Had myself clocked a couple of times and speedometer seems to be off 3mph. Eg when indicating 80 actual speed is only 77.

Anyone else seen this? Spoke with service tech and he wasnt even sure on how to adjust but was going to check with mechanic. Any thoughts?

 

what size wheels are on it? 20?

 

Yep, running stock 20's all around on the GTS.

 

Honestly, I thought every car on the road does that... read fast...

 

I thought some cars if they were originally built with specific tire/rim size if you go bigger then your supposed to have the speedometer calibrate to it.

Just like folks who go from 16" to 18" or bigger need to have it calibrated as the bigger wheel can throw off the speedometer by 1-2 MPH.

Not saying porsche hasn't done that but figured that would have been designed or programed for vehicles that come with 20's or 21"s stock compared to the 19"s

 

You might want to check if your odometer is accurate -- a lot of cars' speedometers provide an optimistic speed reading, while their odometers are spot-on. Probably done for liability purposes (i.e. so folks won't blame the manufacturer for their speeding ticket). Easy to check the odometer using gps or road signs. On my '86 911, my speedo's over 5mph optimistic but my odometer is accurate.

 

Make sure that you have a correct wheel and pressure configuration on the PCM. Manual explains what you ahve to do when you change the wheels. Did you buy the car brand new? with those wheels? If yes, then it must me a bug. Take it to the dealer.

 

My 991 is consistently 2mph optimistic. I think it's Porsche's approach. We can all speculate as to the reason....

 

First owner as car was custom built and have the stock turbo II rims and wheels. Off to dealer for state inspection tomorrow, will be interested in what they have to say about speedometer.

On another note I havent found that the new car delivery inspection was worth much. Car was so out of alignment that went about a mile down the road till I turned around and went back to the dealer. Of course they thought I was crazy till the service mgr got in the car and drove. Wicked pull to the left, took 2 more trips and alignment trys to get it right, been perfect now for over 12.000 miles. Seems like Porsche needs to put a little more effort on new car deliveries straight off the boat. Not to mention the halos I needed to polish out.

What has been others experience?

 

my 2014 PTT speedometer is 2mph fast at any speed. The easiest way to check is download a gps app on your phone and look at the speed on your phone vs the speedometer - thanks to Bill Clinton GPS is now pinpoint accurate for us and our enemies and no longer has the built in variance.

 

Agree, thats how I determined my GTS was off too... Waze is a great app. Did you find a way to recalibrate so the speedometer reads correctly?

 

My dealer says there is no way to calibrate the speedo. Let me know if that is incorrect.

 

My experience with multiple cars and brands (2 recent Porsches) with stock wheels and tires... it is the norm that the speedo is a few MPH higher compared to GPS and speed radar signs.

 

German cars tend to read high. It's because of European regulations that say the reading must never be lower or 10% greater than the actual speed. To compensate for owners potentially fiddling with the tires, the readings tend to be on the high side. U.S. and Japan have slightly different regulations based on a percentage error. Car & Driver had an article about this several years back. Here's the link:
http://www.caranddriver.com/features...ometer-scandal

 

since an optimistic odometer would indicate more miles than you've actually driven, key to me is confirming that your odometer is accurately tracking your mileage despite your optimistic speedometer