Chainring Swap

Sorry if this is a stupid question, I'm really new to this and I'm not too sure about this stuff, but my cyclone middrive e bike is currently running a 32 tooth sprocket at the crank. (The one that connects the front crankwheel to the rear set of gears). Off the ground the bike tops out at about 60 mph, and I know that the bike is going to get no where close to that, so I was thinking of swapping that chainring to a 24 tooth to make it more efficient and maybe make it accelerate quicker. My only problem is that in first gear, the bike wheelies very easily below about 6-7 miles per hour if you give it full throttle with the current gearing set up. Right now, the bike tops out at about 18 mph or so in first gear. So if I were to switch to a smaller chainring, how usable would first gear really be? Would it just wheelie and be uncontrollable, or do you guys think it would be manageable? I do like getting off the line quick, but I'm just worried that with the lower gearing, there would be no point in using the lower gears because it would just wheelie all the time.

Lower gearing on the bike will only murder your chain and sprockets that much faster. If you have problems with wheelies, it's because you have too much torque for the wheelbase of your bike. And if you're getting a no-load speed of 60mph with only a 32t chainring, it's because you have too high a motor RPM from feeding it too much voltage for your application.

More isn't better when it breaks stuff and makes your bike misbehave. If your controller is programmable, you can limit phase current to reduce motor torque, and use gear reduction to raise wheel torque to whatever you need. Be sure you're using the largest possible crank sprocket and the smallest possible shaft freewheel on the motor stage of your mid drive.

What's your rear cassette's range? If you can use a bigger one, do that. 10-11-12-13t sprockets at the small end are destructive to your chain even when only pushed with muscle power. You can lock out the smallest ones with your derailleur's limit screws, so you don't go to those gears and exacerbate wear and tear.

Use the largest cassette your bike will accept, and then fit the largest chainring that gives you the bottom gear you need. That reduces chain tension and articulation, which should make everything last longer and work better.

Check out what fechter did to limit his cassette to just the gears that make sense for him, while maintaining good chainline. I use a similarly modified cassette on my e-bike, with 16-40t range.

https://endless-sphere.com/forums/viewtopic.php?f=3&t=99034&p=1450083#p1450083

Seems like you could limit or reduce your starting power to get the bike moving if wheelies were an issue.

Chalo said:

Lower gearing on the bike will only murder your chain and sprockets that much faster. If you have problems with wheelies, it's because you have too much torque for the wheelbase of your bike. And if you're getting a no-load speed of 60mph with only a 32t chainring, it's because you have too high a motor RPM from feeding it too much voltage for your application.

More isn't better when it breaks stuff and makes your bike misbehave. If your controller is programmable, you can limit phase current to reduce motor torque, and use gear reduction to raise wheel torque to whatever you need. Be sure you're using the largest possible crank sprocket and the smallest possible shaft freewheel on the motor stage of your mid drive.

What's your rear cassette's range? If you can use a bigger one, do that. 10-11-12-13t sprockets at the small end are destructive to your chain even when only pushed with muscle power. You can lock out the smallest ones with your derailleur's limit screws, so you don't go to those gears and exacerbate wear and tear.

Use the largest cassette your bike will accept, and then fit the largest chainring that gives you the bottom gear you need. That reduces chain tension and articulation, which should make everything last longer and work better.

Check out what fechter did to limit his cassette to just the gears that make sense for him, while maintaining good chainline. I use a similarly modified cassette on my e-bike, with 16-40t range.

https://endless-sphere.com/forums/viewtopic.php?f=3&t=99034&p=1450083#p1450083

Click to expand...

