 6 years running now. Contrary to what one might think, our brake system hasn't exploded, immolated, transmutated, had total brake failure, moderate brake failure, light brake failure, or loose fittings - though our original brake rotors did have a wear pattern that resembled the Virgin Mary. In fact, this system has been absolutely dead nuts reliable. Our methods may work for you as well.
That being said, I must issue the following Public Service Announcement:
MotoIQ Projects are sometimes performed by occasionally trained weekend professionals. Do not attempt to replicate unless you yourself have been trained and certified to have a clue. If your knowledge comes strictly from knowledge gleaned from the Googles (and other subsidiaries of the internets), then you should never attempt to touch anything on a car. MotoIQ projects are documentations of our successes and failures for your benefit (or amusement) and are not meant to be the end all be all of race car building. We are not mechanics, just garage monkeys with too much time on our hands.
You may continue with your regularly scheduled programming. :D
Tuesday, May 17, 2011 8:29 PM
Brakes are all about weight, and how you use them. The more weight you are stopping, from how fast, and for how long, makes the difference in what will work for you.
I work on pretty heavy cars, and stock pads, and stock rotors get so hot that they wear the pads quick, and the rotors don't like it much. I saw a big difference in the driver feedback on the brake system with good ducting, and a good heavy vaned rotor compared to a lighter/lesser brand rotor.
So if you are running a stock type brake setup, you will probably benefit from some ducting to the center of the rotor, to keep the brake pads within their operating temperature range.
Good pads, stainless steel lines, and good fluid goes a long way for most drivers, and most cars.
Thursday, May 19, 2011 2:01 PM
It's funny, but on our car, we're about 2:1 on rotors to pads. The Hawk Blues wear like iron. I'm sure they're getting pretty hot (the rotors are often blue when loading the car up), but we've yet to have any fade issues, so we'll leave it as is.
We'll see once the aero goes on, since we've got some dedicated holes available for brake ducts (though we'll have to find a replacement set of ducts for them).
Thursday, May 19, 2011 7:14 PM
If it works, it works. Data is always nice to have. Some rotor temp paint, and some caliper temps.
You go though 2 sets of rotors for every 1 set of pads?
Friday, May 20, 2011 2:33 PM
We've just started using the Powerslots, so we'll keep everyone posted on them, but yeah, Chineseum rotors seem to last about half as long as Hawk Blues.
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