Shimmy when going fast and breaking hard
 

I get a shimmy through out the whole car when I am going fast and then have to get on the breaks real hard. Usually happens over 80mph. The harder I get on the breaks the worse it gets. What could it be? Something with the rotors? The whole car seems to shimmy not just through the front tires or steering wheel.

------------------
Penz
1985.5 944
My 944 page

I guess you wouldn't call it a shimmy, it's more like a vibration throughout the whole car. It can get pretty bad though when I have to get on the brakes really hard. I don't understand why it only does it above like 80 mph? I could be doing 50 and slam on the brakes and get nothing, but if I'm doing lets say 80 it does it untill either i let off the breaks or break hard all the way down to about 20-30.

------------------
Penz
1985.5 944
My 944 page

Make sure you haven't lost a wheel weight but it sounds like your rotors are warped. See if when your driving around town in a 45 -50 mph zone, apply the brakes lightly. See if you can feel a pulsating sensation in your brake pedal. If so, it's your rotors.
Time to have them cut or get new ones depending on the thickness left.

Good luck
Bret

It could easily be a warped rotor that deforms more when it gets hot as it would when you brake from a higher speed. Mine used to do that until I replaced rotors and ducted the fronts.

It vibrated so badly in the front that I blew the seals on my rack and pinion during track use. The vibration was so violent that it was moving the steering wheel about 15 degrees in my hands. This caused huge pressure spikes in the system and blew the seals.

One more thing, upon occasion the brake pads will not deposit their particles evenly on the rotor. This can cause it to happen as well but goes away when the rotors get really hot.

Thanks for your ideas. The pedal doesn't pulsate at all even when it's starting to vibrate. I'm thinking that it could be the front tires are out of balance because I have lost some weights off the front rims.

------------------
Penz
1985.5 944
My 944 page

Also, lawarence it doesn't vibrate that bad! haha

------------------
Penz
1985.5 944
My 944 page