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Wed Jun 09, 2021 9:33 am

I rebuilt the speedo for my bus and it turned out great but the needle has a bit of a bounce to it. I used a clock oil for it but I'm guessing it's a little too thick / sticky.

I've some searches and I've seen a lot of generic "use a lightweight oil" but no real specifics on type or, even better, brand recommendations aside from "mineral oil", but I've seen arguments against that too...

Anyone got info to add some clarity?

Cheers!
Michael

Wed Jun 09, 2021 10:13 am

In most cases of needle bounce I've seen, it's generally the speedo cable that needs lube. It gets dry, binds, then wraps up a bit before breaking free. Other than that, I'd opt for a light silicone oil inside the speedo.

Wed Jun 09, 2021 11:03 am

Hi Michael,

I second this.

In most cases the cable is bent. Get yourself a new one.
Please avoid to use any sort of oil in your speedo. That’ll make it worse. It will end up in wrong reading because of different friction.

Eddy currents induce a force to the small aluminium bell which is attached to the needle by rotating a magnet inside the bell. If this rotation is not stable, the needle will jump.

If you would have problems with the needle bearing, I assume it would read completely wrong if not reading anything. But most probably it would not jump...

Wed Jun 09, 2021 11:32 am

telford dorr wrote: In most cases of needle bounce I've seen, it's generally the speedo cable that needs lube. It gets dry, binds, then wraps up a bit before breaking free. Other than that, I'd opt for a light silicone oil inside the speedo.

I should have mentioned that the speedo cable was replaced as well. Do they need to be oiled before installation?

Wed Jun 09, 2021 11:34 am

Tizian wrote:
In most cases the cable is bent. Get yourself a new one.
Please avoid to use any sort of oil in your speedo. That’ll make it worse. It will end up in wrong reading because of different friction.

Eddy currents induce a force to the small aluminium bell which is attached to the needle by rotating a magnet inside the bell. If this rotation is not stable, the needle will jump.

If you would have problems with the needle bearing, I assume it would read completely wrong if not reading anything. But most probably it would not jump...

I can give that a shot as well. It'll need to be cleaned out anyway, so I can retest with no oil. Any concerns about wear over time?

Wed Jun 09, 2021 5:24 pm

I was unable to locate it for a pic, but I cut of the cable mount from a junk speedo and installed a zerk on the cut face. Then I use a grease gun to pump wheel bearing grease into the cable. If I have a used cable I just keep forcing grease through the cable until it looks clean.

I used to let ATF drip through it. That also worked well. It is a bit less viscous. So, I never really trusted it.