hey my mk2's speedo has always been out, even with standardish size tyres.

with the standard steels (165/65/13's on 5.5j wheels) it would read about 36mph when going 30, and about 60mph when I'm actually only doing 50.

now that i have smaller tyres on wider wheels (175/50/13's on 7j wheels) it will read about 40mph when I'm really doing 30, and about 65 or so when I'm doing 50!!

i know this is common with fitting smaller wheels, but with normal sized wheels it was already out?

how can i sort this?

eric

what can i do bitchesss?

drove to reading yesterday, speedo reading 90, GPS reading 70

atleast ill never get caught speeding hahah

If you are VERY careful, you could try a DiY recalibration!

This would involve some instrument work in the form of gripping the needle pivot with needle pliers and moving the needle by the required amount. You will need a little patience though, as you probably won't get it right first time.

Regards.

i like D.I.Y! haha, so where do i start mate? :)

Tbh mate the power you're running it's probably just wheel spin more than anything

If you are VERY careful, you could try a DiY recalibration!

This would involve some instrument work in the form of gripping the needle pivot with needle pliers and moving the needle by the required amount. You will need a little patience though, as you probably won't get it right first time.

Regards.

That won't work though, as its not say +10mph over the whole range, the faster your going the more its out.

its about 10mph at low end and 20 at top

Yeah exactly, and different in between. Its not a linear error is what i'm trying to say.

Mines about that too eric, you might just have to live with it as it works off of a cable directly for the gearbox.

must be a way.

The manufacturing tolerance for speedometers is ± 10%, (3MPH at 30MPH; 6MPH at 60MPH etc) so no great accuracy to start with!

It is quite possible to do as I suggested, BUT you need two things 1) Lots of patience, as you will likely have to repeat the adjustment. 2) A touch like a midwife!

If you are not used to working with instruments, it would pay to practice on any speedo head that you can get hold of - depending upon its design, you will probably need it out of its case/housing, then it is a matter of grasping the pivot with needle pliers and moving the needle to a new position.

If you wish to lubricate the moving parts, use ONLY good quality CLOCK oil, anything other than that will dry up and cause more problems. The way to apply this oil is to pick up a small spot of it on a very small instrument screwdriver and deposit it on the individual bearing. You only need VERY small amounts of oil, and as I say, applied ONLY to the bearings.

IF you wish to go down this road, clock oil is available from local clock material suppliers or on line from H.S. Walsh (www.cylex-uk.co.uk) or Meadows and Passmore (www.m.p.co.uk)

Regards.

dont these require electrical input of some form? id make sure that 12v is going to the back of the dials (also check on the circuit board as a small voltage drop would effect this! cant you just buy some ones or try them in another mk2 to verify its a fault?

Replace the cable... It's probably slipping.

The mk2 speedos are mechanical buddy, so I'm guessing its all cogs and gears ect

Exactly, with a spinning flexible cable running from box to dial, which is more than likely slipping.

Ill try my spare one! Thanks :)

If you suspect that the drive cable is causing the problem, the thing to look for are rounded corners on the squared off ends of the inner cable at both the gearbox and speedo head ends.

It is also worth checking that the female socket at the speedo head and the drive pinion at the gearbox, into which the inner cable fits, have not also rounded off.

These squared off cable ends are formed by pressing the end of the inner cable into shape.

Regards.

It's a clutch-like design, the cable turns a magnetic disc in the speedometer very quickly, inside an aluminium wheel which is connected to the needle. The faster the magnetic disc spins, the further round the needle's wheel is drawn round. The wheel is turning against a weak spring.

I believe they're 'joined' magnetically, despite the needle's wheel being ally, as the housing around it holds a steel disc. I don't know how it works, seems to be some weird magno-kinetic science..

For over reading, all i can think of is the centring needle in the middle which keeps the wheels centred to each other. I'm thinking two things - one, that dirt here could cause extra friction, giving the needle an extra push forward..? Or otherwise that the spring for the needle has weakened over time, which means it puts up less resistance against the magnetic disc..? Dunno, that's alli can think of.

top bloke mikey ill try and find the spring and put it in some boiling water t make it tension back up as it should!

Good luck with that.

I need new clocks as i've just dropped the trolley jack on mine and tore the printed circuit There's some scene tax going about (especially on .DE the tight gits) but if i get another set with a mph clock i'll send you my one if you have no joy fixing yours.

thanks bro appreciate that!

If changing the cable doesn't work, then you can try to recalibrate it, even though it's not "linear" it may make a difference. What I did a while ago was removed the plastic lens of the speedo then fit it all back on the dash (minus lens) and took off the needle, then got on an empty a road and got up to 30 (reading on tomtom) I held the same speed then stuck on the needle. But if you try this it's best to use a private road. Worth a try in my books.

Hth