Soft Brake Pedal

Wheels, Suspension, Brakes & Tyres questions and answers

Moderators: timk, Stu, zombie, Andrew, -alex, miata

SaM
Driver
Posts: 27
Joined: Sun Nov 21, 2010 11:29 am
Vehicle: NB8A
Location: Sydney

Soft Brake Pedal

Postby SaM » Sat Aug 06, 2016 7:56 pm

Ever since i've had my NB8A the brakes have never impressed me. I have bled the brakes about a thousand times, installed braided lines, greased the slide pins, and adjusted rear calipers so they are almost dragging. All of which has resulted in no significant improvement. I have noticed however, with the handbrake applied 30% the pedal feel is improved significantly. Also, when I push the thing that floats inside the master cylinder, black misty stuff comes out.

After all this I think the master cylinder may need replacing, would you blokes agree? Any advice would be appreciated. Currently running QFM HPX Brake Pads

User avatar
Regie
Speed Racer
Posts: 4259
Joined: Thu May 15, 2008 3:02 pm
Vehicle: NC - V8
Location: Sydney

Re: Soft Brake Pedal

Postby Regie » Sat Aug 06, 2016 8:45 pm

sounds like the master cylinder or brake booster has a leak, probably a hole in the diaphragm inside. you change them both as a whole anyways
MY07 NC, Mazdaspeed Body, Ohlins, Full GWR Exhaust, 17x9 RPF1's, 4.1FGR and lots lots more

manga_blue
Forum Guru
Posts: 4897
Joined: Mon Apr 24, 2006 7:27 pm
Vehicle: NA8
Location: Moruya, NSW

Re: Soft Brake Pedal

Postby manga_blue » Sat Aug 06, 2016 10:19 pm

The seals around the pistons in the master cylinder are deteriorating. That's the black misty stuff you see - perished rubber.

As soon as I see that starting to happen on any car of mine I replace or rebuild the master cylinder. Soft pedal then goes away.
’95 NA8

SaM
Driver
Posts: 27
Joined: Sun Nov 21, 2010 11:29 am
Vehicle: NB8A
Location: Sydney

Re: Soft Brake Pedal

Postby SaM » Sun Aug 07, 2016 1:30 pm

Cool cool, this has been helpful. I'll look into a new one/rebuild.

User avatar
bruce
Speed Racer
Posts: 7707
Joined: Fri Apr 25, 2003 11:00 am
Vehicle: NA8 - Turbo
Location: Victoria
Contact:

Re: Soft Brake Pedal

Postby bruce » Sun Aug 07, 2016 2:19 pm

On an aside, my gasket around the reservoir cap was deteriorating. This caused misty rubber to dirty my fluid.


Return to “MX5 Wheels, Suspension, Brakes & Tyres”

Who is online

Users browsing this forum: No registered users and 27 guests