Brake pistons

[drcoastline]

Hey brain trust.

Are these any good? Slight rust at the top of the piston. It seems to be in the same location on both. This is on the chrome.

[TJJSC]

hi, if these are from an SC also the locking groove for the dust seals have rusted away. (there should be a little collar to hold the seal) I would replace these.

[Ian Comerford]

I agree, replace them

Ian

[kyngfish]

I'll go ahead and disagree with my pelican brethren here. I just rebuilt both front calipers on mine, and mine were actually slightly worse - I had 1 or 2 that had rust slightly farther down on the chrome.

A neighbor that does a lot with his cars recommended I reuse the pistons after giving them a light polish with emery cloth (For the record, one of the MOST knowledgable people on this forum DRACO recommended I not do this - and normally I'm 100% in the DRACO advice camp, but this neighbor owns a few car shops and does all the work on his own classics - so I took a chance).

The caliper seal hits the piston about a quarter inch below the edge - and the rust you have is because moisture and debris got into your boot. The edges of pistons are frequently quite rusty and the boot stands up to them pretty well, so I figure I'm OK.

I polished mine with emery cloth and some brake fluid, cleaned them, put in new seals and put the calipers back on. The first 50 miles or so, the pedal had to travel a bit further than normal, but I think that was the pistons retracting too far into the cylinder with a new seal. After they settled in, I don't have a hint of squish in my brakes. But who knows, I'll tell you in 20k miles.

Each piston from Pelican is like 50 bucks. 4 pistons and you're only 100 dollars off the price of a set of rebuilt calipers.

I polished my pistons and replaced the seals for all of 40 bucks - and if they break again I'll do it again. All that said - DRACO made a recent post on here about a place that would send you pistons from the UK at a very competitive price, if you don't mind waiting - I didn't want to, I hate seeing my baby be a lawn ornament.

Cheers!

Here's a picture of one of my pistons:

[James Brown]

not worth the fuss, replace. And how does the calipers look?

[drcoastline]

Hi Guys,

Thank you to all for the posts. These are out of a 74S. These are the front driver side pistons. They came out relatively easy. One of the pistons on the passenger side is stuck so I am soaking it in Marvel Mystery oil. Hope fully I can get it out tomorrow. I think the driver side caliper is OK. I popped the pistons out with my grease gun so still cleaning all the grease out. I will hopefully know better about these tomorrow also.

kingfish- Nice write up. In ninety percent of the cases I would tend to agree with you and try to reuse if it's worth it. That's why I asked if they are any good. But in certain instances I don't like to take chances, my brakes are one of those cases. Electrical work in my house is another. I don't know about you but my life and that of my family is worth much more than $80.00, and I would never be able to live with myself if they failed and I hit and hurt someone.

[gduke2010]

I recently had one stick of my Ford F-150 and drove it home. Shouldn't have done it . It wasn't a pretty sight. Cheaper and better off to throw them out and start with new.

[DanielDudley]

I use brake assembly grease, and it usually winds up above the rubber ring and below the outer seal. I find it aids assembly, and acts to keep moisture out of the gap between the piston and the caliper. I also smear a thin coating on the outer seal, inside and out, to prevent deterioration.

If you emery those, and use rubber grease, they will hold up fine in a car that doesn't get driven in the rain or snow much. They are borderline, so it is up to you if you use them. I had a lot of problems with Fiat calipers back in the old days because the calipers were aluminum, and I lived in the salty NE. Using the right kind of grease during assembly solved those problems.


A little common sense and care can often accomplish what rigid thinking cannot. There is no pitting on those pistons where they would touch the compression seal, so that is a major determining factor. Of course, it would be hard to justify using those on a customer car, but I'm guessing you could get another 20 years out of them.


As always, Your Mileage May Vary.

[kyngfish]

Originally Posted by drcoastline

kingfish- Nice write up. In ninety percent of the cases I would tend to agree with you and try to reuse if it's worth it. That's why I asked if they are any good. But in certain instances I don't like to take chances, my brakes are one of those cases. Electrical work in my house is another. I don't know about you but my life and that of my family is worth much more than $80.00, and I would never be able to live with myself if they failed and I hit and hurt someone.

Lol. 4 pistons are closer to 200, plus 40 for the seal kit. Just get the rebuilt calipers and save yourself the hassle.

