7 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
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YOUR RESEARCHOdometer/Speedometer off - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Reported or suspected cause
same
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
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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.
Discussions that report identifying a cause
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.
Odometer/Speedometer off - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Leading evidence: 'same' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'same' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check against a gps, not highway mileage markers' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
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.
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
'99-986 Noticed while on a long trip that the odometer and speedometer are off -consistently high by 7% or so when checked against interstate mileage markers.
Odometer/Speedometer off - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Check against a gps, not highway mileage markers
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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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.
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.
Odometer/Speedometer off - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Check against interstate mileage markers
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
'99-986 Noticed while on a long trip that the odometer and speedometer are off -consistently high by 7% or so when checked against interstate mileage markers.
Odometer/Speedometer off - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Coverage and how to read this overview
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.
7 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: 20261026T083035Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
'99-986 Noticed while on a long trip that the odometer and speedometer are off -consistently high by 7% or so when checked against interstate mileage markers. Any ideas? New tires added - same size as old ones.
That was the first clue. Speed on the GPS was about 7% lower than speedometer. Checked against mile markers over a 50 mile stretch of interstate and got about the same answer.
Don't remember tire size off the top of my head and car is in shop for maintenance and to look at the issue.
This is entirely 'normal'. Buddy had a 99 996, and it was the same. My 2001 is the same. Heck, my motorcycle is the same.
I believe it probably has something to do with the calibration erring on the side of caution. You are less likely to get speeding citations if you're actually going slower than you think you are.
It also limits liability of the manufacturer. Can you imagine if your speedo indicated SLOWER than you were going? By 5-10mph at highway speeds? That's the difference between a speeding ticket or not.
Anyway. That's the way it is. There's nothing 'wrong' with your car.
I love my Boxster, but I personally find this characteristic the most annoying thing about the car. I hate merging onto the highway doing what I think is a couple of mph over the speed limit and the next you know I am getting passed by Chevy Vegas and Ford Pintos like I am standing still. I have even had teeny boppers yell at me. "Won't that thing go any faster!" It's embarrassing. :ah:
Porsche calls it a safety factor and it (speedo) averages 5mph over actual speed.
But the odo and the speedo get their info from different sources and the odo is usually spot on. You may have other issues, as stated, tire size or such.
