Thoughts on swapping rear sprocket AND rear tire size

Kickstart70

New Member
Jul 16, 2011
25
0
0
Quesnel, BC, Canada
I've got my 49cc mounted on a bike with 26" tires. Currently I have the stock rear sprocket but am going to put on a 60T when it arrives (I'm 240lbs and we've got hills here...the current one is pretty weak for torque, pushing my bulk around).

I was considering replacing the rear tire with something a few inches smaller at the same time, and then welding on a new crossbar for the rear brake to attach to. I understand that the larger rear sprocket will add to my torque (though it remains to be seen how much difference that will make), but will reducing the size of the rear tire also add to torque substantially?

Thanks!
 

Harold_B

Active Member
May 23, 2012
992
104
43
Grand Rapids, MI
Kickstart, I am in nearly the same situation as far as hills and weight go. I'm at 190 with a 48cc two stroke on a cruiser to which I've added a few things. I'm running a 44t now. I'll work on dropping a few pounds later but one thing I did that helped is I switched to a tire that can be inflated to higher pressure. If you are rolling on mountain bike tires that will make it even worse but the point I'm trying to make is to reduce rolling resistance. Skinny tires, high pressure, slick pattern if possible but you will have to decide. The harder the tire the rougher the ride and the narrow profiles don't do well on soft shoulders.
 

tooljunkie

Member
Apr 4, 2012
663
4
16
Manitoba,Canada
if they supply a stock 44 tooth,then a 60 will be 30+ % more power,or it will behave like its lost 1/3 of the total weight of the bike and rider.
but 1/3 slower.but it will make higher rpm's.
the tires i look for,in my honest opinion should have some kind of smooth rib down the center.anything is better than a mountain bike knobby.
i havent installed my 50 tooth sprocket yet,but hoping it will help me some.
 

The_Aleman

Active Member
Jul 31, 2008
2,655
3
38
el People's Republik de Kalifornistan
The stock gearing is about 18:1, good for 26MPH (~42KM/h) @ 6000RPM.
A 24" wheel would make that 24MPH (~38.5KM/h) @ 6000.

Switching to a 60T sprocket with 26" wheel will change the ratio to 24.6:1, which is 19MPH (~30KM/h) @ 6000.
A 24" wheel with that 60T would reduce it further to 17.5MPH (~28KM/h) @ 6000.

How steep are these hills exactly? I never had problems climbing steep hills with a 26" wheel and 44T with some pedaling.
A 48T and 24" might be your best bet, IMO. That's 19.68:1, 22MPH (~35KM/h) @ 6000.
 

Kickstart70

New Member
Jul 16, 2011
25
0
0
Quesnel, BC, Canada
Thanks, that's exactly what I needed. I will give it a shot at 60T with the current wheel and I expect with what you said that will be good. The hills are pretty substantial (not San Francisco style hills, but still big). I do want to pedal some on them anyway and get some exercise.

The stock gearing is about 18:1, good for 26MPH (~42KM/h) @ 6000RPM.
A 24" wheel would make that 24MPH (~38.5KM/h) @ 6000.

Switching to a 60T sprocket with 26" wheel will change the ratio to 24.6:1, which is 19MPH (~30KM/h) @ 6000.
A 24" wheel with that 60T would reduce it further to 17.5MPH (~28KM/h) @ 6000.

How steep are these hills exactly? I never had problems climbing steep hills with a 26" wheel and 44T with some pedaling.
A 48T and 24" might be your best bet, IMO. That's 19.68:1, 22MPH (~35KM/h) @ 6000.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,620
429
83
Los Angeles, CA.
I weigh 210 lbs & I don't have that much trouble climbing hills with a 40T, 26" wheels & a 66cc engine.
I would think that just a 48T & some proper tuning will get you the power that you need. :)