Cocky Posted August 29, 2017 Report Share Posted August 29, 2017 I've noticed that if I drive past a road speed board telling me my speed in my Caddy me going 30 on the line it says 30. 40 on the line is 39. In the TT 30 is 30. 40 is 39. In the Boxster 30 on the clock is 27 on the board, 40 on the clock is 37. 30 on the line is 28, 40 is 37. I can live with that but just wondered if anyone else had noticed this? Link to comment Share on other sites More sharing options...
That986 Posted August 29, 2017 Report Share Posted August 29, 2017 Yup, I noticed it as soon as i started using the TomTom. Same results as you have there. For the short time i had the slightly bigger 235/40 and 265/40 tyres on when i got my current wheels the speedo was spot on though. Tbh it was the same in my last VAG car and others i've driven, they seem to be that way. I don't mind as i know if the speed limit says 50, there's cameras and my speedo says 50 I know i'm fine. Link to comment Share on other sites More sharing options...
edc Posted August 29, 2017 Report Share Posted August 29, 2017 It's quite normal for the speedo to slightly over read on the standard wheel/tyre combos for all cars. Link to comment Share on other sites More sharing options...
Terryg Posted August 29, 2017 Report Share Posted August 29, 2017 Mines the same Luke, exactly 3mph over Link to comment Share on other sites More sharing options...
myfirstboxster Posted August 29, 2017 Report Share Posted August 29, 2017 no bad thing to be slightly under the limit , better than over ? Link to comment Share on other sites More sharing options...
That986 Posted August 29, 2017 Report Share Posted August 29, 2017 21 minutes ago, myfirstboxster said: no bad thing to be slightly under the limit , better than over ? Totally agree, gives you some margin for error. Link to comment Share on other sites More sharing options...
AMacdonald Posted August 29, 2017 Report Share Posted August 29, 2017 All my cars report a few % higher than real. I know, traditionally, speedos only had to be accurate to +/- 10% and I always thought they read slightly high to give you a little buffer from speeding. Do the latest cars use GPS rather than mechanical means? Link to comment Share on other sites More sharing options...
Cocky Posted August 29, 2017 Author Report Share Posted August 29, 2017 1 hour ago, myfirstboxster said: no bad thing to be slightly under the limit , better than over ? Agreed, I was more thinking is it just mine or common. Link to comment Share on other sites More sharing options...
Terryg Posted August 29, 2017 Report Share Posted August 29, 2017 I must admit I thought that the Boxster speedo was more inaccurate than any other car I have owned recently and I think it probably is a bit. On the other hand the car is also faster than any other car I have owned which also accounts for that feeling to some degree. Link to comment Share on other sites More sharing options...
Boxob Posted August 29, 2017 Report Share Posted August 29, 2017 I discovered early on that the spoiler rises at 75mph (on the clock) which so happens to be 70mph on my TomTom. No need to exceed to speed limit to display your tail feathers ? Link to comment Share on other sites More sharing options...
rowbos Posted August 29, 2017 Report Share Posted August 29, 2017 Just now, Boxob said: I discovered early on that the spoiler rises at 75mph (on the clock) which so happens to be 70mph on my TomTom. No need to exceed to speed limit to display your tail feathers ? I've never seen my spoiler rise - I can only assume it does - I have tried to shuffle myself as high as I can in the car but no joy! Maybe I should stick something to it - like a sink plunger perhaps so I get to see it go up ? (Picture that)... ? Link to comment Share on other sites More sharing options...
Boxob Posted August 29, 2017 Report Share Posted August 29, 2017 3 minutes ago, rowbos said: I've never seen my spoiler rise - I can only assume it does - I have tried to shuffle myself as high as I can in the car but no joy! Maybe I should stick something to it - like a sink plunger perhaps so I get to see it go up ? (Picture that)... ? Job for a passenger or follower but I have heard of people taping tell-tail sticks to the spoiler. Link to comment Share on other sites More sharing options...
Anker BS Posted August 29, 2017 Report Share Posted August 29, 2017 Mine reads 2 - 3 MPH too high. Asked someone to check the spoiler at a track day when I ran down the straight. It came up! Link to comment Share on other sites More sharing options...
pquadro Posted September 3, 2017 Report Share Posted September 3, 2017 On 29/08/2017 at 7:35 PM, rowbos said: I've never seen my spoiler rise - I can only assume it does - I have tried to shuffle myself as high as I can in the car but no joy! Maybe I should stick something to it - like a sink plunger perhaps so I get to see it go up ? (Picture that)... ? Found this on 986forum - copypasta "You can get a stock look switch that you can install into the stock dash that can raise and lower the spoiler. It also has a light that indicates when the spoiler is in motion (it flashes if you use the switch or when it is triggered to raise/lower automatically). When it is fully raised the light stays illuminated. Really neat and relatively simple to fit.The guys ebay member id is stefan118hydraulik he is in Germany. I know he ships to UK as I bought one and am pretty sure he ships to US too." Link to comment Share on other sites More sharing options...
Rev Ken Posted September 7, 2017 Report Share Posted September 7, 2017 Speedos legally must not under read, but can over read by a few %, I think a max of 10%. I guess there are two reasons. If travelling faster than a speed limit, but my speedo shows a lower speed, then I could sue the manufacturer if stopped and fined. The second reason is that manufacturers want to impress us with the speed their cars can reach compared with their competitors! My 986 speedo is more (surprisingly) accurate than any of my other vehicles. For instance my Golf shows 32 for a true 30mph and 64 at 60. My BMW F800GT over reads by about the same amount. Link to comment Share on other sites More sharing options...
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