18in

[400eeeexxxx]

hey guys i just got some new holeshots and went with 18in tires can any body tell me how i could get my bike back to stock gearging right know it is 15/38 so would i go with more teeth in the back?

[Butters]

you would go with less in the back or more in the front. whichever one you want. 1 tooth in the front equals about 3 in the back.

[400eeeexxxx]

so would i just my a new front sproket

[Butters]

it really doesn't matter. the front sprocket is cheaper than buying a rear sprocket. i would bump the front up 1 tooth and that should be really close to stock gearing.

[Jingle 11]

Originally posted by Butters
you would go with less in the back or more in the front. whichever one you want. 1 tooth in the front equals about 3 in the back.

1 in front is about 2 in the back.

[stonerider250x]

the most comman change in gearing for mx with 18's is one up in the front and 2 down in the rear...but it all depends on if u like having high or low end power;)

[ghak99]

Originally posted by Jingle 11
1 in front is about 2 in the back.

I always thought it was 1 front is 3 rear.

[Jingle 11]

i was told it was about 2 in the rear.

[Sprks450r04]

i was told three in the back for one up in the front

[plkmonster2]

1 In the front is actually about 2.5 in the rear. 15 X 2.5 equals 37.5... The best way to find the gearing change needed is to find the circumferences, 20 X 3.14= 62.8 18X3.14=56.5 Then find the stock ratio. 38/15= 2.53 Divide 62.8 by 2.53 and you get 24.82 Then divide 56.5 by 24.82, and you get your new gear ratio you'd need. The new gear ratio is 2.27. 16 tooth in the front would get you 2.37= More low end. 17 in the front is 2.23 More high end than stock. A 16/37 combo is 2.31, more low end, and a 16/36 combo is 2.25, very close to stock.

[Jingle 11]

Originally posted by plkmonster2
1 In the front is actually about 2.5 in the rear.

so i guess we were all right :blah:

[cals400ex]

Originally posted by plkmonster2
1 In the front is actually about 2.5 in the rear. 15 X 2.5 equals 37.5... The best way to find the gearing change needed is to find the circumferences, 20 X 3.14= 62.8 18X3.14=56.5 Then find the stock ratio. 38/15= 2.53 Divide 62.8 by 2.53 and you get 24.82 Then divide 56.5 by 24.82, and you get your new gear ratio you'd need. The new gear ratio is 2.27. 16 tooth in the front would get you 2.37= More low end. 17 in the front is 2.23 More high end than stock. A 16/37 combo is 2.31, more low end, and a 16/36 combo is 2.25, very close to stock.


yep, 1 front =about 2.5 rear

[plkmonster2]

Originally posted by Jingle 11
so i guess we were all right :blah:

Yes, that can be said to be true, lol :blah:

[Butters]

Originally posted by plkmonster2
Yes, that can be said to be true, lol :blah:

don't you just hate that! :D

[wilkin250r]

Originally posted by plkmonster2
1 In the front is actually about 2.5 in the rear. 15 X 2.5 equals 37.5... The best way to find the gearing change needed is to find the circumferences, 20 X 3.14= 62.8 18X3.14=56.5 Then find the stock ratio. 38/15= 2.53 Divide 62.8 by 2.53 and you get 24.82 Then divide 56.5 by 24.82, and you get your new gear ratio you'd need. The new gear ratio is 2.27. 16 tooth in the front would get you 2.37= More low end. 17 in the front is 2.23 More high end than stock. A 16/37 combo is 2.31, more low end, and a 16/36 combo is 2.25, very close to stock.

Perfect flawless explanation.

To find the stock gearing, it's right between 16/36 and 16/37. In theory, the 16/37 gearing is slightly taller than the stock gearing, but since you have so much less rotational inertia in the tires, you'll run about the same or better acceleration than stock.