On a recent TVR meet one of the guys had a puncture driving up north, so filled the tyre with the foam stuff. It appeared to hold up well to 130mph plus driving up through the highlands on twisty roads.

Impressive!

(Disclaimer - he tested it so we don't have to)
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Rory
MkIIa, blue lit buttons, memory upgrade, 1Tb in Subaru Forester STi
MkII, 240Gb in Mark Lord dock
MkII, 80Gb SSD in dock