sprockets

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#1
Can someone help me out with getting sprockets for my crf250r. I dont get the concept like 1:1 ratio that people have been telling me about with getting the front and back sporcket.
 
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#2
I posted a Q. like that I just wanted peoples oppinions on the best trail combo. But generaly they are speeking of front/rear. Front is the first # (small one) and the number is the teath 12-15. Rear is the second. I gatherd for low end power you want a bigger rear or smaller front and just the oppsite for high end power.
 
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#3
would it hurt to go.... say from a 13-48 to a 15-48?
 
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#4
i mean, that wouldnt hurt anything internally right?
 
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#5
going from a 13 to a 15 up from will give the bike a greater speed at any given RPM with a sacrifice in acceleration.

The ratios that you hear mentioned are probably something like 4.00:1 which means that the front gear will rotate 4.00 times for every 1 revolution of the rear gear the . In your case 13-48 is 3.69:1 and 15:48 is 3.20:1. This is a very big jump in gearing. The larger the number the quicker the acceleleration while smaller numbers have a theoretically greater top speed (there are other factors involved). This concept applies to cars and bicycles as well. In fact, take a look at (and maye even ride a) multi speed bicycle. You will notice that the smaller front and larger rear sprockets are much easier to pedal but as you upshift, you go progressivesly faster while keeping the same pedaling speed, of course it does get harder to pedal.
 
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#7
1989kx250 said:
would it hurt to go.... say from a 13-48 to a 15-48?
Going from a 13 tooth front to a 15 tooth front sprocket would be a fairly major change (15%).

It won't hurt the engine, transmission or bike in general but it may just kill your hill climbing ability. To get an idea, just don't use first gear....

I would recommend changing the front by only one tooth and see how you like it. On the rear you can change 3 or 4 teeth have a similar percentage change.

Rod
 
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#8
FruDaddy said:
going from a 13 to a 15 up from will give the bike a greater speed at any given RPM with a sacrifice in acceleration.

The ratios that you hear mentioned are probably something like 4.00:1 which means that the front gear will rotate 4.00 times for every 1 revolution of the rear gear the . In your case 13-48 is 3.69:1 and 15:48 is 3.20:1. This is a very big jump in gearing. The larger the number the quicker the acceleleration while smaller numbers have a theoretically greater top speed (there are other factors involved). This concept applies to cars and bicycles as well. In fact, take a look at (and maye even ride a) multi speed bicycle. You will notice that the smaller front and larger rear sprockets are much easier to pedal but as you upshift, you go progressivesly faster while keeping the same pedaling speed, of course it does get harder to pedal.

That was a great explanation Frudaddy!
 

john stu

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#9
1989kx250 said:
would it hurt to go.... say from a 13-48 to a 15-48?

unless you weigh 80lbs or ride on fire roads only (and are finding yourself topped out a lot) i would not go up at all on the front sproket..........thats a big jump in gearing especaily for a 250 four stroke