(AZC) Brake Shimmy When Warm

[JMortensen]

More frustration. I grabbed my other strut just to be sure that it wasn't the hub face that wasn't square, threw it in the vice, and measured the runout. Then I clocked the rotor 90 degrees and measured again, same runout in the same spot. Then I clocked it 90 degrees again, same runout, same spot, so I did it one more time, and now the runout went from .008 to about .0035 and the high spot is in a different area. WTF???

 

Next thing I'm going to try is indexing the hat and the hub (already indexed the hub and the rotor) and try that and see if I can get anything approaching consistency here. This is driving me nuts.

[JMortensen]

Just tried something else. I have been testing this with two lug nuts holding the rotor square to the hub. So I found the high spot and loosened one lug nut and the dial indicator jumped about .004. So then I put 4 lug nuts on and snugged them all down and total runout went to .008. I think the pilot is still the problem. I'm going to go spend some more quality time out there with some sandpaper and see if that helps. I think the problem may be that Juan didn't adjust his measurements for the thickness of the anodizing. Everything on these hats is tight. They are SUPER tight on the lug nuts too, ridiculously tight IMO.

[240hoke]

Hey Guys,

 

I wrote up a pretty quick method on how to do it in my thread. I just got my dial indicator as close as I could to the inside edge of the rotor and when from there. It was almost perfect the first set of shim and I finished it as good as it is going to get the second time. Took less then 1 hour and the brakes feel great....I got them to less then .002

 

Here is is:

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From: http://forums.hybridz.org/showthread.php?t=152532&highlight=azc

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Okay I finally got everything finished up a couple weekends ago. Heres what I did for shimming:

 

I decided to shim the rotor since this to me was easier to do. I bought several different sizes of stainless steel shims from Mcmaster (.001,.002,.004,and .005). I then cut them down a bit so they didnt stick out from the hat.

 

 

I then set up my dial indicator as close as I could to the hat. I found the place with the least run out and marked it as 0, then as I spun it I wrote the runout at each bolt.

 

 

I then installed all the shims at once. It was really close on the first try and with a couple adjustments I got the rotor to about .0015in of runout. My measuring setup wasnt any more accurate then that so I was pretty happy.

 

 

-Austin

[JMortensen]

I opened up the pilot some more and was able to shim both of the rears to about .002. I think my hubs are just barely out of true because the numbers did still change just a hair when I put the rotor on in different positions, so I indexed the rotor to the hub and was able to get the results I needed. The fronts are going to be a bit more difficult because the rotors I bought are very tight on the hubs that Austin sold me. I think I may just have those turned.

 

What did you do with this setup Austin? I assume you turned them...

[thehelix112]

Just tried something else. I have been testing this with two lug nuts holding the rotor square to the hub. So I found the high spot and loosened one lug nut and the dial indicator jumped about .004. So then I put 4 lug nuts on and snugged them all down and total runout went to .008. I think the pilot is still the problem. I'm going to go spend some more quality time out there with some sandpaper and see if that helps. I think the problem may be that Juan didn't adjust his measurements for the thickness of the anodizing. Everything on these hats is tight. They are SUPER tight on the lug nuts too, ridiculously tight IMO.

 

Jon, are you using wilwood or outlaw calipers or something else? Sorry O/T.

 

Dave

[JMortensen]

Wilwood Superlites in front and Dynalites in rear.

 

Went and tried again on the new front setup with Austins slip in shim vs the shim washer. I think that press fit of the rotor on the hub is really the issue with these. I'm going to have to take the hubs off regardless (dammit, I just repacked the front wheel bearings too). I think I may try opening up the ID of the rotor and see if I can then shim. The slip in shim is a lot easier to deal with than the washers I was using on the rear...

[JMortensen]

Got it done today. I used a cartridge roll on a die grinder to open up the pilot on the rotors, then shimmed them. The first needed one adjustment after the initial attempt, I was done with it pretty quickly. The second was much worse, it was .024" out of true. I had to stack shims as my hole punch wouldn't work on metal thicker than .007 (and just barely worked on .007). Once I did my initial shimming I found when I tightened it down I had gone way too far, so had to back it off quite a bit. Needess to say it took several hours for the second rotor, but now all 4 have runout of .002 or less. Thanks for all the help.

 

I guess the thing to learn from my experience is that if the rotor or hat is tight on its ID, that will throw everything off.

[RB26powered74zcar]

Usually you can see an uneven pad deposit on the rotor, it will look splotchy and streaky.

 

I have never had a problem with the genuine Wilwood rotors. Normally I run the GT48 series, they last longerand normally wear equally with PF01 pads. You might check prices at pitstopusa.com.

 

I've searched for info on correct replacement rotors for my AZC fronts, can you confirm these as the ones you use please..

 

WIL160-3870

WIL160-3871

WILWOOD HD 48 CURVED VANE ROTOR - RH - 12.19" DIAMETER - 1.25" ROTOR THICKNESS - 8 X 7" BOLT CIRCLE - THRU HOLE - 12.7 LBS - 1.25 12.19 CURVED

Pitstopusa

 

Also, can you please recommend a set of "street" pads to fit these. Thanks!

[z-ya]

I just discovered this thread, so bear with me.

 

Just my thoughts on the Wilwood setup.

 

I've had the Wilwood setup on my car for 5 years or so now, and many track days. I didn't measure the run-out on the rotor once mounted to the hub, but I had to turn them to stop the shimmy. So I have only turned them once, and I have not had the problem since. The rotors are showing wear, and I may replace them soon.

