Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Speedometer error

Took our new M3W out on the highway for the first time yesterday. At an indicated 70 mph I was being passed by everything on the road. So I asked Molly to bring up a GPS on her phone. I was only going 64! Now I know why that cop didn't chase me down when I thought I was going 80.

I don't think you're alone. I think similar issues have been reported on here.

I think this over read of the speedometer is a common problem. My speedo reads 76mph when the GPS shows 70mph, about 8% error. I put this on my list of faults for the first 1000 mile service thinking it would be an easy laptop job to do a recal, it is only a glorified bicycle computer after all. I was told it was OK as it was less than +10% error. Later when the car was returned to the factory for other issues, I mentioned the large speedo error. They "had a look at it" but the error is still the same. Most of these type of systems have a datum pulse figure that can be altered to reduce the error but with no information available and the dealer or factory unwilling or unable to do anything.......

Try the VDO web site, I think I have read something on there with regard to calibrating their speedos. Otherwise just remember you are doing 5mph slower than you think.

Squirlz - same with my 4/4 Sport but looking at the BIG plus side, when you enter that 30 or 40 zone and the camera van parked a mile up the road targets you, you can still smile at an indicated 32/43 as you wont be contributing to funds.

It's a bit annoying but you'll learn to live with it!

Cheers

Jeremy

Speedos must not under-read, and are legal up to 10% over-reading. So an indicated 77 for an actual 70 is ok. 78, not so, nor 69.

GPS speed is not totally reliable, although it should be so in a straight line. If you have a local measured mile you probably can improve on the accuracy (ask local traffic or weights and measures - mine are very helpful to folk who want to measure things).

My vintage speedo reads 64/63 for 60mph, but that's the way I calibrated it. PM me if you want the method, but it's only applicable to mechanical speedos so no use for 5 speeders.

Just buy a Bigger Rear Tyre or wheel and get moving

While it is legal for the speedo to be in error by 10%, the local constabulary in Western Australia have removed that margin from ther ticketing, they will now book you for anything over the limit.

I recieved a ticket last week, for 57km in a 50 zone on a Suburb through road at 7.30pm on a Sunday night $75 thank you very much.

Even this will not work as the speedometer pick up is on the front RH wheel, not the gearbox. How about 20" wheels on the front?

If the speedo in the 5 speeder is a VDO, does this apply?
GoMog VDO speedo calibration

If not, there are other guides to calibrating electronic speedometers.