Ajax Bay
Guru
- Location
- East Devon
Correct. They are designed to stretch a small amount.tyres are designed not to stretch significantly
Imagine the tyre laid out as a tube: 2100mm long and (say) 25mm diameter (x-area = 491mm^2): Total volume 1031x10^3mm^3.
Now hypothesise your 'one inch' depression model removes one inch (25mm x 2/3 the tyre area so about 8.2x10^3mm^3).
The displaced air would require the rest of the tyre's diameter to 'stretch' by 4 one hundredths of a mm: that's not a stretch of the imagination is it? And the pressure would stay essentially the same - or specifically for this discussion compared to "1% "(Andrew's assessment - see quote I'm suggesting is awry below) negligible (rough calculation 0.3%).
Now a rise of 3 degrees Celsius would raise the pressure by 1%, and I'm sure we've all been on rides where the max/min is 3+ times that.
Pneumatic tyres work because there is a single air chamber that distributes any change in pressure round the whole wheel. Take a tyre, and squeeze an inch of it down to the rim, and the volume of the air chamber, and hence the pressure, will only change by about 1%.