Louis M

Crrently I have stock size rotors, stock size pads, stock lines... Now if I get Brembo F&R Slotted and Drilled Rotors, Hawk Pads and Stainless Steel Lines, will my braking improve that much? for example: before i went 60-0 in 140 feet, now i go in 120... Also, what kind of Hawk Pads or what other brand is really good?

Brentis

i don't think it is that significant. i did stillen drilled rotors, and hawk hps pads and it feels slightly different, couldn't say it is much better and definitly not dramatic. Get a system with bigger rotors is the best - the larger the rotor the more the caliper can apply lever-age. Brake fade and other things may be improved, but I never have had fade woth the previous setup either.

DamonB

Rotor size doesn't matter. Rotors do not stop cars, tires do; you can't slow the car quicker than the tire will let you.

LouisM if you are strictly talking stopping distance on the street, none of those things will really do much. As I pointed out, once the tires are near locking there's nothing else the brake system can do.

Check our link list: Everything you ever wanted to know about brakes but were afraid to ask by Grassroots Motorsports

cpa7man

iTrader: (2)

Damon good links, I was browsing them the other day. I'm currently trying to decide between (Hawk) HPS or HP+ pads. I'm going to be doing as much track/ autocross as I can. I might just try the HPS now and than next set go HP+ so I get the full effect.

I think the biggest bang for the buck improvement would be to go to ss brake lines. The pedal feel is much improved. The stock brake lines tend to make the pedal feel mushy as they age.

Based on some very good old threads the HP+ pads bite quite a bit harder that the HPS pads on initial brake application. There is a tradeoff on the HP+ pads in noise and brake dust.

Search for Hawk, and you will come up with a number of old threads that are very informative. But its still hard to decide.....

DamonB

I added them somewhat recently and honestly I wouldn't bother with adding them unless the stock lines need to be replaced.

You're right about the pads. The tradeoff is that the HP+ does have a more aggressive bite, but they dirty the wheels very quickly. Look at my race wheels closely For autox the HPS is just fine and still a very nice pad, but it will not live on an actual race track for long. I have not been able to make my HP+ fail at MSR, but after about 4 really hard laps the pedal effort does increase. It seems to stay stable after that point though.

Brentis

rotor size makes a difference despite what others may think. Tires are part of the function but it goes hand in hand with the rotor.

Frictional clamping force from the caliper can only practically be increased so much so as to not dramtically increase rotor wear and pad wear. A larger rotor can more easily stop the car than a smaller rotor given the *same* frictional surface area *and* clamping force. A simple analogy turn you ceiling fan on high - get it going good and fast - then try stopping it by using your hand as close to the motor as you can and time how long it takes. Next, with you remaining working hand start the fan again and try stopping it from the edge of the fan blade. Note the difference and ease of performing it from the edge.

Tires impact is as obvious as saying you can stop faster on ice than asphalt.

Interestingly my wife just got an 03 4runner sport and the rotors are 1" larger in the front resulting in a 130ft 60-0 stopping capability about 17ft shorter than the non-sport - nothing else is different (same calipers,etc, just changed to fit the larger rotor)

DamonB

Brakes are hydraulic and therefore are capable of clamping the friction material ENORMOUSLY hard. Yes a bigger rotor could get by with less clamping force to give the same decel of the tire. But nothing is free. The larger rotor must have more friction material and more piston area to clamp it. If not, the larger rotor will merely heat the pad material every bit as quickly as the smaller one. Since the larger caliper has larger pistons and since it is hydraulic you have to displace more fluid. So you either press the pedal further or use a larger piston on the master cylinder which means you have to push the pedal harder. The pistons at the rotor may be doing less work, but the one in the master (along with your foot), is doing more work. Hydraulics obey the conservation of energy laws just as levers and gears do. Nothing is free. Your fan example obeys the same laws. The fan may be easier for you to stop by grasping it at its outside, but the fan tips will travel farther here than at the inner end since the outer circumference is larger than the inner one. The work to stop the fan is the same whether you grasp is at its inner or outer circumference due to the definition of work (force x displacement). Stopping the fan at the middle requires more force, but less displacement. Stopping the fan at the outside requires less force, but more displacement. Think about the fan's rotation. In order to stop the fan you must deplete all of its kinetic energy. How you choose to stop the fan makes no difference, you still have to absorb the same amount of kinetic energy.

