I have a 6 week old MC Cabrio (Pepper White, sidewalk) and it seems like the speedometer reads high at highway speeds. Last week I was doing 70 in a 60 zone and lots of people were passing me while I was passing no one. It just didn't feel right. It seems like it's reading 4-8 MPH high. But, it could be just me getting used to the MC. Is there any history of this? Can it be tested any way other than getting someone to follow you and check speeds?

 

Mine reads faster than my actual speed, and I've heard countless others comment on the same thing. Mine seems to be about 5-10% faster, which would be about the same as your 4-8 mph on the highway.

 

My speedo says 60, my OBC says 57 or 58. Hmm...

 

I've heard that auto manufacturers routinely skew the speedo on the high side. From their point of view, a speedo that reads too high presents less potential liability than one that reads too low.

 

Uhhh liabilities these days....

If you aren't used to driving in a low car that may contribute to the feeling that you're driving faster. I know that when I drive my SUV I always feel like I'm not going fast at all.

 

I've driven past plenty of those unmanned radars that post your speed. They've always shown the speed to be about 5-10% less than what my speedo or OBC says.

 

10% would be a LOT....

I believe my speedo reads about 4% fast - as confirmed by my GPS - which is pretty darn accurate at cruising speeds.

Variations in tire diameters (even at the same "size", but with different brands) can contribute a bit to this as well.

 

Blimey - thanks for mentioning the GPS. I have a Magellan GPS unit and totally forgot about the page that shows current speed. I'll check it today!

 

When the OBC is saying 60 mph, my gps says it's 58mph.

 

Mine is around 4-5 mph off...question is, can it be adjusted?

 

Mine is off by about 2 mph at 70mph according to my Garmin.......you can adjust the speedo by putting on bigger diameter tires...........

 

are all of you running larger than normal tires? or is the percentage error to high to account for that....

 

Larger tires would mean the speedo was reading slower than actual.

I may have overstated that 5-10% error. Probably closer to a flat 5%

 

My speedometer reads 4mph fast at 70. I have checked it against my gps and by driving side by side with another vehicle. I would imagine it can be corrected by the dealer because different tire sizes affect the speedometer calibration, but I haven't asked them if they can correct it.

 

I put 215's on, but it doesn't seem like that's enough to make a noticeable change.......bigger tires will make a high reading speedo more accurate - the car is travling farther for each revolution of the tire

 

You were all correct ... it wasn't as far off as I thought. I checked it tonight with my Magellan GPS and the speedo was reading 3mph high. And it didn't vary from the 3mph discrepency from 35mph all the way up to 70mph.

 

I remember helping a friend with his hot rod when I was a kid (like 20 years ago). We would go on the interstate with his dad and get the car up to 60 mph on the speedo. We would then use a stop watch to time the distance between mile markers. He would then adjust the speedo manually and try again until he got it just right.

You could try something similar to test for accuracy, but I'm not sure how you would adjust the ecu in a modern car.

 

"....lots were passing me......" I've noticed the same thing, like there is some sort of pleasure gained by passing a MINI. Seems folks will go out of their way to get in front of a MINI...strange.

As far as the speedo being off 3 - 4 mph at 65, so what, how important is it to drive exactly as fast as the speedo says in todays world. Running with the traffic and not going 10 mph over seems to be the norm any more.

 

rc'S - I think you missed my point. I wasn't trying to travel 10 miles over the limit ... it was that I had to run at 70mph on the speedo (in a 60 mph zone)just to keep up with traffic ... and that seemed faster-than-normal to me. I was interested in finding out what the accurate reading really was.

 

No offense here, at first I thought my speedometer was way, way off with all the cars passing me. I had a friend follow me on a short trip and he had a hard time keeping up with me and I was only running about an indicated 7mph over. Cars were still passing me like crazy and my friend was complaining about me driving to fast. I think my Sub speedo is off about 3 - 4 mph at 60 also, but very few pass me at 7 mph over. I really think people just like passing MINI Coopers for some reason. Sometimes it feels like "pick on the little guy!"

 

Not necessarily. We have a Chevy Trailblazer and Chevy Malibu and both of them read 2-3mph below your actual speed. I first noticed it with the GPS and have confirmed it with a couple of roadside radar displays.

My MINI consistantly reads 2mph above actual speed.

 

My speedo is dead accurate. And I have the photo ticket to prove it.

 

Mine seems accurate... now I am wondering..

 

2 - 3 mph off, according to Mr. Garmin. My wife's Element is involved in a class action suit against Honda for bad speedo/odo readings making the warranty expire sooner than the real miles. (Insert lawyer joke/diatribe here)

 

The speed isn't the part that bothers me it's the odometer.

I can put my GPS on the dash, and drive the 35 miles my car tells me it is to get to work, whereas the GPS shows the same distance as 32. If that is correct, I was out of warranty about 4300 miles too quick.