Speed Odometer Re-Calibration
Moderators: GRNSHRK, ron, bfons
Speed Odometer Re-Calibration
I am running a 3.90 gear set/final drive ratio on my 1985 635csi where I once had a 3.46 gear set. What is the procedure for recalibrating the speedometer to read correctly or do you have a to change a physical part? I know that our speed cluster is electronic
regards,
Jay
regards,
Jay
on E28 based cars no recalibration is required- the speedo reads a pulser on the diff crownwheel, so ratio changes don't alter the speedo but wheel diameter changes do.
Earlier E12 chassis cars (pre-82) have a mechanical speedo drive IIRC and here you can 'change gears' for the odometer certainly and maybe the speedo itself as well.
cheers
Earlier E12 chassis cars (pre-82) have a mechanical speedo drive IIRC and here you can 'change gears' for the odometer certainly and maybe the speedo itself as well.
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
So it must be the 17 inch wheels and tires that is throwing it off. I run 235/45 tires on 17 inch wheelsBrucey wrote:on E28 based cars no recalibration is required- the speedo reads a pulser on the diff crownwheel, so ratio changes don't alter the speedo but wheel diameter changes do.
Earlier E12 chassis cars (pre-82) have a mechanical speedo drive IIRC and here you can 'change gears' for the odometer certainly and maybe the speedo itself as well.
cheers
BMW speedos are usually running indicated speed 5% higher or more than actual. I put 235/45/17 on my 6 and it is still reading slightly high according to my GPS. The odometers are usually dead on and I would expect now your odometer reads a little low compared to actual miles.
I don't know if it's possible to change up anything in the odometer gears to correct. The pulse wheel inside the diff would have to be custom fabricated and you could not make a change as small as 2% or so since there are only about a dozen teeth on that wheel. Just adding one tooth might be 10% increase.
I don't know if it's possible to change up anything in the odometer gears to correct. The pulse wheel inside the diff would have to be custom fabricated and you could not make a change as small as 2% or so since there are only about a dozen teeth on that wheel. Just adding one tooth might be 10% increase.
I agree with all the above- FWIW the toothed wheel in the diff has eight or sixteen teeth IIRCTN_M635 wrote:BMW speedos are usually running indicated speed 5% higher or more than actual. I put 235/45/17 on my 6 and it is still reading slightly high according to my GPS. The odometers are usually dead on and I would expect now your odometer reads a little low compared to actual miles.
I don't know if it's possible to change up anything in the odometer gears to correct. The pulse wheel inside the diff would have to be custom fabricated and you could not make a change as small as 2% or so since there are only about a dozen teeth on that wheel. Just adding one tooth might be 10% increase.
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Re: Speed Odometer Re-Calibration
Is this the product Ben is referring to above? Has any one used a product like this to correct their speedometer on a E24?
http://shop.12oclocklabs.com/index.php? ... duct_id=59
SpeedoDRD by 12OclockLabs
http://shop.12oclocklabs.com/index.php? ... duct_id=59
SpeedoDRD by 12OclockLabs