I'm aware that it puts more stress on the gears and the drivetrain but how much more? It's an 8 tooth reduction, and honestly I don't have much of a problem with the bike doing wheelies as long as it's controllable, but I just mainly want to know how usable/ unusable first gear will become then. It's like if you had a 700 hp muscle car with skinny tires (obviously greatly exaggerated), it's basically wasted power though because you'll just spin out. Unfortunately the controller isn't programmable so I can't do soft starts though. My cassette's gear range goes from a 32 tooth to 11 tooth sprocket. As you probably guessed though, I very rarely go past 6th gear unless I'm doing nearly 35, which is not very often at all. But thanks for your idea about limiting the rear cassette though, I think that's something I might consider if I just decide to keep the 32 tooth sprocket.

AHicks said:

Seems like you could limit or reduce your starting power to get the bike moving if wheelies were an issue.

Click to expand...

Yup, I usually don't give it more than 30 percent in first unless I'm screwing around and having fun. I also shift through my gears like a manual car or a motorbike, 1st to 2nd to 3rd and so on. I just want to make sure I'm not going to land on my back constantly if I do this sprocket change. Wheelies are only an issue for me when I can't control them and they end up becoming unpredictable.

I run a 42t front/32-16 rear on a cyclone offroad. I wouldn't want a significantly lower first than that since the gear would be too short to be useful. It'll wheelie in the first 3 but with plenty of control.

Grantmac said:

I run a 42t front/32-16 rear on a cyclone offroad. I wouldn't want a significantly lower first than that since the gear would be too short to be useful. It'll wheelie in the first 3 but with plenty of control.

Click to expand...

Yeah I'm just really debating on whether 15 mph max in first gear (which is what it will be if I swap the chainrings) is too short for me. What's your max speed in first?

Don't have a speedometer. I'd rather have a bit more speed if possible.

speedyebikenoob said:

I'm aware that it puts more stress on the gears and the drivetrain but how much more? It's an 8 tooth reduction,

Click to expand...

It should be more stress by the same ratio (inverse) as the gearing change. If you had a 32 and go to 24, then 32 / 24 is 1.3333.... So 1.3333x more stress than before. Might not be that simple, and might be a curve (worse) instead of a linear change.

Unfortunately the controller isn't programmable so I can't do soft starts though.

Click to expand...

Relatively easy to fix. You can use an RC filter (resistor capacitor) to make a ramping circuit. Resistor goes in series with the throttle signal, from thorttle to contorller. Capacitor goes from the controller side of the resistor to ground. Values would be chosen to make a ramp length of however long you wish it to take to go from zero to full if you were to slam on the throttle. It will slow down *all* throttle application, though, not just hard starts. If you're interested, you can look up RC time constant calculators and see what resistor and capacitor values you might use.

The downside to it is that it *also* slows down the throttle-off (not necessarily by the same amount, depends on the controllers internal circuit for throttle input; some have a pulldown resistor). The circuit can be made more complicated to force dropoff to be faster than ramp up, if necessary.

Zombiess made a Throttle Tamer that does this sort of thing in firmware on an MCU; dunno if he still sells them.

Grantmac said:

Don't have a speedometer. I'd rather have a bit more speed if possible.

Click to expand...

Huh I see. That gear ratio is actually higher than mine, what size wheels are you running? I'm on 29's which is maybe why I find it a bit tall

amberwolf said:

speedyebikenoob said:

I'm aware that it puts more stress on the gears and the drivetrain but how much more? It's an 8 tooth reduction,

Click to expand...

It should be more stress by the same ratio (inverse) as the gearing change. If you had a 32 and go to 24, then 32 / 24 is 1.3333.... So 1.3333x more stress than before. Might not be that simple, and might be a curve (worse) instead of a linear change.

Unfortunately the controller isn't programmable so I can't do soft starts though.

Click to expand...

Relatively easy to fix. You can use an RC filter (resistor capacitor) to make a ramping circuit. Resistor goes in series with the throttle signal, from thorttle to contorller. Capacitor goes from the controller side of the resistor to ground. Values would be chosen to make a ramp length of however long you wish it to take to go from zero to full if you were to slam on the throttle. It will slow down *all* throttle application, though, not just hard starts. If you're interested, you can look up RC time constant calculators and see what resistor and capacitor values you might use.

