Cheap speedometer accuracy

[Steve S]

Very impressed with the Smiths copy speedo bought from Ebay for just £19 including the correct cable; however it's over reading the milometer by a long way and so I thought I would compare the speed readings to my sat nav readings.

Turns out to be very non linear, ie overly high up to 30 mph (true 24) then 40 mph (true 35) but correct at 50 mph. Haven't had the nerve to go faster than this as yet as it's tricky reading the tiny numbers on the sat nav at speed!

Steve S.

[1608]

If its an Indian one ( looks like it ) same as mine, then good value I think. I think they are calibrated for KPM but they just stick an MPH face on it. Best way to check it is to pace somebody with a known true speedo. Anyway, at least its erring on the safe side so you won't get caught speeding.

[39speedtwin]

You will probably have to replace it at around 1,000 miles as they normally fall apart by then! You cannot beat an original Smiths Chronometric.
Best of luck.

[SPRIDDLER]

Turns out to be very non linear, ie overly high up to 30 mph (true 24) then 40 mph (true 35) but correct at 50 mph.

That's about the same accuracy as my concentric except that I'm sure it under-reads substantially at 70 as judging by the distance it takes me to stop I must be doing at least 110mph.

Later edit............

Awright, awright you clever lot - I meant chronometric - it was just a slip of the brain or a smelling pistake.

(Have I told you about my overnight trip on the Cross Flannel Cherry when I slept in a courgette?).

[clive]

I am surprised you are getting a speed reading at all out of your Carb concentric or not!

[Richard Mills]

Turns out to be very non linear, ie overly high up to 30 mph (true 24) then 40 mph (true 35) but correct at 50 mph.

That's about the same accuracy as my concentric except that I'm sure it under-reads substantially at 70 as judging by the distance it takes me to stop I must be doing at least 110mph.

Perhaps it's a Premier Concentric!

[Janet]

Turns out to be very non linear, ie overly high up to 30 mph (true 24) then 40 mph (true 35) but correct at 50 mph.

That's about the same accuracy as my concentric except that I'm sure it under-reads substantially at 70 as judging by the distance it takes me to stop I must be doing at least 110mph.

Later edit............

Awright, awright you clever lot - I meant chronometric - it was just a slip of the brain or a smelling pistake.

(Have I told you about my overnight trip on the Cross Flannel Cherry when I slept in a courgette?).

Was it in a vegetable bed?

[SPRIDDLER]

Was it in a vegetable bed?

It might've been but I couldn't see very clearly due the eye drops after my op for a detached rectum.

( the 'off topic' police will be after me now).

[1608]

Very good Nev. I can never remember the difference btn a Malapropism and a spoonerism

[robcurrie]

Clarified or rectified?