VS HSV C4 brake issue

[ephect]

hey all

I've had the HSV C4 caliper big brake upgrade for ages without any issues until recently. The problem first began maybe 4 months ago and it has 2 issues both only affecting the left hand front. I initially thought warped rotors, they were in need of changing anyway so I grabed some bendex ultimate pads and new DBA T3, and the problem went away until a week ago

first issue, this mainly occurs when hot or had several braking cycles. It fells like the pads are being held against the rotor when the brake is released. Normally its a clean and a grease of the slides and its sorted, but the C4 caliper doesn't have slides. it has a groove for one end of the caliper for the pad to slot in and a half circle for the locking pin the other side. so in a search I found the something regarding the locking pins, so I bought a set from America and replaced them. no change.

the second issue which randomly occurs is it feels like the pad/caliper is bouncing off the rotor, kinda like its rattling against it. The noise/rattle randomly occurs either hot or cold, fast or slow but less when the ambient temp is cooler. it sometimes does it when I pull out of the driveway in the morning or after 20mins driving. The worst is when the brakes are warm/hot it shakes the car and thumps as im doing 60, and its unbearable at 100.
Applying the brakes so the pads touch the rotor stops the rattle/shudder.

Normal braking is smooth and there's no shuddering, the only time it'll shudder is when the thumping is there.

has anyone come across this type of problem or any ideas?


TL/DR
left hand front brake feel like its sticking, and caliper/pad randomly bounces off the rotor and its noisy as fk

 

[ephect]

after some more light reading, its common for these calipers to rattle if the pads don't have the anti rattle clips in place. I checked last night and they're there, the right-hand side doesn't move but I can move/rattle the left-hand caliper by hand. i'll grab another set of clips and replace them and see how it goes I guess.

 

[ephect]

swapped our the anti rattle clips and greased where the pads sit. It doesn't rattle when cold now, but still does it when the brakes are warm.

looking at the cradle it looks like there is a groove where the pads would sit when the clips compress under braking, but doesn't sit there not engaged.

any ideas?

 

[Immortality]

What are the wheel bearings like?

Just to confirm, are we talking about a twin spot or 4 spot caliper?

Have you checked for rotor run out?

 

[ephect]

no play in the wheel bearings

twin pot like this http://home.earthlink.net/~olylt1/Anti_Rattle_Clips/Anti_rattle_clips.html

haven't dialed the rotors, but gave them a spin and eye balled, they looked true. This was done whilst cold, wonder if the rotors have hot spots? With these new rotors I've been very conscious not holding the brakes on whilst stopped to avoid warping.

 

[harrop.senator]

Off topic but what master are you running? I have the same brakes on my car and pulls up worse then a stock vt. Is 1" bolt on pbr upgrade enough or have you gone a bigger aftermarket route

 

[ephect]

hey, I'm still running the stock v6 booster which is 15/16 from memory.

stopping is fantastic and pedal feel isn't spongy at all. I did install new lines at the time of conversion due to hose points being different.

 

[harrop.senator]

Yeah I've got the braided lines slotted rotors and Bendix pads from memory. Feels like first third does nothing. Have tested all master and booster and came up good having never had the stock brakes on it have nothing to compare to. I'll throw the bigger master in n hope it improves. Good look with sorting your shudder out.

 

[BlackVXGTS]

Well, I have AP Racing four piston calipers, 330mm (or 328mm) DBA rotors, and braided lines at the front of my VS Calais and have never had an issue with the standard VS master cylinder/brake booster. HSV cars, whether they have standard brakes (185kw Clubsport etc.) or the upgraded brakes on the 215kw models (GTS etc.), also use the standard master cylinder/booster.

 

[harrop.senator]

I know they've got the same on the 215 as my c4s were factory fitted . Just because came from the factory doesn't mean its optimum. The vt pistons are smaller in size from memory and they're running a one inch master. Just because something works doesn't mean it can't be improved on. I dno if its cause its auto or just heavy but wife's ute with stock vu brakes pulls up much better.