Speedo reading

[sean sherry]

Speedo on my MPH Hong Kong 280 Sl is 8.5% low , both ODO & Speed. It is electro/ mechanical VDO unit. I can't get any definitive answer from any Repairer. Bring it in and we will have a look. i.e., a euphemism for, we don't know if it is adjustable (on the circuit board ) I can't see that Mercedes would have a dozen different units for every diff ratio , wheel size etc. One basic unit that is adjustable ?. No problem sending the Speedo off if I can find someone who knows these units.....
Thanks..... Sean

 

[sean sherry]

To answer my own question, It seems that VDO supplied specific Units for every different Model. Major surgery to match to my car which also now has a higher Axle Ratio. In the too hard basket. I'll go by my Sat Nav.... Sean

 

[Oversize]

Any speedo repairer should be able to calibrate it accurately

 

[Michel]

Speedo on my MPH Hong Kong 280 Sl is 8.5% low , both ODO & Speed. It is electro/ mechanical VDO unit. I can't get any definitive answer from any Repairer. Bring it in and we will have a look. i.e., a euphemism for, we don't know if it is adjustable (on the circuit board ) I can't see that Mercedes would have a dozen different units for every diff ratio , wheel size etc. One basic unit that is adjustable ?. No problem sending the Speedo off if I can find someone who knows these units.....
Thanks..... Sean

Not sure about German speedos, but in my American cars days, Turbo Hydramatics had a unique speedo gear that related to whatever the diff ratio was and had to be changed when your diff ratio was altered.

 

[sean sherry]

Not that easy Mark. The gears need to be changed to set the ODO .The speed can be reset electronically. Problem is the Speedo is not correct for the car, plus the diff Ratio has been changed. How many pulses does the speedo need ? we don't know. And what gears to change to ? we don't know. Hence the to hard basket.. $ $ $ ... The Sat Nav. comes to the rescue....... Sean

 

[sean sherry]

Ditto the local Fords Michel. Simple matter of changing the cable driven gear at the gearbox end. . Different colours identified them. VDO had a digital signal coming in for the Speed reading, why did the ODO have to be mechanical ? complicated and costly.
Ours is not to reason why.... Sean

 

[Michel]

Ditto the local Fords Michel. Simple matter of changing the cable driven gear at the gearbox end. . Different colours identified them. VDO had a digital signal coming in for the Speed reading, why did the ODO have to be mechanical ? complicated and costly.
Ours is not to reason why.... Sean

Sat Nav it will be Sean.. besides they are more accurate than speedos.

 

[Oversize]

I'm sure it could be fixed in Melbourne....

 

[Michel]

I'm sure it could be fixed in Melbourne....

I'm sure too....

 

[sean sherry]

Yes anything can be fixed for $ $ $. and time . Work out the diff ratio, count the pulses per wheel revolution, sort out the gears in the speedo head, if the right ones can be sourced. Then sort out the signal to correct the speed reading. What a lot of agro and who cares. Most speed readings are inaccurate even on new cars. My Subaru 30R was 6% high at 100Ks and so are Fords etc. Our 2010 C Class is accurate to 1 k at 100Ks... rarity ?.......Sean

 

[BenzBoy]

Yes anything can be fixed for $ $ $. and time . Work out the diff ratio, count the pulses per wheel revolution, sort out the gears in the speedo head, if the right ones can be sourced. Then sort out the signal to correct the speed reading. What a lot of agro and who cares. Most speed readings are inaccurate even on new cars. My Subaru 30R was 6% high at 100Ks and so are Fords etc. Our 2010 C Class is accurate to 1 k at 100Ks... rarity ?.......Sean

AS rarity? No - my CLK, ML and Spirit are dead on according to the Tom Tom. Now of course it is difficult to tell if the speedo on any of these is out by a k or two because the needle points don't have a fine hair sight.
Now are you sitting down? The 1933 PII is dead on right as well and it does have a fine point needle for accurate reading....
As for the 450SE I once owned, well the speedo read under by an increasing amount over 80KPH so use of the sat nav is advised for the current owner.
Regards,
Brian

 

[CraigS]

I am just about to take my 6.3 speedo to Lionel Otto in Brisbane. When I mentioned to them that the wheels had been changed from 14" to 15" and could the speedo be calibrated to reflect accurate speed, they said they could, but when they told me what I had to measure, I gave up and will just have it repaired so the odometer works and it goes beyond 65 MPH.

My 300E-24 reads UNDER by about 3 KPH, so I always need to be careful. First time I have ever had one read under.

 

[sean sherry]

It seems that the answer is "How long is a piece of string"
Just as a matter of interest I chatted to a NSW Police Patrol Officer when visiting the local Garmin ( Sat Nav ) Agent. Sat Navs are less than 1K inaccurate. Police Road Patrols usually don't bother cars within a 10 K tolerance if driving is with due care... Fixed Speed Cameras... They hate them to. And apparently Victoria is the Speed Camera Capital of the World !
And Warwick in Q/land runs a close second..........Sean

 

[Oversize]

It has nothing to do with wheel diameter; it's the tyre diameter that will have an affect. Replacement tyres should be the same as the originals if you want the speedo to be anywhere close to what it should read. The Tyre and Rim Association of Australia have a Standards Manual that lists most tyre sizes and their corresponding overall diameter at a control temperature, load and pressure.

Modified vehicle standards allow a tolerance of +15mm -26mm on a passenger car however your speedo won't be accurate (VSB14).

The ADRs used to specify a 10% accuracy for speedos but I believe that's changed for new cars in the last few years.

Most traffic cameras are triggered if you're doing more than 7kmh over the limit and they take off 3kmh for error tolerance. Vic Police can enforce the speed limit along similar lines, but sometimes use discretion if it's appropriate.

 

[sean sherry]

Rim size , Tyre size I'm sure most people get my drift. Yes, the Victorian Police would use their discretion, as the Patrol did when he clocked me at 123 on the Hume Hwy. I overtook him and a Semi in the dark, (did not see the Patrol car ) After a pleasant chat , " on your way and watch your speed ! "

 

[260ebenz]

Rim size , Tyre size I'm sure most people get my drift. Yes, the Victorian Police would use their discretion, as the Patrol did when he clocked me at 123 on the Hume Hwy. I overtook him and a Semi in the dark, (did not see the Patrol car ) After a pleasant chat , " on your way and watch your speed ! "

'Luck of the Irish', there Sean!


Safe motoring Sean.