Gearing and speedo

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DJWALKER
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Joined: Mon Sep 14, 2020 6:10 am

Gearing and speedo

Post by DJWALKER »

Hi gents I can't find an answer to this , which way does high and lower front cog affect speedo reading?
Many thanks.
tony.mon
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Joined: Wed Jul 25, 2007 9:46 pm
Location: Norf Kent

Re: Gearing and speedo

Post by tony.mon »

Less teeth on the front is like more teeth on the rear.
More teeth on the rear gives you more acceleration but at the cost of having higher revs at a given speed.
Same with less teeth on the front.
It's not falling off, it's an upgrade opportunity.
DJWALKER
Posts: 138
Joined: Mon Sep 14, 2020 6:10 am

Re: Gearing and speedo

Post by DJWALKER »

Yes mate I know that , I wanted to know If anyone new how much it effects speedo readings .
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AMCQ46
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Location: Worcestershire / Warwickshire border

Re: Gearing and speedo

Post by AMCQ46 »

If you gear it down (smaller front or bigger rear) the speedo will read high as it measures the gearbox shaft speed not the wheel speed
AMcQ
MK_WF
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Re: Gearing and speedo

Post by MK_WF »

Shorter transmission ratio will also count more miles than actually done.

Good if you calculate mpg and don't remember, bad if you want to sell it later...

The answer is buying a speedo healer. That's a box that accepts a rectangular input at frequency 1 and puts out another rectangular signal, but at frequency 2.
The correction factor can be set to compensate the new gearing.
Last edited by MK_WF on Sat Aug 06, 2022 1:37 pm, edited 1 time in total.
Bye
Martin
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MacV2
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Location: Grain

Re: Gearing and speedo

Post by MacV2 »

DJ came to the MacCave this morning, had a new 16T front sprocket to fit...

Wrangeled the spanners got his front sprocket off...It was a 16T on there already...

He was convinced it had been swapped to a 17T previously... Apparently not it would seem...

On a bright note I cleaned the normal clag from around the sprocket & the inside of the cover, replaced the old sprocket, boxed it back up, tensioned the chain & wiped me greasey paw prints off it...

On a brighter note, DJ says its running sweet after the CCT change, new plugs, TPS adjust & I fitted a heat sheild which was missing...
Lowering the tone since 2007...
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sirch345
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Re: Gearing and speedo

Post by sirch345 »

DJWALKER wrote: Sat Aug 06, 2022 4:58 am Yes mate I know that , I wanted to know If anyone new how much it effects speedo readings .
DJ, I'm guessing after reading Mac's post (re 17tooth front sprocket) your question has been answered :?:

However Healtech have a gearing calculator for their Speedo Healer. You can workout the percentage it's out from that chart once you have added the details of sprockets and rear tyre size etc. Click the link below for the Healtech site, then on the home page scroll down to "Online Calculator" then click the positive sign, then click on "Estimated" followed by "Generate" as shown here:
Healtech Gearing set up (1).jpg

Site link: https://www.healtech-electronics.com/products/sh/

Chris.
DJWALKER
Posts: 138
Joined: Mon Sep 14, 2020 6:10 am

Re: Gearing and speedo

Post by DJWALKER »

Yep all sorted ta gents , thanks again to mac and yes ti's indeed running sweet 👍
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