 

This says a lot about OEM and aftermarket tolerances. The stock caliper is hard mounted, and you can go to Autozone and buy cheap stock rotors and not have to turn anything. There is a lot of junk in aftermarket. Not sure if the hats or the rotors are the culprits. I'm using the JSK hats and Wilwood curved vane rotors BTW.

 

As far as the Wilwood pads, I'm not a fan. They are either way to aggressive, or not aggressive enough. I have three sets (B, Q, and T I think), and they are sitting in a box never to be used again. With T and Q pads, I'm better off with stock brakes and street pads. The B compound has tons of friction, but sound like I'm grinding metal. I've been using the Hawk HP+ pads for a few years now. They are a little noisy on the street, but the friction level and feel are great. They take a little longer to heat up than stock pads. No issues with fade on the track. Most of my track days are at Loudon, which is a track hard on brakes.

 

 

Pete

Edited April 20, 2010 by z-ya

[RB26powered74zcar]

I've searched for info on correct replacement rotors for my AZC fronts, can you confirm these as the ones you use please..

 

WIL160-3870

WIL160-3871

WILWOOD HD 48 CURVED VANE ROTOR - RH - 12.19" DIAMETER - 1.25" ROTOR THICKNESS - 8 X 7" BOLT CIRCLE - THRU HOLE - 12.7 LBS - 1.25 12.19 CURVED

Pitstopusa

 

Also, can you please recommend a set of "street" pads to fit these. Thanks!

 

Can anyone confirm?

[bjhines]

I purchased a set of AZC brakes and got these numbers right off the front rotors that came with the kit. They are only $40-$45 each. There are UL32(ultralight), HD48(heavyduty), and GT rotors. The part number above specs an HD rotor that weighs 12.7 lbs. The UltraLights that Dave is shipping right now are 2.6 lbs lighter each.

 

Current ArizonaZCar front rotor part numbers;

160-2894 UL32CV 12.19" x 1.25", 8x 0.325" on 7"bc, UltraLight, cast iron, 32x curved vanes, 10.1 lbs.

160-2895

 

http://www.pitstopusa.com/detail.aspx?ID=1197

http://store.revolutionbrake.com/160-2895.html

http://www.ptpfab.com/cgi-bin/store/store.cgi?&shop=ptp&cart=69451061x18292&session=4b18dc334774bd35&L=eng&Category=300032

 

If you really want to spend some money then AP Racing has the rotors for you. Here is a 48 vane AP rotor http://www.apracing.com/info/products.asp?product=32mm+Thick%2D177%2E8mm+P%2EC%2ED%2E+%2D+Bolted+%2D+CP3784%2D6080%2F6081_2147_2143

This is a 36 vane AP rotor from Pitstop. http://www.pitstopusa.com/detail.aspx?ID=19620

Here is a 60 vane AP rotor that might fit. http://www.pitstopusa.com/detail.aspx?ID=58792

I think this is the most expensive rotor I have found http://www.pitstopusa.com/detail.aspx?ID=49800

 

I would check hub true first. Then I would check that bearing-race-seats in the hubs are not dinged by a PO. Dave's website instructions include checking these things and turning hubs to true them before assembly.

 

If I have any problems then I will turn the whole rotor+hub+race assembly in the brake lathe.

Edited April 21, 2010 by bjhines

[RB26powered74zcar]

I purchased a set of AZC brakes and got these numbers right off the front rotors that came with the kit. They are only $40-$45 each. There are UL32(ultralight), HD48(heavyduty), and GT rotors. The part number above specs an HD rotor that weighs 12.7 lbs. The UltraLights that Dave is shipping right now are 2.6 lbs lighter each.

 

Current ArizonaZCar front rotor part numbers;

160-2894 UL32CV 12.19" x 1.25", 8x 0.325" on 7"bc, UltraLight, cast iron, 32x curved vanes, 10.1 lbs.

160-2895

 

http://www.pitstopus...il.aspx?ID=1197

http://store.revolut...m/160-2895.html

http://www.ptpfab.co...Category=300032

 

If you really want to spend some money then AP Racing has the 48 vane rotor for you. http://www.apracing....F6081_2147_2143

This is a 36 vane AP rotor from Pitstop. http://www.pitstopus...l.aspx?ID=19620

Here is a 60 vane AP rotor that might fit. http://www.pitstopus...l.aspx?ID=58792

 

 

I would check hub true first. Then I would check that bearing-race-seats in the hubs are not dinged by a PO. Dave's website instructions include checking these things and turning hubs to true them before assembly.

 

If I have any problems then I will turn the whole rotor+hub+race assembly in the brake lathe.

 

Thank You for this info! I went ahead and ordered those from pitstopusa for $41.00 ea.

 

Now, is there any way you can give me a source for the pads? I need the part # too if possible... I just don't know the actual Wilwood caliper model AZC sell's us (4 piston) so I don't know what pads I'm looking for.

 

I just use the car for street driving. Thanks again!!

[bjhines]

I have forged Superlight front calipers that use pad series 7420

I have forged Dynalight rear calipers that use pad series 7112

[RB26powered74zcar]

I have forged Superlight front calipers that use pad series 7420

I have forged Dynalight rear calipers that use pad series 7112

 

Great! Thank You BJ

[clarkspeed]

I never had a problem with the Wilwood rotors. I'm on my 3rd set, and they last a long time. I kept torqueing them, checking the runout, removing, rotate 1 bolt hole, retorque, check runout, etc. until it went away. They are very sensitive to how you torque them. I use the straight vane rotors (HD I think?) because they are cheap and cool plenty well enough. I've never had turned them.

 

As far as pads, I never liked the Wilwood stuff either. Not track, autocross, or street. I race Hawk blues and also use their street pads on my truck.