2007 R56 MCSa question.

Ok, I know this is probably buried in the posts somewhere. In my quick search and look, I did not find a verification or explanation.

Some may remember I did a winter swap to 16x7 et40 wheels with 205/50/16 Falken 912s.

I'm in the middle of a long road trip and has the chance to check my speedo accuracy with my GPS on multiple long flat stretches of highway, think I70, I35, I44 etc.

With my old 205/45/17 on Web Spokes, my speedo error was the expected 3 mph. With the 205/50/16 on the new wheels, I am seeing a 5 mph error.

Example: 75mph on the 07 Speedo, is actually 70mph. Would you expect this 5 mph error?

I suspect it is normal, so what size tire should I have purchased to keep the error at 3 mph or even zero speedo error.?

Does anyone have an online tire calculator that would verify this error.

Not a big deal, since I can do the simple math in my head and getting a ticket for excessive interstate speed is less, but it a niggling little detail that is driving me to distraction.

Thus this post to ask for inputs. Thanks....

 

If you google 'tire size calculator' or words to that effect, you will discovery several; one associated with Miata, and another with 1010 or something to that effect; the latter is nice because it permits you to compare 4 different sizes to whatever you consider 'stock.'

 

here's the 1010 one

http://www.1010tires.com/TireSizeCalculator.asp

 

so what size would bring you closer to the real speed that you are driving? i wanted to run the same size as old81 on my 07 r56s m . can a 225/50/16 work?

 

or would 215/50/16 bring you closer to true speed?

 

minihune where are you

 

Still not sure of the answer, I tried out the online tool, but I got varied results. On your 225 question, I'm thinking you might get rub, if you have lowered your MINI. Not 100% sure, so some of the folks who have lowered R56s could chime in with opinions.


I was hoping minihune would chime in on this question, but I suspect he may have answered it about a 100 times. I will have to do some more searching. I'm still on the road trip, 900 miles into it so far.

 

I run 215/50 on mine. I found that my mini was a little off on the speed with the factory setup, and with this setup it still reads a little high about 3 mph. So next time I may try to go to 225/50/16. I think in real life that will get closer to the real speed. I get no rubbing right now, and I am lowered. I think the R56 might have a little more space. I read a thread were about a 1st gen mini with 225/50/16 and I think he had little enough were it wasn't deemed necessary to do anything about.

 

Go here for a good calculator: http://www.discounttiredirect.com/di...foTireMath.jsp

Using the calculator you'll find that a 205/50/16 would be approximately 0.50 slower than 205/45/17 and 215/50/16 should be 0.50 faster than the 205/45/17.

On my car with web spokes I'm 2.00 slower than displayed. I have checked this in a few local radar zones for comparison. As an example when I run an indicated 40 the radar that's located prior to a school zone displays my speed as 38 mph.

Yes I am driving a 2006 R53 and the speedo error may or may not have changed in the new R56's.

If you use the 15 inch factory tire as the "standard" the 16 or 17 inch factory tires should be in the 3 mph "margin of error for your speedo. In other words your driving 0.75 faster than indicated as you go from 15 to 16 and 16 to 17.

But that's contray to your GPS and my experence with radar so I like to assume that the 16 is the standard and 2 mph is my cushion.

So it's a toss up as to which one, 205 or 215, is better for your car.

If you choose to get rid of most of the error, 2 mph, you can try 225/50/16 and I'll bet on an R56 they will not rub.

Most likely your speedo error is from the manufactures sizes. I don't know the Falkens size but as an example the difference between a Pirelli and a Dunlop in the same size can be noticeable. The overall diameter can vary by a 3 tenths of and inch and it would be noticeable in your speedo display.

The other assumption is your GPS is not quite perfect.

Confused yet? Unless you know for a certainty the "standard" tire size Mini based their speedos on you have to guess. So what I'm saying is you have a 3 mph error, I call it a cushion, that you just have to live with and it will in fact help to keep the police from writing you for speeding.