In the scheme of things (stopping distance) larger rotors have practically no impact, they are not used because of superior mechanical advantage. This can be verified (as thousands have) rather easily by measuring stopping distances on different sized rotors with everything else remaining the same. The 17% difference in your 4Runner example I bet has more to do with ABS software tuning or test variables than rotor size. The only exception would be that if the friction material is woefully inadequate and incapable of good performance. A larger rotor may help there.


I assume you meant the other way around? You can't stop quicker than your grip will let you. Once the brakes are capable of locking the tire, any more braking power in the brakes themselves is completely trivial. Big brakes are a necessity in racing because racecar brakes are running at tremendous temps and their brakes are harshly used corner after corner. The larger rotors are a must in order to provide enough heat sinking area. This is not required on a street car because the brakes get plenty of time to cool between applications.

Bigger rotors do not stop cars quicker, they stop cars more often. The larger heat sinking is able expel the energy into the airstream more quickly and therefore delay the onset of heat fade when compared to a "smaller" brake. With both systems staying within operational temps stopping performance will have everything to do with tires, not brakes.

Pulp Friction

cpa7man

iTrader: (2)

Must mean Niks brake lines are bad or master cyl. problem. His brake pedal feel in very mushy. I always assumed it was the ss brake lines that made the diff.

With the track day in Nov and planning a few more track outings (another drivers edge) this year it sounds like I might just go for the + pads and skip the HPS. Than again I don't go nearly as fast as you do, and given that I don't brake as hard.

Louis M

then why would anyone buy brembo slotted/drilled rotors? its completely pointless unless you get a big brake kit!

OC_

you wont notice much of a difference unless you race.

maxcooper

If your current brakes can lock up all the tires on one stop, better brakes aren't going to make that stop any shorter.

However, as you do more stops in a row, fade sets in. Better pad compounds (better meaning "works at higher temps" here) and bigger brakes are aimed mostly at delaying the onset of fade. Feel can be improved as well, but from a purely "how does it work" standpoint, these items are notable mostly because they delay the onset of brake fade. Brake fade can arrive very quickly on the track with stock pads and brake hardware, but you can make them work much longer with better pads or bigger brakes.

Some bigger brakes are lighter than the stock setup, too. My fronts are 2 lbs lighter per side, and the rears are 4-5 lbs lighter per side, IIRC (and will be even lighter still when I get my 2-piece rear rotors). Brakes are unsprung weight, so lightening them can improve suspension performance (grip, and even ride comfort).

SS lines did make my pedal feel much better, but it might just have been that my stock lines were old or that the bleeding I did with the install of the lines were the primary causes of the change in feel. Whatever the case, the pedal did feel a lot better after the install.

-Max

A'PEXi RX-7

Its not really pointless. Keep in mind that most big brake kits cost around $2000+ and most people here never actually track their RX7.

When your stock brakes die, its actually a nice cost effective upgrade since they dont really cost that much more than OEM brakes. So why not get brembos? You might not have significant increases in stopping power with stock sized replacements but a slotted drilled stock sized rotor will not fade as quickly as a plain jane brake rotor with stock pads. Plus they really provide a nice aggressive look. Although I dont really recommend drilled rotors for the street since they do tend to develop premature stress cracks. Dimple drilled offer a similar look with much more durability. Also, stock rotors will rust and end up looking pretty darn ugly. These are the rotors I use on my FD and I definitely felt much better braking response after install.


http://turboimport.com/catalog/rx7.htm

also stainless steel lines are definitely a plus on a 10 year old 1993 RX7! The old rubber hoses will expand with age and make your pedal feel mushy.

cpa7man

iTrader: (2)

Good link, I've only seen the drilled Brembo rotors. The dimpled ones should hold up better at higher temps. Anyone track these rotors?? Or have any long term experience with them.

