Slimy38
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| posted on 16/1/18 at 10:15 PM |
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MX5 brake master cylinder pushrod
Hi all, I have another question around the MX5 master cylinder. The various braking options all mention removing the brake servo, and using a rounded
off bolt to operate the master cylinder. But if I compare this with the newly purchased clutch cylinder, I can see the clutch cylinder has a retained
pushrod to operate the master cylinder.
This makes me wonder whether I'm missing something for the brake MC, with it just being a rounded bolt pushing on a piston. There's no
retention, no circlip, rubber boot or anything that would keep the bolt in place on the piston. There's the brake pedal movement limiter, but is
it permitted to have a pushrod that is not fixed to the MC?
Am I reading too much into it, is it safe to just have a pushrod 'in place' on the MC, and retained by nothing more than the pedal range?
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ianhurley20
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| posted on 16/1/18 at 10:55 PM |
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Sorry - don't know what your earlier questions were and not really answering this one
I kept everything as it came out of the MX5 including the servo. It all works a treat!
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WallerZero
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| posted on 17/1/18 at 09:10 AM |
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I have rounded bolts for pushrods on my Zero for both clutch and brake. Never had any issues once set up right. Pedal travel has kept them in and
working for 4 years no problems 
http://zachsgbszero.blogspot.co.uk/
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JAG
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| posted on 17/1/18 at 10:12 AM |
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Pedal travel and circumstance will keep the handmade pushrod in place.
BUT if it falls out - you have no brakes!
I'm a Professional Engineer and that's not a risk I would be prepared to take with my life or worse still with the life of my
passenger.
I fitted a Servo on my car and it works very well.
If you insist on removing the Servo then create a mechanism to retain the pushrod in the master cylinder 
Like this....
[Edited on 17/1/18 by JAG]
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Slimy38
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| posted on 17/1/18 at 01:59 PM |
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quote:
Originally posted by JAG
Pedal travel and circumstance will keep the handmade pushrod in place.
BUT if it falls out - you have no brakes!
I'm a Professional Engineer and that's not a risk I would be prepared to take with my life or worse still with the life of my
passenger.
I fitted a Servo on my car and it works very well.
If you insist on removing the Servo then create a mechanism to retain the pushrod in the master cylinder
Like this....
[Edited on 17/1/18 by JAG]
My thoughts exactly, I was thinking it only takes a small amount of wear on some component to allow the pushrod to drop out. I'm definitely a
belt and braces person!
I like the retaining washer idea though, I did think it wouldn't have to be overly complex. The plunger at the moment comes up to the circlip so
I'll have to see what I can do without compromising the return position.
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