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Shimmy when braking

edited December 2011 in Repair and Maintenance
When I'm driving at highway speeds and hit the brakes hard-ish (e.g., if the car in front of me stops or if I suddenly realize I'm going too fast on an exit ramp), my 1997 Honda Accord feels like it's shimmying from side to side. It only happens for a moment, but in that moment I feel like I'm on the verge of losing control of the car. I've only noticed this in the last few months.

Any ideas what this might be? I'm going in for an oil change tomorrow and would like to ask my mechanic to take a look at this, but I'd like to have some theories/guesses in my back pocket before I go in. Thanks!
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Comments

  • edited December 2011
    You should just describe it to you your mechanic & have him/her take it out and do some hard braking. I can't really tell if you're describing a shimmy - that would feel like a vibration, felt in many places but including the brake pedal - or a swerve. The thing about a shimmy is that it normally won't go away completely.

    What you're describing is either a) (swerve) a very dangerous condition involving any number of issues having to do either with brakes or suspension & steering (sticking brake caliper; bad flexible brake lines; bad struts; bad tie rods...); or b) (shimmy/vibration) a less dangerous but far from optimal problem with the brake rotors. A full brake job would be the best way to go. This problem can also come from worn suspension & steering parts though.

    Either way its not good. Your brakes aren't working right. Have it take care of. Its more important than the oil change.
  • Warped front brake rotors would do this, although usually it would start more gently before getting as violent as you describe.
  • I was thinking worn out suspension parts, too. Most people don't realize they're worn out until it's too late...a little extra bouncing around can't hurt anything right? Wrong. It can hurt a great deal, and have a tremendous impact on handling, steering and braking.

    Bounce all 4 corners of the car. Just press down, let it up, and do it a couple of times until the car is moving pretty good. Then stop. It should settle right down, with no extra "up and down" motions. If it keeps on bouncing, then the shocks are worn, at least.

    Wether it's suspension or brakes, you need to get it taken care of. As Cig said, it's more important than just about anything else.
  • I'd go for a warped disc rotor (may be both rotors) but the whole braking/suspension system should be checked.
  • edited December 2011
    I wouldn't be surprised if both chaissos and Dave were correct. A slight warp that normally would show up gradually, a little play in a tie rod end from a pot hole and Elvis and a "whole lot a shaken"....when you're braken....and like both say, "check it all".
  • Have the rear disc brakes inspected for rusty/pitted rotors. If the vehicle has an automatic transmission you probably never use the parking brake. Use of the parking brake is what keeps the rear brakes properly adjusted. If the rear brakes are out of adjustment the brakes pads don't come in contact the rear brake rotors under normal braking. This results in the rear rotors rusting/pitting. Then when the brakes are applied heavily, the rear brake pads come in contact with the rusted/pitted rotors and the rear brakes grab unevenly causing the rear of the vehicle to be unstable.

    Here's what the rear rotors looked like on the wife's 97 Accord when she complained of the same problem. She now uses the parking brake to keep the rear brakes properly adjusted.

    Tester
    ACCORD REAR ROTORS.jpg
    3072 x 2304 - 2M
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