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To drop a tooth or not to drop a tooth....

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by StereoHead, Jan 19, 2006.

  1. Im about to get a new chain and sprockets....

    Some people are saying to drop a tooth on the front and add on on the back for better acceleration....

    Has anyone done this on a 600?

    How much does it affect top speed? (not that it matters all that much)

    How much does it affect acceleration?

    Does it mean you end up having to change gears a lot more?
  2. Talk to deafwish, or check for his thread. He did exactly that, as I recollect, on his 600 Hornet. Said it was fun......
  3. I've got a tooth down on the front and one up on the back. The effects:

    1) More crap wheelies (yay!)
    2) Quicker acceleration :shock:
    3) Slightly more gear changing (this is a plus for me, I like to feel as if I'm working the bike)
    4) Lowered top speed (now it's a zillion minus 15 kmh)
    5) Speedo now over-reading by 10-15 kmh (it was over-reading before, but by less)
    6) Odometer over-reading by the same factor - so the bike now looks like it's done a couple thousand more k's than it has. :?
    7) Larger rear sprocket puts the chain down pretty close to the centre stand. When chain is loose, it comes very close to dragging.
    8) Cruising revs are higher by a noticeable factor. Makes you wonder about fuel economy too.

    So yes, there's sacrifices to be made with this sort of endeavour. However, when I changed my chain and sprockets recently, I went for the same again because I love the extra rocket boost of a downgeared bike and am obsessed with crap wheelies.

    And pfffff, it's not like you need your full top speed that often!
  4. As for incorrect speed reading, we can get 'speed healers' to fix

    Odometer is a different story tho :p
  5.  Top
  6. I still, for the life of me, can't understand why changing the FRONT sprocket should bugger your speedo, but not the rear.

    The way I see it, if the speedo reading is taken from the front sprocket's shaft, all it knows is engine speed and gear. Any change to sprocket sizes front or rear changes the relationship between engine speed and wheel speed.

    Can anyone explain that stuff to me?
  7. Because changing the front sprocket changes the amount off turns your rear wheel does for every turn of the front sprocket.

    So becuase the speedo thought (for eg) that 1 turn = 1kmh but with the changhed sprocket 1 turn now = 1.5kmh

    (obviously those measurements are for example only)
  8. But changing the rear sprocket does the same thing! Just like on a bicycle, if you make the rear sprocket smaller, the wheel turns more for each revolution of the front sprocket.

    Yet I'm told that rear sprocket size doens't affect the speedo...
  9. Yeah, I had the same problem with my old VTR. I just disconnected the speedo/odo sensor wire on track days, and re-attached it at the end of the day, and called it all even...
  10. I think maybe you were told wrong.

    I have an engineering background, and everything you say is true. I can't see how what you got told, could possibly be possible.

    Maybe they were thinking of bikes where the speedo runs off the front wheel. In which case, you could change either sprocket, or both, and have no effect on the speedo's accuracy at all.
  11. Yeah, but lets say the rear sprocket has been increased in size....

    The front sprocket would still make the same revolutions.... but the rear wheel would go around fewer times... so it MUST change your speedo ...
  12. It just chages by how much your speedo is out by. Most bikes determine the speed by measuring the RPM of the final drive shaft (the front cog shaft) and multiplying that by the manufacturer's standard final drive ratio (front/rear sprocket sizes).

    When you chance the sprocket sizes, the speed displayed per revolution is the same, but you actual speed will be different.
  13. i believe whoever told you that has no idea what they're on about
  14. You've been told wrong! Of course it affects the speedo if changing the front sprocket affects it!

    A lot of Hondas have gearbox driven speedos, best way around it is to use a cycle [pushbike] speedo, and unplug your moto speedo. An added bonus when it comes time to sell also...
  15. i am -1/+1. going to +13 soon.
  16. depending where the speedo pick up is from will depend on weather theres error .... 1 tooth on the front +or - roughly equates to 4 on the rear +or -... so if you want a lil more acceleration.. add 2 teeth to the rear sprocket and thats splitting the difference .. one tooth on the front can be a lil savage for a road bike all the time ..... but 2 teeth on the rear would b livable ..