Help me learn about brake compounds, guys!

[Doug S.]

OK, so I bought a used Cobra replica 3 years ago, drove it for about 3 months and then put it up on jackstands....never expected for it to take me 2 years to find the right urethane bushings for the rear parallel 4-bar suspension. Now that it is back on the road, it doesn't seem to stop as well as it did before....significantly more brake pressure and less stopping power. I think I have moisture in the brake fluid and plan on flushing the system, but I wonder if it is possible for the brake pad linings to have "hardened" during the 2 years it was in the garage.

As long as I have it up on jackstands again for it's winter "upgrades", I'd like to put better pads on the Wilwoods. It has discs both front and rear.

The car is driven 100% on the street right now, but an occasional foray down the 1/4 mile is not out of the question in the future. I am WAAAY too unskilled to attempt road racing at this point, but I'd certainly like better street performance if I can get it with a certain brake compound. There are times that driving this thing in the congested Houston traffic can be a bit scary, if you know what I mean :shocked: .

I'd appreciate any information you can provide to help me understand about the different types of brake lining materials and which are best for high performance street use. I don't mind changing them out more frequently than would be necessary on my Honda, that's the reason I bought the Cobra, I like fiddling with those sorts of things (like adjusting the valve lash for the set of solid lifters....it's "entertainment" at times).

Thanks in advance, guys 'n' gals....so far the only experience I have is with the offerings at the local O'Reilley's, so you can see how much I need the help :embarassed: !

Cheers!

Doug

 

[DaveM]

Brake pads don't harden just sitting. They can be overheated with extreme use. Does the pad material look 'chunked out' at all? Your problem is most likely brake fluid needing replacement with thorough bleeding. Also is your brake bias set correctly? What Wilwood compound is on the car now? Wilwood usually supplies BP-10 unless the calipers are several years old. BP-10 is OK for general street use. If you're more aggressive BP-20 will handle heat better. Do not go for hard race compounds. They cannot be heated sufficiently in street use and don't work well 'cold'.

 

[Bill Musarra]

Doug,
Go to the Wilwood web site and match up yor calipers/pads with the ones provided.
Wilwood High Performance Disc Brakes - Brake Pads
Wilwood High-Performance Disc Brakes - Calipers
Check the technical info on the web site to make sure it will fit. Then all you need to do is decide if you want high performance street or racing. If unsure, they have phone #s to call and order. Ask the tech on the other end about the pads and they should be able to tell you all you need for your car. If they can't , I am sure they will forward you to one who can. Most everyone who answers your question will tell you how the ocmpund(s) felt to them,or how they felt they met their expectations. Go with the experts, that is their business. If all else fails, go to the Cobra forums and ask them how they liked xyz compunds.

Bill

 

[Cliff Beer]

Hi Doug, I think there's one BIG preliminary question before you get into any of the detail comparisons between manufacturers and the specific compounds: do you want a pad that needs to be heated up before it works well (ie. a "track" pad), or do you want a pad that works fine on a cold brake (ie. a "street" pad)?

For street work, including the occasional 1/4 mile blast, I would HIGHLY recommend sticking with a good street pad. A track/race pad is going to be horrible on the street if you really need to brake hard on the street in a emergency situation and your brakes are cold. Downright dangerous in fact.

There are lots of good street pads out there. Personally, I like the basic semi-metallic pads - a little less brake dust, and the metallic content helps to transfer heat away from the hot rotor into the caliper and surrounding metal. Ate, PBR, etc. all make good semi-metallic street pads.

As others have mentioned, brake fluid is just as important, both that it's fresh (most brake fluids tends to absorb water over time, lowering it's boiling point) and that it's good quality. DOT 4 is usually good for street work.

Good luck!

 

[Howard Jones]

One bit of advice. Begin your search with "high performance Street replacement brake pad" and google away. Don't get talked into race pads by people who think "race" anything is better than street intended equipment.

Last weekend I went to breakfast on Saturday morning at about 6:45 AM. It was cold overnight (California cold), down to about 37F in the garage. So I jump in my GT40 with Wilwood superlite calipers and B pads on the front and C pads on the rear. I was thinking a lot about warming up the engine and guess what happened when I braked hard into the on ramp entrance. Damn near put it into the wall. Saved it by inches. I have never pushed harder on the brake peddle than that and it was like iron on iron. The Pads on the front are well broke in and remain on the car from Octobers last track day. Their intended temp range is about 600F to about a 1000F (from memory) I bet they were less than 100F.

I put the ceramic street/high performance pads back on the following week. Both sets are several years old and I swap them back and forth as necessary. Good pads will last a long time unless you overheat them or run 1000s miles a year. Most GT40 owners I know run about 2-4 thousand miles a year. Pads will last years at that pace on the street.

Lastly, what do you think about doing a on track high performance drivers school. Cobras can really bite you if you try and learn for yourself on the street. I would hate to hear you put it into the guard rail while trying to find the cars potential.

Anyway here's the data on the pads I am talking about, and one other newer Wilwood street pad (BP10) that might work for you.

Q (ceramic) all 4

http://www.wilwood.com/BrakePads/BrakePadsApp.aspx?compound=PolyMatrix Q

B race (Front)

http://www.wilwood.com/BrakePads/BrakePadsApp.aspx?compound=PolyMatrix B

C race (Rear)

http://www.wilwood.com/BrakePads/BrakePadsApp.aspx?compound=PolyMatrix C


Note the lower friction level of the C pad in relation to the B pad at lower temp range and over all. This tends to make the initial bite (first apply brakes) lower on the rear of the car and results in good balance over all ON MY CAR.

