Recalibrating mechanical speedo

[Mike Goble]

I'm considering changing the rear gears in my Bav to 3.25 when I replace the rear suspension. Are there adapters available to change the rpm of the speedo cable to reflect the gear change? I have some SW boxes made for American cars, but I'm not familiar with what's available or possible with a BMW.

 

[HB Chris]

A speedo shop will swap one of the gears in your speedo. They can get it close but it depends on the number of teeth. If they go from 20 to 19 let's say that will change it 5% so don't expect accuracy beyond that.

 

[Polariscsl]

A company called speedy cables (part of the old VDO business) in the UK could do this - I presume there would be a similar outfit nearer you though.

 

[Ed G]

3.25 speedo

Not sure if they are the same style, but I have a CSi speedo (used with a 3.25 diff) that was professionally regeared to reflect mph on the kilometer numeral scale. The "kmh" script is blacked out with "mph" overwritten on it. You have to inspect it very closely at an angle to discern it.

Yours for $65- includes boxing, postage, and bragging rights for the only speedo on your block that goes to 240 mph.

If you're interested, PM me and I'll dig it out and send a photo.

Best

 

[m5bb]

My speedo got very erratic and was useless.
I sent it to Hollywood Speedo and they got it working very accurately.
Before I sent it they asked me to put a piece of tape on the cable, where it would attach to the back of the speedometer, like a flag.
Then take the car and slowly roll the car 59.5 ft and count how many times the flag went around. IIRC it was 13.5 times.
This gave them the ratio and they calibrated the speedo to match.
I have checked with my Iphone GPS and it is very accurate.

It cost $140.

There are not many places that have the magnetic machine that can calibrate and set one of these speedos.

 

[lip277]

Seeing you are in Fairfield....

I used Palo Alto Speedometer a while back to fix the inoperable speedometer in my 2002. Took about a week and worked great for the next 15 years (till I sold that car a short time back).

I believe if you tell them that when the car is going 'X mph' (in reality) - it reads 'Y mph' - they can adjust the gearing pretty well.
They can also go through your unit and give it a tune up (so to speak) to make sure all's well.

Good luck.