What did I do wrong ?

[simon.r]

The road temperature could be even hotter. However, thinking back to those dim and distant days, I would suggest that your calculations would be right if you used degrees Kelvin rather than degrees Celsius. 10 degrees C is 283 degres K and 30 equates to 303. I would recalculate your equation if I could find my slide rule but would suggest that pressure increase is not quite as high as you calculated.

Slide rule?! Let me get my new-fangled electronic calculator out

OK, using Kelvin:
Pressure 7 bar, temperature 283, constant = 0.0247
Temperature 303, constant = 0.0247, pressure = 7.48 bar

That sounds a lot more reasonable. A 20 degree increase in temperature gives an increase in pressure of about 7psi.

 

[darth vadar]

Everything was good today with the new tyre and inner tube.

No problems with a 20 miler in the lovely sunshine although there was quite a strong breeze doing its best to make it difficult for me on the way home!

 

[deanE]

Slide rule?! Let me get my new-fangled electronic calculator out

OK, using Kelvin:
Pressure 7 bar, temperature 283, constant = 0.0247
Temperature 303, constant = 0.0247, pressure = 7.48 bar

That sounds a lot more reasonable. A 20 degree increase in temperature gives an increase in pressure of about 7psi.

go to the top of the class