New sprocket size?

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#1
My bike right now (29'' tires) has a 44T sprocket on it and currently has a top speed of 39-40mph. It has enough torque with that sprocket to pull away from a stop with minimal pedaling. I don't mind pedaling and was looking to cruise at lower rpms and have a higher top speed :D but I'm not sure with what size sprocket to put on. Is a 36 too extreme, and what would my top speed increase be with a 36?
 


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#2
Need more info about your setup. What engine, what gearbox, what front sprocket?

Roughly, though, 44/36 =1.222 so assuming you have the power your top speed would be 40x1.222 or 48 mph.
 
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#3
2 Stroke Zeda engine dynoed at 5hp (but i dont have the MZ65 pipe), 10T front sprocket. Not sure what you mean by gear box, I don't know the reduction rate from the crank to the front sprocket..
 

Tyler6357

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#4
If you are hitting 40, I don't know how much faster you want to go on your bicycle. If you lose power going up steep hills you might need a higher tooth sprocket but if you put the 36 on it will have great top end but the bottom will be even more sluggish. If you want more low end you can put a reed valve on or get a good expansion pipe.
 
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#5
If you've got 5 HP to play with, you can make that speed. Just for reference, the Land Speed Record for 50cc bikes is 144.9 mph

Hill climbing will suffer, and starts will be sluggish.

I'm not your mom, but if I was I'd tell you to get a good set of leathers and a full-face helmet. Crashes hurt.
 
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crassius

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#6
these are all different, best to try 41T first and go to 36T if that seems OK - then if 36T fails, go back to 41T
 

JerboaJohn

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#8
If you build more than a couple bikes, it'd be no real loss to have a couple diff sprockets as you'll use them at some point.
I have 4 now with just one 2-stroke bike :p, and need to test much bigger ones with a 4 stroke, so I know Im gonna need 2 or 3 just for that
 
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#9
If you are hitting 40, I don't know how much faster you want to go on your bicycle. If you lose power going up steep hills you might need a higher tooth sprocket but if you put the 36 on it will have great top end but the bottom will be even more sluggish. If you want more low end you can put a reed valve on or get a good expansion pipe.
Yep, I definitely should get some better gear, but I wear a full face and denim pants (which I know aren't good enough for higher speeds) every time I ride.
 
S

Street Riderz

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#11
I think I'm gonna try the 36 tooth, they're only like 15 bucks, I'll let you guys know if it has enough low end when I get it on.
I would take Crassius's advice and try the 41t first because without the pipe it's gonna load up the topend if you had the pipe no problem you'd get get what your after!
 

Tyler6357

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#12
I think I'm gonna try the 36 tooth, they're only like 15 bucks, I'll let you guys know if it has enough low end when I get it on.
Yeah, you might have to move your chain tensioner back toward the sprocket and put it on the highest setting to use the 36T because the sprocket is smaller, either that or take some links out of your chain but you don't want to take so many out that you can't go back to the larger sprocket if you want in the future.
 

Tyler6357

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#13
Yep, I definitely should get some better gear, but I wear a full face and denim pants (which I know aren't good enough for higher speeds) every time I ride.
It is good to have better safety gear if you want to break into 50mph club but it's also important that the bicycle parts you are using can handle it. Bicycles are not designed to go 50mph! How good are your rims and hub?, double walled or mag wheels? Are your tires wide enough to lean into the turns? Are they good enough not to blow when they get hot or are they cheap Duro tires for $10? How are the brakes? You got thick disc brakes on the front? What are you using on the back? How is your frame? steel or aluminum? How are the welds? Cheap Chinese welds well crack under excessive stress. Do you have suspension shocks on your fork? What if you hit a big pot hole in the road at 50? Can it handle it, or will it literally melt away underneath you?? Ride safe!
 
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Street Ryderz

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#14
I think I'm gonna try the 36 tooth, they're only like 15 bucks, I'll let you guys know if it has enough low end when I get it on.
You should take Crassius's advice and try the 41 first,Because without the pipe it's just going to load up the topend not being able to breath.With a good pipe no problem you'll still over come the gear up to a point and as also mentioned you'll lose a bit of bottom end torque.
 

Tyler6357

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#17
A 40t works great all around it doesn't gain alot of extra speed just helps hold a good cruise speed of 33mph @ 7k just above or around the sweet spot.
That's about it, I got the expansion pipe and a reed valve which give me tons of low end for the many hills to climb where I live. With these upgrades I can cruse closer to 38-40 mph with the 40T on level ground with my weight of 195 lbs. I could probably drop down to a 38T and get more but, you know, I just want to have fun on it, not kill myself.
 

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