If you drive by the speedo you have a cushion to stay ticket free and in this day and age of canceled insurance and king's ransoms for speeding tickets it can't hurt.

Hope this helps...

 

Good points, but this is not MINI's responsibility, nor should they be trying to "cushion you from the law", if indeed that is their intention. A speedometer should only show you the speed you are going. I'm hoping some 215/45-17s will get me closer to the actual speed, because mine is, as a lot of others, off by 3.

 

Thanks, good information.

When I have the MINI web Spokes and my Dunlop run-flats mounted 205/45/17 my speedo error is 3 like most everyones. My GPS showed that error as well as the various radar scanners around the city.

With the new 16s and the Falken 912s, it shows 5 mph, so I guess you could call it a safety factor.

When I change out the summer run-flats, I will pay attention to overall diameter to see if I can keep it within 2 or 3 mph for the error.

I'm just amazed that the Falken's are 5 mph off.

 

I don't think that Mini is trying to "cushion you from the law" I believe it's actually quite the opposite. From what others that are in the legal profession have posted here before is that "all" vehicle manufactures put a "margin of error" in their speedometers for "their" protection against lawsuits.

The 215/45/17 should get you 0.96 mph closer to a true indication of your speed.

Me, coward that I am, I like a bit more "Oops" factor.

Hope this helps...

 

Actually, it is their responsibility. European law requires it. Why we get it here is a good question, but every car I own has at least a 2 MPH "cushion". I should add that one of my cars has a fixed 7% cushion. 100mph indicated = 93mph actual.

http://www.caranddriver.com/features...r-scandal.html
http://www.caranddriver.com/features...r-scandal.html

 

Lets assume your GPS is correct and when running the stock 205/45-17 tires you do get 3 mph slower actual speed than what you show on the speedo.

For the average owner this is OK and acceptable however if you really want to be showing something closer to your true speed then it is possible for your 16" wheels to use 205/55-16 or 225/50-16 which gives you a nice selection of tires to choose from for the MINI.

215/50-16 doesn't give many good tires but at 24.5" the size is quite good.
Avon tech M500 (ultra high perf tire) has all three of these sizes:
205/50-16 fits 5.5-7.5" rims, perfect for 6.5" rim, 24.1" tire diam.
205/55-16 fits 5.5-7.5" rims, perfect for 6.5" rim, 24.9" tire diam.
215/50-16 fits 6-7.5" rims, perfect for 7" rim, 24.5" tire diam.

while (not in M500)
225/50-16 fits 6-8" rims, perfect for 7" rim, 24.9" tire diam.

Kumho Ecsta ASX also comes in 215/50-16 (UHP all Season tire).

For 17" wheels.
215/45-17 is slightly larger than stock at about 24.6".
225/45-17 is next larger at 24.9" but due to wideness might risk rubbing as does 225/50-16. Wheel offset and suspension height allow for more or less clearance.

For speedo error-
Compared to stock 195/55-16
If you have
205/50-16 you will be going about 1.3% slower than stock so 5 mph slower like you measured is about correct given stock is 3 mph slower than true speed.

If you have 205/55-16 or 225/50-16 then you will be going about 2% faster than the stock sized tire which is very close to actual speed.

Compared to Stock 205/45-17
If you have
215/45-17 then you will be going about 1.7% faster than the stock sized tire which would be very close to actual speed.

 

It also lowers the true mileage coverage on the warranty.
I think Honda or Toyota had a legal problem with this a couple of years ago.
Turned in lease car owners sued because of higher than allowed mileage charges that weren't actual miles used .

 

It shouldn't. If it does there's a problem. Even on my car with the 7% speedo error, the odometer is dead on.

 

FYI
I had a similar discussion w/ a friend of mine about speedo's being wrong. He observed from the past that *MOST* European cars run approx. 3-5 miles faster than American cars. He's observed this from when he used to own a few Volvo cars as well as other Euro-cars. But surprisingly, the American-made cars have the most accurate speed readins.