Sorry if someone has already posted this before...

Is your speedometer off a bit? Mine is.

From what I can tell, my speedometer is showing about 6mph faster than the car is actually traveling. It might not actually be 6mph and may be a certain % off.

I am 99% certain of this as I have noticed my speed on a stationary "Watch Your Speed" radar sign (multiple times on different ones) and even had a friend pace with me and compare his speedo to mine.

* My car is currently 100% stock -- i.e. stock tires.

-John

 

Yep I think my mini is 6 mph over the speedo too. I have checked it against other cars and the speed "checking" stations you mentioned. I don't 100% trust those stations but it is uncanny how I am always going 6 miles over what they pick up. It's definitely over a percentage of your speed, for example if I am going 30, the speedo registers 33, so I think it is around a 10% increase. This topic has been covered before and I just live with it. Apparently most cars out there have the same problem (not just minis).

LG

 

According to my TomTom, my speedo shows about 3mph high at around 60mph. Maybe MINI should have put 215/45-17s on their 17" wheels instead of 205...

 

Makes sense, thank you!

 

Mine runs 3 over at 60 mph as well on 17" 215/45 17 tires

 

You can check with either a GPS or by setting cruise control to 60 on a straight strech of highway with the mile markers... it should take 60 sec. to cover that distance (60 Mi / hr * 1hr/3600 sec = 1 mi / 60 sec.)

While your at it you can check to see if your odo is correct as well.

BTW,
205/45-17s have a rolling dia of 24.26
205/45-17s have a rolling dia of 24.72

That's a difference of 1.9%
So travelling at 60mph, your speedo will show 59mph.

BTW, my stock '06 MCS is dead-on.

 

My 2003 Cooper was off by 5 to 6 miles but the 2007 Cooper seems to be right on the nose

 

Mine varies from about 2-5 MPH over, dependent on my speed. Definitely a percentage rather than reading a static amount over all the time; I just haven't taken the time to calculate it out. For example, it reads 32 mph when I'm doing 30, 63 when I'm doing 60, and 110 then I'm doing 105 (on the autobahn of course; haven't gone any faster than that ).

 

Jakay,

Am I missing something? you're comparing the same tire/wheel configuration? Do you have any numbers for 215/35/18'S? I too noticed that the speedo is faster than my Garmin GPS. I didn' t calculate the difference, but the speedo is definitely 3-4 mph faster.

Am I correct in assuming that the larger the diameter, the faster the car displays, but actual engine "mileage" is less? This would be due to the same number of RPM, but you cover more ground with a bigger wheel/tire diameter?

 

My speedometer is a bit off... to the right of where the speedo is in my truck

 

*pu-dum, ching!*

 

I think there have been other threads on this with the thought that BMW sets your speedo a few miles higher than your actual speed. My BMW 1100S is approximately 3 miles over my actual speed. I've heard from other BMW owners that their Speedo's on their cars is also over the actual speed. (urban myth? fact? got me).

 

How does the speedometer get it's speed in this vehicle? I know it's done different ways by different vehicles.

If it is the old fashioned way do they change anything in the computer from the factory for different wheel sizes? This is the only vehicle I know of that you can get from 15" to 18"s from the factory. We're talking about potential for a huge speedometer disruption. Also say I change my 16"s to 18"s is there any way I can correct the thing?

Anyone have the facts on it?

 

Actually, if you go with larger-diameter tires, the car will be traveling *faster* than the speedometer displays (the speedometer will read low, not high).

With stock tires, the speedometer generally reads a little bit low, while the odometer is usually close to spot-on. With larger-diameter tires, the speedometer will read even lower for a given road speed, and the odometer will read a little bit low as well.

 

There are a wide variety of stock wheel diameters for the MINI, but the overall tire diameter doesn't change much between the various choices. Here are the four stock MINI tire sizes, and approximate diameters for each:

175/65-15 (24.0 inches)
195/55-16 (24.4 inches)
205/45-17 (24.3 inches)
205/40-18 (24.5 inches)

So, even the tallest stock tires are only about 2% taller than the shortest stock tires. I doubt the factory adjusts the speedometer/odometer based on the tire size that comes with the car, but I could be wrong.

The dealer can re-calibrate the speedometer, but don't expect them to do it unless your speedometer is "out-of-spec". The specifications from MINI say that the speedometer is not allowed to read too low, even by 1 MPH, but it's allowed to read too high by 10% of the actual vehicle speed, plus another 2 MPH. So, if your actual speed is 70 MPH, any speedometer reading from 70MPH to 79MPH is "within spec".

 

Thanks Scott. I should have figured on the mm of the sidewalls.

 

mine is 4 mph over according to my gps

 

205-50/16s Kuhmos, and I am reading 2 mph over actual speed according to my hand held Garmin GPS.

 

My dads is 3-4mph off from my GPS speedo... that is going anywhere from 40mph to 70mph


edit: his speedo reads faster than the GPS...

 

The Dunlap SP Sport 01 DSST 205/45-17 runflats that came with my MCS (Sports Package) had (according to Tire Rack) an O.D. of 24.5. However, (also according to Tire Rack numbers) some tire brand/models have different revolutions per mile than other brand/model tires of the same size. So, if you compound the variation in O.D. with the variation in RP-Miles you could get 3 or 4%, or they may cancel each other out.

There was another thread on this subject that was quite long. John might find it interesting.

I haven't figured out where mine is with my different wheel sets. I've got some 17" Michelins with an O.D. of 24.3 and an RP-Miles of 856. Then there are the Pirelli 205/55-16 with an O.D. 24.9 and 836 RPM.