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Help, please to id the correct speedo

Posted: Thu Jul 19, 2012 7:21 am
by keithSB
Hi

I have a 1969 1098cc Traveller, as far as I can tell it has a standard rear axle differential, but I am suspicious an incorrect speedo.

It appears to be registering about 10 MPH more than it should at about 50 mph.

As the traveller has different differential ratio to the 2 door saloon, I assume therefore that the number of revolutions of the rear wheels per turn of the prop shaft will be different to that of a sallon, and so the speed and the distance travelled.

My logic is if this is true then the speedo needs top be different.

Can someone confirm if my logic is correct and if so how how I can identify the correct speedo.

My next question would then be does anyone have one of the correct ones?

Regards

Keith

Re: Help, please to id the correct speedo

Posted: Thu Jul 19, 2012 8:51 am
by bmcecosse
Trav has same final drive as saloon. A 1969 should have 1098 engine - and 1408 tpm speedo to match the 4.22 final drive.

Re: Help, please to id the correct speedo

Posted: Thu Jul 19, 2012 10:04 am
by liammonty
It's common for them to over read- a combination of lower rolling radius radial tyres (compared to the original crossplies), combined with the spring in the speedo weakening over time, meaning that the mileometer will still read reasonably accurately, but the speedo won't. Of all the (6) Minors that I've had, not one has had a speedo that didn't over read by around 10%. However, as you say, it could be the incorrect speedo.

Re: Help, please to id the correct speedo

Posted: Thu Jul 19, 2012 5:43 pm
by bmcecosse
They over - read by a good 5% when brand new! See any of the original road tests...... So yes - weak spring and radial tyres (what size do you have ) will only make it worse.

Re: Help, please to id the correct speedo

Posted: Thu Jul 19, 2012 7:06 pm
by keithSB
Thanks for all the input

I have 155 x14 tyres fitted, do you think these would have made a difference

Regards

Keith

Re: Help, please to id the correct speedo

Posted: Thu Jul 19, 2012 8:07 pm
by bmcecosse
They should help - the 145 tyres are smaller.

Re: Help, please to id the correct speedo

Posted: Fri Jul 20, 2012 6:10 am
by Declan_Burns
When I fitted a 3.9 diff and running on 145x14 tyres I found the speedo (1408tpm) to be dead accurate compared with a sat nav.
Regards
Declan