Hi All,

I know in some ways this have been discussed, but I can not quite figure out the exact answer.

After reading multiple threads I understand that other than stock a very popular tire size is 215/45/17.
I found a guy on craigslist selling MCS 17'' with 215/45/17 Continental Contact Extreme tires in perfect condition.

My issue is there a way not to have an speedometer and/or odometer issue

I used this site: http://www.miata.net/garage/tirecalc.html
and it says that my speedometer will show speed lower than I'm actually traveling (not much but still). I'm not sure what will be the odometer effect. Will it show higher or lower millage? I drive alot, so I don't want to have even more miles and have my warranty expire even sooner.

Is there a way to reset this in the speedometer/odometer settings?

Also quick question on tpms. I have a 2007 MCSm with tpms that measure wheel speed, not the ones in the valve. Will tpms work with these wheels/tire I found on craigslist?

Thank you all, and please forgive my ignorance, since I know this has been discussed in various ways before.

 

I would call around to local speedometer calibration shops and ask them about recalibration. Make sure that you tell them that you have a MINI, and that the speedometer/odometer are driven by speed sensors at the four wheels and not by a traditional cable-drive setup.

With taller-than-stock tires, both your speedometer and odometer will read low. The MINI speedometer typically reads a few percent high, so your readings with the new tires may actually be closer to the truth than the readings you get with the stock tires. The MINI odometer is usually dead-on with stock tires, however, so your new odometer readings will definitely be low.

With the wheelspeed-based TPMS, you can use whatever wheels or tires you wish. As long as both tires on each axle are the same height, you won't trigger the TPMS, no matter what the actual height is.

 

You are making a fundamental assumption that I think is incorrect and that is that your speedo/odo is accurate with your current tires. My guess is that it is not and your MPH is overstated by as much as 5%.

When I went to the 215/45/17 Goodyears being a bit shorter my ODO lost its error and is now within 1 MPH across the range of normal speeds.

It is my understanding that there is no way to dial in any corrections to our speedos even with a professional calibration.

Rich

 

Your speedometer lost its error, right? With stock tires, the odometer error is pretty much negligible, regardless of the amount of speedometer error.

I'm pretty sure the dealer can adjust the speedometer calibration via software, but they won't do it unless your speedometer is reading more than 10% high plus an additional 2.5 MPH.

 

Really? How do you know that, or how would I know that?
I mean this seems strange, so you're saying when my speedo shows 55mph I'm really going like 52?

That seems strange that a manufacturer would allow such an error. Also these cars are German/British and there speeding laws are enforced much stringer than in US, so a variance in speed (if its in the wrong direction) can cost people dearly, I'm surprised . Also like I said odometer discrepancy, effects the warranty.

 

[

 

The variance allows for significant error in one direction (speedo reading too fast) but absolutely no error in the other direction (speedo reading too slow). The EU law on the subject (which I believe the US also accepts when European cars are sold here) is that the speedometer may not read too low at all, but it may read high by as much as 10% plus an additional 4 km/hr (about 2.5 mph).

So if you're actually traveling 60 mph, your speedometer could read as high as 68.5 and still be "within spec".

The best way to check your speedometer is with a GPS unit. Assuming you've got a normal number of satellites locked, the typical speed error for a GPS is much less than 0.5 mph.

EDIT - Also, it's important to remember that with stock tires, a speedometer error does NOT imply an odometer error. For most of our cars, the speedometers are off by 3-5% at highway speeds, but the odometers are pretty much dead-on. So even if your speedometer is reading 5% too high with stock tires, that doesn't mean that your warranty is going to end 5% too soon.

 

good call, I shoul have thought of that

Will do tomorrow, I used to have a mazda 3 and it was dead on

 

I'm not Rich but he is correct. Almost all cars over estimate the speed from the factory. The manufacturers don't want to have the speed understated and have responsibility for speeding tickets or some other problem. Also, they would rather you use up your warranty miles sooner, although it is hardly worth worrying about. (Yes, just my $.02)

The easy way to see your actual speed is with a GPS unit.
Check your current ODO error and then see what the change in tire size will do to you.

