Strip speedo

Maurice Hickey

New Member
Evening all

Is it possible that the strip speedo on my 2000 SC ('73 series II), does not give the correct speed reading?

This has been bugging me since i got the car last year. I have my suspicions that the speedo doesn't read the correct speed or it just my imagination?

When driving up the M20 towards work occasionally, I travel at 70-85 MPH, (so the speedo says!) but it never feels like that speed when compared to the same speed in my wife's Ford Focus and the speed of other cars that pass me. Also on deceleration, the red strip doesn't decrease smoothly, (its more of a staggered/jerky drop off ).

Could this be anything to do with the speedo cable, that I could remedy, or will I have to live with the fact that i'm not going as fast as i thought!?

Anybody got any ideas??

Cheer
Maurice :(
 
Just imagine all the fuel you must be saving ! LOL

The speedo cables can be troublesome, could be worth removing the cable and forcing grease or oil down inside, you can get tools to do it, but you should be able to feel some engine oil down with a bit of fiddling.

Hope this helps

Richard
Webmaster
 
The first reply is worth doing as they do get jerky, but that wont alter the spped reading.

Are you running the correct tyres? 3500 tyres on a 2000/2200 make the speedo run about 10% out as the rolling radius is larger. I dont have the correct size to hand, but someone will or it will be in the book.
 
Hi Richard & Alfesti,

Thanx for your replies, Richard, I'll try what you've suggested, Thanx!!

I' am running on 165 x 14 inch, as quoted in manual.

Regards

Maurice

:)
 
Maurice,
I've always been told not to run oil down the speedo cable as it will damage the mechanism in the speedo itself.
Best way to check the speedo is to "pace" another (modern) car with a pal in it at a mutually agreed speed.
Regards, John.
 
If you are VERY careful it is permissable to oil the cable preferably from the gearbox end.

If it is jerky then it is more likely that the strands on the cable are catching within the outer casing. This friction would initially slow down the speedo reading then as it frees up the speedo could read higher for a short period of time. I think the only real solution here is to replace the cable initially and possibly the speedo head itself if a new cable does not solve the problem.

Regarding tyres the correct sixe for the four cylinder is 165 x 14 so if that is what you are running then it is correct.

Just a point - if you do pace another car make sure you use a hands free mobile to communicate between cars, £60 fine and three points now if you are caught using a mobile at the wheel! No I have not been done! Just got a friendly warning from a nice policeman. ;)
 
My speedo failed so I thought I would replace the cable but it turned out to be fine - the angle drive on the (auto) geabox had failed. These are expensive for such a small item but Clive Annable had a second hand item. I have often found the speedo noisy when working properly so I took out the inner cable and lightly smeared it with Vaseline. I guess you're not supposed to do this but it was the only thing that stopped the noise for any length of time.
 
You could of course add a rev counter and get a very accurate mph figure. From memory 1000 rpm = 19mph in top. Therefore if your on the motorway in top and she's doing 4000 revs your doing 76 mph so LOOK OUT for the cameras. In fact I always use the rev counter to judge my speed, great fun overtaking cars at speed cameras on the dual carriageway cos they don't trust their speedos but I DO trust my rev counter, never been flashed yet!
 
I thought that speedometers had to be accurate to
±2% to comply with legal regulations, although I agree the tacho has to be more accurate being electrically driven and not mechanically driven like the speedo.
Hope you have now resolved this problem.
Regards, John.
 
Sorry, had to pipe up. The rev counter CAN be very wrong, I once played with one on the bench and they are very susceptible to variations in supply voltage (they usually require the instrument voltage 10v ish to work). Variation of only a volt or so caused error upto 1000rpm, so if your instrument voltage requlator isn't spot on then the rev counter will be out.

I used a gps unit to check my speedo and also a bike speedo (they're really easy to fit, cheap and accurate), both gave similar results showing that the speedo was reading fast by nearly 10mph when showing 70. Mostly because I have 195/60/14 on the back.

Richard
Webmaster
 
I found a loop-hole......

.....not sure if I read this right but it would seem that a speedo is not a LEGAL requirement for at least the series 1 cars.

.....mind you they can be handy at times!
 
My opinion is that the speedo is the most "reliable" indicator of speed, not necessarily the most accurate. Being connected virtually directly to the wheels, it should be !. But it is generally very repeatable, if it reads 5mph fast at 70, then it will almost always read 5mph fast at 70, as long as you know then your ok.

The only problems I see are when the cable snaggs (which mine does) and the fact that it can be inaccurate.

What we need is a national network of vehicle speed calibration stations, so you can drive in and find out what your speedo reads at the various speed limits. Or it should be part of the MOT, seems daft that it isn't.

Richard
Webmaster
 
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