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VS to VT 1" Master Cylinder upgrade.

Discussion in 'VR - VS Holden Commodore (1993 - 1997)' started by Fonzie, Feb 8, 2010.

  1. Fonzie

    Fonzie Just lost the game.

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    I've recently purchased some VT brake calipers, discs and pads to do an upgrade on my bog stock VS brakes, and It's been recommended to upgrade the MC too. Incidentally, Philthy has a 1" VT MC lying around that I'm pinching.

    Could someone give me a walk through of how to swap it over? Or if not, anything in particular to avoid doing?

    My assumption is undo the side bolts, drain the fluid. Undo the bolts holding it onto the booster (and i have a feeling there's one on the wheel arch too), slide it off. Bolt the new one on in reverse steps, fill up with brake fluid, and spend eighteen hours bleeding the damn brakes. How far off am I?

    Cheers, Fonzie.
     
  2. DannyboyDS

    DannyboyDS Just hand me the pliers.

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  3. hako

    hako Donating Member

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    Not sure if the excellent "how-to's" include advice on bench bleeding the master cylinder before you fit - this virtually avoids the need to bleed which is very handy if you have ABS. Basically it involves mounting the new MC in the vyce and filling the reservoir with fresh brake fluid - then you attach some plastic hoses to the fluid outlets and run the ends back up to the reservoir...then pump the MC however many times it takes to fully expel air from the MC. Remove the plastic pipes just before you fit up the steel ones.
    This way you have little if any air to remove. Better explanations are found on Google.
     
  4. stocky

    stocky New Member

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    i think the VT M/C is bigger than 1 inch. it bolts right up to the VS booster, and if you can bench bleed it, you may not have to bleed the brakes
     
  5. Fonzie

    Fonzie Just lost the game.

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    A big cheers to DannyboyDS, Even if those links don't mention the MC I'm sure there's loads that's gonna help me when I put the brakes on. Repped you mate :thumbsup:

    As for bench bleeding the MC, I'm not too concerned about that. For two reasons, one is I don't have ABS so it's a relatively straightforward (Albeit boring) job. And secondly, My brakes have been ratshit for as long as I've had the car, And I figured when I upgrade the brakes a full bleed couldn't do any harm.
     
  6. stocky

    stocky New Member

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    ah no ABS. dont have to worry about it then. i only did it to avoid doing the abs cycle thing while bleeding
     
  7. Fonzie

    Fonzie Just lost the game.

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    Yeah pov pack VS, despite the dual front airbags and a few other retarded factory fitted things.

    So was my guess on the process to install it correct?

    And, out of curiosity, what does and abs cycle bleed involve?
     
  8. RX25SE

    RX25SE Real cars are steel cars.

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    VTm/c has a 1" bore and a 1 1/8" fast fill chamber (the bit at the back that looks like the piston. VS has a 7/8" bore and a 1 1/16" fast fill chamber.

    I had to machine up a spacer to use between the m/c and booster as the pushrod was too long, even adjusted in all the way.

    I also fitted the VS reservoir to nthe VT m/c (drill and tap a new hole) so it sits level. (I would think this has been covered in the many threads on this!!)

    For a kick fit the m/c first and go for a drive with the VS calipers and discs still on. Awesome quick acting firm pedal but a little more effort required.

    You should really be flushing the system with new fluid when changing the m/c, especially with ABS, as the ABS unit has filters inside that cannot be serviced and could block if the fluid is allowed to become too dirty.
     
  9. mojododo

    mojododo New Member

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    yes i have also changed mine to a vt 1" m/c

    as above i had to machine a spacer up so that the pusrod wasnt permanently putting the brakes on a bit, but apart from that it was a straight forward job to install.... except for the abs unit... the whole day i could not work out how to get the air out of the abs, but left it overnight and came back the next day and the abs unit was behaving itself...

    very good pedal feel with nice and quick action. i prefer a harder less throw pedal. (running 343mm front discs)
     
  10. stocky

    stocky New Member

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    i remember modifying the rod. i think i screwed something into it. cant quite remember. didnt use a spacer
     

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