 

+1 on the above speedo error allowances by MINI. Depending on whom I've asked (and there have been many including my three local dealers and MINI USA) the 'within spec' error of the speedo is between 10% and 10% + 2mph.

After having a friendly chat with a MD state LEO this past summer over an error in my actual speed vs. what I thought I was going (my fault, and fortunately I just received a warning), I searched (in vain) for any shop, anywhere in the US who will consider tackling correcting my speedo error (about 7%), and none will. I even offered my local dealer $1,000 (yep, it's crazy, but I thought it might be worth a try to see if they could be tempted to fix it), and they refused to even think abut it unless the error was greater than 10%. That's when I contacted MINI USA. Same result. They say they have no way to adjust the speedo, and all they can do is to replace the unit. With no guarantee, or even an expectation, that it would be accurate.

Anyone who has put a speedo on their bicycle knows that there is a simple mathematical formula based on the rolling circumference of the tire that is used to generate a speedo reading. Common sense would suggest that there is a similar process used in the MINI. All we need is someone who can tap into that part of the software and change the number. Any takers?

What's even more frustrating for me, at least, is that I have the factory nav system, and since it's GPS based it already KNOWS how fast I'm driving. And there's no way to get it to display that info. ARGH! $2,100 for a built-in GPS and I have to buy ANOTHER GPS to tell me how fast I'm driving?

Using a Garmin Nuvi GPS over a 100 mile section of straight and level highway, on three separate days, I generated a speed differential chart listing indicated speed vs. GPS speed. Printed it out and taped it on the dash to the left of the steering column for handy reference. The readings were consistent from day to day, and all indicated a 7% higher speedo reading than the GPS. Interestingly, as mentioned by a previous poster, the odometer was only off by 2 miles over the 100 mile course (2%) based on highway mile markers and the GPS (they agreed within a tenth of a mile at the end of the course each time).

Sure wish I had a better outcome to report. Bottom line... just like the previous posters have suggested, get a GPS and take some time to get a feel for your real speed vs. indicated speed. Then keep your fingers crossed that you can remember the difference when you need to!

 

Thanks all who replied.

First of like I said before this is somewhat shocking to me, like I said I had a Mazda and it was dead on, I would expect a BMW build vehicle to have more precision.

Two follow up questions.

1. Can some one tell me which way is the odometer difference with the stock tires? Am I showing less miles than I'm actually driving or more?

2. What will be the effect if I do get 215/45/17 on both the odometer and speedometer. Am I going to be going faster or slower than what is displayed on the spedo and which way will my odometer read.

Thanks all

 

Those questions were answered early in the thread... but I'll try again...

1) Scott R claims that the odo reads very accurate from the factory. I haven't tested this, but I have no reason to doubt it.

2) Changing from 205/45R17 to 215/45R17 has the effect of making your tire circumference larger - and thus makes your speedo read a *little* slower than it currently does for the same speed. The net impact should be approximately 1-2% - thus, if your speedo now says you are running 60mph, with the larger tires, it would say about 59mph. In my case, my speedo read about 2-3% fast from the factory, so it is now MORE accurate, but still reads a bit faster than I'm actually going.

Your actual results may vary. Use a GPS to determine your current setup's accuracy.

I'm curious... how do you know your Mazda was dead on?

 

1. With OEM tires it's most likely the odometer will register more miles than you have actually driven. Check this easily next time you're on an interstate by comparing your odo to the mile markers on the side of the road over as great a distance as possible. Or use a GPS.

2. I didn't see where you posted your OEM tire size (apologies if I missed it... I'm a bit tired), but as previously posted by Zhenya13 you can use the link to the Miata calculator where it will tell you the answer. My best guess is that both instruments will register more mph and miles than with the stock tires if the rolling circumference is less than OEM.

 

Or you can get a ScanGuageII and use the MPH as one of the 4 displays.
This is why I suggested using a GPS unit to check actual speed.
I used a Garmin to adjust the SGII for accurate speed. However I am very close on my set-up with 215/45-17 tires. About 1 MPH at 65.

 

Used my GPS, and the spedo shows about 3-4 mph above actual speed when traveling above 45mph.

Now I'll try to figure out my Odometer variance.

