I wonder if he just let the tube go dead flat. If that was the case, then the tire bead setting may have gone out of whack, even if it was once properly in position. Because at that point, the beads have all the support of a wet noodle.

Once that happens, and you go to finally reinflate the tube, you may as well be inflating the tire for the first time as far as the bead fit is concerned.

I don't know if anyone else mentioned this, and if so I apologize for the duplication.

But, modern HP ties are usually designed and pressure rated for hook edge rims. An older bike may have straight sided rims, which changes the tire fit and pressure rating formula.

If the OP's rims are straight sided, that may, all by itself, explain the problem.

That was mentioned very early on, but we don't know if the OP has a hook bead rim, though it does appear to be aluminum. TO THE OP: Check your rim to verify if hook bead or not -

There's quite a lot of new info for me to assimilate all at once here; and a lot of new vocab, considering that English isn't my 1st language! As recently as yesterday, I never even suspected that bike wheels came in "straight" or "hooked" rims...

I did check the wheels and they are aluminum. The wheels are the original ones.
They are : Ukai 27 x 1-1/8 w/o LA (not sure what the last bit means)
The tires are : Cheng Shin 37-630 (27 x 1-1/8) C-979D-4

As Turtle Speed mentions, the tires might have gone completely flat before I acquired the bike : The previous owner did admit to letting it sit on his balcony since he last rode it, almost 10 years ago. (Before I had a tube explode, my biggest concern with this bike had been to blow-torch the rusted seat post out of the frame...) When I went to his place, the seller inflated the tires before I test-rode the bike; but I don't know if they were completely flat before.

I will read the thread that Turtle Speed posted. I just didn't have much time to spend on this today...

Hi again,

Just wanted to thank everybody for all the helpful and informative answers.

Everything seems fine with the new tube and the lining doesn't show any irregularity. So I'm thinking the one that exploded must either have had a defect or was displaced when inflated the last time... I keep pressure near 85 psi because the bike rides great, w/ or w/o weight.

In any case, thanks to your help, I now have a better idea of what to look for when buying and installing wheels, tires and tubes. And I now carry a spare tube and the tools to change it when I go for long rides.

Cheers !

Another question...

I'm reading about my wheels again. Apparently, my wheels have "clincher rims". But I can't find whether my tires are also clincher... (Google not being very helpful here.) How can I figure that out ?

Wheels : Ukai 27 x 1-1/8 w/o LA
Tires : Cheng Shin 37-630 (27 x 1-1/8) C-979D-4

any tire that has a separate tube
that can be changed without changing the tire
is a clincher

99 percent or more of all bike tires sold today
are clinchers
the only people that use the other style
tubulars
are racers
and some luddites

I see, thanks.