I'm upgradign to 4 pot fronts, and 2 pot rears from a MY2003 Impreza to my MY97 WRX. Do I need to replace the master brake cylinder? Because I have to depress the pedal further down then usual.

 

You could.
I haven't, and mine is a 98 UK car, now running Godspeed Brembos on the front and STi Brembos on the rear.

Are you sure they are bled properly? And that each caliper is fitted to the correct side?

 

I hope not! I'm about to do the same conversion albeit on a UK spec car, MY97 though. Have the brakes had a chance to bed in yet as this can cause temporary lomger pedal travel.

Did you have the Subaru 4pots on the front as standard though?

 

To settle this for once and all I need to know the diameter of the brake cylinder.

My car had volvo 4 pots for the front calipers, which worked perfectly. So I have no idea what was standard on my car.

 

I'll compare mine and the wifees tomorrow. I have two pots as standard hers is a later car with the Subaru four pots as standard so should be able to tell.....

 

Mine had 2-pot front, single pot rear. Not fit for a mini, let alone a Scoob

 

Just what mine is running atm four pots due to go on when I've re-furbed them and bought some godspeed grooved discs......

 

That will be great! Thanks

 

Yes there is a larger master cylinder you can fit , but in all the conversions we have done on Impreza's , we have never found we needed to change them.
If the master cylinder is working properly , its well capable of running with the 4 pot front and 2 pot rears.
The only time we have seen problems is when the master cylinder is on its way out , and then it will give you a long spongy peddle , or if the calipers have been fitted on the wrong side and you get trapped air in the calipers.
Cheers Ian