Speedometer off.

[Tom K.]

Originally Posted by jeremyc74

The Ford truck line I just did speced +0-3% at 70MPH. In reality the units going out the door were within .5%. This is why I don't understand why their tolerance is so high. It's totally unneccesary with todays manufacturing capabilities.

+0-3% is certainly reasonable. I would ask, though, if the Ford trucks have as wide a range of OEM tire fitment as do the BMW 1 series?
Tom

[ARES45]

I think they do, off road packages would likely get different tires, 2wd vs 4wd maybe etc.

[jeremyc74]

Originally Posted by Tom K.

+0-3% is certainly reasonable. I would ask, though, if the Ford trucks have as wide a range of OEM tire fitment as do the BMW 1 series?
Tom

The same cluster is used on everything from a 2WD light duty all the way up to the 4WD diesels, so even more. The tires aren't the issue here. That's an easy calculation that's done in the ECU.


What is happening is BMW is shooting low, so in case of a manufacturing varience they are still within the applicable laws. My question is why are they allowing for so much varience? If my speedometer was at the upper limit of what they consider acceptable (10% +2.4MPH) I'd be raising hell with my dealer. That would mean that at an indicated 80MPH you would only be going 69.6MPH. That's absurd.

As it is it's not nearly that bad, I just question why it can't be better. With factory sized tires on it my GTO was less than 1MPH off. Same goes for my GF's Prius. I just don't get why BMW doesn't dial it in a little closer.

[Tom K.]

Maybe I've been lucky, but my last three BMW cars have been off by no more than 3% at 60 mph; that is reading between 60 and 62 at a true 60. And as I posted to another thread, I've disovered that my 1er's odometer actually is almost 2% slow. So it seems as if the errors aren't consistent although no one seems to be reporting anything greater than 5%.
FWIW, my '06 BMW RT motorcycle reads 7% high at 60 - the identical error that Motorcycle Consumer News reported in their test of that model.
Tom

[1Ronnie]

Again ... if this really annoys you, switch on the secret menus, select option 8.0, and tadaa ... there you have it, the real speed. In my 323i, the secret menu usually reads within .2km/h out from my GPS.

[jeremyc74]

Originally Posted by arrons1969

Again ... if this really annoys you, switch on the secret menus, select option 8.0, and tadaa ... there you have it, the real speed. In my 323i, the secret menu usually reads within .2km/h out from my GPS.

Knowing the speed isn't the issue. Obviously we've got GPS systems displaying the speed....that's how we know it's off in the first place. It's the fact that the needle doesn't match the actual speed that bothers everyone. Why should you have to get into some menu to display your actual speed when you've got a big ass indicator that's right in front of and put there for that purpose?:iono:

[1Ronnie]

Because you bought a $40000 car from a safety minded, litigation anal, German car manufacturer. And ... they're not going to let you adjust it, get over it !!

[jeremyc74]

Originally Posted by arrons1969

Because you bought a $40000 car from a safety minded, litigation anal, German car manufacturer. And ... they're not going to let you adjust it, get over it !!

Or maybe....you could just bow out of the thread because you're not going to covince anyone here that we've just got to live with it. What's the point of making comments like that? It brings nothing to the discussion.

[1Ronnie]

Of course it adds to the thread, and you do have to live with it. This topic has come up a number of times, and readers need to know quickly ... it is not a fault, it is a design feature, it can't be changed.

And if you are concerned you can actually work out the true differential using the secret menus so you know what is really going on, without having to spend money on a GPS.

[Jai2008]

Nvm....I won't bite and stay nice. I'm sure somebody else will do the dirty work for me =P

[Night1]

Driving along the interstate earlier doing (I thought) 78 mph. My Escort 9500i picks up a cop ahead and displays my speed (with it's built-in gps) as 72.

6 mph off?!!!! :iono: I tested it a few more times. 6 mph off every time. That's worse than the digital speedo on my bike. That sucks.

[atr_hugo]

I'm going to merge this with the existing speedo off thread:

http://www.1addicts.com/forums/showthread.php?t=11429

[gatorfast]

Meh, I dont think its a huge deal. When the MkV GTI's came out a few years back it was discovered that the speedos were off about 10% (reading on the fast side). I just got used to it and I drive accordingly.

I think someone mentioned earlier in the thread that BMW's may have a secret electric readout (like my VW does) accessible to display the actual speed. As long as the speeds reading slow then I dont see what the big deal is.

[ARES45]

I guess what bothers me is if they have a secret display that tells the actual speed, why not display it in the first place. Oh well.

[jeremyc74]

Originally Posted by ARES45

I guess what bothers me is if they have a secret display that tells the actual speed, why not display it in the first place. Oh well.

