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Speedo
Dave Bailey - 4/12/11 at 04:51 PM

Hi... getting close to IVA now and was talking to someone a few days ago about my speedo pickup.... I have a sensor on the front wheel which is obviously undriven.... I was told that during IVA the speedo is checked on a set of rollers... Is this going to be a problem? WillI fail being on an undriven wheel?

Dave B

rb968 - 4/12/11 at 05:22 PM

All I can tell you is at my IVA at Carlisle my speedo would not read correctly on the rollers. He tried it several times and eventually drove it round the car park and assessed it. My sensor is on the near side driveshaft inner joint and as speed increased it went off.

I think there is some flexibility for he examiner to determine.

Rich

stevegough - 4/12/11 at 09:12 PM

the speedo is tested on rollers up to 70 mph - mine was tested on the rear wheels as the sensor is on the prop. If your sensor is on the front, he will surely put the front wheels on? Not sure if the rollers can be powered if necessary, but I'm sure it isn't a fail having it on the undriven axle.

iank - 4/12/11 at 10:11 PM

If it can't be measured on the rollers they are supposed to do a driven test at speeds between 35mph and 70mph.

quote:
17 Speedometer and Reverse Gear

Where the accuracy of the device is in question, (I.E any vehicle other
than an original unmodified speedometer fitted to an mass produced
vehicle which its self has no modifications that would affect the accuracy
of the device) and with the vehicle positioned on, or fitted with a speed
measurement device, operated to the manufacturer’s instructions, drive
the vehicle at a stable speedometer indicated speed of 35mph and note
the true speed. Repeat at four more speeds up to and including 70mph
as is necessary to confirm compliance.
Where the speed of the vehicle can not be measured with the available
equipment it may be necessary for the applicant to demonstrate
compliance.

matt_gsxr - 4/12/11 at 10:43 PM

My sensor was on a rear wheel for SVA. The rollers at Leighton Buzzard are not driven, and I have an open diff (no LSD).

So, the readings were off because one wheel was running much faster than the other.

They checked it by driving around the car park in a rather comedy fashion.

If I did it again, then I would set up my phone to video to record my GPS and speedo together on the way to the test (which is why I knew the calibration was correct all along!).

Matt

stevegough - 5/12/11 at 05:49 PM

quote:
Originally posted by matt_gsxr
My sensor was on a rear wheel for SVA. The rollers at Leighton Buzzard are not driven, and I have an open diff (no LSD).

So, the readings were off because one wheel was running much faster than the other.

They checked it by driving around the car park in a rather comedy fashion.

If I did it again, then I would set up my phone to video to record my GPS and speedo together on the way to the test (which is why I knew the calibration was correct all along!).

Matt


Good point, Matt - When I was watching my tester doing mine, I noticed that the left rear wheel was only turning slowly during the test, so I asked the tester if a brake binding on one wheel would upset the reading? -His answer was that it wouldn't as the equipment takes an average of the speed of the two wheels.

Dave Bailey - 5/12/11 at 08:48 PM

Thanks all for the info.....

I will check the pickup and hopefully it will get tested by driving around the car park....

thanks
Dave Bailey