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I have an 07 Chevy Impala and I'm trying to pinpoint the shaking that occurs when braking. Only shakes when braking slowly on highway. The whole car does shake pretty badly. I just put in a new set of tires also so it can't be that. Rotors or alignment?

  • Almost certainly rotors. – Bob Jarvis Mar 23 '17 at 15:26
  • Did you use a torque wrench when you put on the new tires? If the lugs were cranked on too tightly this can easily have been the cause. – J... Mar 23 '17 at 16:03
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There are a number of possibilities here, including:

  1. bad tire
  2. bent rim
  3. unbalanced wheel
  4. bad shock absorber mount
  5. other suspension parts loose/worn/missing
  6. steering rack
  7. faulty wheel bearing
  8. warped brake rotors
  9. alignment problem

Although you have just put on new tires, there is still a possibility that they weren't properly balanced or that they were, but a wheel weight has come off since then. Since most vibration issues stem from tire and wheel imbalance, check the first three on the above list first.

Because the problem only happens under braking at highway speeds (if I understand your description correctly), suspension parts are another good thing to check. Worn or missing bushings, failing ball joints, etc. can all cause annoying vibrations. Do a good visual inspection of the suspension, especially in the front.

Steering rack problems and wheel bearing failures usually make noises in addition to vibration, and they're both relatively easy to check.

Finally, warped rotors and alignment problems can cause this, but are, in my opinion, much less likely to be the culprit here. If you have the equipment, it's not hard to check the runout on the rotors and determine if they're warped or not.

I'd suggest checking things in about the order I've listed.

  • great answer! I drove my grandpa's car yesterday and it shook violently while braking at highway speeds. Just last week he passed a safety inspection from a trusted mechanic so I was surprised that he could have missed something so bad. This will help me make sure I've got my bases covered when I tear into it. – rviertel Mar 23 '17 at 0:30
  • I replaced both wheel bearings on the front, also replaced the two front struts. Rims are not bent – Noah Mar 23 '17 at 1:05
  • Alignment problems don't cause vibration. Very specifically, if a vehicle is out of alignment without any other problems, this will not cause vibration. If there are loose components in the front end, this might cause vibration. Loose front end parts will cause the alignment to go out but fixing the alignment with loose front end parts is impossible. – vini_i Mar 23 '17 at 1:08
  • comprehensive answer, well laid out well done. – Solar Mike Mar 23 '17 at 6:29
  • @vini_i: good point. What I had in mind is that if the car is misaligned, this can and often does lead to uneven tire wear which causes vibration, but it's not the misalignment, per se, that causes the vibration. – Edward Mar 23 '17 at 11:42
2

This seems to be more of the problem on warped brake rotors or brake cylinders itself (had the shakiness once from the 2nd one as brake caliper had gone and cylinder was touching the rotor).

I do not think this can be unbalanced wheel as you would feel the effect of unbalanced wheel without braking on highway speeds.

Also, there was suggestion that shock absorbers are defective, but I would rule that out too, as I have driven car which had faulty shock absorbers and you couldn't feel it as shaking when braking, moreof feeling like being on a boat that goes up and down alot.

  • I've had bad wheel wobble (as in, unbalanced wheel oscillating) which was made much much worse by worn shocks unable to control the movement. New shocks actually cured it without rebalancing the wheel. – John U Mar 23 '17 at 11:45
  • Well, in that case it is still good idea to balance the wheel, as it is still too much unneeded extra work for shocks – Geit Mar 24 '17 at 11:04
  • that's true but the tyres are 37x12.50 mud terrains with various chunks taken out by rocks so they ain't easy to balance and never stay balanced for long. – John U Mar 24 '17 at 13:19
  • Well, that changes everything, didn't know you had such tires – Geit Mar 28 '17 at 6:06
1

Classic symptom of warpped brake rotors. Logic say if it only happens when braking, it's a brake problem.

0

My prime candidate would be shock absorbers being defective. Without the damping effect of shock absorbers you are basically bouncing on your springs. Every little bump or roadway imperfection would be felt. It would be very noticeable when braking for the simple reason of your tires having intermittent with the road. One of the things that shock absorbers do help the tires maintain contact with the road surface for improved cornering, braking effectiveness, and overall vehicle stability.

  • The car doesn't have any of the other symptoms associated with shocks though.Doesn't shake when moving only when breaking from a high rate of speed (70MPH) and it's so bad I shave to left my foot off the break so I don't tear the wheels off! I had my break pads changed so I'll check my rotors and see – Noah Mar 23 '17 at 14:32
  • Stopping at a high rate of speed.....Maybe ABS system kicking in. Warped rotors would be noticeable any time the wheels are spinning. – Old_Fossil Mar 25 '17 at 5:12
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Control arms will do that if you have a bad bushing, you should have it inspected by a shop, some people on the internet dont know what they are talking about

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