NOSLO6

Hoping for a little brainstorming help with a major vibration that I picked up on the way home from a track day last week. Details and question below:

• I ran a track day at NJMP last week without issues. During the last 15 min of my hour drive back home (just after I pulled off the highway) I developed a major front end vibration-- audible and could feel it through the steering wheel and chassis.
  
• I'm not talking something small like a wheel out of balance, it shook the car enough that my first instinct was that the motor was giving up the ghost.
  
• Vibration happened whether in or out of gear and I quickly noticed that light brake pressure made it go away. Speed sensitive, but at least somewhat inconsistent-- didn't do it at all a few times at lower speeds.
  
• Stopped and did a visual inspection expecting to see a majorly cracked rotor or something obvious, didn't, and limped the rest of the way home applying light brake pressure when the vibration appeared.
  
• I pulled the front wheels today and inspected the rotors, pads, calipers, abutments, wheels-- basically anything I could lay hands and eyes on. Nothing. Hubs seem okay-- no play and they spin without noise or unusual resistance.

Anything else you'd look into? What am I missing here? Any assumptions in the above you'd check?

I'm ruling out motor/trans as a source given the super light brake pressure cures it, but frankly I was expecting a "holy crap, look at that!" moment and didn't get one. Fact that light brake pressure resolves it is odd to me if suspension or something else came loose...

Thanks,
Scott

whatcop?

Did you possibly bend a wheel? Did you melt a wheel weight off? Most importantly are the wheels torqued down properly?

Jason

Did it come and go when you turned left or right?

John Shiels

control arm lose?

NOSLO6

Thanks for thoughts, keep em coming.

• Checked lug torque before pulling wheels, all were tight. Looked for missing wheel weights and didnt see any obvious missing weights or clean spots or cracks, but this vibration/shaking felt like more than that kind of wobble.
  
• Didn't think to try turning left/right to check hubs, but that's a good thought if I road test her again.

Bit I can't figure out is why brake pressure would fix a prob with hub/wheel/etc...

CHJ In Virginia

1) Check all suspension parts and retorque bolts - A Arms, Sway Bars & Links, Front Cradle, tie rods, etc. 2) Check engine mounts 3) Check torque tube bolts 4) Check harmonic balancer for delamination and trueness 5) Check front tires for possible ply delamination and Balance 6) Check hubs carefully on both sides ---- Good luck those types of vibrations can be a PITA to find / fix.

fatbillybob

Did you shake the hub with wheel on north south east and west with wheels off the ground? That provides more torque on the hub.
Steering rack?
Tierod ends?
blown bushing out of control arm

A quicky check of alignment can sometimes help you focus in on the problem part.

VTME13

I had a hub go out that acted like that. Needed some heat to get out of shape and loose. So I couldn't tell by manipulating it by hand. However, driving for a few minutes and loading the affected side while turning gave me a vibration like you describe.

sperkins

Gotta be a hub or loose eccentric CA bolt.
Check the codes in the DIC. There may be one in 28 TCS for excessive wheel speed variation. C1225 or C1226 I believe.

TrueBlueCoupe

My guess is hub or tie rod end

DarkMastyr

Had this exact problem a few weeks ago where the vibration would go away with brake pressure. I thought it was hubs at first, but it turns out to have been the pads. They were a bit too thin and I was rubbing on some of the circular posts that I believe are used to help provide better grip for the pad material during the casting process.

NOSLO6

Many thanks for all of the suggestions. Went through every bolt on both sides this morning and nothing was loose. Pads only have 1 day on them and have plent of material left so can cross that one off the list.

Just took her for a 10 min test drive and it was totally silent and vibration free even under hard side-to-side turns. Since I did nothing but take the wheels on/off I'm guessing the source of the problem needs to get hot (as it would have been after the original hour of highway driving).

Years of wrenching on the Buick makes me hesitant to buy parts without a completely known cause, but I don't know what this could have been other than a hub. Still can't talk myself through why light brake pressure would kill the noise if it was a protesting hub, which is what keeps me from just ordering 2 and replacing the originals. Any final thoughts?

fatbillybob

If those hubs are OEM hubs those have been known to silently destroy themselves. It starts with a crack then a fail. Inspect them carefully. There are youtube video of my race buddys grenaded hubs. We all went to skf hubs from hardbar or vansteel for tracking. If you got a crack it is possible to have intermittance early in the failure.

Jason

When in doubt, replace the hubs. If you find out later that wasn't it, you have two spare hubs.

froggy47

Are hubs original? How many miles? Can you identify if it's driver side or pass?

NOSLO6

Hubs are original with 10k miles and about 10 track days on them. Sounded like the passenger side but I'm not certain-- that's what I was hoping my test drive would tell me, but I got no noise / vibe.

If I do hubs, I'll likely do both sides.

SteveDoten

caliper pins, binding?? doubt it

caliper pistons sticking?? maybe

sperkins

Now there's a good posibility. A binding caliper will drag the pads and create a lot of heat over time. I had to rebuild a buddy's LF caliper a few weeks ago for that reason. The wheel wouldn't spin as freely as the other side. Check each rotor for hot spots.