Type 3 and 4 front caliper rebuild "how-to" part 1 and 2

[Pepperbilly]

Ray,

Date of manufacture was 9/72.

Bill

[raygreenwood]

Yep....it was highly possible at that early of a build date in the 1973 model year that the original calipers still had pins in them and they were removed when one or more broke off while servicing the calipers somewhere in their life. Its most probable that the newer "hollow" piston...is the odd man out that replaced one of the other pistons.

Typically when you see the solid piston with the dimple in the middle of the piston on the outer face like three of yours are....those are the same piston casting as the ones that had the little clutch mechanism in them for the pins.

They were used for a little while in the transition period...with or without clutch/gripper installed....in some of the newer calipers without pins installed.....because the newer rotors did not have the flexing issue so the pins were not needed.

The later pistons....are the same length, diameter etc....but had a hollow center.

Also....the pistons from early calipers...up to August of 1972...which is also the late type 3 caliper.....used the same piston diameter.....but typically the rim on the piston where the outer boot fits used a different boot. All of those had pins.

So what marks your pistons as "oddly transitional"....is that they have the little clutch mechanism in the back of the piston for the pin....and this is why they have teh dimple on the outside....but...they are machined with the outer edge to take the late caliper boot. This is why the rim of all four of your pistons matches and fits the same outer boot.

So I would say you have calipers made in this odd transitional period of time.

Ray

S

[Pepperbilly]

Ray,

It almost makes we want to set these aside as a museum piece and just buy a new set of calipers. I don't care for things that are mixed and matched like that. Apparently some where in this 412's young life, ( before it came into our family ) the calipers were worked on. Did not ever know this. The other discovery I made a couple of weeks ago, the rear hatch had been replaced due to a hi hit rear ender. The hatch lift door is Texas Yellow! They did a good job of respraying with Maya Gold. I was polishing the paint and the yellow revealed itself. Now I am sure the VW dealer did this because we bought it from them. Avalon Auto Sales it was known had an iffy reputation... but as a kid I loved going there and and looking at all the new 60's and 70's coming in. Ah...the memories!

Bill

[raygreenwood]

[Pepperbilly]

Ray,

So are you saying I can get pistons? I really would like to replace all 4 so they all match. If they are available I have no problem going that route.

Bill

[raygreenwood]

[Pepperbilly]

Thanks Ray!

Bill

[Tvättbjörn]

Are the piston identical between early type3 (1969 ) and late models like 73 ? Rockauto does list two different part numbers. I was thinking they were the same. Am i wrong?

[raygreenwood]

[Tvättbjörn]

[KTPhil]

[raygreenwood]

[KTPhil]

My car doesn't help matters... it's an early '71 but has the later front axle, including the later disc brake setup, following an accident some 30 years ago!

[batoni]

mr Ray,I just got an email from rockauto today that they have Raybestos cylinder for my late type 3.
I know you suggested Centric,but it is still out of stock.
Any toughts about Raybestos as an solution?
Thanks in advance

[raygreenwood]

[batoni]

thank you mr Ray,you are,as always,so kind

[Porschedave]

Hi Ray

Can you tell me if the between-caliper halves o-rings are the same size for the both the early and later calipers?

Thank you.

Dave
_________________
1977 911S
1958 Karmann Ghia build thread here: http://www.thesamba.com/vw/forum/viewtopic.php?t=571683
1965 Sunroof Notch build thread here: http://www.thesamba.com/vw/forum/viewtopic.php?p=5600139&highlight=#5600139

[raygreenwood]