car shakes violently when braking

[Tom_1569]

The drilled rotors are more suited to a track, and are prone to cracking.

Personelly I'd be running RDA, or DBA Slotted rotors with new Bendix CT pads. Torque your wheel nuts correctly and change your driving style*.

*After a heavy brake, put in neautral and take your foot off the brake so your not resting hot pads in one area, especially when you just slammed them on for that redlight camera. Another thing is to brake early, then for the last 10 metres or so, just roll it out to let your brakes get some air and cool, before coming to a complete stop. There the only things I do differently in the VT and it hasnt come back yet, though mum is going back to driving the VT now so it will interesting to see if the shudder comes back, caus shes a hard late braker and doesnt care much lol.

 

[Not_An_Abba_Fan]

When you brake, do you stomp on the brakes and leave them applied until you come to a complete stop?

 

[98 vt olympic]

hey not an abba fan yeah look because of the current problem i have i brake any where from 100m or further back the only time i brake hard is pulling up to a amber light changing to red or if im late to work

RDA slotted rotors were going to be my next choice along with RDA pads hopefully see some results

 

[Sabbath']

I really dont see why you're going slotted either.

Just go for normal, run of the mill discs. Bed them in properly and take it from there. Dont waste your money on things you dont need, such as cross drilled or slotted.

 

[Tom_1569]

I really dont see why you're going slotted either.

Just go for normal, run of the mill discs. Bed them in properly and take it from there. Dont waste your money on things you dont need, such as cross drilled or slotted.

Apparently they also warp from getting to hot, and that is the common problem with them, and being twin piston makes it worse, apparently. Slotted helps keep them cool and prevents warping, no idea if theres any truth to it, but its what solved our warping problem.

 

[98 vt olympic]

i spoke to a guy who used to be a mechanic for shacks and said that the vt had these problems as it was the first commodore to come out with bigger rotors and twin piston calipers but what i dont understand is if that were the case then y the back warping for there still only single piston calipers or is it just because there PVR branded

 

[Drewie]

My VX SS has just started to develop a slight run-out vibration when braking, very slight,
it has done 60,000km original pads and discs haven't been surfaced yet.
What I wanted to ask is it possible for a run out to be felt when not braking, I have just put new tyres on my VX and I have had them balanced twice and I can feel a slight vibration at certain speeds similiar to the run out feeling when braking, only slight and on some roads I can't feel it at all, I thought it may be that the new tyres are a bit more sensitive to the small iregularities in the road, hence why I can feel it some times and not others.

I have tensioned the wheels with a tension wrench, not sure if the VX is different but in the driver's handbook it says 100 to 125nm, I did them up to 120nm.

Just thought you might have some ideas on what the vibe might be.

 

[98 vt olympic]

no sorry mate i would'nt have a clue im just starting to think it may be a similar problem in all the new commodores as when my dad had a vy commodore he had slight vibrations whilst braking he also used to have a vp calais that was a nice car never had a problem

 

[Thumpin]

Sorry to re-birth this post but I did some experimenting with my personal car which has had 3 sets of discs due to steering wheel wobble when braking. Seems to be more pronounced when light braking by the way.
Anyway, I performed a detailed run-out check of the discs whilst fitted to car. The maximum axial runout on either side of rotor was 0.02mm or 0.0007". Run-out variation between each face (at the same time) was about the same 0.02mm.
I then took the discs off and mounted in a precision lathe and pretty much zero'd the inner mounting face and the run-out improved to 0.01mm. Thats about "two tens of Fu#k all".
The holden specs for disc runouts are about double what I achieved with discs mounted on the car.
Some years (maybe 20) ago, torquing of wheel nuts in a cross-pattern to the correct torque value was more important to prevent brake issues due the the bearing hub and disc being intergrated, however, the design incorporated in the vt's which effectively sandwiches the disc betwwen the bearing hub and the rim should not adversely effect disc runout after tightening. I did try torquing the nuts as unevenly as possible and the runout figures did not change. That said, it is good practice to torque wheel nuts evenly.
I personally haven't had much luck with DBA discs on various cars and as some other have commented, drilled discs are a waste of time unless you race a rally car. The DBA life span seems short IMO and they tend to develop brake squeal issues.
I've had the best run from genuine GMH discs and these are the ones I've tested above.
I fitted a new set of Lucas pads and the shudder was gone. The old pads seemed to have worn evenly which rules out caliper sticking or wear.
Maybe I've previously throw out good discs

 

[howler31]

change drivein style losse cross driled rotors go bak to o.e replacement and do u have a stickin caliper or is the ABS playin up and holden pressure on the brakes???