So my GPS has a speedometer built into it. There was a discrepancy of about 4 miles per hour. When the GPS said I was doing 70, the speedo was at about the 74 mark. when the speedo was at 70, the gps reedout was 66. Also, in a 100 mile drive on the gps, the odometer on the car read 99.1

so, cant figure out what all this means, do i believe the speedo/odo of the car or the gps? and what does this mean to the overall odometer reading as well as MPG.

I am running my winter tires 175/65 /15 vs my usual 195/55/16

 

MINI speedo reads a little high

discussed in many many threads

the GPS is right

(it is said that BMW's read high as well and that this is a conscious action of BMW .... you think you are going faster then you are and hopefully get fewer tickets... I'm not sure I buy that logic, but . . .)

 

Your 15s are about .4" smaller in diameter than your 16s, so the 15s will "over-read" mph on the speedo and miles traveled on the odo more than the 16s, which might also over-read a bit. From what I've read posted here, apparently most stock size wheels/tires over-read a bit compared to GPS measures. Most apparently believe that the GPS measures are more accurate than the speedo reports.

 

What you're seeing is normal. MINIs are programmed in accordance with the European laws on speedometer accuracy. By law, they're allowed to read as much as 10% high, PLUS an additional 2.4 MPH. But, they're not allowed to read even 1 MPH too low.

This is also why it's very hard to get the dealer to reprogram the speedometer to make it more accurate. As far as they're concerned, if the car is actually traveling 70 MPH, any speedometer reading from 70 MPH up to 79.4 MPH is still "within spec."

The odometer is usually just about spot-on, though. In your case, the odometer was within 1%, even though the speedometer was off by about 6%. And 1% is pretty good - variance in tire diameters between sizes/brands or even variances in tread wear can account for that much error.

 

This is the norm with pretty much all vehicles.
As mentioned earlier, it's the law in some areas and in America it's a liability issue (Darn Lawyers)
Think of it this way.

Sceneiro 1:
You crash. Speedo said 70. Actual speed 66. Blame self for driving too fast.

Sceneiro 2:
You crash. Speedo said 70. Actual speed 74. Blame MINI for accident. Get Lawyer and sue big time, and win.

The manufacturers can't risk Sceniero 2 so they build in some cushion to make sure #2 never happens.

 

So glad to see this reply. I have seen this with my speedo and gps also and noticed that in my american car it is almost exact. I like the idea of fooling me into thinking I'm going faster...lol

 

All above info is correct. MINI speedo reads high. I have verified with gps and scanguage II. Always believe the gps speed.

 

Seems like most Mini speedos read about 5% high. Mine is 4.5% high.

 

Dang! glad I have found this thread. I was blaming the worn tires!

 

While the speedo will be off, the ODO will be as close to accurate as possible, some people once claimed it was for MINI to get out of warranty claims sooner...not the case entirely.

 

Agree. Speedo reads high, ODO reads very accurate. I have checked the ODO using both GPS and interstate highway mile markers. Also have found the MPG displayed by the MINI to be slightly optimistic.

 

wheels----------speedo----------gps
15".................... 70 ..................65
16" ....................70 ..................66
17" ....................70 ..................67

 

Why does the odo read accurately while the speedo reads high? The two must not be reading from the same input data (wheel rotations?) for their respective computations.

 

I had the same thing happen to me on my 2006 Suzuki Forenza car. I kept noticing that everyone was passing me by when I was doing 70 mph (doing 66 by GPS later). Thinking that everyone was speeding on highway, I pulled up beside 18 wheelers and ask what speed they were doing and found out that my speedometer was reading fast. Complained to dealer about problem and even called US headquarters to discuss problem. Suzuki replaced my speedometer with a new head and speedometer read right on. It even matched reading with my GPS, so I was reading accurate MPH from then on. I sold the Suzuki and purchased my 2006 MCS in June. My 2008 Dodge van reads right on with the GPS.

 

It is not just a simple counter and cable anymore. The digital input is calculated to overestimate the speed read on the digital and analog speedo needle. The ODO calculation and history of all service and CBS stuff is correct to the true distance traveled.

 

Thanks. I'm still being dragged into the 21st century; where data are rigged to display inaccurate information to drivers; but at least distance traveled is accurate now (with OE tire sizes anyway), and we can always check speed with a GPS or roadside radar stations.