Joeywhat

I have a V6 with performance package. I'm planning on tracking the car a few times a year, and have been thinking about brake upgrades. Is it worthwhile to upgrade to GT rotors? I'm just not sure the slightly larger diameter will be worthwhile, especially considering the calipers are the same. I thought about take offs, but I'd really prefer to get new, aftermarket rotors and pads if I did that (likely Stoptech stuff).

Or would I just be better off getting a BBK and not wasting money on GT stuff? I'd really rather avoid $2000+ kits, but if that's the only way to get noticeably better brakes then it is what it is.

Also, FWIW I'm mostly concerned with brake fade. More stopping power would be nice but the stock setup isn't too bad. These pads seem to fade fairly easily (and this is just on the street). Also thinking about just a pad upgrade...

5.M0NSTER

At first I'd recommend you just try swapping out pads. I use Carbotech XP10s which are fade resistant to 1475F. You certainly notice more bite. If you need more resistance to fade they also make compounds with even higher temp resistance.

Start out with that, and better fluid, and see how your braking performance is after a few sessions. Then you can decide if that will do.

I wouldn't waste your time on a stock GT brake setup, unless you go for Brembo 4-piston unit.

P.S. I have the TP with the Brembos, and with XP10s I experienced no fade at all yet. Even after 30 minute track sessions.

Joeywhat

Yeah I can try those. If I don't go for the stock GT brakes it'll likely be a new BBK from whoever. I don't see the point in paying for the Brembos when you can get a new kit that's even better for not a whole lot more money.

How much dust do those pads create? That's another issue...the stock pads seem to dust way too much.

5.M0NSTER

Ahh, dust . So majority of the track specific pads are not very well suited for daily driving. I swap my pads a week before my event, and then I change them back to stock the following weekend. I can't deal with the noise. And yes, your wheels will be dirty in a few days.

If you want a slightly better pad you can still drive daily, perhaps you could try Hawk HP+. The Carbotechs are great for track duty. I went through only 1/5 of the pad in one weekend (~4 hours of track time).

Have you tried an event on stock pads just to get a good idea of the starting point and subsequent improvements when you start modding your brake setup?

Ltngdrvr

GT swap is super easy and super low cost.

But, you don't just swap rotors, you also have to swap to GT caliper brackets.

Lots of these swaps have been done.

And even if you do swap to the larger GT brakes, you should also swap to the better pads as well.

Joeywhat

I haven't. I'm trying to make it out once or twice this year to get an idea of what needs upgrading.

I'd prefer not to swap pads...I don't need to run ***** out on the track, but I do want to run it pretty hard. So I'll look for something right in the middle that works for both.

5.M0NSTER

Which brake kit are you thinking about?

I've had nothing but great experience with Brembo, so I may be a bit bias towards them. AM has this kit for just over $1k. Is the BBK kit comparable?
http://www.americanmuscle.com/svt-brakekit-0509gt.html

Also, your car is a few hundred pounds lighter than the GTs, so I really think something like this would be more than capable for what you need.

Joeywhat

Yeah that's not a bad price...I've been looking into Wilwood , Stop Tech and the bigger Brembo kits. One reason for a BBK is to just fill out the wheels a bit. That's really the rub, if I do get a BBK I kinda want the biggest I can fit inside my 19's, purely for the looks. If I'm spending that much cash, might as well spend a little more and have it look better, too. I think I can get 15" rotors under those wheels...

But I'll have to see what the budget allows, and see how it fairs on the track with just better pads. The more budget friendly options will likely be what I go with.

dmichaels

Unless you get out quite a bit and are pushing the car you don't need bigger brakes. I tracked an Audi s4 with stock brakes for 3 years before upgrading to Stoptech. Like 5.0 said above get a set of track pads for front and rear and that should get you thru your first several events. I would recommend flushing the brake system with a high temp fluid like Motul RBF600.

Also what track will you be driving? Some are hard on brakes, others not so much.

If you upgrade, I have had good luck in the past with Stoptech ST40 front setup. I also like my brembos on my GT - they are not inferior to the stop techs in my opinion. Not 2 piece rotors, but with brake cooling I have had good success so far. I have had fade though, but I think it was brake bleeding issues combined with year old RBF600 fluid.

I bet you could find a set of brembo take offs for half the price of a Stoptech or similar kit

dmichaels

You should be able to get big 15" rotors and 6-piston calipers under 19's. I am sticking with the brembos cause I run 18" wheels for my track setup.

Consider a brake cooling setup before thinking BBK?

Joeywhat

Yes, a cooling setup is also on the list.

lajntx

They have, and Rousch has been a good supplier for that. This isnt going to be an issue for the OP since he already has the larger wheels from the factory, and his spare ( if it came with one ) should already be sized accordingly.

One thing that is often overlooked by those who have V6`s with 17" wheels - AND - the car came with a spare tire from the factory, is upgrading the spare to at least an 18" spare -- Or just just getting an extra rim & tire for a full sized spare when they get the bigger wheels ( which obviously is done at the time of the switch or before ), since the 17`s wont clear those larger caliper brackets.

Joeywhat

Mine didn't come with a spare, and I probably won't put one in there. It's very rare I'm ever too far from civilization, and I'd prefer not changing a tire on the side of a busy highway. I'll call for a tow truck first.

One concern does seem to be wheel clearance in terms of offset. I'm not sure I can fit a BBK with these wheels as they're already pretty close to the calipers. I might need spacers (or new wheels) to make that work.