However, as with some people who replied I think that with the 215/45-17 will actually be more precise

 

It is sad but true. The 215/45/17 will actually improve the accracy of your spedometer. However, 215/40/17 is a closer diameter match to the manufacturer recommended sizes. The 215/40/17s will offer much better handling and acceleration, the 45 profile will offer better fuel economy.

 

I am certain they can't. And I have called Hollywood Speedometer the guys who used to help me with my BMW clusters and a couple of others and they say it cannot be corrected other than changing the circumference of the tire.

I miss the old days when I went to my Chevy dealer and asked for a new speedo gear and was done. OTOH, hopefully in the future there actually will be Chevy dealers.

Rich

 

I guess when my dealer said they would fix it if were out-of-spec, by "fixing" it they were referring to replacing the speedometer, not actually reprogramming the computer.

 

BMW/Mini is being a total arrogant jerk,
Spec is 10% +2.4 MPH and never read lower. I have their memo stating they will not attempt repairs out of this spec.
Folks, that is 15% at 50 MPH.
I do not believe speedo can't be calibrated like the old days. It is SOFTWARE in the ECU not a flying magnet in the gauge. BMW has decided they are too cheap to calibrate for the various size tires and wheels. Almost 2% between them. My 2009, 195/55-16 reads 2 MPH low across the board. In the days of digital sensors ( we have at least 4 speed sensors) there is no excuse.
To add insult to the owners, they said it reads low to compensate for tire wear. Well, how stupid do they think we are? Tires get SMALLER when they wear.
Between the gas gauge being off by half, sunroof won't open when hot, and the speedo errors, that is three times the delivered new defects as my last five Honda's combined.

Lets hope someone cracks the ECU so we can fix them. It is a real nuisance. It would be easier if it was an analog gauge ( I won't look at that abomination in the center, (almost did not buy it because of it). But looking at the digital, we have come to expect it to be within 1 digit. Everybody else can. Don't tell me this is British charm. My MGA, TVR, Morgan, and Spit were all closer. So was every car I have ever had with the exception of my 66 Mustang.

I like my Mini, but wish I my knees were not so bad I had to get an automatic or I would have kept my RSX (KW coilovers) for another 100K. It handled better, ergonomics were better, more confortable. Alas, it did not have the kick from the turbo.

How SHOULD it work? We should be able to go to the dealer, pay a nominal charge like one hour rate, and have them plug in the revolutions per mile of whatever tire we select. (If it was user adjustable, just imagine the lawsuits)

This ain't no stripped Kia. They should not treat us as such if they expect to stay in business. Hey, anybody bought an oil filter yet? Better be sitting down first.

 

Here's another way to calibrate for those (like me) who don't have a GPS: Next time you drive by one of those speed displays that local cops or highway patrols put up - the ones that tell you "Speed Limit XX. Your speed is YY" - check your speedo against the displayed speed. If it's convenient, you can drive by multiple times at different speeds to get a more complete calibration.

 

My 08 Cabrio was off by 10%. Got rid of a dead on Civic to buy it. Contacted MINI and they would not do anything. My new 09 Cabrio is more accurate but sitll optomistic by 2-3 MPH at 70. This was all checked by my GPS. I'm with many of you. No reason to have a premium car this inaccurate when a run of the mill Honda Civic is dead on.

 

Exactly what alerted me to the problem in the first place. I pass 3 all the time. All of my other cars are very close. This is clearly a problem of arrogance on the part of BMW, and does very little to entice repeat buyers.

 

I just bought my Cooper and it has stock 175/65/15 tires now. I just got a set of 195/55/16 stock rims and tires that were take offs. The 16's are about 1/2 inch diameter larger than the original 15's. So thats about a 2% difference.

Do they program the ECU for the specific tire and wheel combo the car came with from the factory or do they just assume the difference is just within tolerance? the 15's, 16's and 17's all have a different tire OD so are there different spedo calibrations for each?

 

I have 215/35/18's and when my speedo reads 65 I am really doing 59 (according to the beside the road radar machines)

 

If the British/Germans are such good engineers why not just make them adjustible. Have their standard optomistic adjustment in from the factory and sealed. If the seal is broken the manufacturer is not accountable.