Steering wheel shaking during braking

Discussion in 'General Motoring' started by HyperCube33 \(Life2Death\), Jul 26, 2007.

  1. Just to double check before I tear the front end of my car apart - I've had
    rotors replaced a year ago along with pads. Car was recently aligned.
    Checked at Saturn dealer. mentioned car was in previous accident, thus why
    the sunroof was stuck closed (duh?.) Saw no other problems. was too foolish
    to ask about brakes - was more focused on the secondary engine oxygen sensor
    after the cat, but I'll have that problem taken care of (just need to weld
    in a new pipe.)

    So anyway, at highway to stop, it goes like this. the harder I brake, the
    more the steering wheel shakes and shutters like I'm driving over someone's
    stairway. (Shakes back and forth.) Peddle has some shake, but I don't pay
    attention to that as my hands are shaking all over. As the car slows down to
    about 20mph, you can feel a steady "grip and slip" in the brakes, esp. if I
    back off to a light brake. the car jerks as if its braking, then coasts,
    then feels like they grip again.

    Also, if it is my rotors as I suspect, any tips to get the caliper bolts out
    without breaking them again?
    (I don't have a cutting torch so don't suggest that?)

    I have new pads and rotors in my trunk!
    HyperCube33 \(Life2Death\), Jul 26, 2007
  2. HyperCube33 \(Life2Death\)

    Oppie Guest

    Sounds like the rotors again. They probably warped from overheating due to a
    dragging brake pad.

    If they are only a year old, they might have enough meat to have them
    re-cut. Personally, I'd get new rotors. Make sure that the calipers move
    smoothly and are not bound and the pistons move easily. Are you fairly
    certain that it is the front brakes and not the rears? Some cars have the
    handbrake act on the rear service brakes (not so with my L series that has
    disc service brakes on the rear along with drum park brake - fairly common
    for ABS / traction control systems). If the handbrake acts on the rear disc,
    pull it gently while moving to see if it has a similar pulsation. Worst come
    to worst, remove the wheels and check for runout as the rotor is turned.
    Doesn't take much to create the pulsation especially if it is a thickness
    variation rather than a wave warp.

    I had a stuck pad on my LW300. When I replaced the rear rotors, found the
    pad solidly jammed into the calliper. Took it all apart and cleaned out any
    rust in the guide channels so that the new pad would slide smoothly. Then
    applied silicone brake grease to all sliding surfaces and re-assemble. Works
    **much** better now. This especially since the unbalanced braking force on
    the rotor caused stress cracks (radially out from rotor hub)!

    Stuck bolts - a good penetrating fluid (I use Kroil from )
    and an impact wrench. A good impact wrench is worth the purchse. I had a $40
    1/2" drive model that was better than nothing. Got a $180 thundergun and the
    difference was night and day on the same compressor and tools. If you don't
    have access to an impact wrench, get one of the hammer driven manual impact
    tools. Again, it is better than nothing but swinging a 2-5# hammer in tight
    quarters can be pretty hard. The idea is to break loose the rust which is
    brittle. Also there is often blue thread-lock compound on the calliper
    bolts. I have sometimes had to heat the assemblies to about 300F in order to
    soften the thread lock - but you said you don't have a torch...
    Oppie, Jul 26, 2007
  3. If you have rear drum brakes you will want to check the brake cylinders. I
    had the same type of problem and found that the brake cylinders were leaking
    making the front brakes work harder to stop the vehicle. Front pads were
    unevenly worn.
    Jim Newsgroups, Jul 27, 2007
  4. Well, I did a ton of reading. And I'm certain its the rotors...Also they
    mention that you should adjust them so the pads hit the rotors right (??)
    not sure how to do this and what equipment I'd need. I'm curious if I could
    toss them on and have Midas bleed and adjust them before I brake the pads in
    too much? I also need them to weld on a joint in my exhaust so perhaps
    that'll work. Hmm. Something about "runout?"

    Perhaps my dad will let me bleed the brakes in the garage, we'll see.
    Haven't talked to him yet. Though after conquering the hub bearing on my
    own, I think this should be trivial (I may be able to get him to buy a
    torch. any suggestions?)

    Oh, and my car doesn't have rear disk brakes, it has drums!
    HyperCube33 \(Life2Death\), Jul 27, 2007
  5. HyperCube33 \(Life2Death\)

    Oppie Guest

    The brake fluid should be almost clear. When you do a brake job, always
    bleed the cylinders. If it is dark, keep bleeding (and adding the correct
    fluid to the reservoir) until the purged fluid runs clear.

    Runout is wobble in the rotor. The wobble comes from either the wheel
    spindle or mis-seating the rotor on the spindle face. The pros will usually
    sand off any rust on the spindle face that the rotor seats against to ensure
    a flat mating. Runout is measured with a gauge anchored to the caliper
    usually. The gauge should be perpendicular to the rotor surface and as the
    rotor is turned by hand, the height variation can be read on the gauge. I've
    done this so long that I just rest my thumb against the caliper bracket and
    lightly drag my thumbnail against the rotor surface while spinning it with
    the other hand. Works well down to about .010". If you need better than
    that, break out the gauges and magnetic base...
    Oppie, Jul 30, 2007
  6. Is it necessary to check? In other words- Do I need to go rent a gauge?

    As for getting the caliper bolts unstuck - which should I purchase:
    Mapp Gas/Oxygen Torch ($50, but may serve more than this use)
    Propane Torch
    Mapp (only) Torch
    HyperCube33 \(Life2Death\), Aug 8, 2007
  7. HyperCube33 \(Life2Death\)

    Oppie Guest

    Unless you are a purist or can't fix a pulsation problem any other way,
    don't bother with a gauge. When you put a drum or disc rotor onto the hub,
    make sure that there is no rust or dirt build-up that would keep it from
    seating flat to the hub.

    With the wheels off the ground and enine off, pump the brake pedal a few
    times and then try to rotate the wheel by hand to find any binding spots. If
    you have removed the wheel and are turning the rotor or hub, make sure that
    you use at least 3 lug nuts to keep the rotor flat against the hub.

    I've used a turbo torch with mapp /air. works pretty well but the flame is
    large. There are times when you would like a spot heating which you get
    better with the mapp/ oxygen. Both options are much hotter than propane
    alone. You can also use propane/ oxygen but it is not as hot as mapp/oxy.

    When using any torch, be aware that you want to heat the area around the
    bolt and not the bolt itself (usually at least). Heating too much will
    destroy the temper of a bolt and it will have to be replaced (not a bad idea
    to replace cirtical bolts anyway*). You also don't want to burn seals or
    boil the brake fluid. If you don't have a decent impact wrench, it is a good
    tool to have on hand.

    * Many bolts are specified for a single tightening. These are 'stretch
    bolts' that keep tension. Mostly used on cylinder heads where you torque to
    a spec and then continue so many degrees further. Steering knuckle to ball
    joint lock bolts used on many cars are specified to be replaced every time
    that they are removed. Most everybody re-uses the old bolts and the spec is
    more to keep the lawyers happy since it is a critical joint.
    Oppie, Aug 8, 2007
  8. HyperCube33 \(Life2Death\)

    sowhatofit Guest

    Just get some PB Catalyst at the autoparts store or walmart, spray it
    on, tap the thing pretty hard with a hammer, wait and repeat.
    Shouldn't be that stuck. They might be in pretty well, but I'm sure
    you can get them loose.
    sowhatofit, Aug 16, 2007
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.