Taller Gearing to Offset BS Speedo? - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 47 Old 07-17-2015, 11:03 PM Thread Starter
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Taller Gearing to Offset BS Speedo?

My speedo reads about 10% high. From other threads, it sounds like that's a common problem.

The question is, if I put in a 16T front sprocket or a 38T rear, would that offset the speedo lying to me? If I'm spending money to remedy this anyway, I may as well improve my fuel economy while I'm at it.

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post #2 of 47 Old 07-17-2015, 11:47 PM
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A speedohealer will rectify the issue. I put a 13T sprocket on the front and haven't fixed up the speedo yet. Untill i have the spare cash to do so, I've been using a music app through my Sena headset that relays speed at set intervals. I have it set to call out when I hit 60, 70, 80, and 100km/h. I think it's called RadioDrive. It works for the time being.
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post #3 of 47 Old 07-18-2015, 12:54 AM
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Originally Posted by Aus Rider View Post
A speedohealer will rectify the issue. I put a 13T sprocket on the front and haven't fixed up the speedo yet. Untill i have the spare cash to do so, I've been using a music app through my Sena headset that relays speed at set intervals. I have it set to call out when I hit 60, 70, 80, and 100km/h. I think it's called RadioDrive. It works for the time being.
RadioDrive - sounds like what we complain about cagers for...

RadioDrive is the music app designed for motorcyclists and drivers. It reads out notifications relevant to you in between songs, such as new text messages, weather conditions and more. Now you can stay up-to-date without interrupting your ride or taking your eyes off the road.
Features

- Speaks selected notifications (using Text-to-Speech) in between songs so you can stay focussed on the road
- Reads out new text message info including sender name, time received, and full message
- Reads out local weather conditions including temperature, wind speed and direction
- Missed call notification including caller name and time received
- Current time and phone battery notifications
- Customize which announcements play and how often (all are enabled by default)
- Simple and elegant music player and library browser
- Organise your play queue with gestures - swipe away songs to remove, drag to rearrange
- Shuffle/Repeat
- Safety feature for the road: auto-pauses playback when battery level is low to conserve power for your phone
- No setup required. All your music queued when you first open the app - just hit play and you're off

https://play.google.com/store/apps/d...diodrive&hl=en

I thought we were supposed to be piloting vehicles on public roads? Not seeing how much we can get away with with multitasking.


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post #4 of 47 Old 07-18-2015, 01:45 AM
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The app has pleanty of features, all of which are optional. I just have background music and speed announcements active.
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post #5 of 47 Old 07-18-2015, 07:42 AM
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Originally Posted by tegs View Post

The question is, if I put in a 16T front sprocket or a 38T rear, would that offset the speedo lying to me? If I'm spending money to remedy this anyway, I may as well improve my fuel economy while I'm at it.
I changed the front sprocket on my 250R to a 15T and this reduced the error to only 3% . Still reading fast, but its a heck of a lot nearer than 10% and cheaply done.
There's not enough room between the outside diameter of the chain and the engine casing for a 16T sprocket. However, if you got a 37T rear sprocket custom made and fitted that in conjunction with the 15T front your speedo would then read pretty much bang on.

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post #6 of 47 Old 07-18-2015, 08:22 AM
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U.S. speedo's are bang on from the factory. The tachs are a little optimistic.

Tis better to be thought a fool and remain silent, than to open one's mouth and remove all doubt.
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post #7 of 47 Old 07-18-2015, 10:57 AM
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Originally Posted by cbrlocal View Post
U.S. speedo's are bang on from the factory. The tachs are a little optimistic.

Only difference woulsd be the conversion to MPH.


1kph = 0.621371mph




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post #8 of 47 Old 07-18-2015, 12:42 PM
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Honda lost a lawsuit in the USA about inflated mileage due to optimistic speedometers linked to total mileage. That was for cars, but I think the settlement may have affected all Honda products.

I know that the speedometer on my CB500X is very close to correct, based upon multiple inputs of "my speed" from radar devices warning you of your speed as you approach a lower speed zone.

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post #9 of 47 Old 07-18-2015, 12:58 PM
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As far as I know USA tyre size & std final gearing are identical to world markets.


There is no way it can be different if the countershaft sprocket is turning at the same speed.




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post #10 of 47 Old 07-18-2015, 01:09 PM
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GPS and radar verified for me. I'm within 1MPH indicated versus actual at all speeds. Can't speak for other markets though; seems they commonly report a 7% overdisplay.

Tis better to be thought a fool and remain silent, than to open one's mouth and remove all doubt.
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