You should do what feels safest. But uh, I think you're overestimating the impacts of a slightly corroded piston above the seal line. I care about my family just as much as you do. Was just adding my 2 cents so you could see all available options.

[drcoastline]

Originally Posted by kyngfish

Lol. 4 pistons are closer to 200, plus 40 for the seal kit. Just get the rebuilt calipers and save yourself the hassle.

You should do what feels safest. But uh, I think you're overestimating the impacts of a slightly corroded piston above the seal line. I care about my family just as much as you do. Was just adding my 2 cents so you could see all available options.

Hey kingfish, First let me apologize if I offended you. That was not my intention. I very much appreciate your .02 and in fact I think it was more like .99. Great write up. My point was only that I am not trying to save $80 or even $200.00. It is purely about safe operation.

I am not over estimating anything. I don't know, that is why I posted the photos and asked the question. If they are safe and are reusable great if they are questionable they become paperweights. Daniel Dudley seems to be agreeing with you that they aren't that bad and can be reused. So I will see what a few others have to say.

Again, my apologies.

[RichardNew]

It's time for replacement.

I think rebuilt calipers may be the way to go. I've seen factory rebuilt for $200 and that seems very reasonable to me. Plus I like Plug and Play parts.



btw - If you change your brake fluid every 24 months you'll avoid a lot of braking issues.

Richard Newton
How Hot Do Your Brakes Get?

[drcoastline]

So here are the pistons out of the passenger front. The one to the right was the one that was frozen. These photos are after I cleaned them up.




And how about this cylinder? Is that left edge ok?

[drcoastline]

Originally Posted by RichardNew

It's time for replacement.

I think rebuilt calipers may be the way to go. I've seen factory rebuilt for $200 and that seems very reasonable to me. Plus I like Plug and Play parts.



btw - If you change your brake fluid every 24 months you'll avoid a lot of braking issues.

Richard Newton
How Hot Do Your Brakes Get?

Thanks for the post Richard.

[drcoastline]

I think my question has been answered on the driver side. Time to replace the whole shebang?

[chris_seven]

Are pistons pictured above are for the Aluminium 911S Caliper as they have both the 'flange' for the dust boot and the rear location for the anti-retraction bush. these pistons are around 35mm long.

The normal M Type Cast Iron Caliper with this feature uses a 30mm long piston and tends to have a 3" mounting centre.

There is something unusual about the photographs posted.


The first photograph seems to show a caliper piston that would work with an Anti-Retraction pin on the caliper.

The second and third photographs show a photographs appear to show SC pistons and don't have the anti-retraction feature.

The photograph of the caliper shows the anti-retraction pin and is cast iron. can you measure the mounting centres?

Are the calipers mismatched? and may be the struts have different caliper mounting centres?

[drcoastline]

Hi Chris,

Thank you for your reply. The car is a 74 S Targa. It is my understanding I should have the 911S caliper. That being said. This car was hit in the driver front prior to my ownership. So it is quite possible the strut assembly was replaced and a different caliper installed at that time. This would have been some time between 1974 and 1983. I actually posted sometime ago about the mis-matched brakes.

So the caliper in the photo and the first set of pistons go together. They have the anti- retraction mechanism.

The second set of pistons goes to the passenger side of the car. I did not post the caliper as it is still soaking in cleaner to get all the grease out. This caliper appears to be in good shape and does not have the anti-retraction mechanism.

I will take measurements.

Thank you.

[drcoastline]

Drivers side




Passenger side



Tanks again for the help everyone.

[Cook&Dunning]

Hello Dr - I had a similar situation on my car - I felt like my calipers would need to be fully rebuilt and the caliper pistons replaced. I did not want to tackle it myself as a diy project - I looked at rebuild service, but by the time I factored in shipping, new pistons - it was virtually the same price to buy new Porsche Classic calipers. Just another option for you to consider. (edit: These were for my 89 - not sure of pricing on your setup)

[chris_seven]

If you take the pins out of the one caliper, which is an early M Type you will be able to use the SC Type piston in both calipers and the braking will be quite even.


Budweg Pistons with this design are available here in the UK at around $20 each.

Brake Parts | BrakeParts.co.uk

We make our own but in a Grade 5 Titanium

[RichardNew]

I'm always amazed at how an "original" car can have so many "non-original" parts. I've been there on more than one occasion.

Richard Newton