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| Origin of 7/15 speedo drive?? https://www.ausmini.com/forums/viewtopic.php?f=2&t=73868 |
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| Author: | smac [ Tue Nov 01, 2011 6:22 pm ] |
| Post subject: | Origin of 7/15 speedo drive?? |
Because of a short and boring story I am running a Jaeger 100MPH speedo. TPM (from the face) is 1376. From memory it came from a Riley Kestral or something...I forget. Anywhoo.....with a 3.44 diff it's reading ~80MPH at a GPS checked 62MPH. Consistant through the range....so actual 31MPH reads 40MPH etc. Using the various calculators around (links below) the closest I can see is that the pinion must be 7/15....with some speedo wear/error thrown in...maybe.....? If it's not that, every other possibility seems to give a lower reading....engine is in car so not overly keen on checking it. However wear usually means a low reading, not high, so who really knows. So, anyone know enough about UK engines to know where on earth I might have got a 7/15 from? Also, am I right in thinking that the common as muck Aussie 6/17 will get me pretty damn close...in fact maybe even spot on if this speedo is reading high for some reason? |
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| Author: | drmini in aust [ Tue Nov 01, 2011 6:38 pm ] |
| Post subject: | |
3.44 diff with 10" wheels and Oz gearbox gears takes a speedo with 1280 turns/mile (Cooper S) My calcs show that your speedo `should/ might' be right in an Oz Mini box with a 3.698 diff (which doesn't exist). So I doubt these Oz drive gears would fix it for a 3.44 diff. |
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| Author: | smac [ Tue Nov 01, 2011 6:59 pm ] |
| Post subject: | |
If I ever get around to changing my diff ratio it would be to 3.1 or 3.2 or whatever is available these days. This is more about curiosity than anything, incorrect speedo doesn't particularly bother me. Oh except that of course it winds off the clock REAL easy so I'm probably damaging the spring 
If I come across a more standard speedo I'll pick it up....usual story, sold a bunch of them a while back. I have a couple boxes sitting here, I should open them up and see what pinion they all have. |
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| Author: | kiwiinwgtn [ Tue Nov 01, 2011 7:38 pm ] |
| Post subject: | |
Hi Uk is best for these parts, they where fitted to 12inch Mayfair if I recall. good luck finding one here. http://www.guess-works.com/Shop/Parts/d ... htm?id=144 Not cheap but at least he has them I was also thinking the gears couldl be 3D printed in plastic if you have access to CAD etc. I have started soem investergation on doing this as I need a special set for my set up 10inch wheels 1275GT speedo and 3.1 dif TA Kiwiinwgtn |
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