Again don't waste your money on B-C pads on a street car. You will take them off within days and waste a lot of money.

Now compair the above B-C to the BP10 high performace street pad.

http://www.wilwood.com/BrakePads/BrakePadsApp.aspx?compound=BP-10

 

[Doug S.]

Thanks so much, guys.

Dave....the calipers are probably 18 years old....the word I got was that the car was constructed in 1994. Thanks for the info regarding the age of the caliper, I would have never considered that. I can check on the caliper model numbers when I get back home where the car is stored....as for the bias, there is no way to adjust, the braking system uses a standard Ford factory master cylinder. If any biasing is to be done, I guess it might need to be done with different compounds on the front vs rear.

Bill, I'm a big believer in taking the advice of experts....in fact, I've been a member on ClubCobra for quite some time, and I think I'd follow the advice of the experts at Wilwood much more quickly than the CC members, although everyone there does seem to have their opinions (and there are as many different opinion as there are members, I've noticed).

Cliff--strictly street driven, so no track pads for me.

Howard...my yearly mileage is quite similar, so far less than 3,000 miles in the 3 years I've owned the car. It didn't get many miles for the two years it was on jackstands, so I'd suspect that 2,000 miles a year is about right (although, my speedometer is running almost 20% high, so that means the mileage is also 20% high, too). That's the first thing I'll work on when I get it back on jackstands.

I had an experience much like your on-ramp experience at a recent car show "cruise night"....everyone was doing burnouts, so I was too. I couldn't stop before the car "left" the parking lot, if there had been anyone on the street I would have caused an accident. I was much more careful after that, you can bet on it!

OK, so here's what I know now:

1. NO RACE PADS!! I am fully onboard with this! I've never warped a rotor by riding the brakes, so I doubt that I could heat up the pads enough for safe stopping.

2. Flush the old brake fluid!! I have no idea how old it is, but I have not changed it since I bought the car and I have no idea how long it had been in the car at that time. Thanks for the DOT 4 suggestion, Cliff, will do!

3. Still not certain about the relative merits of semi-metallic vs. ceramic. I have had both on street cars I have owned, and have had both types on my Honda Civic, and can't tell much difference, but they have anti-lock power brakes, the Cobra has just standard manual brakes. I like the higher mileage of the ceramic pads, but I also like fiddling with stuff on the car and would not mind changing pads more often, considering it gets limited mileage.

If I were to want to do track days, I'd not even consider trying it before I took some instruction. The Cobra swaps ends quite easily....there is a freeway underpass near where I live and I use to enjoy "spinning corners" when I was a kid, so I took the Cobra out there one night for some drifting fun. OOPS!!! Ended up looking backwards on the first corner...it does not handle anything like a factory car, scary at times.

Thanks so much, guys....at least I now know where to start looking for info.

...anyone with additional advice, I sure would appreciate knowing what you think.

Cheers, guys!!

Doug

 

[Mike Drew]

Doug,

You failed to mention whether your Cobra is equipped with power brakes? Because your symptoms sound somewhat like a power brake booster, that isn't. If your car has power brakes, temporarily disconnect the vacuum line to the booster (plug the line off to prevent a massive vacuum leak in the engine), and then test the brakes. If they aren't substantially worse than before, then your brake booster isn't working.

If you don't have power brakes, then disregard.

FWIW my Contemporary Cobra has Wilwoods up front and stock Jaguar E-type calipers in the rear. With no power assist, the brakes totally sucked. I upgraded to Hawk HP+ pads and things improved somewhat--now thanks to the ancient tires, the brakes work but the tires lock up and thus the stopping still sucks. I'm considering an upgrade to power brakes one of these days--but since I broke the motor last week (think I spun a bearing), I no longer need to worry about the brakes. :veryangry:

Oh, and I use Wilwood BP-20 pads on my Pantera. They are the very best dual-purpose street/track pads I've ever encountered. They work fine on the street, but continue to work better the hotter they get, which really inspires confidence on the track. So much confidence, in fact, that I broke THAT motor too, last time I was on the track. :sad:

 

[Doug S.]

Hi, Mike....no power assist, sadly....and inadequate room between the master cylinder and the driver's side inner fender to install one, so continuing with the standard Ford manual brakes is where it is.

Since I have no way to adjust brake bias, I might experiment a bit with the BP-20 pads and the BP-10 pads Howard mentioned. One thing I notice on the graph Howard linked re: BP-10 pads, the grip does not increase as much with increased heat as the other BP series pads, and it seems to me that increased grip with additional heat might well go a ways toward dealing with brake fade.

However, for right now it's a really cool daily driver when the weather allows (which hasn't been much for the past month here on the rainy Gulf coast)....not a competition ride.

Still kinda like ceramics, too....anyone with experience with those on a high performance automobile?

Thanks, again, guys....you've already taught me more than I ever thought there was to know!

Cheers!

Doug

 

[Tim Kay]

http://porterfield-brakes.com/images/portrace2008_11_06_02_43_53.pdf

I'm thinking of trying this R4-1 after comparing the graph to the Wilwoods. Appears to be considerably higher cf at low temp. Any reason not to install on street cars?

Currently using Porterfield R4S front and Wilwood B20 rear. Very happy with them but only after putting heat to them.

 

[Trevor Booth]

Firstly I would suggest overhaul the calipers , they have been sitting for a long time
Secondly overhaul the master cylinder
Thirdly, have a very close look at all the brake hoses and replace as necessary
Completely flush all the brake lines in the process

All the fundamentals will now be in working order , then you can start playing with pads if necessary.

brake bias is more easily adjusted with a limiting valve in the rear circuit.
I would not play with different pad compound front to rear