M's

Well, rotor size will make a difference and that is simply because you are increasing the surface for the pad to grab. In addition to that as you more the rotor outward you are able to get more torque on the hub which transmits to the tire which slows the car down. SS lines will help but it really depends on the manufactuer, some have better stock lines than others, fluid is what will always make a difference in addition to having properly bleed brakes. Slotted or drilled rotors are really only for looks, at least with today's technology. In the past rotors were drilled and or slotted so that the gas emmited by the brake pads had a place to escape. With today's pad technology there is no need for this and it is effectively reducing the braking surface as well as creating a weak point in the rotor. If you don't believe me go out in your garage with a magnifying glass(may not need one) and check around the points where the rotor is drilled. Real racers do not need slotted or drilled rotors

DamonB

So why not use a small rotor with bigger calipers and pads and get the same thing with less weight? You still misunderstand.

This is still a popular misconception. Go do one 100 mph on "small" rotors and punch the brake pedal as hard as you can. You'll lock the tires nearly instantly. Now go do 100 mph on "big" rotors and punch the brake pedal as hard as you can. You'll lock the tires nearly instantly. How did the bigger rotor improve your stopping distance? It didn't. Stopping distance was the same in both cases. A brake merely needs to be powerful enough to stop the tire.

The bigger rotor will not stop the tire quicker; once the tire locks everything else doesn't matter. Larger rotors do not make tires lock quicker than smaller ones.

Here's some good reading for everyone:
Why bigger brakes?

M's

it's simply physics, create a bigger lever arm and you'll get a bigger torque. THe rotor in this case is a lever arm. I garuntee that the larger rotor will lock the brakes quicker than the smaller rotor on the exact same set-up. same pads same lines, same booster, same master cylinder.


the problem with a bigger caliper and a small rotor is that if you're using a huge caliper and a tiny rotor you;re gonan to experience tremendous fade. You're incredasing the braking surface but not increasing the surface area of the entire rotor. YOu're not going to disappate very much heat at all. so unless you're running the world's highest opperating temperature pad you're gonan run into trouble.


what do you run on your FD?

DamonB

If we need mass in the brake rotor to absorb the heat and release it into the airstream to keep the brakes from heat fading, how do you figure having LESS mass in the rotor (drilling and slotting removes material) helps? Answer: It doesn't!

Slots are not there to improve heat fade performance, they are there to help keep the surface of the friction material on the pad clean by sweeping away the spent friction material and not allowing it to stay between the pad and the rotor. Ideally you would like to not slot the rotor and therefore give up mass, but keeping the pads clean over an entire race is a preferable trade off.

DamonB

Your lever arm is example is correct in showing torque, but your guarantee does not apply (see my "Brake from 100 mph" story above). The reason this does not apply to stopping distance is because you left out another variable: brake pedal pressure. The bigger rotor will stop the car with less pedal effort in your example (in real life with bigger pistons, etc it may be different), but it will not stop the car in a shorter distance. See my "Brake from 100 mph" story. You disagree with that example?

Exactly right! This is why we use bigger rotors. They do not decrease stopping distance, but since they have a higher thermal limit they can handle more braking energy without reaching temps that will overheat the pad material and brake fluid. Bigger rotors give us more time to play so to speak, they do not give us shorter distances.

Brake are a simple physics problem. Brakes turn the kinetic rotational energy of the rotor into heat. The rotor then expels this heat into the airstream. As long as the rotor can get rid of the heat in the system quickly enough the system stays at top performance. This means you can get every bit as much improvement in braking performance by cooling what you have now more efficiently than by adding larger (heavier) rotors. If you could water cool the rotors (some GTP cars did it) you could get "small" brakes with as much heat capacity as "large" brakes!


