I have a 2000 blaster that I put 20x10x11 wheels and tires on. Now I have very little top end. I am wondering if there is any one that has done this and changed sprockets and chain to increase top end performance. I am thinking of going with the stock size 13 tooth front sprocket and a 38 tooth rear, that will supposidly give me a 2.92 ratio. I would like to hear what worked for others, prior to purchasing new sprockets and chain. Any advice will help.

Later, Mad4mud

 

I think the stock blaster tires are 20's so you shouldnt have had a difference. If you would like to gear up then go to 14/40 (almost same as 13/38 only front sprockets are cheaper).

 

Thanks for the reply, The stock size rears are 21x10x8 and my new rears are 20x11x10. So with that being said, is your reply still the same? Also I have been told not to just change the front or the rear sprocket because of the sprocket and chain wear, Is this true or not? As you can tell on my original forum I had the new rear tire size back words they are 20x11x10's not 20x10x11's!! Thanks again for the response, I am interested to see if this changes your thoughts any. later, mad4mud

 

What I've always done is take the number of teeth on the old rear sproket, and divide it by the old rear tire diameter. Then multiply that by the NEW tire diameter, and pick the sprocket that most closelt matches that number. Like this:

42 teeth on old rear sprocket divided by 21' tire diameter (42/21=2)

2 * 20" new tire diameter (2 * 20 = 40) 40 is the new rear sproket size you need to maintain the same overall performance.

Once you know this, you can figure out how to change the FRONT sprocket instead of the rear:

Lets say you have a 20 tooth front sprocket, and a new 40 tooth REAR is what you NEED (2.00:1) ratio, you can get the same with your OLD 42-tooth sprocket and a NEW 21 tooth front (Still a 2.00:1 ratio). (Ratio is (rear sprocket/front sprocket) :1)

OR Front sprocket size (20 teeth) x Old tire diameter (21) = 420

420/ new tire size = needed front sprocket size .. . OR
420/ new front sprocket size = needed Tire size


Most likely you will NOT end up with intergers, but rather something like a 13.64789898 size sprocket needed. Then you will have to use some judgement. .. If it says you need a 13.5 tooth front sprocket, just know that you will have to pick a 13 or a 14, and that the 13 will give more low end, the 14 will give more top end. If course if you get 13.1 or 13.9, ,, round to the nearest.



BTW, the 10x11 or 11x10 are the width and wheel sizes if you didn't know, which aren't needed in these formulas, the first number is the diameter. (I may have the width/wheel diameter backwards)

 

Heres an easier way. 3 teeth back = 1 tooth front = 2 inches on the tire

 

when i had my blaster i ran 14/38 gearing...with 20x11x8 rear tires, i also had ALOT of engine work donw to be able to pull that gearing.
your better off going with a 14t front sprocket and calling it a day.