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VB Commodore brakes

Lowcroozer

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G'day guys, next issue to tackle is the brakes on the car. The brakes are soft/spongey. I have bled the brakes several times. They are VT brakes running off a double diaphragm booster and a 1 inch master cylinder. Hoppers Stoppers suggested a thicker brake booster bracket which runs from the shock tower. If there is firewall flex it's supposed to help. Has anyone put one of these on, did it make a difference and where can i get one? If that fails then i'll be taking the car in for further investigation. I'm running the SLE 15"wheels so cannot go bigger brakes. Any help appreciated.
 

Tonner Matt

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I won't suggest worn parts as I presume this is a new upgrade kit.
Spongy is a sign that there is air still in the system somewhere.
Did you bleed the master cylinder first before bleeding at the wheels ?

I remember reading a thread on here about this conversion where someone suggested that you had to swap/adjust/modify the pushrod length to achieve the correct pedal feel. A few members on here have done similar upgrades so I'm sure someone will come along and point you in the right direction.
 

vc commodore

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Strange one....I have a VT upgrade on my VC with a 15/16" M/C, VK booster...The VK booster is smaller in length, compared to the VB/VC one, so I am unable to fit the bracket from the M/C to the strut tower...I am also running rear discs as well.....I have no soft pedal feel at all....

Perhaps a M/C rebuild and a proper bleed at the M/C before bleeding the rest of the system
 

Vc4.7v8

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I used to have the double booster and 1 inch master with my brakes and they were spongy aswell with vt fronts changed to vt mc and vt booster from race brakes Sydney firm pedal now and I think it would out brake my vf now as for the firewall brakes the one from Lowe fabrications fits sweet with the old and new set up
 

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I have VT brakes on my VC which although registered is used as a track car only. I started off with VT brakes front VL discs rear with stainless steel flexible lines and 1" MC. Brakes were good, booster died so I fitted a double diaphragm booster, brakes improved a bit. Pedal was never high but not low either and it passed engineering road test. Then I upgraded to a plastic booster from a VS, unlike the VT booster it requires no mods to fit and also used a VZ MC. The difference is very substantial, full pedal and much more braking grip. I found one downside, the rear brakes locked before the fronts, this could be because my car is gutted and only weighs 1160kgs. I have fitted a proportioning valve beside the MC to adjust rear brake bias. The only modification you need for the VS booster is when looking at the front of the booster you will see an adjusting screw, remove it and cut the head off the screw. Now add some Loctite and screw the remainder of the screw back in so it's flush. The VT to VZ MC is 1.25" and is "quick fill" which is what the VT brakes need to work at their best. You will also need adapter fittings for the lines at the MC. I used a Falcon AU reservoir as it sits at the correct angle, there is also a Holden reservoir which will fit but I don't know which model. The Falcon unit just fits straight on. I went to Pick and Pull and swapped the reservoir over before I paid for it.
 

Lacksballs

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You haven't mentioned what rear brakes you are running, if its drums pull the brake drums off & check the wheel cylinders for leakage (they always leak), check all the rubber brake hoses, if it's a disc setup start by bleeding the LHR first - RHR next until the fluid runs clear, make sure that you have someone checking the brake fluid level so it doesn't run less than 1/2 fill at any time whilst bleeding is in progress. Then move onto the LHF & finally the RHF. Even with a 1" master cylinder, the pedal will get hard (if the brake system is in perfect working order) but it will have long travel.

Do yourself a favour & do the complete VT master & VS booster upgrade, all bolt on, the pedal feel & functionality will amaze you. The VT front calipers need the fast fill master cylinder to work properly as they are twin spot calipers (it's all bolt on & there are good threads with pics on this site). The bracket you mention is to control the flex of the booster-master cylinder from the firewall when stomping on the pedal, the original bracket bolts straight back on to the end of the master cylinder and attaches to the strut tower and controls this flex.
 

wasted_days

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Tried braided brake lines instead of rubber? That ontop of the above comments!
 

Lowcroozer

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Is the VS master going to foul on the rocker cover (VN). Is it bigger in diameter?
 

NPreston

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No it won't foul as I had a VN V6 in my VC with the VS booster. Just cut the adjusting screw off flush with the end of the rod, put some Loctite on the thread so it can't unscrew.
 

Lacksballs

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The VS plastic booster fits in conjunction with normal std height rocker covers, bolts straight in as NPreston states above just cut the end of the adjusting screw off flush before fitting the VT master cylinder. It also pays to fit a VS or AU reservoir as the fluid angle is more neutral.
 
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