The downside to it is that it *also* slows down the throttle-off (not necessarily by the same amount, depends on the controllers internal circuit for throttle input; some have a pulldown resistor). The circuit can be made more complicated to force dropoff to be faster than ramp up, if necessary.

Zombiess made a Throttle Tamer that does this sort of thing in firmware on an MCU; dunno if he still sells them.

Click to expand...

Yikes okay actually that's a lot. I do want this thing to last too. I'll probably just keep this chainring then. Eh, I do like the quickness and power of the bike right now, maybe if it was something that could be turned on or off, but I don't think you can do that with resistors can you?

I'm on a 26".

What are your primary sprockets (motor side)?

Grantmac said:

I'm on a 26".

What are your primary sprockets (motor side)?

Click to expand...

13 tooth on the motor which connects to a 44 tooth (I have one of the triple chainring versions) Then 32-32 tooth to the rear cassette in first gear.

speedyebikenoob said:

Eh, I do like the quickness and power of the bike right now, maybe if it was something that could be turned on or off, but I don't think you can do that with resistors can you?

Click to expand...

Sure. Just put a switch between the "top" of the capacitor and the signal line. Then it isn't in the circuit to "delay" the signal.

If you want to bypass the whole thing, you can use a double pole doulbe throw switch, and wire the switch for the cap to one side of it, from center contact to one end. Then wire the center of the other side to one end of the resistor, and the other end of that side to the other end of the resistor. That way, in one position, the swtich will connect the capacitor and not short out the resistor, so the ramping will occur. In the other position, it will disocnnect the capacitor and short across the reisstor, directly connecting the throttle to the controller.

speedyebikenoob said:

Grantmac said:

I'm on a 26".

What are your primary sprockets (motor side)?

Click to expand...

13 tooth on the motor which connects to a 44 tooth (I have one of the triple chainring versions) Then 32-32 tooth to the rear cassette in first gear.

Click to expand...

If you go for a 42 front and wider ratio 11-40 rear that will keep you in bigger rear cogs which generally is much better for the chain. Especially if you space the cassette out to get the chainline straight in the bigger gears.

amberwolf said:

speedyebikenoob said:

Eh, I do like the quickness and power of the bike right now, maybe if it was something that could be turned on or off, but I don't think you can do that with resistors can you?

Click to expand...

Sure. Just put a switch between the "top" of the capacitor and the signal line. Then it isn't in the circuit to "delay" the signal.

If you want to bypass the whole thing, you can use a double pole doulbe throw switch, and wire the switch for the cap to one side of it, from center contact to one end. Then wire the center of the other side to one end of the resistor, and the other end of that side to the other end of the resistor. That way, in one position, the swtich will connect the capacitor and not short out the resistor, so the ramping will occur. In the other position, it will disocnnect the capacitor and short across the reisstor, directly connecting the throttle to the controller.

Click to expand...

Maybe I'll try this, thanks! Right now I'm the only one really riding the bike though and I don't find it that necessary with how its set-up, I just have to have a gentle wrist, but maybe in the future though.

Grantmac said:

speedyebikenoob said:

Grantmac said:

I'm on a 26".

What are your primary sprockets (motor side)?

Click to expand...

13 tooth on the motor which connects to a 44 tooth (I have one of the triple chainring versions) Then 32-32 tooth to the rear cassette in first gear.

Click to expand...

If you go for a 42 front and wider ratio 11-40 rear that will keep you in bigger rear cogs which generally is much better for the chain. Especially if you space the cassette out to get the chainline straight in the bigger gears.

Click to expand...

I think I'll do this if I start to see excessive wear on the cogs, it seems okay as of now and I don't want to risk changing it if it's already working. I haven't had any problems with my chainline yet, but the chain tends to slip if I'm going really fast (30 mph +) on a bumpy road. I added some nuts to the chainring so they "catch" the chain before it gets stuck in between the motor and the chainring and snaps. More spacers would probably work better though.