edmundu Posted May 17, 2005 Share Posted May 17, 2005 I have had some uneven pad transfer onto the rotors, which was corrected under warranty, by resurfacing the rotors and replacing the pads. Now, when I am just braking from say 60-80 mph, to exit a off ramp, I have no issues. Perfect smooth application of brakes! But when I do a few repeated 100mph down to 60 mph brake applications, I start to get brake shudder? I am not doing this in short rapid succession, there would be a few hundred yards between them. If I just drive a few miles without using the brakes, to allow them to cool, I find that they are feeling smooth again. I pretty much do alot of highway miles, and I also enjoy letting the car stretch its legs out. So I have a feeling that the stock pads are not able to handle the heat being generated? If so, what do you guys recommend to correct this problem? New pads only? New pads & rotors? I don't really feel like spending 2K on a BBK. Will different rotors actually help? PS What I want from the brakes, is to be able to rapidly slow down from triple digit speeds without fade or shudder a couple of times in a row (Ie;130-70mph). This way, if I have a 15-20 seconds between applications, they will have had a sufficient enough time to cool down. I would also like to be able to use them year round, including winter season, and not as important, if they could be quiet! I don't care if they dust! Link to comment Share on other sites More sharing options...
praedet Posted May 18, 2005 Share Posted May 18, 2005 Try some of the endless pads or the carbotechs... Just pads, no need to do rotors also. Ted Link to comment Share on other sites More sharing options...
Xenonk Posted May 18, 2005 Share Posted May 18, 2005 +1 ^ You just need a pad that can handle the heat and have a LARGE wide temperature range (such as the Endless SS-Ms that I am using from 30F to 990F).. since you are not tracking the car, you will have less of a likely chance to glaze your rotors and pads anyways, so slotted or dimple or cross-drilled is not neccessary. I am not sure what kind of bite you are looking for, but the bite (coeff. of friction) is only good as your tire compound. And tires too.. the final result is really from tires for maximum stopping power. Keefe Keefe Link to comment Share on other sites More sharing options...
edmundu Posted May 18, 2005 Author Share Posted May 18, 2005 Xenonk, I'm looking for a better initial bite than the factory pads. I was looking at Endless, but I am hesitant about them being over 50% more expensive than competitors? I don't mind shelling out more $'s if it gets me the results, that others cannot provide. That being said, I was thinking the SS-S's would better suit me, and they seem to have almost the same heat capacity? BTW I have changed to Pzero Nero's M+S in stock size. I don't have a problem with being able to outbrake them, just that the brakes start juddering & fading way to easily from higher speeds. And that is what I usually am braking from on my long 45 mile commutes to work. Link to comment Share on other sites More sharing options...
Xenonk Posted May 19, 2005 Share Posted May 19, 2005 Xenonk, I'm looking for a better initial bite than the factory pads. I was looking at Endless, but I am hesitant about them being over 50% more expensive than competitors? I don't mind shelling out more $'s if it gets me the results, that others cannot provide. That being said, I was thinking the SS-S's would better suit me, and they seem to have almost the same heat capacity? BTW I have changed to Pzero Nero's M+S in stock size. I don't have a problem with being able to outbrake them, just that the brakes start juddering & fading way to easily from higher speeds. And that is what I usually am braking from on my long 45 mile commutes to work. I have over 5000 miles on my brake pads and they are still nearly close to the thickness as new. Currently, the pads that I have are worth every penny. I think your style of braking is exceeding the heat limits. SS-S (700 degree max heat capacity with a super high initial bite) or SS-Y (850 degree capacity with an initial bite just under the Bobcats) would do you fine. The SS-Ms I have just a slightly better initial bite than stock, but not much.. I chose this pad because I know I can just modulate the brakes to approach the threshold braking limit more smoothly. The higher heat temp ranges allows me to do later braking repeatedly for the track use without having to worry to really lay on the brakes early by the end of the day of the 80th minute on the track. I assume your car rolls just fine so that can't be a flat-spot or tire-balancing issue. Are your commutes 45 miles one way? I drive 50+ miles a day to and from work.. on the weekends I do over 200 miles. I am not sure what kind of studdering you are getting. I have driven my car at the track and I slow down from 120 mph all the way down to 30 mph more than a handful of times even on stock pads and I get very little fade. Try adjusting your brake inputs as well that might help it some to relieve the brakes from glazing over as well. How much of a difference will there really be in stopping power with different pads? I performed a "test" emergency stop the other day in the rain and the bite was pretty minimal. The ABS only kicked in momentarily (I have good tires for the rain) so I know it wasn't a grip issue. I was actually somewhat disappointed with the braking performance (first time I had tried this) and I know now that I will leave even more space when driving in the rain :~ The pads doesnt supply you the final and major result of a one hard stop situation (especially when you get dedicated track pads that require warm up, this goes for the same for R-compound tires). Tires is usually the main issue.. I can prove to everyone that the GT brakes are more than enough to lock up the wheels (just take out the fuse for the ABS and just slam on your brakes, you'll lock the wheels up with no problems, even with stock pads because there's a lot of clamping force). With that said, heat wouldnt be an issue if the rotors are not spinning and the brake pads are clamped on quick and tight. The brake pads job is to deal with the transistion time and friction/heat generated when the brake pads are in contact with the rotor. You want a brake pad that doesnt require warmup time for street use (as I am sure you want to be able to stop your car at the first stop sign out of your neighborhood). Heat capacity is how often you are riding on your brakes or how much heat you can really generate from the kind of braking you do. The initial bite is how much the pad can really dig into the rotor (think of it as wearing cleated shoes for football practice vs sandals). Jamming on the brakes wont help, it's all about the correct pedal modulation for the brakes to maximize the brake pads are biting. Granted that stock pads have low bite, but in my opinion of the kind of high performance driving I do, the stock pads are good enough for autox events. My solution to you all is this: Practice brake modulation, that should get rid of some of the vibration (you might want to get Subaru to look at the caliper as the brake fluids are probably not being distributed properly through the caliper) or even do a brake fluid flush to get the tiny bits of air bubbles out of the lines. Brake pads and tires only do so much, it's up to the driver to bring out the potential out of the parts anyways. Keefe Keefe Link to comment Share on other sites More sharing options...
