Sign in to follow this  
heygibb

Warped rotors?

Recommended Posts

I recently noticed a warped effect from my wheels when brakes are applied. I haven't removed the wheels lately so I am a little confused about the source of the problem. I know the lug nuts need to be torqued @100 ft/lbs, I believe, and use a torque wrench when I rotate tires or do brake work. I had my yearly inspection done several weeks ago, so maybe the inspection folks took my wheels off and air ratcheted them back on...not sure.

Anyway, I re-torqued all my wheels, thinking the problem would go away, but it has not. The effect is really pronounced after driving awhile and then applying the brakes. Is the best way to handle this the obvious route of replacing the rotors? I feel it is mainly the front brakes, so, should I replace all rotors? Can I salvage the pads or are they damaged, too?

Thanks for your input.

Tim

90 coupe

Share this post


Link to post
Share on other sites

Heygib,

You could remove your wheels, clean all contact surfaces, then replace the lug-nuts and torque them down. Doesn't have to be the full 100ft/lb, just tighten so they are all the same.

Mount a dial indicator and spin the rotors to determine whether or not they are warped or, just remove the rotors and have them turned.

(ROJ may have a tutorial on this. You could check and see.)

Reinstall and see if the issue is resolved.

John F.

Share this post


Link to post
Share on other sites

The torque on the lug nuts (alone) should have no affect on (warping) the rotors.

When the wheels are removed the rotor can seperate from the hub. Dirt, dabris, pebbles could fall between the rotor and hub and affect the seating at that point.

More likely you have a brake pad issue. Sometimes they glaze and if one pads friction varies from the other you can get some odd feeling in the brakes.

Recently my grandsons Mazda had similar symptoms (according to my daughter) We pulled the wheels, indicated the rotors, only .001-002 run out. Put on new pads and the brakes were as good as new. We probably could have lightly sanded the pads and reused them but we chose to go with new pads.

When working on the brakes, mark one stud and its mating hole so you can return the drum or disk to the same location. If you find runout in a rotor, remove it and clean the mounting surface on both the rotor and hub. If there is still runout after cleaning, index the rotor a couple of studs and see if it gets better, often you can "fix" runout just by indexing the rotor.

Share this post


Link to post
Share on other sites

If you are experiencing a shimmy in the steering wheel it could be caused by hitting a curb or some similar incident that knocked the front end out of alignment.

Share this post


Link to post
Share on other sites
Heygib,

You could remove your wheels, clean all contact surfaces, then replace the lug-nuts and torque them down. Doesn't have to be the full 100ft/lb, just tighten so they are all the same.

Mount a dial indicator and spin the rotors to determine whether or not they are warped or, just remove the rotors and have them turned.

(ROJ may have a tutorial on this. You could check and see.)

Reinstall and see if the issue is resolved.

John F.

New rotors can be purchased at such a low price in the Reatta Store that it doesn't make much sense to turn old ones anymore. Some are currently as low as $14.56 for the Bendix brand. I prefer to pay a little more and get the ACDelco brand but they are all good brands.

Buick Reatta Brake Pads & Rotors

Share this post


Link to post
Share on other sites

Turning rotors/drums is a waste of money these days (unless you have really rare rotors/drums). Do what Barney said to check runout. If out of spec, replace.

Uneven heat is the enemy here. If one pad is making constant contact and the other side is not, that is a problem. Closely inspect the caliper for proper function. It needs to float. If it doesn't, you get uneven pressure when braking and improper release when not braking. Clean and inspect the pins. If they are the slightest bit rusty, replace them. If the bleeder screws are rusty, or worse yet snap off, replace the caliper. Loaded calipers are also a bargain theses days. Brake hoses can also collapse and cause the calipers to maintain improper pressure.

Share this post


Link to post
Share on other sites

John,

I did clean the rotors well and blew out the dust. I don't have a tool to measure warpage. I could remove the calipers and check it on a flat bench. Thanks.

Share this post


Link to post
Share on other sites

Barney,

I cleaned out all the dust and debris. Since this problem appeared out of nowhere, I think your idea re the pads is a good place to start. If one of the calipers isn't working smoothly, it won't brake evenly and creates a lot of heat. The heat creates swelling, I imagine, and contact is made w/ the rotor even when brakes aren't engaged. That is how it feels after I drive a little while. There is friction even when I'm not braking. I'll dismount the calipers and see what I find out. I did check their thickness when I remounted the wheels and they were all pushing 3/8" thick. Thanks.

Ronnie and Vincent,

New rotors it will be if that is the problem. Turning isn't cost worthy anymore, from the looks of it.

I'll inspect the calipers, as noted above, more closely. Hopefully, I can find the issue w/ the mechanics of the pad movement.

