arizonazcar Posted March 29, 2006 Share Posted March 29, 2006 With a modular rotor you have three dissimilar rotating parts all bolted together: the hub, rotor center, and rotor casting. Any small imperfections in ANY of the parts can and will cause runout (wobble) at the rotor surface. Also this frequently happens if there is a nick or ding where the stock rotor has been pried off the back of the stock hub. The very large rotor diameter used in my kits magnifies the amount the parts are out by. Some users mistakenly think that the parts are warped. Warp is a change in dimension due to excessive heating, obviously this is not the case with brand new parts. In my instructions (often overlooked) I specify that the rotor, center, and hub be turned (cut) as an assembly on a brake lathe to make it run true. I consider this standard installation practice for racing brakes and doing so removes any runout (wobble ) of the rotor. I like to see less than .007" of runout and less is better. Sometimes I like to bed in the rotors and pads and then cut them after they've undergone a number of heating and cooling cycles. Something else to watch out for is if you had new bearing races installed and thay have not been seated correctly, I have a $1500 hydraulic tool to do this job perfectly and it sure beats a hammer and punch. Hope this was helpful/useful. Dave ARIZONA Z CAR 2043 E. QUARTZ ST. MESA AZ 85213 480-844-9677 dave@arizonazcar.com http://www.arizonazcar.com Quote Link to comment Share on other sites More sharing options...
2126 Posted March 30, 2006 Share Posted March 30, 2006 Dave, Now thats what I call customer service!!!! Someday I may step-up to your brakes when $$$ allows it. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted March 31, 2006 Share Posted March 31, 2006 Thanks Dave...I just had mine turned and they were only out .oo2 +- but it most likely would have caused a pulse in the pedal. Top quality parts, cant wait to try them out. Quote Link to comment Share on other sites More sharing options...
jagster Posted July 15, 2008 Share Posted July 15, 2008 I agree on this situation, and the more parts you bolt together on an assembly that is expected to spin at high rpms, the more likelyhood of an imbalance. That is why smart people spend the extra money to balance an engine. On wheels, brakes, and even tires, it is a good idea to use a dial indicator to make sure you are wobble free. Some folks will actually put their new tires on a lathe and turn them down if need be to make them round. Sound extreme? Tell me about it when you have a truly fast car. Quote Link to comment Share on other sites More sharing options...
aziza z Posted July 15, 2008 Share Posted July 15, 2008 I bought my kit from jsk and they never mentioned that. I should probably get that done though. So basically there should be .007 removed on anything rotating on the brake assembly correct? Quote Link to comment Share on other sites More sharing options...
getZ Posted July 15, 2008 Share Posted July 15, 2008 I just bought a bunch of different shim washers from .001 to .004 and stuck them in between the rotor and hub. It worked perfect. I didn't think about rechecking it after a few heat/cooling cycles. Quote Link to comment Share on other sites More sharing options...
jagster Posted July 16, 2008 Share Posted July 16, 2008 Well, my machinist told me that .004 thousands is the thickness of a human hair, so that may be overkill to clear that up. On the spacers and washers, please don't do that! Ok for lining things up, but your life rests in the quality of your brakes, wheels and tires. Buy the correct spacers or make good friends with your local machinist and do it right. Safety first! Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted October 8, 2008 Share Posted October 8, 2008 GET YOUR ROTORS STRAIGHT FROM DAY ONE I had much success with ordering 0.001" and 0.002" stainless steel washer-shims from McMaster.com. You need a dial indicator with a magnetic mount or any mount that allows you to clamp to the strut tube, a magic marker, and bags of shims. It takes patience. Here is what I did... HAT *Clean all rust dirt grime off of the hub. *Run a dental pick in all of the fillets to get out the grit. *Mount the aluminum hat to the hub and torque everything to spec. *Mount the hub onto the spindle and torque to spec. *Place the dial indicator on the inside surface of the hat, where the rotor mounts to. *Establish ZERO, clocking to one of the four hub bolts that reads off (outwards) by the most. *As you turn the hub, get a magic marker and write down the dial indicator reading at each of the four bolt location. (the base one will be zero) *Remove the hub from the car and the hat from the hub. (mark the hat so it goes back on clocked the same way it came off). *Add shims to any bolts that were reading off by more than 0.002" or so. Add the amount of shim equal to the number you wrote from the dial indicator, err on the thinner side. *Reassemble, torque, install, take more readings with the dial indicator. *Repeat until you see +-0.002 difference at all four hub bolt locations. *Ignore any dips/peaks on the aluminum hat that happen in between the four hub bolts, as long as they are under about 0.005". (if more, you need to surface the hat and hub assembly on a lathe.) NOW you have a true, straight place to mount a new rotor. You should never have to do this again, although it doesn't hurt to check it when replacing the rotor. ROTOR *Install the new rotor. *Check for runout at the center of the swept area with the dial indicator. *If it's less than 0.003" you should be good. If it's more than 0.006" you may feel it in the steering wheel and should have the rotor lightly cut after a few heat cycles. TIP: if you really want to, you can try re-clocking the rotor on the hat to get better results, but this is a longshot. NOTE: If you have to shim anything above 0.010" or more, you should be looking for a machine shop, or new hubs. Here are the shims I used for the four hub bolts: McMaster Part Numbers: 98126A126 18-8 Stainless Shim 1/2" ID 0.001" thick (10 per pack) 98126A168 18-8 Stainless Shim 1/2" ID 0.002" thick (10 per pack) http://www.mcmaster.com/ Based on my experience: You can't feel 0.003" but you can feel 0.010" heavily in the steering wheel. An additional beneft of having little or no runout is that the pads remain nice and snug to the rotors. When you hit the brake pedal, the brakes are "right there". As a matter of fact, after I did this, I needed to back off my brake light switch. The pedal travel was reduced enough that my brake lights would only come on under medium braking or harder. Quote Link to comment Share on other sites More sharing options...
Spooler Posted October 12, 2008 Share Posted October 12, 2008 I agree on this situation, and the more parts you bolt together on an assembly that is expected to spin at high rpms, the more likelyhood of an imbalance. That is why smart people spend the extra money to balance an engine. On wheels, brakes, and even tires, it is a good idea to use a dial indicator to make sure you are wobble free. Some folks will actually put their new tires on a lathe and turn them down if need be to make them round. Sound extreme? Tell me about it when you have a truly fast car. Funny you say this. I have had brand new tires trued up do to bounce, or out of roundness. Works like a charm. And I also love to have my tires spin balanced on the car. Very hard to find a place that will do either one anymore. Quote Link to comment Share on other sites More sharing options...
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