Bonefishblues wrote:OTOH, and taking a different tack, how much additional weight is carried around for how many miles by how many cars at what environmental cost for the once-in-a-blue-moon event of a puncture?
The last one I has was on the bottom end of the A40 and I decided it was simply too dangerous to do anything other than call the man.
My blue moons - or rather, blue language - seem to occur every 18 months or so - at present I have languishing in my garage yet another wheel with a perfectly good tyre on it with a screw embedded in it near the edge. The day after it happened I was cycling along near where the puncture happened, and found a pile of the screws in the gutter! (So I picked them up and kept them, very useful).
When the family bus finally expires I always look for a replacement with a proper spare wheel, when these things happen its rarely just outside an open tyre depot with a tyre in stock that exactly matches the other three!
A friend's experience was "interesting" - didn't notice the pothole until it was too late, and there he was stranded at the roadside with a burst tyre, a wife and a car full of luggage. A two seater with a skinny spare - and nowhere to put the wheel that came off the car! On Mull. Someone came out from the nearest town (opposite side of the island) and sorted him out with the only tyre he had in stock of the right size - a cheapo, which he then had to replace later with a tyre to match the rest.
A former colleague found his brakes wouldn't work after he fitted his skinny spare one rainy day - the ABS kept going nuts 'cos the tyre wouldn't grip! Great safety aid that.
The gunge? - I was horrified to find my Mazda puncture kit (no spare) had printed on it a warning about driving over 50 if the gunge was used, and almost as an afterthought pointing out that the gunge would wreck the tyre even if it was otherwise safely repairable (not to mention specialist cleaning of the rim before a new tyre can be fitted)! That is of course even if it did work, and even if you were able to use it correctly - anyone whose read the instructions or actually tried to use this stuff will know what I mean.
I'll settle for the old-fashioned approach thanks, much safer and easier and lower impact!
As for the weight penalty - marketing! If the manufacturers were that concerned they would make the cars an inch or so smaller all round (keeping the spare wheel, not to mention glass in the headlamps so they don't cloud over), not keep making the "same model" bigger and heavier with each new version. Seen the latest Mini, Micra and Fiat 500?
Best grip at the front? Perhaps not, there were some interesting safety films on TV a while back, comparing sliding into a kerb front wheels first and doing so going sideways after the back wheels lost grip first. The one that understeered into the kerb rode over it, causing damage to the front susp and bits under the car. The one that oversteered flipped-over - much more dangerous!