GregLo

New tires just had front end checked no Ppoblems:
Problem Im having is a low hum & vibration that I'm feeling at various speeds 55- 65mph less noticeable as I increase speed to around 80mph feelings as if it was right under the car. I also have been experiencing that when I put the car in park on an incline that it seems to roll a little more than it should ( this was just to test I usually use emergency brake) in other words, in park I can move the car a few inches, is that ok
Doesn't seem right
Greg

TSHong

Sounds more like a balancing problem. New tires can spin on the rim so the balance needs to be checked. A common problem if you use too much tire lube. Also do you have aftermarket or factory wheels?

SCL

Mine moves quite a bit in park too -- I also thought it was odd, but I since nothing else seems to be wrong, I guess it's normal.

I once had a RWD car that had a bad vibration above 90 MPH...and I never was able to fix it but I think that the rear end (maybe the pinion bearing) was worn or damaged. I also had another RWD car with a worn rear transmission bushing and that caused the driveshaft to vibrate -- and I noticed it would vibrate less under load -- like if climbing a hill on the highway or accelerating slowly -- but if coasting in neutral or feathering the gas a little, it would vibrate more.

One way to narrow it down is to try to figure out the frequency of the vibration -- tires roll at around 800 RPM at 60 MPH, but the driveshaft spins at about 3 times that speed...so a damaged or unbalanced driveshaft or damaged final drive will vibrate faster -- kinda like a pager or cell phone in vibrate mode. The half axles spin at the same speed as the wheels/tires, so if you have a bad CV joint, it would probably have a similar vibration as a bad tire. Without driving it, it's hard to speculate, but your description (a hum from underneath) sounds more like a drivetrain issue. Tire balance is usually more like a shaking than a vibration. The driveshaft isn't so easy to reach, but if you can lift it up and remove some of the shields, you could see if it seems loose anywhere.

GregLo

Got the car back from my local repair shop to have brakes inspected turns out I have bad rotors which I kinda already ne . I'm hoping this what the source of the Vibration.
I do want some opinions on rotors
I was thinking about drilled rotors from I-Rotors or stock Zimmerman any pros or cons

SCL

Hmmm... I don't think rotors would cause that. Rotors either get scored or they warp...and the warping would cause a pulsating effect in the brake pedal, the frequency increasing with speed, and most noticeable below 20 MPH. All of this is, of course, IMO. I think the shop focused in on something they could identify easily. They can make a lot of money on the job, and at the same time rule out the slim chance that the brakes are the problem...IMO. If the brake rotors are the problem, I think you should be able to feel it in the brake pedal...but to inspect them, you can take the wheels off and spin each rotor to feel if it grabs, then spins free, then grabs again. To narrow down whether it's the front or the back, roll down the street at various speeds and pull up the parking brake a few clicks -- if there is no vibration, then you can at least rule out the rear brakes. If you do have a bad rotor, it's problably ONE bad rotor. I would replace the one rotor as long as the other ones are not seriously worn down. The car might very well need brakes soon, but I would keep looking for that vibration. A fast vibration (at 60-80 MPH) that feels like a cell phone or pager on vibrate points to the driveshaft or other final drive component. If a lower frequency like a shake or pulsing, then it might be wheels, tires, rotors...maybe even an axle shaft or CV joint. First cut the possibilies in half, then you can keep narrowing it down from there.

If you go with the brake repair route, I don't have a specific rotor recommendation for you, but I can share my experience. I've always bought the cheapest rotors available, and never had any problems, except for one thing -- brake dust. Some people have problems with warped rotors, but that is usually because they are hard on the brakes or towing a boat or something. I recently bought and installed Zimmerman stock front rotors for about $70 each. They work fine, but I have to assume the cheap rotors are softer steel, and I think some of the dust I see is iron dust, in addition to the pad dust. More expensive rotors are made of harder steel and will not wear down as fast -- although that means that the brake pads wear out sooner too. If you go to a parts site with a large selection, some of the rotors and/or pads listed will have a note about the pads or rotors and what combinations not to use. I think somewhere on the Audiworld site there is a write up on brakes.

As for the vibration problem...try to determine if you can feel it in the brake pedal -- possible rule out the brakes -- and try to figure out the frequency to see whether it matches the wheel/tire revolutions or (3 times that) the driveshaft revolutions.

Hope something in all of that helps.

TSHong

Like SCL mentioned, unless you are getting a pulsation when braking, rotors are not your problem. It is in your tire and wheel combo usually. Eliminate a bad tire or balancing problem first.

TerminA8r

I think you are on to it. For more info on the D2, click on my signature.

GregLo

I am getting a pulsation when Braking that has actually gotten a little worst since I started this post
I'm ordering new pads and disc
I'm kinda leaning toward drilled only rotors from IRotor ,but trying to get the pro's and cons concerning them or Go OEM Lucas Girling or Zimmerman
To Many choices
IRotors gets me the drilled rotors and pads for 188 to my door
The Zims and the Lucas G are about 180 w/out pads
But I hope overall this willhelp cure some of the Vibe , i plan to change the sway end links at the same time because I'm getting the Klunk again also

David Michael

Take the car up to vibration speed, kick it into neutral and let the engine idle as you coast. If problem goes away, vibration is somewhere in the drive shafts. It not, it is in the wheels.