Steering Wheel Vibration

[vtssgeniii]

Have noticed the car's been gettinga real bad steering shudder at highs speeds (>80Km/h) when hitting the brakes. Have had an on car wheel balance and alignment to rule out other possibilities but have noticed two things that are odd:

1. When taking the front passenger wheel off the nuts weren't very tight at all.

2. Strange marks on the surface of the disc, (only on the outside face though) as shown in the pics I took today.

Anyone have any ideas? There;s still plently of brake pad material and it only does this at high speed.

http://www.haroc.1337thing.com/ls1/VTSSGenIII/Brake1.JPG
http://www.haroc.1337thing.com/ls1/VTSSGenIII/Brake2.JPG
http://www.haroc.1337thing.com/ls1/VTSSGenIII/Brake3.JPG

[vtssgeniii]

Forgot to mention rotors are DBA4000 330 x 28 and calipers and pads are PBR sports.

[HARMSY]

Maybe need to be machined.......?? i don't know alot about brakes but when i get the same thing thats the first thing i think of.....

[clarkey62]

Maybe need to be machined.......?? i don't know alot about brakes but when i get the same thing thats the first thing i think of.....
I'd say thats exactly what the problem is

After looking at the rotors again, check that you still have meat on the pads

[daza]

As wazdog has mentioned they will defiantly need to be machined or ground (Does any one still do this?) Loads of hard spots and what looks like a some rotor distortion. I would say these have been red hot at one stage.
Classic wear pattern from single sided brake calipers. The rotor once hot distort under the uneven load as does the pad. The tear shaped marks around the rotor are normally due to lock up or stopping when the brakes are still very warm and the heat soak through the pads harden the rotor in spots . It can be caused with a poorly mixed batch of cast iron but I would be surprised if this still happened today. The last time I saw those marks was when I used to work machining brakes. The fire brigade were able to do this in 20kms normally due to the urgency of the run and a tank full of water in the truck. Check the piston side pad for flatness after machining as it will probably be distorted and will benefit from machining/replacement. Also check your dust boots on the calipers as they may be cooked as well.
Cheers
Daza

[vtssgeniii]

Hi thanks everyone, will get them looked at this week. Rubber seals are fine from what I saw. The only other thing I thought was strange was the caliper had some slight play although the slider was rock solid.

[PhatAs]

set up a dial indicator and check the disk runout, this will tell you if there warped or not :)

[TUFFIE]

I would say get them machined as well, Sounds very much like warped disc's. Very common with the commodores . standard discs are just not up to too many hard stops and when putting the wheeels on make sure the nuts are tightned in a criss cross pattern. this makes sure ther is even pressure on the disc.

[Scharge]

If your steering wheel vibrates upon braking your front disc rotors require machining, if the body vibrates your rear rotors need machining. Those spots on your disc's are called hot spots and a machine would sort that out as long as your disc's are not undersize.

cheers

[Doug]

vtssgeniii - how long have you had the DBA 4000's for? I've had mine for 30,000km, and they are in need of their 3rd machining. (The first two were only very fine, but this time they seem much worse.) I spent extra on them thinking I'd get a longer, less troubling life, but it certainly hasn't turned out that way.

[vtssgeniii]

Have had them for just over a year and haven't had them machined yet and running on original PBR pads. I went through changing radius rod bushes, all front end suspension and frame adjustments, various alignments and wheel balances. Going to a brake place this Sat morning, will let you know how it goes as I'll be change the pads as well, anyone have any recommendations as it's only street use, eg: Bendix, etc?

[wh_2000]

Have you checked that if the pads are moving in the caliper.Try CRC anti squeal as that may fix the problem. Nine times out of ten if you are getting vibration thru the wheel or the car it will be the pads are moving when you are braking