12 replies to this topic

[Miki Leyland]

Hello all,

 

Last year I had my engine rebuilt and a servo installed. She is a 998 with drums all around. I wonder what the red thing is for and if it is a good idea to have it, as I haven't seen that in other cars.

 

Thank you in advance

 

 

[nicklouse]

a 10 PSI pressure regulator, strange as it should not be needed if set up correctly.

[Ethel]

The idea is it holds a minimum of that pressure in the lines down stream of it to take up some of the slack so improving response & reducing pedal travel.

 

As Nick says it shouldn't be necessary, especially on a road car where it could just cost you mpg if it makes the brakes bind.

[Miki Leyland]

Thank you guys. I myself didn't see the point also having a servo, but...

[viz139]

As your car has drums all round the springs pull the shoes back against the adjusters preventing them going any further. On disc brakes there is technically nothing to stop the pistons returning into caliper when there is no fluid pressure , this unit holds a minimum amount of pressure in the brake line. If you ever drove a car with a warped disc that pushes the pistons back more than normal you would know the difference this makes in pedal travel. As above this is more suited to race or track day car.

Edited by viz139, 01 July 2020 - 09:45 AM.

[sonscar]

I thought they were fitted to cars with underfloor master cylinders to stop the fluid potentially draining back?Steve..

[Spider]

The standard Mini Brake Master Cylinders all have a Residual Pressure Valve built in to them, so I wonder if someone has fitted a Clutch Master here ?

[Miki Leyland]

The standard Mini Brake Master Cylinders all have a Residual Pressure Valve built in to them, so I wonder if someone has fitted a Clutch Master here ?

After some research it seems that you are right, as brake master cylinders are of golden metal. Silver for clutch.

 

OMG I hope there is no big difference with the external pressure valve...

[imack]

Don't think you can go by colour, judging by the orientation of the reservoir it's a brake master.

[Spider]

 

The standard Mini Brake Master Cylinders all have a Residual Pressure Valve built in to them, so I wonder if someone has fitted a Clutch Master here ?

After some research it seems that you are right, as brake master cylinders are of golden metal. Silver for clutch.

 

OMG I hope there is no big difference with the external pressure valve...

 

 

It's a little hard to say for sure from your photo, but the foot plate on both your Masters appear the same thickness. Usually, the Brake Master has a thicker mounting foot than the Clutch. Other than that, it might be a case of removing it and measuring the bore diameter to be sure - Brakes are 0.70" and Clutch is 0.75" diameters.

[viz139]

I was thinking more about this pressure regulator but have no experience of using one. On a race car I would think the slight pressure of the pad against the disc would build up heat and the pads would be at working temperature when you need them but on standard pads could this lead to overheating of the brakes?

[Ethel]

Possibly,

 

I think they're mostly intended to allow huge calipers to work with the smallest bore masters possible.

[Miki Leyland]

I was thinking more about this pressure regulator but have no experience of using one. On a race car I would think the slight pressure of the pad against the disc would build up heat and the pads would be at working temperature when you need them but on standard pads could this lead to overheating of the brakes?

After some reading, I understand these are mostly intended for drum brakes only, where the pedal travel could be longer before it makes any action against the wheel (at least these 10psi model of the valve)