edmundu Posted May 19, 2005 Author Share Posted May 19, 2005 Thanks Xenonk! When I was referring to getting the brake judder, it was after repeatedly stabbing the brakes from say 80-90mph down to 60mph in succession. If I only step on them 1-2 times, then all is fine! I was just looking to increase the performance to be able to sustain this cycle for say 4-5 times in a row. Since I've already had Subaru resurface my rotors, I really wouldn't want them to be cut further, so I figured I would get the new pads(SS-S), and if I still feel the judder, then I'll just replace all the rotors myself. Link to comment Share on other sites More sharing options...
Xenonk Posted May 19, 2005 Share Posted May 19, 2005 yea, your braking style needs to change, you shouldn't jab the brakes.. it all should be easy on the brakes and easy off the brakes.. but as you reach threshold braking, the force from your leg/foot/toe should increase right up to that point and be firm to hold it. Jabbing will only get you in trouble if you dont know much about weight transfers. It's possible that your juddering is that you are creating crushed impressions onto the rotor and when it gets hot, the rotors get soft on you, hence the juddering. Keefe Keefe Link to comment Share on other sites More sharing options...
edmundu Posted May 19, 2005 Author Share Posted May 19, 2005 So do you think I need to replace rotors? Or should I just try the pads, and see what happens? Link to comment Share on other sites More sharing options...
Xenonk Posted May 19, 2005 Share Posted May 19, 2005 just do the pads for now.. if you already turned the rotors at the dealership once, you should be ok.. I have 20k miles on my car already and I dont have any indications of a bad rotor.. this includes track days and autox events. Just remember to modulate the brakes and get your braking down smoothly. This should make your brakes last a lot longer. Remember, race car drivers have to make sure that the brakes have to last an entire endurance event.. imagine the 24-hour races.. or even 8 hours for that matter. Smooth driving is the key. Keefe Keefe Link to comment Share on other sites More sharing options...
ChruiSSer Posted May 19, 2005 Share Posted May 19, 2005 Wouldn't the shuddering be from warped or "semi-warped" rotors? That's what gives you that pulsing effect. I noticed with my car if I drive around like a normal good boy, it's fine. If I'm on the highway @ 80mph and a get on the brakes a little aggressively, I sometimes notice the shudder. The pads shouldn't have anything to do with the studdering, it should be from the rotors being warped, or the thickness is different on one point on the rotor, than another point on it. I worked at the dealership last summer doing brake jobs and all, and the brake lathe trues up the rotor making it perfectly parallel. It was amazing to see how far off the rotors would be sometimes. Link to comment Share on other sites More sharing options...
Xenonk Posted May 19, 2005 Share Posted May 19, 2005 Read post #8 of this thread. You might also want the read his actual syptoms. His first 2 to 3 stops at high speeds are fine.. it's the later attempts of braking is when he feels the studder. the ACTUAL warping process is when the brakes cool down (like forging process, metal is bendable when hot and such, it's when it cools down to harden back up is the problem). If you are coming off the highway and you just made a really hard braking session just coming right off the off-ramp, then you want to cool your brakes down by driving about 2 to 3 mins without using the brakes. Most of the time, coming off the highway and making all those braking sessions and entering in a city zone, you are doom to use a lot of the brakes through stop and go traffic. At the same time, while the brakes are still hot, and all that clamping that you are doing in the city is just crimping the rotors and causing them to have some really odd shapes. Basically you are molding your rotors into a different shape while it's cooling down. Keefe Keefe Link to comment Share on other sites More sharing options...
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