speedo cable snapping

[Dean]

hello

i have now gone through 3 speedo cables in 15 miles!!
i have a mk1 with a centre speedo, twin carbs with MED stub stacks and filter
speedo i a NOS smiths one with only 10 miles on it, would be more if my speedo worked

the first one was a 26"
2nd was another 26" and it screwed it self up at the gearbox end
3rd one did the same thing but this time i decided to use a 30" and thought it was due to it being under too much stress due to the air filter , but with in 1 mile it did it again

its a pain in the arse. i know it more than likely due to my air filter, and it may be to much of a tight bend but is there anyway to get around it ,
i do have a long cable but then i have way to much laying around in the engine bay,

i have read about 90 degree speedo thingy , but i can't see that working on the back of my speedo,

anyone had this problem, and how to get round it

[dklawson]

I was going to suggest the longer cable but you have obviously tried that.

Have you been taking the core out of the cable and lubricating it before installation? Also, have you tried spinning the speedometer input by hand to feel for tight spots? While this may not be the case with your speedometer, I have seen the pinion gears for the odometer distorted which caused binding on the gauge's input.

[rich@minispares.com]

it could be a seized / tight speedo head, you can stick a bit of an old cable into it and GENTLEY run it with a battery drill to see if it works ok.

my er' has a 90 on the speedo head and the cable then goes through a hole that's been drilled to the left of the heater. this means that it follows a really smooth path and is out of the way of the exhaust and the carbs.

you also need to make sure that the inner cable locates tight and hard into the drive in the gearbox, if it gets hooked up the inner cable 'snakes' up the outer and breaks in no time.

I always take the speedo drive out the box and make sure that the cable is fully home, and if needs be fit the two together into the gearbox

[Spider]

Maybe a pic or two may help.

If the cable's going through a tight bend (tighter than about 4" radius) then it will break, or indeed if it's kinked over something.

Two things spring to mind;-

If the cable route is tight, maybe an angle drive head at the speedo may help?

Also, are you 100% sure that the cable is going in to the drive in the gearbox. I had a similar issue about a year back and what I eventually found was the square on the speedo drive was a tad too small. Initially thinking it was the cable, I then ground it smaller but then it was slipping down between the drive and the outer housing. It did as yours is doing in that it appeared to work for a short time. I ended up pulling the drive out to see what was going on and finally resolve it. The speedo drive was a genuine one by the way! I swapped it for another, problem solved.

[Dean]

yes the speedo into the gearbox was fitted correctly, it was fitted and made sure it was seated down correctly before i refitted the engine again Tuesday. i even greased the threads as so it would make like easier to remove
the cable was free to move and i pulled it up and down the sleeve a few times

i am sure its where it has to have a 90 degree bend from under my air filter towards my speedo.

i will try the other long cable i have , i sure its around 39", use it to test with as it is too long. and see if i can get a straighter route to the speedo,

it would be good if you could have a 4-5" length of speedo cable to clear to the bulk head , then a 90 drive box, and then a speedo cable from that to the gearbox.

i will get some photos later, as i am over the garage finishing off the car for Beaulieu tomorrow.

[dklawson]

When you are checking this out, do take a piece of one of the broken cables and try using it to turn the speedometer input as Rich and I suggested earlier. If you find tight spots after making several (a lot of) turns, there is likely a problem in the speedo odometer drive that is contributing to the cable breakage. You need to turn the input enough that the odometer pinion gears make at least one revolution to feel for possible tight spots.

[Dean]

ok got the cable off and again it has snapped at the gearbox end just after to solid bit that goes into the square hole.

i dug out my spare long cable , made sure the cable was free sleeve, and even connected to the to my drill to make sure it did not snag up.

i then plugged it into the speedo and i could not turn it by hand, i connected the drill to it and and lightly pulled the trigger,
it turned but fell it tighten up once released it spun back.
after a while it just spun its self inside the square hole of the speedo. so there is resistance there

so my NOS speedo has some kind of problem. something is sticking inside.

it did work for about 8 miles then since then its just eaten cables.

so instead of letting it eat more cable, i take it off and have a look

[woodypup59]

The grease of your NOS speedo has solidified.

You need to strip it down and re-lube it.

You may find that, once the speedo is working, the odo won't work properly due to the number wheels being "stuck" together by the same solified grease.

I have several with this problem - they stick at every 1000 miles.

[dklawson]

Hopefully it is just the gummed up grease on the speedo input shaft.

You said you got this to turn using a drill. Apply a small amount of light oil to the area around the square drive hole and hold the speedometer "face down" while you use the broken cable in a drill to run the gauge at low speed. With luck you will get the oil to work down into the gap and free things up. It will feel quite different when this has happened. When done, turn the speedometer "face up" and allow any excess oil to drain back out of the gauge. Too much lubricant can be as bad as too little or dried up.

The odometer number wheels do get grimy with age and can stick as Woodypup said. However, since you have a NOS gauge, there should not be any build up on the interior components yet. You may find the odometer works fine, just keep an eye on it.

[pad4]

Just a slight diversion - having recieved yet another fking speeding ticket ive gotten me a gps speedo - 37 quid from tweeks (how far out was my mini speedo 30mph was 37) - speedo cables disconnected permantly now



pad

[Spider]

The top end of the Cable Route appears quite OK to me.

Have all cables broken roughly in the same place?

<Edit: Have you tried leaving the Cable not connected to the Speedo, Jacking a Wheel up and spinning the Wheel while checking what the Cable is doing? If you can get someone to help you with this, have a look down the lower end where they are snapping to see if the outer Casing is moving about and also just to see if it's sinning quite freely. If you haven't someone to help, then you can try it by running it in gear with a wheel clear (assuming you haven't an LSD)>