Brake Vibration

I'm pretty much a still a noob at DIY car stuff so I'm hoping some of you veterans can help me out. The car is a 2008 Mazdaspeed 3 used for daily driving and autocross duty. The car has 62,000 miles and still has the original pads (still have decent thickness) and rotors. I replaced the brake fluid a few months back.

A few weeks ago I started noticing some vibration while braking. I tried doing some repeated high speed stops to clean off the rotors but that didn't seem to fix the problem. I figured I would just need to replace the rotors; "no big deal, I've got 60K on them and I'm planning on doing pads this fall anyways....I'll order a new set from Mazdaspeed."

But, recently the vibration has been getting worse, prompting me to do a little but more investigation. What I have found has me a bit baffled. Anything under 30mph and the car stops perfectly...very smooth. At speeds over 50mph I can't notice anything wrong; maybe a very slight vibration but nothing I would notice if I wasn't looking for it. However, between 45 and 35 mph I have a strong vibration. There is a noticeable light vibration in the 5mph surrounding that range. If I do a slow stop from 75mph it starts out smooth, vibrates for a while, and then ends up smooth. I would expect any problems with the pads or rotors to be present at all speeds, so what's up? Does anyone have any ideas?

-- Check tires and balance
-- Check any/all rubber bushings
-- Check wheel bearings
-- Check tie rods, ball joints, CV joints

Check the lug nuts.

Something that rotates is out of balance. Either tire/wheel, rotor (doubtful), axleshafts, or hub/bearing assembly (doubtful). When a vibration is there at certain speeds, but not above/below those speeds it's almost always a tire/wheel out of balance. I'm assuming the wheel isn't shimmying in your hands, or pulsing the brake pedal under your foot?

I swapped out my tires/wheels with my winter set to see if wheel(s) out of balance was the problem. While I had the wheel off I looked over the suspension and shook everything. I couldn't find anything loose or see any rubber boots that look torn. The brake vibration is still there between about 35 and 45mph. I can definitely feel the vibration in the steering wheel.

Is replacing the pads and rotors the next thing to do? I'm assuming the dealer or a garage is going to do that almost automatically on a car with original rotors and a vibration under braking? I would be sure that it is the rotors is the vibration were there at low speeds too but since it's not I am a little skeptical.

The vibration starting out smooth, getting worse, then smoothing out again says 'balance' to me, but not in the way you might think.

Check carefully for a loose or worn inner tie rod. IIRC the inner TRs have a super strong spring in them which takes up the slack as the ball/socket wear, once that gets to be enough to lower the spring's preload then the wheel on that side can wobble under braking as the wheel's speed goes through the range where the axial balance is off (not unusual). Fixing the axial balance may mask the problem but only for a while.

I'm sorry. Did you in fact replace the rotors yet? Your description seems to indicate that you considered it, but haven't done it yet.

Doubtful its the pads. The focus is out of balance and shakes more under braking.

It could be the pads. IF you have checked everything else and found it all good then I would replace the pads. I had some problems with vibrations with the brakes on my car and just replaceing the pads fixed it.

Once you check everything (tie rods, bearings, bushings, tire/wheel balance etc.) I'd go ahead and change out the pads and rotors anyway, as it's probably about time for new pads with 60K+ on that set. I had a similiar issue with my Bonneville, new pads and rotors fixed the issue.

Ive got the exact same issue on the turbo brick....my front tires are worn and my mechanic is telling me thats the problem

Thanks for all of the help and advice so far guys.

It doens't feel like brakes to me because I would expect the vibration to be there at all speeds if the pads or rotors were the problem and upon further investiagtion I seem to get more vibration from the steering wheel than the brake pedal. I don't want to completley rule out the brakes since it is a problem only when braking.

Since a lot of the focus seems to be on the tie rods I jacked the car up again today when I got home (one side of the car at a time). I grabbed the top and the bottem of the tire (12:00 and 6:00) and tried to pull the tire back and forth (pulling out with one hand, pushing in with the other) and I could get no movement at all. I then moved by hand the sides of the wheel (9:00 and 3:00) and pulled back and forth hard. I could get A LITTLE movement along with a light "clunk-clunk" at the ends of the movement. I couldn't determine where the noise was coming from and could not replicate by pulling on any of the individual suspension pices (I can't apply nearly enough torque that way). Does this indicate a tie rod problem OR was I just taking up the natural slack in the steerting somewhere?

If you grab at 9 and 3, work it back and forth and hear a clunk, yeah something is loose. You need a bud to shake the wheel the same way while you observe (or vice versa).

I was able to get it to move a little bit and clunk on both front wheels which is interesting. I took the wheels off to try and get a better view but without the wheels I couldn't get enough torque to move anything other than the rotors (which were a little loose without the wheels holding them down).

I'm thinking I may just take the car in and let the professionals diagnose. If it turns out to be brakes I'll be kicking myself (since I can handle that job) but if it's anything in the suspension I would probably be taking the car in anyways.

to save the self-butt kicking ... go ahead and do your brake work ..sounds like you might need it anyway ... then if not fixed try the pros

Curmudgeon's first post up there is laden with diagnostic gold.

AngryCorvair .. PM sent

thanks