Gear change and speedo correction

Hello all i know this topic has been talked about before and i can not locate a good thread about this so i am going to ask again and maybe we can get some solid answers.

I have changed my gearing to 12/47 and my speedo is way off now i think over 10% off (faster than i am actually going)

Does any one know how much exactly (in percentage) my speedo is off with those teeth?

Is the only way to 'heal' the speedo is one of those 100 dollar speedohealers?

You can get a nicer one from Brooks at 12 O'Clock Labs. Way better price and his stuff is A-1.

+1

The 12o'clocklabs unit is tiny and easy to use.
Installation is easy.
Don't cost an arm and a leg.
Don't leave home without it. :)

Speedohealer V4 is tiny, waterproof and mounts and installs perfectly. Flawless operation. Also perfectly available at Europe :)
There are two different settings storable and switchable and settings can be checked at 1 digit LED display. And you got a tiny remote button attachable at handlebar which would make it display top speed reached for a short time at speedometer display, also clear this value when being pressed 2 sec.

Love my 12 o'clock labs unit. I couldn't stand to have my speedo off. It's dead-nuts accurate now

Installed a 12 o'clock labs SpeedoDRD today. It was very easy to install and went without a hitch. With my 13/47 sprocket combination, I made my initial setting -16.2%. After careful testing I have had to set it to -21.2%. WTH! Really?

I have an SUV with oversized tires that is right on the money whenever I encounter a radar speed check. It is right on at 35, 45, and 65. So I did a stopwatch comparison test over a 5 mile straight stretch of asphalt and had to go to -21.2% to get my WRR speed correct. Yikes! Hurts my feelings a bit to learn that I am not as fast as I thought I was...

My gearing is 13/47 with a 120/80 T63 rear tire and my correction factor is -19.6 with gps calibration. You may want to check your speed with a gps, but at least you are pretty close.

Duanew,
After subsequent testing, I settled on -20.9%. So I am pretty close to your numbers. I had just installed a brand new TW 120/80 tire as well. I was just shocked at the adjustment required and still am... dang.

Mine was -22% gps confirmed, I've got a D606 on the rear as I recall--too cold to go look

Me thinks there is a lot of "mine will do 90 etc" as a result of the very optimistic speedo.

Exactly!

Akasy wrote:

Mine was -22% gps confirmed, I've got a D606 on the rear as I recall--too cold to go look

Me thinks there is a lot of "mine will do 90 etc" as a result of the very optimistic speedo.

Well, mine will do over 90, GPS (a professional GPS, no less) - but you need a long stretch of road and no wind. I weigh a little over 200 with gear.

On the other hand, find me a little featherweight rider, and I'll bet they'll go significantly faster than me. Reducing the drag even a little bit makes a big difference on a little quarter litre bike.

I have to confess I don't care, because somewhere around 70 MPH is about as fast as I find comfortable with my dirt bike helmet and other gear.

I have the speedo fix, which I've chosen to use to correct the speed, not the odo. If I need the odo, I'm running my GPS anyways, which offers far more useful information than an odometer.

Pity we couldn't correct both.

When your GPS is running beside your odometer all the time, it is amazing how you notice just tire wear throwing speedo/odo readings out.

[quote="Jäger"]
Well, mine will do over 90, GPS (a professional GPS, no less) - but you need a long stretch of road and no wind. Quote

Did not mean to imply that under a given set of circumstances that it cannot reach 90--but as you note hills wind and drag have a very big impact on any 250cc bike in regards to cruise capability. With a -20% or better correction factor needed to get a close to accurate speedo, this may have resulted in a lot of riders extrolling virtures that are not present, except on the display of an overly optimistic speedo.

Akasy wrote:

With a -20% or better correction factor needed to get a close to accurate speedo, this may have resulted in a lot of riders extrolling virtures that are not present, except on the display of an overly optimistic speedo.

I think the inaccurate speedo was one of the first things that people remarked about regarding the bike. Back in '08, anyways. I don't think too many who were hanging out on the WR threads missed that. But I could be wrong, of course.

My speedo was off 12% with the stock tires. Curious how different bikes with the same tires had significantly different error in their speedos.

I just installed the Speedo Drd. It was easy to install and program. I used 19.9% as a starting point. Rode it with a GPS and it looks like I right on the mark.

I know this is an old thread, but +1 for 12 o'clocklabs. My wife got me a speedometer correction device and it was installed and powered up in less time than it took to brew a pot of coffee!

Can you install the speedo drd to correct for the mileage instead of MPH? I could careless how fast it says I'm going, but want the mileage to be correct.

You input what ever correction factor you want. Zero you trip meter at a mile marker, ride to the tenth one away & do the math between your odometer & 10 actual miles. Enter that correction factor, ride back & your odometer should be dead on.

4play wrote:

You input what ever correction factor you want. Zero you trip meter at a mile marker, ride to the tenth one away & do the math between your odometer & 10 actual miles. Enter that correction factor, ride back & your odometer should be dead on.

Ah, great.....thanks!