Shaky speedo/tach needles

burkbuilds · 04-02-2014, 09:06 PM

Hi, it's been a while since I've posted anything. I'm not sure exactly where this should fit but I put it here.
Over the years I've often wondered what caused some speedo's and tach's to "jiggle" instead of run steady like they always do in a car for instance. I've finally learned at least one answer to the question so I thought I'd share it.

The cable which runs from the speedo or tach is not technically a cable, it's a shaft, a flexible drive shaft to be specific and the company I now work for once supplied about all the OEM speedo "cables" to the big three automakers. The difference in a shaft and a cable is this, a cable has all the wires wrapped in the same direction around a central core wire or sometimes a rope, depending on the application. A flexible drive shaft is wound with every other layer going in the opposite direction of the previous layer and, at least at our company, it's always wound over a central wire. Really well made flexible cable will not give you much vibration in the needle of the speedo or tach. If the cable is not held to fairly close specifications during the winding process, you will get vibration, and the needle will shake. We still make some of these shafts for speedometer use but most speedo's and tach's in automobiles today are electronic and don't have a flex shaft turning between the gage and a gear or sprocket but most if not all motorcycles still use the flex shaft for that purpose. Like many things made today, price is the top priority for manufacturer's and a lot of this stuff for speedo's and things is made overseas and not held to very high quality control, so your speedo and tach needles jiggle.

Well, that may not actually help anybody, but maybe it will at least answer the question of why we have those shaky needles.

Water Warrior 2 · 04-03-2014, 01:39 AM

Why thank you BB. I have now learned something new today.

I have only had one speedo bounce or vibrate over the years and that was in a cage with well over 100,000 miles on it. Pulled the inner core out and sprayed it with a little chain lube while slowly sliding it back in. Just like new after that. It was still smooth 10 years later with my friend driving the old rust bucket as a daily driver.

peanut · 04-04-2014, 12:01 AM

Huh, I just assumed it was the smaller vehicle with more vibration. But it's the instrument itself... Cool! Thanks Burk! Glad to see you back too.

04-02-2014, 09:06 PM	#1
burkbuilds Senior Member Join Date: Mar 2009 Location: Shannon, Georgia Posts: 1,268	Shaky speedo/tach needles Hi, it's been a while since I've posted anything. I'm not sure exactly where this should fit but I put it here. Over the years I've often wondered what caused some speedo's and tach's to "jiggle" instead of run steady like they always do in a car for instance. I've finally learned at least one answer to the question so I thought I'd share it. The cable which runs from the speedo or tach is not technically a cable, it's a shaft, a flexible drive shaft to be specific and the company I now work for once supplied about all the OEM speedo "cables" to the big three automakers. The difference in a shaft and a cable is this, a cable has all the wires wrapped in the same direction around a central core wire or sometimes a rope, depending on the application. A flexible drive shaft is wound with every other layer going in the opposite direction of the previous layer and, at least at our company, it's always wound over a central wire. Really well made flexible cable will not give you much vibration in the needle of the speedo or tach. If the cable is not held to fairly close specifications during the winding process, you will get vibration, and the needle will shake. We still make some of these shafts for speedometer use but most speedo's and tach's in automobiles today are electronic and don't have a flex shaft turning between the gage and a gear or sprocket but most if not all motorcycles still use the flex shaft for that purpose. Like many things made today, price is the top priority for manufacturer's and a lot of this stuff for speedo's and things is made overseas and not held to very high quality control, so your speedo and tach needles jiggle. Well, that may not actually help anybody, but maybe it will at least answer the question of why we have those shaky needles. Login or Register to Remove Ads
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04-04-2014, 12:01 AM	#3
peanut Member Join Date: Dec 2010 Location: Joliet, IL Posts: 64	Huh, I just assumed it was the smaller vehicle with more vibration. But it's the instrument itself... Cool! Thanks Burk! Glad to see you back too. Login or Register to Remove Ads
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04-03-2014, 01:39 AM	#2
Water Warrior 2 Senior Member Join Date: Dec 2006 Location: Squamish B.C Canada Posts: 11,409	Why thank you BB. I have now learned something new today. I have only had one speedo bounce or vibrate over the years and that was in a cage with well over 100,000 miles on it. Pulled the inner core out and sprayed it with a little chain lube while slowly sliding it back in. Just like new after that. It was still smooth 10 years later with my friend driving the old rust bucket as a daily driver.
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