graememk
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| posted on 22/3/07 at 09:27 AM |
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i'm being thick and lazy today
what numbers do i need to type into my etb speedo to get the correct reading ?
3.62 lsd
205 - 45 - 16" tyres
Gear Ratios
1st 3.321
2nd 1.902
3rd 1.308
4th 1.000
5th 0.838
Reverse 3.382
Final 4.363
the sensor is on the prop with 2x magnets
205 45 16 bridgestones cover 1800mm
many thanks for your help
Graeme
[Edited on 22/3/07 by graememk]
[Edited on 22/3/07 by graememk]
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David Jenkins
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| posted on 22/3/07 at 09:31 AM |
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Missing one vital statistic - the rolling radius of the wheel/tyre, in other words, the actual distance the centre of the wheel is off the deck when
on the ground.
Alternatively, the circumference of the tyre is pretty close when working out the maths.
Plan C is to mark the side of the tyre at the bottom, and the ground, with a bit of chalk, push the car forward 10 turns of the wheel until the chalk
mark is at the bottom again, then mark the ground once more. Measure between the two marks.
THEN you can start thinking about the maths! 
Oh yes - also need to know the number of magnets, and where they're mounted.
(Damn - you edited your post to give the sensor location & magnet count! )
[Edited on 22/3/07 by David Jenkins]
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mookaloid
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| posted on 22/3/07 at 11:20 AM |
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If you call ETB with diff ratio, tyre size and magnet location and number they will read it off a chart and tell you in about 20 seconds.
mark
"That thing you're thinking - it wont be that."
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DarrenW
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| posted on 22/3/07 at 11:27 AM |
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or download digidash tools from the website and use the calculator. I had to make some minor changes at SVA to calibrate it in but was easy to do.
Managed to get it within 1mph at 70 (SVA guy wouldnt let me get it closer, needed to get on with the test)
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DarrenW
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| posted on 22/3/07 at 11:30 AM |
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Assuming they are road tyres, ive just plugged your figures into my calculator and it gave me;
Circumference 1856mm
Speedo Cal 6275
Gear Cal 1000
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graememk
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| posted on 22/3/07 at 12:10 PM |
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many thanks people that gives me a very good starting point
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nick205
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| posted on 22/3/07 at 01:34 PM |
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I can only recomend speaking to ETB and gettting a figure from them. I did and it was absolutely bang on at SVA. Speedo reads ~2mph faster than
actual road speed - i.e. 38mph road speed = 40mph on the speedo.
Go on giv'em a call 
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graememk
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| posted on 22/3/07 at 02:29 PM |
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so let me get this right
the higher the number the slower the speedo reads ?
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James
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| posted on 22/3/07 at 03:22 PM |
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quote:
Originally posted by nick205
I can only recomend speaking to ETB and gettting a figure from them. I did and it was absolutely bang on at SVA. Speedo reads ~2mph faster than
actual road speed - i.e. 38mph road speed = 40mph on the speedo.
Go on giv'em a call
Same here.
Cheers,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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