SPEEDOMETER READING ERROR

[bmwe34]

SPEEDOMETER READING ERROR bmw e34 520i

I noticed that my car reads the speed wrong IE: on my gps i am driving @120km/h but my speedo says 130km/h i have 15" tyres on 195/65/15?
could it be that my car came out with 17" wheels? plus will this effect my rev counter? how do i go about fixing this problem?



kyle

 

[STREETRACER]

Most definatly the wheels! But normaly its about 6km/h fast..
No your rev counter works of you ignition system!

 

[bmwe34]

so what do you recomend? 17"

 

[double-n]

There's probably not a car on the road that gives the correct reading on its speedometer. Yeah it's caused by the size of the wheels, but even tire profile and tire pressure can influence the reading. I just use my GPS to get my actual speed (and to make sure I'm driving exactly 129km/h on the highways ).

 

[bmwe34]

i know but i am a whole 10km out... maybe 12km?:bawling:

---

No your rev counter works of you ignition system!

Thanks i got worried:thumbsup:

 

[veridico]

My bakkie, which is relatively new, is 15km out, my e36 is only about 5km out, all cars read incorrectly..

 

[STREETRACER]

My bmw is 12km/h out after diff swop! if you know the gap you know what clock speed you can drive and were!
i wouldnt be bothered if i was you! its going to feel sluggish with 17''

 

[///M_POW]

STREETRACER ---- What dont u use the hidden feature on the OBC to get your true speed.. :excited:

 

[STREETRACER]

STREETRACER ---- What dont u use the hidden feature on the OBC to get your true speed.. :excited:

hidden feature??? but that should be out aswell! the whole ecu speed system runs of speedsensors of your gearbox and your diff!

are you talking about resetting your avarage speed????

 

[///M_POW]

no....

U dont know about the hidden features :dropjaw: :slap:

like
- digital speed reading
- l/km as u drive
- fuel left in ur tank (litres)
- battery volt
- etc

 

[STREETRACER]

no....

U dont know about the hidden features :dropjaw: :slap:

like
- digital speed reading
- l/km as u drive
- fuel left in ur tank (litres)
- battery volt
- etc

not at all!! please share!! so hidden i never found it!

 

[///M_POW]

hahaha...

u got mail.... i think i said to much on this forum BM is gonna come looking for me lol

 

[///Marksman]

Other than the fact that wheel dimensions will effect speedo error. it is not simply a fact of 10km/h error at any speed. Instead it is a certain percentage (which may not be static).

Just for example here is the november 2007 CAR magazine tested calibration for the e92 M3

Error was 0.77% over...

Calibration: 60 80 100 120
True speed: 57 76 96 115

>>True speed 258 at 7 000 r/min in top gear<<
>>Speedometer reading 273<<

The higher the speed the larger the difference. Look at the error at 60 compared to 273 (from 3km/h to 15km/h)

BTW. This error will not be the same in every car, for eg. The RS4 which was tested at the same time showed 0.35% over.

This is just one of a few reasons why i questioned your claimed top speed in your e36M SPEEDRACER. But you said you have reached a true 280+ and Anile8 mentioned that there are plenty e36M's doing a true 290 top end in Durbs. I still remain a non beleiver until someone can show some data logs.

 

[bmwe34]

thanks guys helps alot thought my car was haywire,,,, any how i also want know if a tuen up at bosh service centure is worth the money ?

 

[calypso]

STREETRACER ---- What dont u use the hidden feature on the OBC to get your true speed.. :excited:

The digital readout isnt true speed. That would be impossible to calculate with the sensors on the car, as the wheel size changes.

 

[STREETRACER]

thanks guys helps alot thought my car was haywire,,,, any how i also want know if a tuen up at bosh service centure is worth the money ?

what tune up? you want to tune the engine?? were are you based?