Stock blank rotors and stock calipers with Hawk HP+ pads and stainless steel lines. My open track running is on a 1.7 mile roadcourse and generally in 30 minute intervals. My current setup is marginal on racing slicks after about 15 mins, but I am unwilling to modify the system as it would kick me out of classes I race in. Again, even with bigger brakes my car would not stop any quicker, but it would be able to stay on the track longer without over heating the brakes.

redrotorR1

Unfortunately, increasing rotor size does NOT increase the surface area for the pad to grab, if you are still using the same size pad! Big brake kits usually come with larger rotor, larger calipers and larger pads. And even then, you braking force is still the same.

SS brake lines have a very widely misused conception that they improve braking performance. They are a reliability modification. They improve endurance and consistency .. but do they make your car stop in a shorter distance? Nope. Ditto on the brake fluid. Take your typical Castrol vs. Motul RB600 and test which one stops faster ... on a 60-mph one-stop brake. If there is any difference, it will be minimal. Now, try and do this repeatedly over a 1.3 mile stretch ... that's where you'll find that Motul is a much better product. But, you are absolutely correct about having properly bleed brake lines. It does make a world of difference.

Couldn't agree more. With most of us "grassroots" type racers, slotted and drilled rotors are more of a detriment due to their high frequency of cracking.

And lastly, Damon has been hitting the nail on the head over and over. TIRES STOP THE CAR!!!! Most of these upgrades that get oohs and aahs are for endurance and reliability. As Maxcooper pointed out, mostly to prevent brake fade ... something which non-track drivers will very rarely experience. If you want to make your car stop on a dime on the street, do yourself a favor ... toss those POS $60 cheapos and buy some decent tires. Maybe invest some money into decent pads that have good cold bite.

DamonB

When's the last time the brake fluid was changed? It absorbs moisture over time and since water will compress the pedal will travel further and be mushy on old brake fluid. Could be the lines or cylinders too, but if I didn't see any leaks I would assume they are fine and just change the fluid.

M's

Basically we are all in agreement here, the thing is that i am compelled to throw in more variables. IF you keep everything constant and change one thing the only thing that will actually show an imporvement is the pads.This is with the assumption that your tires are more than suffiecient for your brakes.

MY example witht eh fluid was of course assuming multiple stops. I personally do not like motul because it has to be bleed a whole lot.

It's good to see that there are a few of you guys out there that aren't complete morons. My friends always give me crap because every track day they go to there are fd's going on track left and right.


And jsut to finalize it, It's funny that you guys feel the need to validate my statements, i'm relatively intelligent and i know what i am talking about. we're jsut not on the same page.

cpa7man

iTrader: (2)

???? dont know. Will change this weekend. Waiting on Power Bleeder. All work on his car has been done at RP. It looks too dirty to have been changed recently. They did put Bonez stage 1 pads on it.

Brentis

I'm in M's camp.

Give me larger rotors with the same clamping force, same surface area, same tires, same weight, same suspension, and same frictional coefficient pads as the person shod with smaller rotors and I guarantee I will stop faster than you...

Please raise your hand if you disagree.

crazysuprakid

Yea but do the SS brake lines actually give you more stopping power? I wouldn't think so...It's more just replacing something that fails on the car than anything else IMO.

Brentis

SS brake lines just put the hydraulic fluid to work more quickly. If the stock ones do the work needed in 50lbs of pressure, the SS lines will do it in 51lbs of pressure. Now if the max force you could apply is 100lbs of pressure and you needed 102 then the ss lines may be of benefit. Chances are the master cylinder will more than accomodate the difference.

The 1lb of pressure difference comes from the expansion of the stock line and loss of directed energy through expansion of the stock rubber hose.

My $.02