What size innertube do I need for a C38 motor rim (Commander Pro) and a kenda 340A tire?

[BKW]

I ripped my innertube for my Commander Pro and I need to replace it.

What size innertube goes with a Kenda 340A tire and a C38 motor rim?

Ewheels innertube sizes say 18x2.5" and 18x3" but i'm not sure which one to get for a kenda 340a tire and a c38 rim for my commander pro?

[mrelwood]

18x3” is correct.

Edit: It’s been said that you can use a tube one size bigger or smaller, but I wouldn’t be comfortable using a 18x2.5” tube in a 3” tire (= 2.75 = 80 wide motorcycle tire), unless the tube specifically has both sizes stamped on it. Even then I’d much prefer a pure 18x3” tube.

Edited May 16 by mrelwood

[BKW]

8 hours ago, mrelwood said:

18x3” is correct.

Edit: It’s been said that you can use a tube one size bigger or smaller, but I wouldn’t be comfortable using a 18x2.5” tube in a 3” tire (= 2.75 = 80 wide motorcycle tire), unless the tube specifically has both sizes stamped on it. Even then I’d much prefer a pure 18x3” tube.

I really do appreciate your help.

I was told not all C38 rim sizes are the same? Someone said while the motor can be the same for different EUCs, the rim sizes vary depending on different EUCs, even with the same motor. If this is true, I do wonder if I got the correct tire (K340A) for the Commander Pro's C38 rim size?

A lot of my questions are lazy questions, and I suppose I could google and try to find the answer, but I do like asking others that have knowledge on this subject.

Keep in mind, I was able to install the K340A with, I assume, a 18x3" innertube on the CP previously before I ripped the tube. The tire was slightly wobbly however, and upon further inspection I noticed the tire bead(?) lining was not even around the entirety of the rim. Because of this, it prompted me to try and "massage" the tire to seat it properly and take out the wobble, but in doing so I tore the innertube.

[mrelwood]

39 minutes ago, BKW said:

I really do appreciate your help.

I was told not all C38 rim sizes are the same?

The rim widths vary slightly, but it doesn’t affect the tire or tube sizing. The diameter is still the same. Tube is chosen based on the tire. And the tire size is limited by the tire cavity of the wheel.

So, Commander Pro fits a 2.75-14, 18x3.0”, or 80/90-14. All are the same size. (No point in putting in a narrower 2.5” wide tire.) And there is only one K340 of the mentioned sizes. And 18x3.0” is the tube size for it.

 

39 minutes ago, BKW said:

Someone said while the motor can be the same for different EUCs, the rim sizes vary depending on different EUCs, even with the same motor.

Again: Widths, sure. One could also say that a 16” and a 18/20” EUC could have the same motor, only different rim size. But the rim is a fixed part of the motor, so one could argue it being a different motor then.

 Either way, CP has a 14” motor. And if you were able to install the K340 on it before, it’s the correct size. The sizing increments are quite large.

 

39 minutes ago, BKW said:

I noticed the tire bead(?) lining was not even around the entirety of the rim. Because of this, it prompted me to try and "massage" the tire to seat it properly and take out the wobble, but in doing so I tore the innertube.

I can’t even imagine how massaging a tire can tear a tube! It’s like your girlfriend massaging your shoulders but ended up snapping your collar bone in half…

EUC rims don’t automatically center the tire like a motorcycle rim does. So it usually needs to be manually centered. Here’s how you do it (without tearing the tube!):

 

Edited May 16 by mrelwood

[BKW]

On 5/16/2023 at 3:03 PM, mrelwood said:

The rim widths vary slightly, but it doesn’t affect the tire or tube sizing. The diameter is still the same. Tube is chosen based on the tire. And the tire size is limited by the tire cavity of the wheel.

So, Commander Pro fits a 2.75-14, 18x3.0”, or 80/90-14. All are the same size. (No point in putting in a narrower 2.5” wide tire.) And there is only one K340 of the mentioned sizes. And 18x3.0” is the tube size for it.

 

Again: Widths, sure. One could also say that a 16” and a 18/20” EUC could have the same motor, only different rim size. But the rim is a fixed part of the motor, so one could argue it being a different motor then.

 Either way, CP has a 14” motor. And if you were able to install the K340 on it before, it’s the correct size. The sizing increments are quite large.

 

I can’t even imagine how massaging a tire can tear a tube! It’s like your girlfriend massaging your shoulders but ended up snapping your collar bone in half…

EUC rims don’t automatically center the tire like a motorcycle rim does. So it usually needs to be manually centered. Here’s how you do it (without tearing the tube!):

 

Thanks for the video and response!

I quoted "massaged" because that's not what I technically did. I listened to a guy from facebook who told me to deflate the innertube to where it's just barely ridable, ride the euc with low psi a few feet, allow the tire to adjust itself that way, and add 5 PSI periodically, repeat until tire is seated evenly. I had the PSI too low, the tire went sideways and ripped the valve from the innertube due to the valve going through the rim; hence, "massaged".

Needless to say, lesson learned. I won't do that again.

[mrelwood]

12 hours ago, BKW said:

I listened to a guy from facebook who told me to deflate the innertube to where it's just barely ridable, ride the euc with low psi a few feet, allow the tire to adjust itself that way

I never had any success with that technique myself, which is why I searched for better solutions and eventually made the above video. Good to know a data point of the riding deflated method tearing a tube!

I think the technique might work with other than EUC rims though. EUCs just have too much room for the bead for it to be able to center itself. Hence, manual centering is required.