Question about speedometers & gearing

[Desmo]

Ok I know we don’t get a lot of technical questions on this (motorcycle forum) so I hope this does not throw anyone off..
I have a question about speedometers once you change your sprocket…………. I know when someone changes the gearing on a bike the speed-o tends to read incorrectly.. Is there a way to fix this problem? If so how do I do it??

[Quick636]

They make a device called a speedo healer or a yellow box. You have to calculate the percentage your speedometer is off. Mile markers on the highway are an easy way to figure it out (go what shows as 60 and time how long it takes to go a mile. Should be a minutes, but you can figure out the percentage off from that). Then you just input the percentage into the device and it sends the corrected MPH to your speedo/odometer.

http://www.calsportbike.com/cgi-bin/...ex.cgi?pid=800

[rybo]

Frank,

If this is about your ducatis I don't think that you have a problem with changing gearing as ducati ran the spedo drive off of the front wheel until the advent of the 999 and multistrada. This means that all of the data is gathered off of the front wheel and gearing won't affect it. Changing front tire size will, but probably not to an extent worth correcting.

If the issue is with one of the japaneese brands most of them take the spedo info from the transmission, so gearing will affect it. Most of them no longer have a mechanical drive so the issue with recalibration is a change to the bikes computer. I'll see if I can scare it up but I had some info on a tool that can help you do this. The trick is being able to know what speed the bike is actually traveling at in order to do the recalibration. One way to do this is with a dyno.

I just checked my ducati spedometer with a GPS on the road to discover that it reads about 10% faster than I am actually traveling. With a mechaical drive spedometer (which my 01 748 has) there is no way to correct it.

If you are really concerned you can install a bicycle computer on your bike. these are usually very accurate and can be programed for your exact wheel size. There was a post about it on here not too long ago.


Hope that helps

Scott

[rybo]

Jason,

thanks that's the tool I was talking about

Scott

[Anonymous]

If the issue is with one of the japaneese brands most of them take the spedo info from the transmission, so gearing will affect it. Most of them no longer have a mechanical drive so the issue with recalibration is a change to the bikes computer. I'll see if I can scare it up but I had some info on a tool that can help you do this. The trick is being able to know what speed the bike is actually traveling at in order to do the recalibration. One way to do this is with a dyno.

Quick already posted a link to a device that does this. It's called the Speedo Healer. It just intercepts the signal going from the speed pickup to the gauges, and modifies it.

As for knowing your speed, you're making that way more complicated than it needs to be. The odometer on signal-driven (as opposed to mechanically-driven) gauges is based on the speedometer. So, to find your percentage of error, just go find a mile marker and set your trip meter to zero. Ride for about 10-20 miles and stop at another mile marker. Note how many markers you've gone to, since this is an accurate measurement of your distance; also note how far your trip meter says you've gone. figure the difference, that's how much to put into the speedo healer.

There's already another thread in here (use the search) on specific instructions for doing this. And it's free, as opposed to a $45 dyno run.

[Desmo]

Frank,

If this is about your ducatis I don't think that you have a problem with changing gearing as ducati ran the spedo drive off of the front wheel until the advent of the 999 and multistrada. This means that all of the data is gathered off of the front wheel and gearing won't affect it. Changing front tire size will, but probably not to an extent worth correcting.

Hey guys thanks for all the info..
Scott, this issue I’m having is concerning my Ducati, This weekend the wife and I took a ride.. My bike has stock gearing (15/36) when we stopped my bike trip meter said 90 miles and hers said 95miles. Her bike has (14/41) on her bike stock was (15/41)..
So do you think this may be another problem?
Her bike is a 2000 Monster 750.. do you know if that year and model also ran off the front tire?

[rybo]

Frank,

I believe that the monster has the spedo pickup on the front wheel.

Motorcycle spedometers are notoriously optimistic and generally inaccurate. You are welcome to borrow my GPS to test out your spedos if you want, my spedo reads about 10% faster than I am actually going. I've just applied the formula in my head and lived with the inaccuracy. I am not aware of any way of making the correction mechanically on the ducati.

Scott

[Desmo]

Frank,

I believe that the monster has the spedo pickup on the front wheel.

Motorcycle spedometers are notoriously optimistic and generally inaccurate. You are welcome to borrow my GPS to test out your spedos if you want, my spedo reads about 10% faster than I am actually going. I've just applied the formula in my head and lived with the inaccuracy. I am not aware of any way of making the correction mechanically on the ducati.

Scott

Thanks for the info Scott i will just live with the problem..