Rudiger Wicke
Member
Any advice if a speedometer (P6 V8 Series 2) seems to over-read by approx. 15 mph?
speedometer over-read
- Thread starter Rudiger Wicke
- Start date
Rudiger Wicke
Member
40 mph +
By the way - I´m referring to a LHD P6 V8 with km/h speedometer - so the indicated speed is 80 instead of 60 km/h - and so on
By the way - I´m referring to a LHD P6 V8 with km/h speedometer - so the indicated speed is 80 instead of 60 km/h - and so on
Rudiger Wicke
Member
No - it wasn´t my car and I don´t know if the owner resolved the problem (car has been sold in February 2018)
mikecoombs
Active Member
Check your tyre diameter. Changes in width or side wall bulge or brand can reduce the rolling diameter causing speedo to read high. Correct numbers are in the manual
M
M
Thanks Rudiger and Mike.
Agreed on the tyre size affecting the speedometer. However, I would expect the tyre size would throw off the speedometer at any speed (More or less linearly). Our speedometer is pretty accurate at speeds below 40MPH or so. Anything higher than that it reads high (Compared with GPS readings) the further away from 40MPH the higher than actual it reads. At about 65MPH the speedometer reads around 74MPH as a data point.
Agreed on the tyre size affecting the speedometer. However, I would expect the tyre size would throw off the speedometer at any speed (More or less linearly). Our speedometer is pretty accurate at speeds below 40MPH or so. Anything higher than that it reads high (Compared with GPS readings) the further away from 40MPH the higher than actual it reads. At about 65MPH the speedometer reads around 74MPH as a data point.
Yes, quattro I agree it has to be the speedometer. Thanks for the reply! I recently picked a used speedometer and using a drill to spin it compared the one I bought with the one in the car. The one I bought appears to be more accurate. I will switch it out in a week or two to compare in the car with GPS readings.
Has anyone changed the odometer values? Is it relatively easy without affecting the speedometer inner-workings? If the speedometer that I bought is more accurate, I would like to set the odometer to 00000 to match roughly the same value that's in the car.
Has anyone changed the odometer values? Is it relatively easy without affecting the speedometer inner-workings? If the speedometer that I bought is more accurate, I would like to set the odometer to 00000 to match roughly the same value that's in the car.
classicalgreen
Active Member
mine reads on average 5 less than real speed ( 2 sat nav's and a car following checked) so have to be careful with speed cameras as easy to forget and cruise past a few mph over limit! I was doing a healthy 65 mph in slow lane .then when we stopped got asked why I was thrashing the odd girl at over 70 ( slow lane) nice to see not only one with speedo issues. I thought mine was tyre rolling radius ..but as 5 new tyres fitted not going to replace those in a hurry.
Me too!
I felt I was going faster than the speedo was telling me so I hooked up a sat nav and found that when the speedo was reading 60 mph the speed was actually 66 mph.
I don't think I'm going to do anything about this but will have to keep alert to it when driving the car.
Most other cars on the road will be indicating nearer 70 mph at a sat nav speed of 66 mph.
I felt I was going faster than the speedo was telling me so I hooked up a sat nav and found that when the speedo was reading 60 mph the speed was actually 66 mph.
I don't think I'm going to do anything about this but will have to keep alert to it when driving the car.
Most other cars on the road will be indicating nearer 70 mph at a sat nav speed of 66 mph.