TC Speedo cable - lubricate?

[Certified Lotus]

My brand new speedo cable failed at 243 miles. No sound, just stopped working. I haven’t pulled it yet to see where it broke.

While I was at LOG39 I asked a number of people about there own experiences with the speedo cable and I got responses like:

* I’m on my 5th one and it wasn’t until I bought a right angle adapter at the speedometer end that they stopped breaking.

* Never had to replace mine. Always works

* my speedo hasn't worked for years. I got tired of replacing cables.

* you need to lube the cable before installing.

* i’ve Never lubed the cable. Just be careful of the angle the cable goes into the speedometer.

So what is reality? Does the cable need to lubricated and if so, what do you use?

[jbcollier]

I have a hall-effect sensor attached to my transaxle so I can’t comment specifically.  That said, after too many years as a mechainic, I’ve installed my share of speedo cables.

Speedo and tach cables are usually shipped dry.  You need to lube them before installing them.  I use either light grease or gear oil, sometimes both.  The cable is so long on a Europa, it’s hard to lube it thoroughly.  I would be inclined to use gear oil and hang the cable to make sure it goes all the way through first.  You could also “push” light grease through until it comes out the end as well.

Routing is very important.  Any tight bends will mean eventual failure so make sure any bends are as wide open as possible.

[BDA]

The alternative to speedo cables is aN electronic or GPS speedo. Smiths sells an electronic unit that can be driven by the hall-effect unit JB has, a sensor that counts "bumps" such as the bolts holding your front brake disc on, or a GPS driver like I have. Speedhut has a unit that is also popular (though it is slightly larger. An early member here described his installation here: http://www.lotuseuropa.org/LotusForum/index.php?topic=660.0. The only downside is that it takes a little while to acquire the satellites when you first drive off so your odometer will understate your mileage slightly. I don't know that it's ever taken a mile.

Of course either are several times the cost of a new cable. Depending how you mounted yours and if you wrapped wires on yours, it may be difficult to get out.

[EuropaTC]

I've had a couple over the years and whilst I'd say they have all failed prematurely compared to normal cars, 240-odd miles is definitely on the early side of failure.

As John says, routing is all important on such a long run of cable. You can get it reasonably smooth without a right angle adapter and while lubrication is good, I think considering the length of cable you need to be careful on what you're using.  I would imagine if you used grease then the drag over the length would impart quite a stress on the drive end, which incidentally is where I've seen failure. 

For the current one I just removed the inner wire, wiped it with engine oil and put it back. Speedo is smooth, no jerking about and seems about right based on the revs so that's what I'm going with. If we could get a screen-printed dial on am electric one that looked original and not like a modern speedo, I'd be very tempted to go with a sensor driven speedo.

Brian

[jbcollier]

I run a Smith GT40 electronic speedo with a Ford Hall effect sender at the transaxle end.  I opted for the 180 mph version but calibrated it to read in kilometres.  There is an actual kilometre version but it reads to 320 km/h and the needle would hardly get off the peg in normal traffic.

The rest of the gauges are from the GT40 line as well.  The temp gauges are mechanical which I prefer and are available with the long sensor tubes required for mid/rear engines cars.  The only non-GT40 gauge is the outside air temp gauge which I had fitted with a black bezel and, thus equipped, matches nicely.  The outside air temp gauge may sound frivolous but it is very useful in the shoulder seasons when you have to be mindful of black ice.

[Pfreen]

Find where it broke and that will be where the problem was.  I also found if the needle bounces, there is a tight bend, since the wire winds up and then releases.  You can also test the new cable by driving the cable with a drill motor from the transmission end.  I don’t remember what grease I used but there are a lot of opinions on the internet.  I may have used graphite.  Not sure.

[Lotuswins]

I found out the hard way not to use grease on the speedo cable.  It hardens after years in service, and restricts the turning....I think I have it cleaned out now and put some light oil in there.  It still bounces, but at least its working.
A trick to alleviate the sharp bend at the speedo end is to swap positions of the tach and speedo which gives more room for a wider radius. 

Jerry Rude
4005R

[jbcollier]

Good point.  Anything that is greased needs to be regularly re-greased.  That should not detract you from using grease though.  If you use oil you will also have to refresh it at regular intervals.  As long as you don't let the grease dry out completely regular refreshment will be all that is required.

[Kendo]

Can you just pull out the inner wire, re-oil/grease, then thread it back in? Or do you have to remove the whole jacket as well?

[jbcollier]

Just pulling  the inner is all that is required.

[shootingsight]

What fatigues metal is bending it back/forth, and it eventually fails.  The number of times it can be bent before failure is affected by how far it is being bent.

Taking a rod that goes around a corner, and rotating that rod means it is being bent back/forth every time it rotates.  So the tighter the bend radius, the higher the bend stress is, and the sooner it will fail.  Net, you want to route the cable such that it has the most generous bend radius possible.

That said, as I restore mine, there are some cool digital gage options available that will be more reliable (including screens, rather than mechanical needles).  I have not decided if I want to go that route, or if that is blasphemy.

[jbcollier]

Sorry, pretty much straight to heck (or your cultural equivalent) for that heinous crime.

:-)