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Sorry if this horse has been beaten to death...What are the cons of dropping 1 tooth on the front sprocket in search of the ever so critical optimal gear ratio?
I know chain torque will increase, but it seems like I've heard people say its more taxing on the transmission? Any guidance is much appreciated!
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Hypothetically, you reduce the torque effect from the center of your countershaft to the edge of the sprocket, thus reducing torque. (Imagine turning a short wrench vs. a long wrench.)
In practice, I don't know what difference it could really make except for the reduction in gearing, which is what I assume you are going for.
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It might eat your chain slider a bit quicker... and bring your top speed down. It's a pretty aggressive ratio jump.
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It will have a little more snap off a jump etc. than doing the 3 in the back. Marginally more sprocket wear. I can't imagine any effect on transmission durability?
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Depending on how small you’re going (12 teeth I presume) you may be putting more stress on the chain as it has a tighter radius to come around. That’s along with the other issues noted.
I wouldn’t mess with the front sprocket. Just do it with the rear sprocket.
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Pros:
don't have to torque the rear sprocket bolts when changing the front sprocket
Cons:
you should always check the torque on your sprocket bolts
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If you go from 14 to 13 in the front you will have more bottom end out of the corners. The draw back is you will have to shift slightly sooner and maybe more often. The other con is that with one less tooth there will be more stress on the remaining teeth causing your counter shaft sprocket to wear out slightly sooner.
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We run a 12t on our Endurocross bike all the time, even when not racing EX. Probably about the same as 3-4 up in the rear. The smaller sprocket does wear a little faster, but other than that no ill effects.
I sometimes wonder if it wouldn't be better to do that, then also go to a smaller sprocket on the rear to reduce un-sprung weight and be less prone to damage. However then you deal with more friction from the chain making tighter turns. In the end I don't believe it would make any difference you could feel.
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You dropped one in front AND added two in the rear? Do you start in 3rd?
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The bike in question is a 1983 XR200 that has been modified for MX. There is a huge gap between third and fourth gear and in lots of situations on the track third was too low and fourth was too high. I got rid of the gap by going one tooth at a time and finally settled on one smaller in the front AND 2 larger on the rear. I can pull third gear starts and race in 3rd, 4th & 5th mostly. Once in a while on a longer track I might use 6th gear. I really don't use first or second for anything. I do start in third gear.
Bret Bonham
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If you already have a spare set of wheels with the same sprocket size...then a PRO would be just changing the one up front 
I've gone at it both ways and with no ill effects.
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If you drop to 13 just make sure you don't use 52 in the back. Otherwise you're good to go.
I don't think it's noticeable that you save less torque on the chain with a smaller sprocket. If anything, you will notice the loss of power due to the Polygone effect. 13 is still okay though, 12 is a little more critical
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Falcon wrote:You dropped one in front AND added two in the rear? Do you start in 3rd?
Bret wrote:The bike in question is a 1983 XR200 that has been modified for MX. There is a huge gap between third and fourth gear and in ...more
fullysicmate wrote:This is unique scenario.
Pretty unique indeed. I weigh 225 and race the bike in a class for small bore (max 230cc) air cooled four strokes so I had to get creative or keep getting lousy starts. I holeshot on occasion. I would never go this crazy on a bike these days. One or two teeth on the back would be plenty.
Bret Bonham
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That is Rick Doughty's bike. I race against him and always lose. It is a fun class. It is called the 2x4 class. Only three rules. 1) Air Cooled, 2) Four Stroke, 3) Max 230cc
XR200 is the most popular but we have a TTR225 and CRF230 that recently started lining up.
Bret Bonham
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Bret wrote:The bike in question is a 1983 XR200 that has been modified for MX. There is a huge gap between third and fourth gear and in ...more
fullysicmate wrote:This is unique scenario.
Hahaha! Props!
That sounds like a fun class.
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Thanks for the response guys. I'm well aware of the effects on the power. I currently ride a '17 KTM350 and I went +1 on the rear. I'm considerimg going to 13/50 (stock is 14/50). I'm prettt heavy and I ride a lot of soft dirt. I didn't mention my bike initially because I didn't want this to turn into another "ktm 350 gearing" thread.
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Yep, a bit of power is lost due to the smaller sprocket working harder to make the chain turn tighter. Not that any of us care...
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inthebadboycorner wrote:I am confused, which sprockets make you faster, Red or Black?
Dude....if you were a real Vitard you would know the color doesn't matter as much as the sprocket bolt torque. Add a factory ECU and you've got a monster.
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Most of my 125's always had a smaller countershaft sprocket. That way I never went to first gear, could pull 3rd gear starts..
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