"Rotor Rub" - Saturn Forum - Saturn Enthusiasts Forums


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Old 06-26-2017, 10:22 PM
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Default "Rotor Rub"

Ok,

Help me figure this one out.

I took off my right front wheel with the SC2 up on the lift to get a good look at the condition of the pads and rotor.

Everything a OK. Lugs finger tight. Drop car. Lugs torqued to spec.

Now, when I drive, as I brake, when I get enough pressure to push the pedal to slow down to about 20 mph, I get a rhythmic rubbing of what I assume is the rotor and one of the pads. If i close the pads further (slow down), the sound goes away.

The rotor and pads did not undergo a spiritual transformation while on the lift, so I can not figure out what the deal is. SEEMS as though the rotor is not being held parallel to the pads or vice versa, and there is just enough play to bring them parallel again when my foot brings the pads tighter.

The rotor is not warped. I removed it and rinsed w cleaner. Same with caliper bracket, pads, and caliper. Re mounted wheel. No improvement.

Pulled wheel and wire brushed all surfaces that mate when the rotor mounts to the hub. Rinsed. Remounted. torqed. No dice.

Repeated again. No dice.

Is it that the hub is shifting relative to the caliper mounting bracket, thus indicating it is a bearing issue? I can't see much else letting the two lose their parallelity.

It is different every time I put the wheel back on.

I do not feel a vibration through the steering column at low speeds where it makes noise.

Interestingly, the wheel on/wheel off cycle changes the severity of the 70mph + vibration through the steering column. It actually DECREASES. The vibrations do not kick in until higher speeds.

I have not tried rotating wheels, as there is ZERO reason to believe anything happened to the wheel while it was leaning on the wall while off of the car. I minimize variables whenever I can.

The front bearings are original w 257k on them. I suspected their involvement in the high speed vibration........

Last edited by derf; 06-26-2017 at 10:24 PM.
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Old 06-26-2017, 10:40 PM
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The lug nuts need to be much tighter than finger tight before you let the car off the jack. Probably 50 ft/lbs or more before you put weight on the tires. Do you still have factory wheels on your car or are you running some aftermarket wheels. I prefer factory wheels always if available, they have the correct center hole size.
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Old 06-27-2017, 06:53 AM
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I agree with Andy. I usually tighten mine at least half way before letting the wheel back on the ground. Try putting it back on the lift and doing it this way. BUT, while you have it back on the lift, remove the wheels and just for the hell of it, check the pad clips and hardware.
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Old 06-27-2017, 08:28 AM
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Quote:
Originally Posted by Rubehayseed View Post
I agree with Andy. I usually tighten mine at least half way before letting the wheel back on the ground. Try putting it back on the lift and doing it this way. BUT, while you have it back on the lift, remove the wheels and just for the hell of it, check the pad clips and hardware.
Sweet. So I have been doing this wrong for 35 years? THE most basic operation on a car?

When I say finger tight I mean wheel has no wobble left, is pinned against the hub, no play, and I have tightened crosswise by hand all of the lug nuts until I can't anymore. Basically enough to ensure the lug nut tapers are well centered in the bores through the wheel.

But you two have more experience combined than I have years on this planet, so I will do as you indicate.

Surprised it hasn't been an issue before.
Will be overjoyed if it is simply a fundamental **** up.

Oh, they are stock orig 97 SC2 wheels.
My baby is stock as they come.

That's why slipping an lsj in there will be so much fun. I'd prefer s red V8 but I'd entertain a biturbo from an old Audi S4 tuned to hell.

Post back later today.
Never even had any uneven tire wear. Might the lugs in the hub or the lugs themselves be worn thread wise?
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Old 06-27-2017, 09:33 AM
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Studs and nuts are usually not a problem unless they get over tightened and stretched. Sometimes aluminum wheels show wear if they have high miles. The problem is they do not hold proper torque due to taper wear. So unless your wheels come loose on their own they are not the problem. Street car calipers are supposed to float on their pins and forgive a little runnout. Race calipers are not very forgiving, you have to set them up correctly. Back in the 70s we ran Willwood calipers and I had to shim them to fit each time I had them off.
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Old 06-28-2017, 12:58 AM
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It's the complete transformation from silent to cyclic rubbing with nothing else removed but the lug nuts that confounded me.

