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Gear Ratio Question

KSHAFFER

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#1
BIKE 01 CR250. i am replacing my chain and sprockets this winter and i'd like to change the gearing a bit. i have stock 13/50 right now but i'd like to make 3rd gear a little more easier to get into to be able to hit large jumps out of corners. i was thinking of going with at least 13/51 but would that make much of a differerence or should i go with 13/52. the problem is last year there was a jump that was out of a corner that i would hit 2nd gear pinned and would case it every time. when i would try 3rd it seemed like i wouldn't be it the power enough. i think it would help everywhere going a bit lower on the gearing also everywhere on the tracks. what is your recommended gearing? thanks.
 
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Chief

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#3
Hey K !!!

 

      I went down 1 in front and it was WAY too low. It's always healthier for chain and sprockets to add teeth to any sprocket rather than take teeth away. You can buy 'primary drive' rear sprockets cheap. (MXSOUTH or ROCKYMTN CYCLE) Buy 1 and 2 teeth (2 sprockets) more and experiment and you will find what works best on different tracks. Going up 3 on the back = appx. going down 1 in front and makes 2nd gear roughly = to what 1st gear was stock. Not what you want. Lose too much topend speed.

 

      The reason you aren't getting any replies is because this topic is beat on a regular basis. If you can do a search here you will get more than enough info. Maybe Jaybird can help you if he sees this post. He is a chain/sprocket  enthusiast and would give you more info. I'm in the ballpark anyway.

 

Goodluck,

 

Joe Chief  
 

KSHAFFER

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#4
i'm changing the rear sprocket tooth amount only. i want to make 3rd gear more usable but wasn't sure if one tooth would be enough or if i should go to 2 teeth more on the rear. i'm not changing the front spocket tooth amount.
 

darringer

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#5
If you are asking whether you will "feel" enough with a 1 tooth change, you will. But when I had my RM125 I went from 50 to 52 teeth and it made a huge difference in how well it would pull. I went from a 48 to a 50 on my 99CR250 last year and liked the change. It tightened up the gap in the gear ratios nicely. If you are still unsure which sprocket to use, try buying a steel sprocket. They are dirt cheap and last forever. If you don't like the change, you are only out about 25-30 bucks.
 

Jaybird

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#6
If it were me, I'd change out the rear to a 52t.
That would net you a 4:1 ratio, which I find to be a nice choice for tighter MX on both 125's and 250's.

You could also get a 14t CS sprocket when you go for the 52t. You may find that you still aren't just where you want to be with the 13/52. You could then change out the 13 with the 14 and go the other way. (make third gear jumps 2nd gear jumps)

13/50 3.85:1
13/52 4.0:1 (cure problem by gearing shorter (lower))
14/52 3.7:1 (cure problem by gearing taller (higher))

You may want to steer away from the steel. It adds weight and you can get a set of aluminum w/hard front for the same money as a full steel set-up.
 
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#7
Originally posted by KSHAFFER
22 views and no one has any experience with wanting to gear down a little bit???
Either that or nobody has ridden the same track as you so does not know how to gear for it
 

KSHAFFER

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#8
Originally posted by demographic


Either that or nobody has ridden the same track as you so does not know how to gear for it

you can't tell me no that there's not other track anywhere that has a large jump right out of a corner.