I have seen different sizes for latex tube both for road bike wheel (700C)
One size is 700X18-20C and other is 700X22-23C
So what's the better one or right one?

What size tires are you using? It'll be printed on the sidewall.

If you're using 19 or 20mm tires, then you'll want the 18-20C. If you're using 22 or 23, you'll want the 22-23C. Similarly for 25C and 28C tires.

Yes git it very true
By the way what the 3 figures stand for?

I use the 20 and 23 size tubes in my veloflex 22s no problems. I like the 20s ,easier to install. The 23 is baggy, you have to really watch it when fitting.

exactly because the latex is so soft when I installed it I pinched the tube. It looked to me as if the tube was too big for the tyre but I have 23c tyre (i think) so I don't know, I'll check it when I'm home!

Yep very difficult to install imo, certainly need new coats of talcum powder every install because the tubes just stick to the tyre and scrunch up(without powder)

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Focus Izalco Pro

I didn't know that so you cover the tubes with talcum powder before installation?

it isnt 100% needed but it does reduce the chance of pinch flatting and flatting due to stretching/stressing.
This is probably why most latex tubes all come with some amount of powder on them from the factory?

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Focus Izalco Pro

If you're looking at Michelin latex tubes and running a 23c tire, you should get the 18-20c tube. Michelin tubes tend to run large and will leave a bunch of excess tube that you'll have to fold and stuff.

Very poor advice...you want to avoid over-stretching a latex tube (e.g, 18c tube in a 23-25c tire) in order to maximize the ride quality and insure maximum durability of the tube. Remember, you are not using latex tubes to save weight but rather for the ride quality and the increased durability (flat protection). The trick is to learn proper tire/tube mounting techniques with the slightly larger and more pliable latex tubes, and avoid using the smaller and incorrect size tube simply because its easier to mount.
EM3

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My 2011 Cervelo R5

Yep, I lost $20 in 20 minutes by not taking my time installing my Mich latex tubes. Not to mention an elevated heart rate for a split second when I got the big bang.

The good thing about latex is that you are able to patch them up. This depends on the severity of the pinch though (patchable when the flat looks like a puncture, not when it has exploded!)

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Focus Izalco Pro

I'm not the only person on this board that does this and as far as I know, nobody has suffered any ill effects from it.

so whats your trick?

Anyone can advice if it's a better technique to put the latex tube inside the tyre when you mount when it is a bit inflated? Maybe like 20-30psi?