Can the speedo be recalibrated?

I realize most speedometers read high by design (mine shows 80 mph while the actual speed is 76 mph according to GPS). Is there a way to adjust the speedo?
Thanks, Pete '02 530i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No.
FloydR
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well, it's a meter with a pointer, and the pointer is usually a taper fit on the pivot. Moving it slightly could make it correct at least at one spot speed.
There must be a way, though. UK police use BMWs and their speedos will be accurate.
--
*I'm pretty sure that sex is better than logic, but I can't prove it.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Remember, they're not mechanical any more (other than the sender unit.) Probably a different capacitor/resistor or software.
FloydR
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The actual speedometer still has a pointer which turns, though, unless I'm out of date with new models. And repositioning the pointer on its pivot will obviously work - although it's probably a job for an instrument maker.
--
*Geeks shall inherit the earth *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

That would only work if the correction is linear. If it is 1mph at 10mph and 5mph at 80mph, moving the needle won't work.
Tom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Within reason yes. Which is why I mentioned 'spot speed'. But although the return spring is designed to be fairly linear it will still have a slightly greater effect at some readings than others.
--
*Eat well, stay fit, die anyway

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Scales wrote:

The car's computer uses a conversion number to convert the revs of the rear axle (or of the wheel on newer models) to mph/kmh for the speedo. I believe this can be reprogrammed. They did it this way to allow for different final drive ratios but I guess it might be fixed now if the speed is taken off the wheel sensors.
As for the police I'm pretty sure they'll use their own speedo equipment for the purposes of trackign cars rather than the BMW speedo.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 6 Nov 2006 05:43:35 -0800, snipped-for-privacy@yahoo.co.uk wrote:

I used to have a document that showed the way to re calibrate Speedo - odometer inaccurate's and change other factors in the ECU. Seems to have disappeared but I think it was on or came from http://www.unixnerd.co.uk - the BMW nutter (self proclaimed ) or if not he would know about it.
Hugh
Sir Hugh of Bognor
The difference between men and boys is the price of their toys. Intelligence is not knowing the answer but knowing where and how to find it!
Hugh Gundersen snipped-for-privacy@h-gee.co.uk Bognor Regis, W.Sussex, England, UK
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If it's the ODBC 'trick' to recalibrate -- I've not run into a single person that says "yes it worked"
--- AntiSpam/harvest --- Remove X's to send email to me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Wouldn't it be easier to find out what the error is at various speeds and then just make up a new number back-plate to sit behind the speedometer needle? Paste it on with glue if necessary. No messing around with the electronics then.
Steve

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Bognor Regis, W.Sussex, England, UK
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This is a BMW "feature." It has something to do with German law requiring speedometers NEVER be pessimistic, so BMW insures that's not the case. Your error is just about standard for the E39.
R / John

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You can put on larger tires to slow the speedo.
Having said that, setting the cruise at 80 and actually doing 76 could save you a ticket or two in your life. Your speedo is 95% accurate though, pretty good in the grand scheme of things.
If you are not the first owner, it is possible that the tires have been changed to a cheaper model that is smaller than what should be on the car. You can bring the speedo to about 98% accurate if you swap a 235/40x17 with a 235/45x17.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Post your tire size and I will tell you a new size that should solve your "problem" the next time you buy tires.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Jeff Strickland" wrote

The tires are 235/45/17.
Going up to 245/45/17 would increase dia. by 1.4% 235/50/17 - 3.7% 245/50/17 - 5.2%
The thing is, I don't want to increase the sidewall height because steering response will suffer. And I don't want to have to deal with rubbing issues either.
BTW, which axle does the car read the speed from - rear, front, or both?
Thanks, Pete
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you car is like my '94 3 Series, the speed is taken off of the rear diff.
I can't imagine how you would feel a few millimeters of extra sidewall. If your tires are 235/45s, then you can see if you can get 235/50s, and this should just about make your speedo dead-nuts-on. This would be 1" larger in diameter, or one-half inch in radius. You could also go with a 245/45 and get a half inch in diameter and about 3/8 inch in width.
Unless you live where it rains alot, I think I'd go with the 245/45s and take a bit more width and the added traction that it would provide. Your speedo would read about like mine (when it says 80, I'm doing about 77.5), which is pretty good.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Speedohealer.com
while they started out for motorcycles; the same can apply to cars. I had ordered one for my car a while back -- worked like a charm.

--- AntiSpam/harvest --- Remove X's to send email to me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I have a spare speedometer from my e30 so I thought I'd have a close look at the circuit board to see if there was an adjustment on it. Sure enough there is a small 'trimmer' potentiometer on the circuit board. I can't say for certain that it's function is to calibrate the speed but I can't think of any other reason for it's presence. There is no access to the screw from outside of the cluster so making the adjustment would be somewhat onerous.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Feed the output of a variable oscillator to the head?
--
*If God had wanted me to touch my toes, he would have put them on my knees

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.