Vibration while Braking - that old story!

[lemonaed]

Hi all.

Although this item has been discussed in the past, I felt compelled to ask the question regarding a vibration in my VYII SS when braking as it is
driving me mad!! I had the unfortunate bad luck to have someone crash into my driver side front. I had to have the bumper, fender and lights
replaced. However since the accident I used to have a gentle vibration while driving at 120km/hr. This would disappear above 140km/hr. I did the worst thing to all you enthusiasts out there and kept driving as the tires were only new and I didn't want the cost of replacing new tyres, and
most of my speed was below the annoying vibration level.

Recently I got around to changing all the tires which did indeed fix the problem of the vibration in the car at 120km/hr, but now I have a vibration
when braking! I've even had the rims checked and indeed one wheel was slightly warped. I've had the warped wheel fixed and this has eliminated
the general minor vibration while driving. However the problem now exists that I have the steering wheel shake while braking - This is particularly
noticeable when braking down from 80-50km/h. The funny thing I have noticed that if I brake hard the vibration only occurs very briefly and then
it stops. What do you guys think that it may be? I am leaning towards warped rotors, however I have after market HSV - 4 pot brakes and rotors
on my car, and I don't really brake excessively. I've recently changed the tires and have had the car balanced. So it could be a suspension
component either? The car coasts beautifully in neutral. There is no vibration while accelerating either - just when braking gently at the above
speeds in particular. However I don't feel any vibration through the brake pedal. The wheels are the standard VYII SS 18".

If you could list the most likely culprits that would be great - because I live in Ireland and getting parts shipped from Aussie is a nightmare (and
costs a packet too!). It is very annoying to have such a great car (only VY V8 Sedan in Ireland) and yet to have a bloody vibration!).Any of you
guys who can help me out can rest assured that your expertise is helping out a Commodore enthusiast on the other end of the planet!

Thanks guys,

Lemonaed

[Hangman]

+1 for warped rotor from the info given

[lemonaed]

Thanks Hangman. I should also mention that the vibration in the steering began after I took my car for a little back country spin to test the grip of the new tires! This might also be a factor!! Any other feedback is appreciated

[Fletch_QLD]

I would be super confident it will be warped front rotors. Quite often the culprit is an overzealous wheel fitter with a rattle gun - though not definite, and impossible to prove. I always make sure I fit my own wheels by hand - per the correct method of nipping up opposite nuts gradually.

I would normally say don't bother getting the rotors machined - it may seem cheaper, but it's a false economy as the shudder will return. Of course, given your unique circumstance, you could try getting them machined - this will confirm the source of the problem and give you time to get new rotors shipped in ...

[letthiswork1]

Yeah i would go for Warped rotors... Happens often..

How long have you had the aftermarket rotors for? Have you taken it to a track or something??

[lemonaed]

Hi. I've out about 40000km on the new rotors with no heavy driving, and not a single track day! - apart from a short burst I gave her on the back roads when I replaced the rubber- to check the grip!
Come to think of it I recall a mechanic using a rattle gun when I got the wheels balanced a few months ago.
I'm just hoping its nothing more serious caused by the first accident and driving with the slight vibration, but it certainly sounds like a warped rotor.

[confucius]

Problem: steering vibration under light braking.

Cause: What can be done to eliminate steering vibration under braking?
Solution: Disc thickness variation is the cause of this problem. Usually it is caused by the disc being out of alignment when originally fitted. Machine the discs. If they are thinner than the manufacturer's minimum thickness specification, replace the discs.

[Dr HaxZaw]

If getting new discs doesnt solve it you should look at the castor bushes and also the strut top bearings... had both of these cause braking vibrations in the past

[lemonaed]

If getting new discs doesnt solve it you should look at the castor bushes and also the strut top bearings... had both of these cause braking vibrations in the past

Thanks to all. Hopefully it's only the discs. If not I'll then look at the Castor bushes and strut top bearings. I will let you know how I get on - though this may take some time regarding shipping times etc! Maybe I'll get lucky and source similar rotars in the UK as they sold the Monaro and the VE HSV clubsport there.

[Dr HaxZaw]

strut top bearings you can tell need replacing when there is a gap between the clamping plate and the top of the strut tower... you can see these easily from your engine bay so you will be able to see if they are gone

the castor bushes depending on if they have been replaced before you can see if you get under the front of your car and see if they look ok or have split

sounds like its just a warped disk though so you should be ok but i figured this would set you on the right path. If it doesnt it saves you having to come back and ask again

[Not_An_Abba_Fan]

VT-VY had a problem with rotors when the wheel nuts aren't torqued correctly. It doesn't come straight in, more of a gradual increase in vibration. Doing wheel nuts up with a rattle gun will cause this.

The only solution is to replace the rotors and do the wheels up by hand to the correct torque.

If you are after new rotors I can do you a good price on standards or slotted.

[lemonaed]

VT-VY had a problem with rotors when the wheel nuts aren't torqued correctly. It doesn't come straight in, more of a gradual increase in vibration. Doing wheel nuts up with a rattle gun will cause this.

The only solution is to replace the rotors and do the wheels up by hand to the correct torque.

If you are after new rotors I can do you a good price on standards or slotted.

I might take you up on that offer once I get the rotors looked at. Problem will be shipping. They'd need to be shipped separately for weight (and taxman) purposes! I'm pretty sure the front are 343x32 slotted, but i'll need to check this with the old measuring tape!

[lemonaed]

To all who replied to my original query. I've had my rotors looked at and there were indeed warped. I've also had them skimmed and the vibration is now gone! Thanks to all for taking the time to give their advice.

Interestingly, I had the rotors skimmed at a BMW specialist who skimmed the rotors while they were still in position on the front hubs. This machine rotates the rotor and measures the ovality using lasers and then uses two cutting tools to trim the discs. All this is done automatically. I had never heard of this process before. I believe this is the only garage in Ireland to do the rotor skimming in situ. This has saved me the cost of importing some rotors (for now). I'll keep you all posted on whether this fix actually lasts.

[letthiswork1]

That's awesome!

I have seen heaps of people who spend hundreds of dollars on trying to fix these issues so lucky you got it first off the bat!

[lemonaed]

That's awesome!

I have seen heaps of people who spend hundreds of dollars on trying to fix these issues so lucky you got it first off the bat!

True. Still, it took me the best part of 4 years, a new pair of tyres, countless wheel balances, one alloy wheel repair, and finally the skimming of the front rotors to finally find the solution! But boy am I happy now! Finally a vibration free ride!!

[Fletch_QLD]

Pffft, all that and all you had to do was ask us ;-)

[letthiswork1]

Pffft, all that and all you had to do was ask us ;-)

Should start charging for work! Because we are so qualified and all.. :P

[Richard Moss]

Interestingly, I had the rotors skimmed at a BMW specialist who skimmed the rotors while they were still in position on the front hubs. This machine rotates the rotor and measures the ovality using lasers and then uses two cutting tools to trim the discs. All this is done automatically. I had never heard of this process before. I believe this is the only garage in Ireland to do the rotor skimming in situ.

One thought - if you have to remove the discs, mark their position on the hub to ensure that they go back in the same place.

Also, you may find that you can get things like brake parts from RockAuto Auto Parts and get them shipped in at a reasonably sensible overall cost. I know that Monaro parts in the UK can be ridiculously expensive (I guess that ireland has the same problem). The crazy parts prices are what will stop me bringing my Lumina coupe (Monaro) back to the UK when I finally leave the middle east.