Morris Minor Owners Club

PJR2601 wrote: ↑Wed May 13, 2026 4:40 pm Hi all, got the brakes "sort of" working

Has anyone got the instructions for fitting a servo - would be helpful to have a read of these so that i can judge whether i am capable of doing the job

Thanks in advance

Peter

svenedin wrote: ↑Wed May 13, 2026 4:56 pm
Before you even consider whether you have the skills to fit a brake servo it is important to be clear about what a servo actually does.

A servo reduces the force you have to apply to the brake pedal in order to achieve maximum braking (which without ABS, is locking the wheels). A servo does not in any way improve the performance of maximum braking. In fact, a servo complicates the braking system with another component that can fail and can prove a source of irritation and annoyance with trapped air when trying to bleed the brakes.

Fitting a servo to a poorly performing braking system without diagnosing and rectifying the original fault will not improve matters at all.

A servo can be useful to reduce driver fatigue and for those with limited physical strength.

Stephen

PJR2601 wrote: ↑Wed May 13, 2026 4:40 pm Hi all, got the brakes "sort of" working

Has anyone got the instructions for fitting a servo - would be helpful to have a read of these so that i can judge whether i am capable of doing the job

Thanks in advance

Peter

Bill_qaz wrote: ↑Wed May 13, 2026 6:41 pm So marina discs with same 13/16" master cylinder needs a lot more pedal pressure than 8" drums 118 lbs (with same diameter master cylinder).
Hence servo helps with front disc set ups.135 lbs requirement.

ManyMinors wrote: ↑Wed May 13, 2026 7:36 pm And let us not forget that the "modern" disc brake equipped BMC 1100/1300 range, MG Midget and MGB plus the first Marinas managed perfectly well without servos

svenedin wrote: ↑Wed May 13, 2026 7:11 pm

Bill_qaz wrote: ↑Wed May 13, 2026 6:41 pm So marina discs with same 13/16" master cylinder needs a lot more pedal pressure than 8" drums 118 lbs (with same diameter master cylinder).
Hence servo helps with front disc set ups.135 lbs requirement.

Yes but actually my drums all round but Wolseley 9" front brakes works out at 131 lbf and I can't say I even noticed an increase in the pedal pressure required from 118 lbf. Original Minor 7" all round 142 lbf.

It does show you have to push quite hard on a Minor brake pedal though!

Stephen

Bill_qaz wrote: ↑Wed May 13, 2026 8:47 pm

svenedin wrote: ↑Wed May 13, 2026 7:11 pm

Bill_qaz wrote: ↑Wed May 13, 2026 6:41 pm So marina discs with same 13/16" master cylinder needs a lot more pedal pressure than 8" drums 118 lbs (with same diameter master cylinder).
Hence servo helps with front disc set ups.135 lbs requirement.

Yes but actually my drums all round but Wolseley 9" front brakes works out at 131 lbf and I can't say I even noticed an increase in the pedal pressure required from 118 lbf. Original Minor 7" all round 142 lbf.

It does show you have to push quite hard on a Minor brake pedal though!

Stephen

So Stephen am I reading the chart wrong?
Wolsey fronts, minor 7" rear 13/16" master is 104lbs pedal

Bill_qaz wrote: ↑Wed May 13, 2026 8:57 pm Are I see cylinders changed as well
Funny you posted as I was editing including wrong cylinder diameter
Even with my servo discs when I get back in my mitsubishi the first few stops are headbutting the screen moments.

svenedin wrote: ↑Wed May 13, 2026 9:01 pm

Bill_qaz wrote: ↑Wed May 13, 2026 8:57 pm Are I see cylinders changed as well
Funny you posted as I was editing including wrong cylinder diameter
Even with my servo discs when I get back in my mitsubishi the first few stops are headbutting the screen moments.

Yes I have to be very careful in my modern car. Not just the brakes but it's bigger and has more than 6 times the power. I quite often end up putting on the windscreen wipers rather than indicating.......people probably think typical Audi driver, doesn't bother to indicate!

Stephen