Tire tubes: little bit big or little bit small?

marc

Speeding Up
#1
Bike maintenance rookie here.

I was buying some spare tubes a couple of weeks ago at Y's Road in Okachimachi (did they change their name from Ueno Classic?) when I encountered the following dilemma: My tires are 700x23, and they had Panaracer tubes in 700x18-23 and 700x23-27 sizes. Which one do I get?

I asked a clerk and he advised me to get the smaller ones as they'd be easier to install, and indeed they were (my previous spare was the larger size, which unfortunately had a hole that had escaped notice). But I wonder, is there any trade-off, like shorter lifespan or lower safe air pressure? I've put about 250km on it in the last two weeks and it feels fine so far.

Thanks.
 

AlanW

Maximum Pace
Jan 30, 2007
1,214
435
103
Tokyo
#2
The smaller tube is more suitable. The limit of pressure is from your tyres (or possibly rims, if you have full carbon ones). The tube cannot support more than a few kPa on its own; without the tyre it will stretch and stretch and BANG burst.
The smaller tube is stretched a bit more inside a 23mm tyre compared to the larger tube but well within its limits. Enjoy the weight-saving and easy fitting.

AW.