Changing the Gearing

[JD_MXRacer]

Hey right now I have a 51 tooth rear sprocket. I am soon going to be buying a new sprocket/chain combo. Would going down a tooth or two on the back sprocket make more acceleration or top speed? What difference would I feel in the bikes handling? I heard that going down a tooth or two would be a change for the better.

 

[robwbright]

Less teeth in back = more top speed.

More teeth in back = more acceleration.

 

[JD_MXRacer]

for some reason I thought it was the opposite. But does it really make that much of a difference.

 

[mox69]

Yes it will make a noticeable difference. Unless you hit 5th gear top speed at the place you race/ride. Going down sizes makes no sense.


As a "C" rider, I rarely hit 5th gear. I went up 2 teeth on the back and was very happy with the results. Easier to get out of corners, and much easier to slowly chug along in the woods when necessary.

 

[robwbright]

Depending on the track, it could make a significant difference.

For example, a gearing change could make it easier to get enough drive out of a corner to clear a double that has a very short run up.

Just try it and see what you think. It doesn't take that long to change the sprocket.

 

[_JOE_]

The track I ride at has a big uphill tabletop that requires pretty much 5th gear wide open to completely clear. If you are really fast and use the bikes speed more, you would want to go down a tooth or two to get a bit more top speed.

Now if you ride like me and race from corner to corner because you suck and slow down for big jumps, go up a tooth or two so you get through the gears quicker coming out of the corner. Also good in tight woods.

 

[kschilk]

Here are a couple links, for gear ratio calculating.

http://www.gearingcommander.com/
http://dirtjapan.com/myscript/gear_selecter.php

 

[rmc_olderthandirt]

There are a few complications to the basic equation. Answer this question: what do you run out of first: torque or RPM?

If you are in your top gear and are holding it WOT and reach maximum RPM then you could get a top speed improvement by going to a smaller rear or larger front sprocket.

On the other hand, if you are holding it WOT and you are NOT reaching red-line RPM then you may actually want to go the other way.

Unless you just like riding the smooth roads at maximum speed then the issues can get even more complicated. Take _JOE_'s example: There is a jump that he needs to be screaming in 5th gear to clear. He could gear down a bit and then use 6th gear (if he has one) or gear up and hit the jump in 4th.

Keep in mind that when you change gearing you may improve one area but it may hurt another. Gearing up for higher top speed can make your hill climbs suffer.


Rod

 

[JD_MXRacer]

Yea I think im going to go up a tooth or two on the rear. I never hit top speed in 5th or 6th. There are a couple uphill parts on the track i usually race at, one where you need enough speed coming up it to be able to skim the whoops. So going up a tooth or two sounds better to me. Currently im at a 50 or 51 cant remember right now.