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Speedo Error Questions

Old 08-18-2006, 01:44 AM
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Speedo Error Questions

Now that I have completed a 520 conversion with 15/43t sprockets, does anyone know what the speedo error is for indicated speed compared to actual? Thanks.... I was indicationg 90mph on the freeway the other day, in traffic that I think was maybe 65/70.....
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Old 08-18-2006, 04:43 AM
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Best way to find out is to take a ride with a gps.
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Old 08-18-2006, 07:45 AM
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Have a look at the Knowledge Base section. I have added a link to a site with an Excel spreadsheet that will help you to figure it out. I am running the same gearing and in top gear, every 1000 rpm works out to 25 km/h, or about 16 mph

cheers
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Old 08-18-2006, 02:32 PM
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Thanks for the info.... can't wait for break in to end so I can experiment....
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Old 08-18-2006, 03:14 PM
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Originally Posted by 99Hawk
Best way to find out is to take a ride with a gps.
I have a Yellow Box on my '99 VFR. I was suprised how much error I still had in my speedo especially at slow street speeds after I rode with my GPS. As much as 8 to 10 mph. The slower speeds were way off but the highway indicated speeds were pretty close. Only about 2 to 3 mph optimistic indicated on the speedo. I haven't checked either of my VTR's yet.
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Old 08-18-2006, 03:51 PM
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I did some testing with my GPS a week ago, and on average you could say the speedo to GPS was 9% out.

This was with stock gearing:

I did all "INDICATED" speeds from 10mph to 90mph (the latter on a private road!) ahem.

Here are the actual figures.

The 1st figure is the Speedo Indicated Figure.
The 2nd figure is the SatNav Figure.

I double tested these on 2 different roads, just in case different directions made any GPS variations.

Anyway..............

Indicated 10mph = Actual 8mph

Indicated 20mph = Actual 18mph

Indicated 30mph = Actual 26mph

Indicated 40mph = Actual 36mph

Indicated 50mph = Actual 45mph

Indicated 60mph = Actual 54mph

Indicated 70mph = Actual 64mph

Indicated 80mph = Actual 72mph

Indicated 90mph = Actual 82mph


As you can see, by the time you get to 100, I guess you could be around 10mph out.
I'm quite supprised. I would have guessed say 3 or 4 mph out at 80 but not 8 !!!!

As you can see from the above figures (if you get your calculator out) your REAL speed is almost exactly 9% LESS than your indicated (speedo) speed.

Quite a lot eh?

I've just put a 43 tooth on the back of my bike, so I've got to re-do it.

I did come up with a FREE speedo fix.
Took quite some time in photoshop with angles and percentages (to get the lines in the right place)

Name:  clocks.jpg
Views: 7
Size:  122.2 KB

Ok, perhaps not totally professional, but cost me only my time
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Old 08-19-2006, 04:02 AM
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Originally Posted by Tempest
I did some testing with my GPS a week ago, and on average you could say the speedo to GPS was 9% out.


Tempest,
Most Excellent
I've thought about making a new scale myself ... especially with my 43. Is that some sort of adhesive material you printed the new scale on? (or just paper??)
I've just been doing a guesstimate up till now but having an accurate scale has got to be better. (what version of Photoshop did you create your scale in? )
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Old 08-19-2006, 12:35 PM
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lol good on you. I had that idea too but I only wanted 50 and 100 markings. Too many lines to see when its all a blur
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Old 08-19-2006, 02:32 PM
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Hey Tempest.... How much for you to make me one of those waazu labels for my 15/43t sprocket setup? Darren
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Old 08-19-2006, 11:00 PM
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15x43 is out 18-20 % depending on tyre wear. go to jaycar and buy the speedo corrector, if you have q's [email protected]
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Old 08-20-2006, 01:05 AM
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Thanks for the tip on the Jaycar Digital Speedo corrector... They have a USA 800# (784-0263) and the corrector costs $44.95.... I plan to call them during the week.... I will post up any info for others as well....
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Old 08-20-2006, 07:45 AM
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Originally Posted by Rufion
15x43 is out 18-20 % depending on tyre wear. go to jaycar and buy the speedo corrector, if you have q's [email protected]
Looks like that Jaycar speedo corrector is an OZ product - a kit - designed for cars.
http://tinyurl.com/of282

Does it work on bikes?
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Old 08-20-2006, 02:11 PM
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Sorry guys, been laying a new floor down for a lady friend all this weekend, and only just got back home on my PC.

