If I was to pump up my commuting tyres beyond the maximum pressure stated on the side wall of my tyre (65psi) to say 80 or 90psi is a blowout and certain death a foregone conclusion?

To whom do we send the flowers?

why would you want to?

My next pint will be solemnly quaffed in your memory.

why would you want to?

Tyre pressure on a road bike is a trade off between comfort and grip (low pressure) and lower rolling resistance (hence faster), less tyre wear and less likelihood of a puncture (high pressure). So by increasing your tyre pressure you can ride faster, your tyre will last for longer and you have less likelihood of getting a puncture, but your ride will be harsher and grip in corners will be reduced. Larger volume tyres tend to require lower tyre pressures than low volume ones.
On no account should you go above the recommended maximum tyre pressure. It’s akin to disconnecting your brakes in order to increase your average speed. If you want harder, faster tyres – buy some new ones!
FWIW – for purposes of commuting and fast pootling I’ recommend the Continental Gatorskin.

i just do my tyres to 140psi and let them deflate over a few weeks.

My commuter’s usually at 60-ish, quite lumpy roads so comfort apart, it’s not any slower on most of it- slower on the fast bits, faster on the slow bits and tbh that feels just fine. (26 inch Marathons though)

I see little point in anything higher than 60 or so in town, but then I like the 15% idea.

I do wonder what makes one tire safe only to 60 and another to 120.

cynic-al “I do wonder what makes one tire safe only to 60 and another to 120.”

The construction differs with plys and how they are laid up, a bit like asking why can’t you put those 165/70/R13 T80 on a Porsche

You should be able to get away with a bit more than what they say because like most limits there will always be a margin of error/safety.

Having a front tyre blow out going flat out down some country lane at the bottom of a twisty downhill section bounded by unyielding dry stone walls won’t be fun A similar effect can be had at speed dicing with traffic at rush hour 😳

So too high a pressure would burst the tire by making tha carcass split?

Possibly – if you had an area of weakness from riding along on the rim with a puncture or grazing against the sidewall and you’ve over inflated the tyre past the manufacturer’s rating and then you are riding along and hit bump that causes the psi in the tyre to spike and at that point catastrophic failure is a possibility.

FWIW – for purposes of commuting and fast pootling I’ recommend the Continental Gatorskin.

Nearly tried the Gatorskins – I would have gone through with it too if I could get the damn things on the rims without pinch puncturing the tubes!

After two failed attempts in perfect kitchen conditions, I didn’t fancy having to do it should the worst happen in the great outdoors.

http://www.schwalbetires.com/tech_info/inflation_pressure

http://pardo.net/bike/pic/fail-026/000.html

http://pardo.net/bike/pic/fail-026/RIM-004.html

http://www.michelin.co.uk/bicycle/learn-share/bicycle-guide/bicycle-pressure-curves

i just do my tyres to 140psi and let them deflate over a few weeks.

I do the same with my GP 4 seasons, except I start at 120 (the max stated on the tyre). I’m also even more slack about pumping them up over winter for more grip.