Brake pistons

[Peter Douglas Winn]

Paul I have just come back from the garage. What you suggested worked.

What you forgot to say was:- have 99 various screwdrivers because the one is too long, the next too short, the next too fat, the next too thin, the next too blunted, the next too sharp etc. Secondly my rubbers were in a very good condition as well as the pistons. This meant a large amount of suction. The only way was to ease the piston a very little bit, wait for the rubbers to pull it back. Then start again and after 1/2 hour one piston comes out. No matter what I tried the pistons did tip a very small amout. You can see it without measuring. So the leaverage points had to be continually changed. Thirdly without a vice it is a 2 man job.

Inspite of everything your way works.

[Z320]

Hi Peter,

this means the pistons glued in the seals and did not want to slide?

That is what the seals are made for, but too much causes the effect I described.

What about fitting the piston back with some brake grease on the seals?

Ciao, Marco

[Peter Douglas Winn]

The rubbers were wet with brake fluid. I was looking for Red Grease but Triumph said use plenty of fluid. I do not know, if in this respect there is a difference between DOT 3 and DOT 4 which is what I use.

[RogerH]

14 minutes ago, Peter Douglas Winn said:

The rubbers were wet with brake fluid. I was looking for Red Grease but Triumph said use plenty of fluid. I do not know, if in this respect there is a difference between DOT 3 and DOT 4 which is what I use.

Hi Peter,

there is a difference between DOT 3 & 4.

DOT 4 now contains Borate.  For what reason I do not know.

They are essentially the same. DOT 4 has a higher operating temperature.

Roger

[Peter Douglas Winn]

Oh good High boiling point, does that mean I can have my foot on the brakes all the way down from the mountain.

I assume that the old braking systems did not generate so much heat. With the more modern cars the braking system is under stress more of the time. I seem to remember that DOT 4 was the standard for cars built after 1989 but I may be completely wrong on that one.

 

[Peter Douglas Winn]

I looked up in the internet and it said DOT 4 has borate which helps to increase the boiling poiunt but ........ the hydroscopic qualities are worse and the fluid should be changed  at least every 2 years. They are interchangeable.

[Mike C]

Changed my DOT 4 last week and let the old fluid settle in a glass jar. A reasonable   amount  of water separated out from the used fluid - leading me to think that the moisture content of old fluid could cause corrosion of the brake cylinder bores as well the loss of braking effect .

I'm also going to chance the clutch fluid as fluid moisture content could corrode the clutch system bores.

 

[Peter Douglas Winn]

I havw a little fluid tester like a fountain pen with LEDs this tells me when I need a change. Very cheap in the internet. 8 quid or so.

[Mike C]

7 hours ago, Peter Douglas Winn said:

I havw a little fluid tester like a fountain pen with LEDs this tells me when I need a change. Very cheap in the internet. 8 quid or so.

They're basically conductivity testers. The problem is the moisture settles in what looks like white clouds at the bottom of the fluid. A conductivity tester might not sense it. In the master cylinder that will be the piston under the reservoir- and hence moisture migrates, down to the cylinders.

I'm wondering what the effect of syphoning and replacing just the fluid in the reservoir on an annual basis would be. This saves bleeding but it is pretty pointless if the water content has drained down into the MC.

[stuart]

10 hours ago, Mike C said:

They're basically conductivity testers. The problem is the moisture settles in what looks like white clouds at the bottom of the fluid. A conductivity tester might not sense it. In the master cylinder that will be the piston under the reservoir- and hence moisture migrates, down to the cylinders.

I'm wondering what the effect of syphoning and replacing just the fluid in the reservoir on an annual basis would be. This saves bleeding but it is pretty pointless if the water content has drained down into the MC.

Water will mostly be in suspension with standard fluid, it separates in SBF.

Stuart.