Re. my speedo label thingy.

Using Photoshop CS2 (but I think almost any version will do as it's VERY basic) just fiddly.

Also it's just printed on plain white paper with my laser printer, cut out and then laminated (then cut the laminate nearly to the edge of the paper) then 3 small bits of double sided tape to fix it to the front of the speedo.

Not super technical, but it works

Here's (roughly how to do it)

Make a circle to match the size of the speedo face.
Print it out, cut it out, place onto your speedo and mark on the paper the position of the ORIGINAL lines from your speedo dial.

Come indoors, get the protractor out and work out the angles.

Easiest to take the 10mph one and 180mph (although you will have kilometers I guess) and divide them to get the equal spaces.
(the 0 speed line is closer to the 10 than the other lines are apart.

basically, you need to work out (on a bit of paper) ALL the angles for all the original marks.

then get your GPS out, and go for a ride, writing down all the errors.

then some maths, work out how many degrees per 1mph on your scale (mine was 1.47 degrees per mph.

then draw fresh lines in photoshop to the NEW angles.

All just took time.

then drew white circles to cover up lines, added numbers etc.....

I'll just post up my Photoshop image with all the layers so you can see how it's constructed.
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Old 08-20-2006, 02:29 PM
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I don't actually have any file hosting (the .pdf file is 1.25mb)

If you want a copy (so you can modify it) just private message me (your email address) and I'll email you a copy of the original file.

Re drawing the lines, it's just the LINE command in photoshop, and have SNAP on, (I've got some centre lines) so it's just draw a line from the centre out towards the edge, at the correct angle.

The original file (I'll send anyone who wants it) has all the layers, and original and new lines on it.

If you use photoshop a little bit, you should be able to suss things out.
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Old 08-21-2006, 01:15 AM
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Umm, this is out of control...

If you could simply plug in an electrical device that changed the ratio of pulses coming from the gearbox to the computer...that would be the fix dont you think?

btw the jarcar kit works a treat, I have made many for the boys here in oz, they pay me to put the kit together and for the install instructions.

I am happy to help anyone out if they want to make one.
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Old 08-21-2006, 06:34 AM
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Originally Posted by Rufion
btw the jarcar kit works a treat,
I am happy to help anyone out if they want to make one.
Thanks!
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Old 08-21-2006, 06:47 AM
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Originally Posted by Rufion
Umm, this is out of control...

If you could simply plug in an electrical device that changed the ratio of pulses coming from the gearbox to the computer...that would be the fix dont you think?

btw the jarcar kit works a treat, I have made many for the boys here in oz, they pay me to put the kit together and for the install instructions.

I am happy to help anyone out if they want to make one.
PM sent.
Thanks

Erik
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Old 08-21-2006, 09:57 AM
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Originally Posted by Rufion
Umm, this is out of control...

If you could simply plug in an electrical device that changed the ratio of pulses coming from the gearbox to the computer...that would be the fix dont you think?
Indeed and you can of course buy commercial units to do just this.

Just that a Unit costs (in the UK) about 60 UK Pounds
Wheras a printed piece of paper costs about 0.01



I would like the proper electronic device of course.

the other option would be to strip the speedo apart and put a new (Corrected) dial in (Over the original one)

Would be easy to do, and also print your own colour.

but how easy to get the speedo apart in the 1st place?
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