Re-calibrating speedo manually

[srb7f]

So I got pulled over this weekend, and when the officer asked me how fast I was going, I gave a generous underestimate by saying that my speedo said 60. Turns out I was going 73, but he was cool and said that if I got my speedo re-calibrated before Nov 15th, I'd get off (but of course the speedo would have to read lower than actual speed for this to work).
My wife and I paced the car on the highway, and as expected with 195/60/15 tires, the speedo reads higher than it should....rats. Is there any way to adjust the speedo myself so that it reads lower than acutal speed, so that I can then have it re-calibrated and documented?
How much does it cost to have the speedo recalibrated, and what type of shop would be able to do this for me? Steve

[Jared at Pelican Parts]

You cant calibrate them manually. Unlees you know what you're doing, I wouldnt try this yourself. (Ask me how I know) As for getting it calibrated, Idont know of any shops in your area, but THE gauge shop, at least on the west coast is North Hollywood Speedometer. I dont think it would be much to have the gauge calibrated

http://www.nhspeedometer.com/

[Dave at Pelican Parts]

Heh. NH Speedo is the "second location" of Palo Alto Speedometer, http://www.paspeedo.com . Of course, they're in Northern CA, not down south like you (and Pelican's office).

The only ways I know of to tweak the speedometer's reading are to get different size tires (you'd need very large ones indeed to get a 60 reading at 73 MPH), to put some sort of gearing in the speedo drive cable (old rally-ists may know where to find such), or to tweak the spring that the pointer attaches to. The latter tends to give very unpredictable results...

Pelican used to work with another VDO shop; we offered similar work to that done by NH Speedo and PA Speedo, but less expensive. Sounds like that may not be the case any more? (Tom or Wayne might remember who it was and if that's still something we want to offer.)

--DD

[BigD9146gt]

Yes there is. It involves dissasembling the speedo though, and i've often though about doing this by getting a spare speedo off Ebay. Heres what to do:

The black metal ring that goes around the glass is made up of two rings, an inner and outer. The outer ring is what is crimped to hold everthing together. Use a small screw driver CAREFULLY and slowly pry the hem up. Work around the parameter as many times as possible, bending the metal up little by little. The less you bend the metal each time, the less it will stretch, thus make it easier to hem back over when done.

Once the hem is opened, then slide the rings off. Make sure a soft pad is down so you don't crack the glass if it falls out.

Once the glass is off, then you can adjust it several ways.

1) Install the speedo back in the car without the face on it. Very carefully, lift the needle over the stop at the 0 mph spot. The speedo needle has a pre-tension on it, so it will stop on it's own past the 'needle stop'. Then mark with a the edge of a peice of tape where the speedo needle is pointing. Then pull the needle off, rotate it the distance 10mph would be on the speedo hash marks, and press it back on, and very carefully twist the needle back over the needle stop. Now start driving. You can check your pace with mile markers on a freeway and a stop watch. 60mph is 60 sec/mile,, or another car pacing you.

2) Use an electric screw driver and install a square drive in it that will fit into the back of the speedo drive receptical. With the electric screw driver on full blast, mark where the needle is pointing. NOW fallow the directions above for removing the glass and needle. Once you've moved the needle back 10mph and placed back on the needle stop, then use the electric screw driver on full blast and see if the needle is 10mph less (or whatever percentage less it would be at for 70 mph).

FYI: Palo Alto speedo is its own company. Even though they probably do good work, North hollywood is the king. The founder of North Hollywood was/is the US/West coast rep for VDO. Palo Alto could only dream of having as many old parts as North hollywood.

Have fun messing with the police! Don.

[Jared at Pelican Parts]

Originally posted by BigD9146gt
Yes there is. It involves dissasembling the speedo though, and i've often though about doing this by getting a spare speedo off Ebay. Heres what to do:

The black metal ring that goes around the glass is made up of two rings, an inner and outer. The outer ring is what is crimped to hold everthing together. Use a small screw driver CAREFULLY and slowly pry the hem up. Work around the parameter as many times as possible, bending the metal up little by little. The less you bend the metal each time, the less it will stretch, thus make it easier to hem back over when done.

Once the hem is opened, then slide the rings off. Make sure a soft pad is down so you don't crack the glass if it falls out.

Once the glass is off, then you can adjust it several ways.

1) Install the speedo back in the car without the face on it. Very carefully, lift the needle over the stop at the 0 mph spot. The speedo needle has a pre-tension on it, so it will stop on it's own past the 'needle stop'. Then mark with a the edge of a peice of tape where the speedo needle is pointing. Then pull the needle off, rotate it the distance 10mph would be on the speedo hash marks, and press it back on, and very carefully twist the needle back over the needle stop. Now start driving. You can check your pace with mile markers on a freeway and a stop watch. 60mph is 60 sec/mile,, or another car pacing you.

2) Use an electric screw driver and install a square drive in it that will fit into the back of the speedo drive receptical. With the electric screw driver on full blast, mark where the needle is pointing. NOW fallow the directions above for removing the glass and needle. Once you've moved the needle back 10mph and placed back on the needle stop, then use the electric screw driver on full blast and see if the needle is 10mph less (or whatever percentage less it would be at for 70 mph).

FYI: Palo Alto speedo is its own company. Even though they probably do good work, North hollywood is the king. The founder of North Hollywood was/is the US/West coast rep for VDO. Palo Alto could only dream of having as many old parts as North hollywood.

Have fun messing with the police! Don.

You know, this is exactly how i tried to calibrate mine, except that I didnt have a drill that spun the shaft fast enough, and kept it at a constant speed. I think that would be the biggest problem here.

[BigD9146gt]

Jared, your absolutly right. Maybe a dremel will spin fast enough? I just figured that anything spinning it enough to get it up, like 20mph would be good enough. Then again, its not that accurate at 20. So.... scratch the second idea and just install it in the car and adjust it that way!

Thanks, Don.

[Jared at Pelican Parts]

Yeah, the Dremel ought to do it.. hmm... might be worth a shot.

[SGB]

I suggest a paper semi-circle taped to the speedo face with "60" wherever the needle was when you got pulled. This isn't as flippant an answer as it sounds. Did the officer say "professionally recalibrated"?

[Joe Ricard]

Yup thats what I did. moved the needle. Actually got lucky the 1st time. I have measued it with those sleeping policeman radar displays. You know it flashes your speed is xyz. Comes out within a mile per hour. On the street I also run 205/60-15 on the back which is pretty cose to stock size. Autocross is 205/50-15 these are like 2" shorter. really helps with the torque.