Todd TCE

I won't fuel the debate on what you 'need' and don't as I believe that's in part personal preference as much as anything. I will however point out you can obtain complete front and rear Big Brake Kits for well under $2500. To the door. Of course there are larger (14") rotor options and larger (W6A) caliper model options that push that final four wheel cost into $3000 also. All depends upon what someone wants.

And of course all are available as "single axle" purchases also with a private price quote.

If I can be of any assistance please let me know. MUSTANG KITS

Automatic 5.0

Stock GT brakes will not help you much. Stock Brembo would be much better.

5.M0NSTER

I was curious about some of the BBKs out there. They call some of them "BIG" brake kits, but yet the rotor diameter is smaller than the 14" Brembo brakes you can get from the factory by close to an inch! I know they pack more pistons in, but let's be honest. Pad surface area is really the big thing. Sure 4 pistons is better, and 6 is better still. But if the pad surface area is not that large, you have to build more pressure to get same deceleration, and you get more heat as a byproduct. No thank you. If you want to go big, might as well go 15".

Todd TCE

Pad size doesn't have a huge impact on braking force nor does piston quantity tho. Keep in mind that some folks still prefer to run 17s also where rotors larger than 13" don't usually fit.

5.M0NSTER

Hey Todd,

I can see your point about running 17" or 18" wheels. There it makes total sense to use one of the aftermarket brake kits. Performance will be way improved over the stock setup.

But I have to respectfully disagree with you regarding your statement that pad size does not effecting brake performance. Cp is the measure of brake torque per unit pressure. Usually measured in Newton-Meter per Bar (Nm/Bar) of brake pressure. So brake pressure being equal, there are 2 ways to achieve higher brake force (which is what big brake kits try to achieve):

1) Higher friction material of the pad, or higher mu of the pad-rotor junction. So more friction = more force, and
2) Higher contact area between the pad and the rotor, or higher pad surface area. When doing brake force math this often translates to surface area of the brake pistons themselves due to piston's limitations on symmetrically distributing pressure across the brake pad ... and this is where the number of pistons comes into play. More pistons/larger the piston area = more surface area of the brake pad the pressure can be distributed across. And more surface area @ a certain mu = more force

Todd TCE

On the surface that appears correct. However you're a bit off, and I'll explain why.

Assuming were are not talking about putting a bicycle pad on a car something stupid...when you change pads size it (for the most part) does not change torque.

Let's compare the common Wilwood BSL/FSL pad to the newer Wilwood W6A pad.





It's easy to see and follow is why I chose it. The same principals however apply between the stock oe pad and the race pad. And as you point out the pad Cf would be the same for comparing them.

Both of these pads are available in Wilwood calipers. Both have six pot set ups. From a 100% technical point the larger pad produces less brake torque. Huh?

First let's establish that piston qty has no direct bearing on clamp force. Clamp force is not qty, it's area. The same forces from a caliper with 4"of area be it a 2.26" single pot, 1.625" four pot or the popular 1.62/1.12/1.12 have same total area. Thus the "power" or clamp load is equal. When we install a larger pad we spread that same load over a larger surface. And as the pad grows longer we move from 2x to 3x to even 4x or more the pistons behind each pad. So long as the area is the same; the clamping is the same.

When that pad gets larger is takes the same total force and spreads it out over a larger surface area. That means less PSI but the same total load. But pads we know are not stationary parts, they move (or the rotor does) with frictional force. Frictional force however is simply the pressure applied multiplied by the Mu or Cf of the pad. The larger pad has more area but it's load is equal also.

Comparing the two pads to the max you can argue that the Er or effective radius of the larger pad is actually lower on the larger pad. The Er by definition is the average pressure point of the clamping on the pad by the caliper. The total area of the three pistons is the same but due to the larger pad and caliper body this imaginary line is a tad further in from the edge of the disc. It has to be that way or the pad will wear in a tapered fashion favoring the spot closest the pistons- concentrated rather than balanced pressure points.

But while this W6A pad is larger it does not produce more clamping or braking (*The lesser amount actually pretty minimal- you can do the math and see if you like) Buy fitting a larger pad you only add to the total amount of material available. If you want more torque you have to either (as you stated) 1. Increase the pad Cf (bite), 2. Increase the rotor diameter (leverage) 3. Increase the piston AREA (the clamping) or simply 4. Increase the line pressure (thus clamping harder)

Not the first discussion on this and probably not the last. But if you feel that's incorrect please dig deeper. You'll find this state not only from me but on Wilwood's site, on Stop-tech's site and on AP's site. And as always you invited to experiment with the math of brake torque on either my Bias page or more in depth on my DUAL MC page.


A simple way to look at this for many is this: Stand on your bath scale with your shoes on. Then put on some shoes that are 3 sizes too large and check it again. Aside from the shoe weight, you weigh the same. *But it's not moving. True. Take three pieces of cardboard, a 12" square, a 24" square and a 48" square. Put 50lbs on each and tie a rope to them. Pull. The weigh is the same. The Cf is the same. And the same effort is needed to pull them.

5.M0NSTER

Todd, thanks for a good information! This has turned into a nice technical post, and being an engineer in automotive brake modulation, I really appreciate that!

I agree with what you said. I think we're on the same page now. When we're talking about surface area of the pad we also have to talk about clamping, pressure, Cf, and diameter all at once. After all they are all used in the same equation when calculating brake torque

And Cf, pressure, and clamping being equal, this is why I originally advocated larger diameter (if possible given wheel diameter constraints). It aids in more torque by it's own virtue, as well as pad area.

Thanks again for a good discussion!