When I pulled the wheel today, I noticed that the inside center of the wheel has 4 equally spaced areas milled out. Is this for balancing at the factory, or should there be some type of raised area on the center of the rotor around the studs to aid in centering the wheel?

Before yesterday, I had removed the wheel, both pins, and cleaned and greased them. Maybe I need to dig some gunk out of the caliper slide pin holes in the caliper. The greasing made no difference.

-------

I didn't mention (yes I am a hypocrite) that I did indeed find some of the lugs "less tight" than they should have been when I pulled the wheel the first time I investigated this. Is it possible there is a slightly bent stud that is throwing things off just enough?

-------

So today, I did as you both recommended above.

I was totally anally retentive about how each nut centered itself in the taper of the wheel. Actually, with the 1st 3 just sitting in the front of the taper, the 4th lug nut would not properly align with its wheel taper, even w the remaining play in the wheel location (nothing tightened down). I found this odd. I swapped it with a different lug nut and they both fit just fine. Half tightened in the air, tightened on the ground.

Much quieter, still there a tiny bit but ok for now. I will get perturbed if the noise begins to worsen as i then fear that either the studs, lugs, or tapers in the wheels are the issue, and the lugs are working loose. An increase in the noise this week prompted my initial post.

I certainly understand the preferable physics with getting the wheel half tightened before on the ground, but I have never in my life had an issue hand tightening the way I described. Of course, maybe it was that gap between the lug and the taper that was getting unevenly worn when the wheel shifted once put on the ground, and tightening was just an exercise in jamming slightly misaligned lugs through the wheel tapers...almost.

Seems to me to be down to lugs, studs or wheel. Also, note that rubbing noise is in same spot on rotor when wheel is removed and remounted.

Shall I try some new lugs and see if they hold it more evenly?
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Old 06-28-2017, 05:38 AM
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I can't say 100%, derf. Nobody can, really. I've always tried to make sure that I put the same lug nut back on the same stud on my wheels. Been doing that since I was a kid because that's what my Dad taught me. I also like to use a little anti-seize compound too. I'm not sure what the proper torque is on your Saturn, but my Mopars all 3 get 100 ft.lbs.
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Old 06-28-2017, 10:21 AM
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note that rubbing noise is in same spot on rotor when wheel is removed and remounted. This sounds like your problem, it is magnified when the car is driven. If there is enough runnout in the rotor to show up while turning it by hand it will shake when on the road.
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Old 06-28-2017, 03:12 PM
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I totally agree.
And I have had the ongoing high speed 70 mph + vibe in the steering wheel for quite some time.

But why was the rub not present before I removed the wheel the very first time, and why am I able to increase or lessen the low speed rub by taking the wheel of and on. That rotor has been on the car trouble free for 15K (est). Yes it could have warped at the very moment before I pulled onto the lift but that would be a hell of a coincidence.

Note: my same place comment was made in the context of removing and putting the tire back on in the exact orientation I removed it from the car. I had the other front wheel up on jackstands so I could spin this wheel and listen for the rub before road testing.

I know rotor runout is in the thousands of an inch for rotors. Is it that there is enough slop when you add up all the other possible sources of misalignment that it now actually makes a difference? I had an LCA issue on the other side that, I assume as a side effect, produced a tiny tiny rub after the control arm to stabilizer bar bushing went bad, presumably pulling on the ball joint connection at the knuckle. All I can see this doing is acting as a static force on the knuckle that shouldn't make a damn bit of difference. But by the time I was done (also replaced stabilizer bar bushings and R LCA same time, the left side rub was gone.

I hate to be **** retentive pain in the ***, but I have never had such a seemingly simple issue pop op out of nowhere and be so troublesome to diagnose. It should never have occurred, so WHAT HAPPENED?
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Old 06-28-2017, 10:01 PM
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I think it is like the air conditioner in my Lincoln. It worked fine on Friday and when I backed it out of the garage on Sunday it did not. I ran to town and right back home, I hooked up the quick charge can/gage setup that was sitting on the bench. As soon as I squeezed the trigger the compressor switched on. So the system was finally at the low cutoff point, it still needs a little more freon to be back up to snuff. I have owned this Navigator for almost 10 years and this is the first trouble with the a/c.

I would say your rotor has been warped for a while and it has reached the point of causing a rub.
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