24v swap, 25mm master, e21 booster, e36 calipers....ROCK HARD BRAKES

[psyber_0ptix]

Wrapping up the 24v swap and noticed that the brakes feel VERY stiff. The car does not roll easily but it's been sitting for so long, I didn't know if it was a function of rust formed on the rotors. It drives as though it has the ebrake on. The 735i master cylinder and calipers were installed on the car pre-swap. The pedal feel was stiffer but not rock hard.

The only thing that changed was the booster. Is there a way to tell if the booster is toast? It looked to be in pretty awesome shape preinstall but what do i know. Maybe it's just a bunch of little factors adding up....maybe check valve...maybe in need of vacuum reservoir. Any help would be appreciated.

[M-technik-3]

The bigger master is gonna add to the harder to press the pedal. It's not always consider an improvement.

[psyber_0ptix]

ok! i'll try swapping out for a stocker. I didn't realize it would make this much of a difference on a bmw. Honda/Subaru's it's not nearly as noticeable.

OT:
Also thanks so much for your help re: gauge wiring. Those two fuses you mentioned were replaced and everything is perfect once again.

[jlevie]

A simple check of the brake booster is to pump the brakes a few times with the engine off. While holding a good bit of pressure on the brake pedal, start the engine. If you feel the pedal sink a bit the booster is working. If it doesn't sink the booster is bad or isn't being supplied with vacuum.

[M-technik-3]

I have a 25 mm master and it made the pedal feel, imo significantly harder. Before swapping it out I would drive the car a bit in a parking lot. Get everything moving about and see if the car starts to free roll, E30's are light and you should be able to push them with ease.

[FredK]

I have a 25mm master as well, and in comparison to the stock master, is terrible to modulate with street pads. When you're exerting your leg muscles harder, it's also harder to modulate. It's akin to playing the piano with lead gloves on. I bet with track pads on the track it'd be fine, but for a dual purpose car, not so much.

[BenM]

Are you running E36 M brakes or standard ones. I have the exact same setup with E36 M Front & Ti Rear and the pedal feel is great with street pads and even better with track pads. Like Greg said, if you are running E36 non-M I would definitely start with the stock 22mm and see how it feels.

[psyber_0ptix]

Brakes:

e36m3 fronts
318ti rears
735i 25mm MC
e21/320i brake booster
braided lines
stock pads

Could pad choice, or lack thereof, be the problem? I think i'll just have to take it for a spin, clear the rust off and see from there. The car has been sitting a while but it almost feels like a seized caliper. The rears are in rougher shape, but I do have a backup set of e36 rears where the bleed nipples will be upside down. I'm probably just too paranoid, but it seemed like a valid concern at the time. I'd hate to run around with practically non-functioning brakes.

[M-technik-3]

Bust out the one man bleeder and flush the system.

[Gnarles]

The e21 booster is smaller than the stock booster and will provide less assist. This coupled with the larger master cylinder could be the cause of your stiff brake pedal.

[psyber_0ptix]

Bust out the one man bleeder and flush the system.

Fluid is 2 month old ATE Super blue, but i'll definitely give it a shot before driving. Things were apart anyways and i have a fresh bottle on standby.

The e21 booster is smaller than the stock booster and will provide less assist. This coupled with the larger master cylinder could be the cause of your stiff brake pedal.

This is what I was thinking initially. Has anyone used a vacuum reservoir?