letitsnow Posted June 9, 2012 Share Posted June 9, 2012 This is the second time I've warped the front rotors on this car, I have to check with the dial indicator, but I'd bet on it. This set lasted ~7k miles and 5 autocross events. They were mid grade raybestos rotors with porterfield r4s pads and valvoline fluid, stock configuration. Very rarely do I build much heat in them and I try not to sit on the pedal at stop lights coming off the highway. Am I doing something wrong installing them? Driving? Is this just how long a somewhat aggressively driven set of rotors lasts? Quote Link to comment Share on other sites More sharing options...
1 tuff z Posted June 9, 2012 Share Posted June 9, 2012 Funny, I never warped the stock rotors on my z-ran over 100 auto-x's but normally had some inexpensive off the shelf pads-which seemed to work ok. At the track [road course] was another story... Perhaps you need a less aggressive pad. Also, you can't go fast with your foot on the brake! Quote Link to comment Share on other sites More sharing options...
letitsnow Posted June 9, 2012 Author Share Posted June 9, 2012 (edited) I just measured them with the indicator, the drivers rotor is perfect on both sides (*<.001 runout), the passenger side is out .004 on the outside and .001 on the inside. So it's not as bad as I thought. I just rotated the tires, the rears were pretty bad, fronts were in good shape. Maybe I should replace the bad pair and have them balanced on a fancy road force machine. Edit: these pads also squeal, BAD, but just about every pad I've had on this car has, from cheap organic to the porterfields. Edited June 9, 2012 by letitsnow Quote Link to comment Share on other sites More sharing options...
johnc Posted June 9, 2012 Share Posted June 9, 2012 In most cases a "warped" rotor is still straight. What you may have is an uneven deposit of pad material on the rotors. The actually braking contact is pad to pad material not pad to bare metal rotor surface. Its very important to lay down a nice, even layer of pad material on the bare metal rotor surface. That's the whole point of the elaborate brake bedding process. The street/track pads like the Porterfield R4S are the worst as far as laying down an uneven layer. Because they are used on the street for miles and miles with cold rotors and light (relative to autocross/track use) application the pad layer on the rotor gets worn off. Then when you arrive at an autocross or track even and start hammering on the brakes the pad material gets deposited unevenly. Tale some garnet sandpaper (not aluminum oxide) and clean the rotors surfaces on both sides. Then do a proper brake bedding. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted June 10, 2012 Author Share Posted June 10, 2012 Garnet paper is apparently difficult to come by around here, I'll order some and give it a shot. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted June 10, 2012 Share Posted June 10, 2012 The road force tire machine helps when you still have a vibration, after having the tires balanced. It can help identify if a tires high spot can be matched, to a rims low spot to reduce the vibration. Some people do not know that a wheel and tire can be balanced and shows on a machine as so, But it can still be out of round and cause a vibration. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted July 27, 2012 Author Share Posted July 27, 2012 (edited) It's been a while, but I got the paper and tried it a while ago. It maybe kinda helped so I let it go, well, they've started pulsing worse and worse, today I tried sanding them again. First garnet, then aluminum oxide. I made no discernible difference. Started out with .006 runout, ended with .006 runout. Looks like I can warp a rotor. Edit: drivers rotor is still straight, passenger rotor is now warped .006 vs the .004 I posted earlier. I had these: http://www.rockauto.com/catalog/moreinfo.php?pk=391334 Considering these: http://www.autopartswarehouse.com/sku/Nissan/280Z/Brembo/Brake_Disc/1977/Base/6_Cyl_2-dot-8L/W0133-1624756.html?loc=Front%2C+Driver+Or+Passenger+Side http://www.lpiracing.com/Nissan-Power-Slot-Brake-Rotor-Front-126-42004SR-37p168597.htm Edited July 27, 2012 by letitsnow Quote Link to comment Share on other sites More sharing options...
letitsnow Posted July 28, 2012 Author Share Posted July 28, 2012 I got them turned tonight, it turns out it was very uneven wear. Back on the car, they still have a very minor shutter, I wonder if something isn't quite as parallel or perpendicular as it should be? Quote Link to comment Share on other sites More sharing options...
