The X on caliper; Group 6/98/00

[blue72s]

According to the workshop manual, the X mark on the light-alloy S caliper was introduced in 1970 and these calipers have greater piston clearance (tolerances I think), so I'm wondering whether the bore in the X caliper body is slightly larger or the piston itself is slightly smaller in diameter?

Second paragraph in the appendix - I think there's a typo because there were some '69 and '70 calipers with the circle indents but without the X stamp, so I think that's what it was referring to, do you agree?



The photo below shows the new groove at the top of the piston. Why did Porsche/ATE make that modification? What was the reason?




Lastly, when looking for caliper seals and gaskets on the PET, it asks you to see Group 6/98/00, but where do I find it?

Thanks.

[davep]

The replacement parts are in the repair section. So Group 6 is the brake system, and the repair section is always at the end. Repair parts will generally have a 98 code, so part # would be 901 698 xxx xx

It would appear that the piston diameter may have decreased a few hundredths of a mm on the X (grooved) pistons.

[Jerry L]

Call Eric at PMB, I am sure he can answer the question as well as send you the correct seal kit.

Regards

[blue72s]

The replacement parts are in the repair section. So Group 6 is the brake system, and the repair section is always at the end. Repair parts will generally have a 98 code, so part # would be 901 698 xxx xx

I've just taken a look at my factory workshop manual (service), Volume V, from model on 72, Group 6, but there's no mention about the seals or part numbers or am I missing something? I can't find the repair section.

Is the repair manual different to the service manual?

Call Eric at PMB, I am sure he can answer the question as well as send you the correct seal kit.

Thanks but I just want to fully understand the differences between the early and late S calipers.

[davep]

The repair parts are in the Parts Manual; how to repair things is in the Service Manual. Just download the parts manual for your car; you need to use the two together.

[blue72s]

Just download the parts manual

This is what I was trying to talk about..

[davep]

On the left side you have Main Group 6, and below that is 601-00 602-00 602-00 604-00 then 698-00

[blue72s]

OK got it. Thanks.

So, the seals for the newer piston (X marked caliper) have the same part number as the earlier version, even though the pistons themselves are not interchangeable? Strange.

Doesn't anybody know what was the groove at the top of the newer piston for?

[davep]

There was absolutely no need to change the seals. The groove was only there to identify the piston as the new type.