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Brake Caliper Piston Question - 986 Forum - The Community for Porsche Boxster & Cayman Owners

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YOUR RESEARCHBrake Caliper Piston Question - 986 Forum - The Community for Porsche Boxster & Cayman Owners

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Install on the car)

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Performed · outcome unconfirmed · Original poster

They are 36mm diameter, but I need a measurement off the piston (and of course I put the calipers back together and installed on the car).

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Brake Caliper Piston Question - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Leading evidence: 'Install on the car)' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Install on the car)' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.

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Replace corroded pistons

Suggestion or failed attempt

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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

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Suggestion · Original poster

I cleaned them off, but now it's bugging me, so I'm going to replace the corroded pistons.

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Brake Caliper Piston Question - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Frequently discussed actions (2)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Install on the car)

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that performed work without a confirmed outcome
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster

They are 36mm diameter, but I need a measurement off the piston (and of course I put the calipers back together and installed on the car).

Original post Read captured discussion
Brake Caliper Piston Question - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Replace corroded pistons

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster

I cleaned them off, but now it's bugging me, so I'm going to replace the corroded pistons.

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Brake Caliper Piston Question - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.

4 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

  • 986Forum: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261026T105141Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

I'm hoping someone has a loose piston and can take a measurement for me. I rebuild my front calipers on my 09 Cayman S, and found some corrosion on a few of the pistons. I cleaned them off, but now it's bugging me, so I'm going to replace the corroded pistons. They are 36mm diameter, but I need a measurement off the piston (and of course I put the calipers back together and installed on the car). I'm looking for the measurement from the bottom of the piston to the start of the narrowing where the dust boot fits. The piston is 30mm tall..... Thanks for any help (worst case I pull the calipers off and apart again.....) -Eric 99 986 09 CS

POST 2Original post

No specific help here but make sure you order from a reputable source. The tolerance in seals is very very tight. I’d give Giro disc a call they likely have the answers you need and the parts available.

POST 3Original post

Quotes source post: 650507

What he said. I tried to rebuild calipers once with aftermarket parts bought from a brake specialist company that begins with a ‘Z’. I struggled with the pistons and seals. Long story short… ended up going with OEM parts and the reassembly was a breeze after that.

POST 4 / ORIGINAL POSTEROriginal post

Thanks. I found the part number for the pistons as used in the 993 era cars, and bought those..... still have to put them in, but they look right..... Strange how they won't list a part for the 986, but it's the same part...... -Eric

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