speedo accuracy

JohnnyB · Post by **JohnnyB** » Tue May 02, 2006 10:19 am

Are they generally accurate?
having just moved from a Hornet which has a wildly optomistic speedo thought I'd best check.

How many mph per 1000rpm in top on standard gearing?

It could be the fact that now I'm now on a bike with a faring and plenty of grunt of course......

VTRgirl · Post by **VTRgirl** » Tue May 02, 2006 10:51 am

May I add my own question to this thread?

If the odometre is out, does that automatically mean the speedo's out? And by the same amount? My odometre is out by 10%...

JohnnyB · Post by **JohnnyB** » Tue May 02, 2006 11:20 am

Yes You may

Post by **kevg** » Tue May 02, 2006 1:05 pm

i've found when i'm out with mates on the motorway i'm sitting at about 105mph and they say they haven't been above 95. has happened with different folk on bandit 12's and a BMW GS, bit annoying when i think i'm gonna get done at any minute and they are getting away from me because i slow down to below a ton.

mik_str · Post by **mik_str** » Tue May 02, 2006 1:58 pm

Hello everyone,

According to info posted on the Speedohealer Web site, it is not uncommon for odometers to be right on with speedos being optimistic. A few years back (when I was still running OEM gearing), I tested the odometer (have areas on highways here in Canada with mileage indicated in tenths of a km specifically for this purpose) and found it to be dead-on. The speedo is about 5.7% off I believe. If you go to the OzFirestorm site, there is a downloadable Excel spreadsheet that allows you to calculate the actual speed (hence speedo error). The beauty of it is that you can enter your own gearing (if non-OEM) and get accurate info.

Hope this helps

Mikstr

xxxrated · Post by **xxxrated** » Tue May 02, 2006 3:56 pm

does anyone know how much difference dropping a tooth on the front will make to the speedo??

Max · Post by **Max** » Tue May 02, 2006 4:12 pm

http://www.kamware.com/free.htm

He has written a exe that does the calcs for you
primary reduction 1.682 44 74
1st gear 2.733 15 41
2nd gear 1.813 16 29
3rd 1.429 21 30
4th 1.207 29 35
5th 1.080 25 27
6th 0.962 26 25

tyre sizes etc are variable approx 24.8 inches 77.91 for my storm

the sheet agrees within 1 mph with the sigma on my storm

eddvtr1000 · Post by **eddvtr1000** » Wed May 03, 2006 8:48 am

i think the standard for vtr's out of the factory is 8% give or take.
when ive had the gps going its been 78 on the bike when im actually only doing 70 on gps.
the speedo's are very optomistic

Stormin Ben · Post by **Stormin Ben** » Wed May 03, 2006 11:14 am

Whats a speedo?

My bikes only got a rev counter, some warning lights, an oil temp guage and an economy meter (needle straight up = most economic, needle either side = less economic)

gcs · Post by **gcs** » Wed May 03, 2006 11:27 am

Stormin Ben wrote:Whats a speedo?

My bikes only got a rev counter, some warning lights, an oil temp guage and an economy meter (needle straight up = most economic, needle either side = less economic)

Like your style, man.