Speedo adjustment?
Discussion
With the assistance of a fellow PHer and a SATNAV I have now convinced myself the speedo is consistently reading low by very nearly 10 mph (like 9.8 mph) at all speeds in my 96 Griff (T5 box).
A calculation from the Rev Counter indicated a speed that tied up with the SATNAV so it appears that when the speedo reads 30mph I am actually doing 21, likewise 31 when the speedo says 40 and 41 when it reads 50. This constant difference exists right up to 70mph and beyond.
I have standard wheels with standard SO2s and I am at a loss as to what could be causing this amount of constant difference. Is the speed sender mechanism adjustable in some way (I suspect not)
Any ideas and especially suggestions as to the corretive action would be most welcome.
Thanks, Paul
edited to say the speedo needle gives a smooth transition to all speeds and otherwise appears to work normally.
>> Edited by Dutchone on Tuesday 13th September 13:36
A calculation from the Rev Counter indicated a speed that tied up with the SATNAV so it appears that when the speedo reads 30mph I am actually doing 21, likewise 31 when the speedo says 40 and 41 when it reads 50. This constant difference exists right up to 70mph and beyond.
I have standard wheels with standard SO2s and I am at a loss as to what could be causing this amount of constant difference. Is the speed sender mechanism adjustable in some way (I suspect not)
Any ideas and especially suggestions as to the corretive action would be most welcome.
Thanks, Paul
edited to say the speedo needle gives a smooth transition to all speeds and otherwise appears to work normally.
>> Edited by Dutchone on Tuesday 13th September 13:36
Hi Dutchone,
Mine is exactly the same - the worst bit is that as it is 10% out it is putting on 10% more milage as I have measured it over a measured mile!! so i have a 55k car that really has only done 50K!!!
Unfortunately there isnt much that can be done unless you get the speedo re-calibrated or get a new one. A friend told me this is a common issue as they are 'allowed' to be up to 10% out, and this is usually on the plus side to aid in speeding etc.
I think that you will just have to try and accept it - I have!
I only do 6k miles a year so am not too fussed, but if you are doing lots it maybe worth having the unit recalibrated. - I know that there is nothing you can do regarding the speed sendor near the diff.
Sorry its not what you really want to hear but hey ho...
Regards,
Lig.
Mine is exactly the same - the worst bit is that as it is 10% out it is putting on 10% more milage as I have measured it over a measured mile!! so i have a 55k car that really has only done 50K!!!
Unfortunately there isnt much that can be done unless you get the speedo re-calibrated or get a new one. A friend told me this is a common issue as they are 'allowed' to be up to 10% out, and this is usually on the plus side to aid in speeding etc.
I think that you will just have to try and accept it - I have!
I only do 6k miles a year so am not too fussed, but if you are doing lots it maybe worth having the unit recalibrated. - I know that there is nothing you can do regarding the speed sendor near the diff.
Sorry its not what you really want to hear but hey ho...
Regards,
Lig.
Lig,
I had not thought about the adverse effect on the mileometer!
So for every true 100 miles travelled, I have a mileometer that states 110 miles covered.
This then affects my fuel consumption figures and makes them worse than I thought!
I know what to do, I'll get bigger wheels on the back!
What does a Griff look like as a Santa Pod dragster.
I had not thought about the adverse effect on the mileometer!
So for every true 100 miles travelled, I have a mileometer that states 110 miles covered.
This then affects my fuel consumption figures and makes them worse than I thought!
I know what to do, I'll get bigger wheels on the back!
What does a Griff look like as a Santa Pod dragster.
Dutchone said:
Lig,
I know what to do, I'll get bigger wheels on the back!
Hey, nice Griff!
At about the time your car (and mine) left the factory they were on 235/50 at the back which have a bigger circumference. I very much doubt it will make up for 10% (not difficult to work out but it's just too late in the day!) but it will obviously help. Mine is very similar.
Pardon me for straying from the Chim forum - but I found that there was a small hole in the side case of my speedo which gave access to an adjustment potentiometer. After a few tweeks of the pot and a few road tests I managed to get it to read reasonably accurately.
I used a stopwatch and a measured mile on the M4 to check it at 60mph (bit scary keeping to only 60 on the M4 near Slough).
Back to the Chim forum now (then off to play golf).
Nick
I used a stopwatch and a measured mile on the M4 to check it at 60mph (bit scary keeping to only 60 on the M4 near Slough).
Back to the Chim forum now (then off to play golf).
Nick
Ummmm!
Can anyone confirm that a 94 Chim has the same speedo as a 96 Griff. If so, I assume access to this hole for the potentiometer means a dash out job.
Harrow Chim,
If you are monitoring this - How did you deal with a dial out / drive / adjust - repeat activity or is a
Chim speedo easy to get at?
Can anyone confirm that a 94 Chim has the same speedo as a 96 Griff. If so, I assume access to this hole for the potentiometer means a dash out job.
Harrow Chim,
If you are monitoring this - How did you deal with a dial out / drive / adjust - repeat activity or is a
Chim speedo easy to get at?
Once the dash top has been removed (which can be a PITA) the speedo is relatively easily accessed. It is held onto the dash by a U shaped clamp. I undid the clamp which then allows the speedo to be pulled out of the dash towards the driver enough to get to the adjuster without disconnecting the electrical connectors on the back of the speedo. I was then able to rest the dash top back in place and take the car for test drives with the speedo resting back in it's normal position. When I wanted to adjust the speedo it was just a matter of stopping sliding the speedo out a bit adjusting it and sliding it back into place ready for another test drive.
Once I was happy with the adjustment I fixed it back into place.
I have no idea how similar our instruments are but they are both electrically driven rather than mechanical so they can't be all that dissimilar.
Once I was happy with the adjustment I fixed it back into place.
I have no idea how similar our instruments are but they are both electrically driven rather than mechanical so they can't be all that dissimilar.
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