Brake Boosters and Master Cylinders

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Brake Boosters and Master Cylinders

Postby GTB25T » Fri Feb 03, 2023 1:49 pm

Did a search on this topic but still not sure.

Is the brake booster and the Master cylinder the same on a Post Face LGT and a tbSTI?

I have read the Brembo's uses a different diameter Bore on the master cylinder but not sure about the brake booster as the part number says; G215T on most.
Some have extra info like 97E and ZF.

From what I understand, please help here, The larger MC piston pushes (maybe 13%) more fluid for the Brembos volume but the end result is shorter pedal travel less force.
On the 07-08 LGT OE brakes a smaller MC diameter pushes less fluid but has a longer travel pedal feel with greater force at the brake piston.

Which has a 25mm bore and which has the 27mm bore? Can the master cylinder be swapped without the brake booster?
Is the tbSTI booster different to the LGT? Personally I feel more comfortable with less pedal travel. I'm using Intima SR pads and slotted rotors.

Appreciate your help.

I believe my LGT has enough force as the ABS is easily activated and the Potenza 225's grip well. However, if I want less pedal travel, could I just swap the master cylinder to a larger WRX STI bore?
Last edited by GTB25T on Fri Feb 03, 2023 3:46 pm, edited 1 time in total.
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Re: Brake Boosters and Master Cylinders

Postby bigBADbenny » Fri Feb 03, 2023 2:55 pm

Ok iirc it's a GD booster and master cylinder combo.

Makes for a woodier pedal.

Jezza did it on the forum on his H6 6mt with VDC so all the info and considerations are written up.

Because his car is VDC he had to change or adapt some ABS related hard brake lines.

He stuffed some threads in the process and had to swap out the abs pump iirc.

Is that the upgrade, harder pedal you're referring to?

Iirc it’s discussed in this thread and or post :swoon:

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