Thanks

Share this post


Link to post
Share on other sites

Do not forget brake hoses. They can collapse inside and prevent fluid from going back thus warping a rotor

Share this post


Link to post
Share on other sites

Good advice. I replaced those a couple of years ago.

re a comment above about possible shimmy due to misalignment. It has no sign of that...just a hard, uneven braking once the pads/rotors heat up.

I'll get to it this weekend, hopefully.

Share this post


Link to post
Share on other sites

I just wanted to close the loop on this thread. I resolved the problem I was having. My right front brake cylinder was sticking and not contracting like it should. Unfortunately, I waited too long to investigate and grooved out that rotor pretty bad. I ended up buying new through Ronnie's link. I bought a pair and got free shipping, so thanks Ronnie.

To challenge myself, and potentially, save a few bucks, I rebuilt that caliper piston with the $7 rebuild kits available. After watching a couple of you tube videos, I felt comfortable in the attempt. It wasn't too hard to do. Like anything, the first time is a trial and error process sometimes. Breaking the cylinder down and cleaning it up was the easiest part. Resetting the cylinder in the caliper was tedious , having to compress it into the cylinder. The inner seal has to be "lasso-ed", and with it being enclosed, you have to do it by feel. Once seated, I remounted all the hardware. Lubed up the pins w/ caliper lubricant, bled the brakes and took a short test drive. Everything seems to be working ok.

I was wrong in an earlier comment, about having replaced those brake lines before, and have ordered replacements for both front wheels from Rockauto. Should I go ahead and change those out or wait until my current ones fail? I'm leaning toward changing them out now, but wondered what the board's consensus is on that.

Thanks again for the encouragement and tips. Great board.

Tim

Share this post


Link to post
Share on other sites

even though i'm usually a "el-cheapo guy" - when it comes to brake calipers, pads, brake lines, etc. - i think they should probably be replaced before a catastrophic failure. you'll never know when the line could fail - maybe in a "panic stop" where you need all 4 brakes to stop in time.

my ABS has been out, but i can stop well and live with it until i can get to them - which will be very soon!

besides, you've already had one brake failure on one side - plus you already ordered them!:)

EDIT: i'd also check all the rear brake components!

Edited by Corvanti
add'l info (see edit history)

Share this post


Link to post
Share on other sites

I was wrong in an earlier comment, about having replaced those brake lines before, and have ordered replacements for both front wheels from Rockauto. Should I go ahead and change those out or wait until my current ones fail? I'm leaning toward changing them out now, but wondered what the board's consensus is on that.

Thanks again for the encouragement and tips. Great board.

Tim

If they aren't leaking or keeping the piston from retracting I'd put it on the list to do when the next brake fluid flush is due. Doesn't make sense not to do both at the same time.

Share this post


Link to post
Share on other sites

Any time I see a sticking caliper, I suspect the rubber brake line collapsing internally. It happens more than you might think. Change the hoses.

Share this post


Link to post
Share on other sites

My new hoses just got delivered. wow...2 days. I decided I am going to replace all components on the left side, too. I will be done with it for the foreseeable future, and will feel safer. As stated, I already have the parts in hand.

I haven't even thought of looking at the rears...not a bad idea.

Thanks everybody.

Tim

Share this post


Link to post
Share on other sites

Glad you found and fixed the problem. Like many other automotive problems, it is difficult to pull one answer out of the air and fix a problem long distance. When a car stalls, you get out and raise the hood and so far I have never seen a flashing arrow pointing to the problem. It takes some trial (inspection) and sometimes error to get to the problem.

I did want to comment on checking rotor run-out when you don't have an indicator. With something heavy... like a cement block, a piece of 2 x 4 clamps and a screwdriver you can clamp the 2x4 to the cement block and then clamp the screwdriver to the 2 x 4. With the wheel off and the rotor held with the lug nuts, move the piece of test equipment in position so the screwdriver tip is about to make contact with the rotor (you want to make contact about 1/4 inch from the outer edge. Rotate the rotor and "adjust" the 2x4 with a hammer until the screwdriver tip just touches the rotor.

Now turn the rotor and watch for space between the rotor and screwdriver tip. You can buy a cheap set of feeler gages if you don't already own them. Measure the gap with the feeler gages.

I suspect the rotor run-out is speced in the service manual but if the rotor is really warped .... the space will probably be .015 + I am not sure when you start noticing them.

There may even be an APP for your I-phone that is an optical reader that will tell you the gap.

Share this post


Link to post
Share on other sites

When a car stalls, you get out and raise the hood and so far I have never seen a flashing arrow pointing to the problem.

Barney, I'm surprised you never got this fixed! It's either the watchamacallet stopped working or the gizmo gave out. I don't know how you get along without it, especially since you don't have a CRT to look at diagnostics with. :rolleyes:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this