It's worth noting that the averge speed display is accurate. If you set the cruise at 80MPH indicated, and then reset the average speed and drive for a while, the average will show 77MPH. I bounced this off my average moving speed on my GPS over several hunderd miles and the two were withing a couple of tenths of each other.

[lannypoffo]

Glad I found this thread instead of making a new one..

Now I know an OBDII reader isnt the most accurate thing in the world, but i saw something very strange when using my live data today...

Cruising EXACTLY 80mph on the speedo for a long while. Hooked up my OBDII reader.. went to live settings, mph. It said 73-74mph exactly. So either the OBDII is inaccurate, or the speedo is WAY off. And I've seen speedo problems this bad on some of my previous cars also. Like my 2006 GTI.

[lannypoffo]

Originally Posted by ARES45

Hello all, as some have mentioned and I have verified with a gps, the speedo is about 3mph fast at 60 and progressively more so as speed increases.

Discuss.

At 80mph speedo, I showed 5-6mph fast. I was really going 74-75mph.

[Qube]

Guys, just read Mad Dragon's post again, PLEASE!

http://www.1addicts.com/forums/showp...3&postcount=12

This is a fact of life. There IS no right or wrong. This is the way it was, from the 1989 E34 I owned up to the two 1ers and the E39 I have now.

If it's off by 10kph, then that's BAD. Complain. If it's in the range of 5kph, that's THE WAY IT WAS DESIGNED.

EDIT: Just an FYI. On a GPS, your position is determined every ±1 sec and calculates the distance travelled from the last logged position. The speed is in fact an average over the last few seconds. Take that with an extreme grain of salt. Factor this in and you COULD potentially see that ugly 8kph or so differential because of GPS error.

Next, as your tires wear, the speed will change AGAIN. The car manufacturers have to compensate for this as most people aren't smart enough to understand. The new Golfs have a Winter tire mode that actually compensates for several size changes I hear. For a good calc of speed deviation due to tire size, plug it in here: http://www.miata.net/garage/tirecalc.html

[J312]

It could be you got larger wheels in a package, or after you bought it, and the spedo has not been recal'd.

[ARES45]

Originally Posted by Qube

Guys, just read Mad Dragon's post again, PLEASE!

http://www.1addicts.com/forums/showp...3&postcount=12

This is a fact of life. There IS no right or wrong. This is the way it was, from the 1989 E34 I owned up to the two 1ers and the E39 I have now.

If it's off by 10kph, then that's BAD. Complain. If it's in the range of 5kph, that's THE WAY IT WAS DESIGNED.

EDIT: Just an FYI. On a GPS, your position is determined every ±1 sec and calculates the distance travelled from the last logged position. The speed is in fact an average over the last few seconds. Take that with an extreme grain of salt. Factor this in and you COULD potentially see that ugly 8kph or so differential because of GPS error.

Next, as your tires wear, the speed will change AGAIN. The car manufacturers have to compensate for this as most people aren't smart enough to understand. The new Golfs have a Winter tire mode that actually compensates for several size changes I hear. For a good calc of speed deviation due to tire size, plug it in here: http://www.miata.net/garage/tirecalc.html

I have timed it on the mileage markers as well, here in the U.S. we have those on the interstate so that you can determine more accurately your speed. The GPS was spot on, the speedo was greater than 5% off. As to the tire wear, if your speedo is already reading fast on new tires, it will only get worse as the smaller radius/diameter creats a smaller circumfrence meaning you travel less with each revolution.

Still curious to know if this can be recalibrated by the dealer?

[clived]

Given the diameter of the tyre will change by ~2-3% during its life, the "error" you measure at one extreme will be somewhat larger than at the other. Manufacturers need to make sure that the speedo reads *at least* the real speed under either condition... Given there isn't a mechanism for the car to measure the wheel diameter, buidling in some "contingency" speed reading is the only way to do it...

[ARES45]

Originally Posted by clived

Given the diameter of the tyre will change by ~2-3% during its life, the "error" you measure at one extreme will be somewhat larger than at the other. Manufacturers need to make sure that the speedo reads *at least* the real speed under either condition... Given there isn't a mechanism for the car to measure the wheel diameter, buidling in some "contingency" speed reading is the only way to do it...

But the tires aren't going to get any bigger than when new (or am I missing the growing tire option). So why can't it read accurately at the recomended inflation when new from the factory? Or if they want to build in an error that is fine, but give us an opportunity to recalibrate this 'engineering marvel' that bmw claims it is. So much for German Engineering being the best, my parents Toyota minivan was less that 1% off when I checked it.