I see many aspects of my question was covered while I was MIA this weekend.

I'm just saying, that if the brakes become too touchy they become less usefull for every day driving or heck, even for track driving.

Either, I love the idea and the enginuity.

 

I don't think anyone is going to find that to be the case, Chris. Like I said, during normal driving you can't even tell anything has been done. It is when you need to extra stopping power or when you are in situations where the shedding off of heat helps that you will notice the difference. But hey, if no one asked questions there wouldn't be any answers, huh?

 

Yeah... I just like to think things thru.

 

Nothing wrong with that. I am the same way, but in this case I am not educated on it so I have to trust Chris' experience. A guy that can put all of this in the back of a Fiero and make it work is pretty good in my book! haha



This is an Aurora 4.0 turbocharged with NSX 6-speed manual trans and all of the computer controls working.

You can see more of the goodies he build for Fieros at http://www.westcoastfiero.com.

 

I hate to seem a pest here but there's a ton of holes in this "Brakes 101" story.

Rotor diameter: While correct that rotor diameter does increase leverage and thus torque it's entirely related to the amount of pressure the caliper is exerting as well. A bigger rotor alone does not equate to more braking, it simply uses more "leverage" relative to the same clamping pressure and pad coefficient of friction. The tire still locks up at the same threshold as before, you just don't exert as much line pressure as you would on a smaller rotor.

Power is not increase at all. Total rotor toque remains the same- a skid is a skid regardless of how you achieve it; rotor size, piston area, line pressure or pads.


Pad size has little or nothing to do with brake torque. A smaller pad does not create less torque or a larger pad more. It's simply related to the pressure being applied to it. (like saying my 185lbs weighs more if I buy a shoe two sizes too large!) Bigger pad simply last longer than smaller one. Carrying that one step farther...effective radius of the pad does have an impact but that's not what were working with here in general terms.

Lastly bigger calipers don't have "more pistons" for more braking force. They have more pistons to better spread the pressure over a larger surface area.A bigger pad not only lasts longer but also with 2 or pistons per side apply a more linear pressure to the pad and prevent bending of the pad under high pressure. Also many are staggered in size so not to over power the leading edge and prevent pad taper wear.

Clamping force has nothing to do directly with piston qty. You can generate more clamping with the oe caliper than some six pots. It has nothing to do with the quantity and everything to do with the total area of the pistons- and for comparing purposes; only one side of them as well.

I have no horse in the race about the kit being describe here but as one who does brake kits for a living I get steamed up reading some of this bunk that people toss out as factual. The TCE web page in fact includes an interactive brake bias page where you can compare things and learn more.

 

Todd TCE, thanks for the input. However, I'm not the only one with this opinion on mechanical advantage and bigger rotors: "...sports cars and race bikes typically have much bigger discs or rotors than your average family saloon car. The reason again is to do with heat and friction. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area, which as well as meaning more area for the pads to generate friction with, also translates to better heat dissipation. [NOTE: This was already discussed in a previous post - LewiSS] On top of that, the larger rotors mean that the brake pads make contact further away from the axle of rotation. This provides a larger mechanical advantage to resist the turning of the rotor itself. To best illustrate how this works, imagine a spinning steel disc on an axle in front of you. If you clamped your thumbs either side of the disc close to the middle, your thumbs would heat up very quickly and you'd need to push pretty hard to generate the friction required to slow the disc down. Now imagine doing the same thing but clamping your thumbs together close to the outer rim of the disc. The disc will stop spinning much more quickly and your thumbs won't get as hot. That, in a nutshell explains the whole principle behind why bigger rotors = better stopping power."


Read more: http://www.carbibles.com/brake_bible.html#ixzz13u7K161N

 

Bigger, better is good, but your biggest enemy is and always will be heat soak and glazing.

 

Interesting... I have already said that I don't know a lot about brakes. But the guy who built these for me has been doing them for 25 years. He has successfully put these kits on thousands of cars, for both street and track. And at a fraction of the cost of Wilwoods. As has been stated, this is the entry level kit for people who want a small performance gain and a big bump in cosmetic appeal. We do realize this is not a race ready performance brake set. but I did put a couple of hundred miles on them on the Pacific Coast Highway last weekend and let me tell you, no matter what scientific stuff may be thrown out to confuse people, these are head and shoulders about stock HHR brakes and won't put you in the poor house.

Todd, I don't know you and don't have anything against you, but you do have a horse in this race. You want to sell your Wilwood kits. You even changed your signature to Wilwood brakes, which was the sway bars until this post. And that is fine, but lets not try to hide that fact. You do indeed have a horse in this race. And it is fairly obvious to me that the powers that be on this forum are trying to help you with that. That is why I can't get any information about my friend becoming a Supporting Vendor on this forum.

Wilwoods are nice brakes kits. They are not Brembos, but they are nice. Unless something has changed, Wilwoods are also not street legal. Brembos are. The ultimate kit that Chris will build will use Brembo calipers and two-part rotors, and will still be less than the Wilwoods AND it will be street legal.