bjhines Posted July 29, 2012 Share Posted July 29, 2012 I have had trouble with rotors in the past. My problems were related to adapter plates, rust and corrosion between parts, etc. The thing I did was to have the entire assembled HUB-ROTOR machined at once. They can chuck the hubs by the bearing races and get the whole assembly unbelievably straight. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted July 29, 2012 Author Share Posted July 29, 2012 (edited) I don't think my friend with the brake lathe has those adapters and the other local places want like $70 to turn them. If it was FWD he could do it on the car. I think I'm going to have to go at it with a dial indicator and measure as much as I can. Edited July 29, 2012 by letitsnow Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted July 29, 2012 Share Posted July 29, 2012 I know your problem is in the front, but I had a bent stub axle in the back of my car when I did the disc brake conversion. I imagine that would have really been a problem had I not fixed it when I did (during mockup I noticed a lot of runout when I rotated the rotor by hand). Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted August 1, 2012 Share Posted August 1, 2012 I once had the same problem with warped rotors.the cause was my front wheel bearing making the wheel turn uneven when i pressed the brake pedal. so might check your wheel bearings. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 2, 2012 Author Share Posted August 2, 2012 The bearings feel good, I've had them apart several times recently, right now I'm leaning towards some runout in the hub on the passenger side, I'm going to measure it tomorrow. I may be able to get away with shimming the rotor a few thou to get it straight. If it is out, and I don't want to shim it, will a hub from my '71 240z parts car work? Quote Link to comment Share on other sites More sharing options...
dexter72 Posted August 2, 2012 Share Posted August 2, 2012 Torque the wheels down also if you don't normally do that. Quote Link to comment Share on other sites More sharing options...
bjhines Posted August 2, 2012 Share Posted August 2, 2012 Sometimes noobs will damage the hubs when they try to remove and install new bearing races. Dings in the seat area for the races can be fixed with a small die grinder. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 10, 2012 Author Share Posted August 10, 2012 Shimmed the rotors, drivers side less than .001, passengers side didn't need to be shimmed, indexing it worked, under .002. Steering wheel still shakes, pedal still pulses, both have improved, but not as good as it should be. Different problem maybe? I'm not really sure where to look now. Based on this thread, my rotors should be more than straight enough. http://forums.hybridz.org/index.php/topic/69784-azc-brake-shimmy-when-warm/page__hl__%2Brotor+%2Brunout Quote Link to comment Share on other sites More sharing options...
bjhines Posted August 11, 2012 Share Posted August 11, 2012 I dont know why some people have so much trouble with this. I really think something else is wrong. Are you sure the bearing races are seated correctly? You can dent the hubs where the bearing races seat in them if you are not careful removing the old races. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 11, 2012 Author Share Posted August 11, 2012 I've never changed the bearings, so it's possible the previous owner messed it up, I should be able to tear it down next week. Wouldn't the bearing races not being properly seated manifest itself as runout in the hub and rotor? The steering wheel on this car has always had some shake to it no matter how many times I balance the wheels, so you may be on to something. Anything else I should check while I have it apart? Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 11, 2012 Share Posted August 11, 2012 How are your inner and outer tie rod ends and t-c rod bushings? I've never really heard of anybody having a t-c rod failure but bad tie rods (especially inners) are super common. Might cause your problem. Was it you who posted some funny tire wear problems a few weeks ago? Quote Link to comment Share on other sites More sharing options...
LowCarbZ Posted August 11, 2012 Share Posted August 11, 2012 I would assume you're using the wrong compound of pad for your driving style. "Melting" the pad and having pick-up on the rotor. We had this problem with my dad's Porsche 930 Turbo that we both track at a recent HPDE where there's a braking zone from 135MPH, the pads were vibrating. Changed to a better compound, problem went away and the pads last longer. Reading material: http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths http://www.hendonpub.com/resources/articlearchive/details.aspx?ID=207857 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.