The problem with all of these is that they are just too dang expensive for most people who just want a little extra performance bump for their street vehicle. What I contact Chris for was to put something together that gives just that but is still affordable. And I think we have that. No, it is not going to please everyone, just like the, in my opinion, crazy priced big name brakes aren't. But there is enough room around to have more than one supplier selling more than one kit.

And foolmoon, thank you. That is what I have been saying from the start. The larger rotor will shed heat better and give better braking when it is needed. And even though I don't know fancy science to try to impress and confuse people, after nearly 1000 miles on them I can tell you that they do improve braking immensely.. and they look cool as he... And those two things are what they are intended for. And for barely more than a normal brake job done at a shop, or buying normal size slotted and drilled rotors and doing them yourself. And this package will give far better braking than either of those options.

 

I don't really need to image anything but I appreciate the visual! lol

You're not wrong in what you are driving at but you're not grasping totally what is going on here. Bigger rotors however do not equal better stopping power- that much I can assure you.

What you do have right is that larger rotors create more leverage. What's missing is that you're assuming this is the only part of the equation of torque that is important. I do agree that larger rotors are important for thermal capacity and fade resistance but let's pass over that and focus on the notion that simply having larger rotors will create more "stopping power"- a term I hate as it's really only torque.

Braking works on four principals: leverage (Effective Radius actually), Clamping (piston area, not qty), Pad Coefficient of friction (for conversation we'll call it .40 on everything) and Pressure (the line pressure used to squeeze those pistons)

Larger diameter gives us more leverage.

Multiple pistons may or may not generate more clamping.

Pad size has nothing to do with much of anything- NO you do not generate more friction with a larger pad, you just use more pad (or less) to generate the same load based upon the pressure)

More line pressure squeezes the pad harder and is altered by the amount of effort you put in (leg) or the size of the master cylinder. *As a side bar to your incorrect assumptions here you could argue that simply putting in a smaller bore mc makes more pressure thus it too creates more "brake power" right?

What you and others are missing is that maximum torque or skid is where the tire no longer turns. How you get there is based upon the input of all four of the above factors. Changing any one of these does not make more power- it simply alters the input of the others. You can create more brake "power" by fitting a track pad than a larger rotor in fact. A 13" rotor on street pads can make less torque than a race pad on a 11.5" rotor. So what? You can add larger pistons or a smaller bore mc and get more "power" than you can with the stock brakes. So what? My point is that any one or combo of those elements are limited by the adhesion of the tire to the road.

Now for my visual....you're on a wet road. You slam on the brakes and the ABS kicks in to prevent lock up. Does it change if you have 11" rotors or 14" rotors? Answer: no, the point of lock up remains the same. Only how you achieve it has changed. In the case of the 11" rotor you pushed harder to get more pressure, the 14" rotor didn't take as much pressure as it has more leverage working in the equation.

Coming at it the other way; you torque a wheel to 100lbs. Does it matter if you use a 6" ratchet or a 12" ratchet with that slip on extension? Did you make more power? Of course not; you still torqued it to 100lbs. You exert more effort one way yes but the net is the same.

As for heat you are correct that the efficiency of the disc goes up with the larger rotor. Putting aside the potential for overheating of pad material for a moment (one stop at the end of the 1/4 mile) you don't create any more (or less) heat with the smaller rotor. Assuming the same car at the same speed slowing to the same stop it generates the same heat. It's kenetic energy and is a constant with the same weight and speed. Again here only the use of the larger rotor absorbing the heat (and shedding it really) is a benefit to the durability of the brakes but won't change the total demand.

I'm sure we can both go on but while some of what you are stating is correct in general terms much of it is way over simplified and incorrect from a math standpoint and functional reality. So why do I and others in the business push larger rotors? Because (other than the aesthetics value) it increases the overall efficiency of the system and lowers the duty cycles. Most big brake kits don't promise shorter stopping distance, but the ability to do it over and over and over. *If you run all season tires and buy a big brake kit hoping to stop 10ft shorter it won't happen- you'll remain tire limited. But if you have some good R compound tires you can apply more torque (easier) then you could with the stock brakes and modulate them better with a larger set up. On the other hand you can fit 13" rotors and big calipers (pistons) on the front of you car and actually lengthen the stopping distance! "Man, I hit the brakes hard and the nose nearly hits the ground!". Really? Tells me the brakes are poorly balanced- think about it.

 

Some good reading... Looks like most agree that larger rotors are good for braking. And that is all this kit is about. You guys are talking about calipers and lots of other stuff that is not even involved with what we are doing here - yet. But it does appear that lots of big name companies think that larger pads, causing more friction, do help braking. Read the Audi page especially.

http://www.xtremeimportperformance.c...ed-rotors-myth
http://www.camarotech.com/brakes.html
http://www.audiworld.com/tech/wheel16.shtml