Reply to HM's post about tyre pressure
Posted: Wed Jan 07, 2004 9:54 pm
For your shorty, I would run around 30psi on the road. A good way to measure correct tyre pressure is to use a hot and cold test, and visually to see if the tyre is getting full contact on the road, not just the crown of the tyre.
As tyres heat up through normal use, the air within will expand, increasing the pressure. Measure the tyre pressure when cold (ie before you have covered 5km on road), then measure the pressure when at operating temp (about 15 minutes or so constant road driving) the reasonable pressure difference between the cold and hot pressure should be around 4psi - any more (excessive - like 15psi) means that the tyre is underinflated and excessive heat is building in the tyre carcass. Most bias ply tyres do have a heavier carcass so they will be hotter than normal radials, but like I said, excessive pressure difference is what you have to avoid. Overinflation will result in the tyre wearing in the crown area of the tyre and the associated uneven wearing of the tyre overall. this can usually be seen, but it will be harder with a heavy bias carcass.
I run 20 psi on the road in the Camolux on JT2's, around 35psi on the Mav wagon with JT2's, to give you an idea of weight difference and pressure.
As tyres heat up through normal use, the air within will expand, increasing the pressure. Measure the tyre pressure when cold (ie before you have covered 5km on road), then measure the pressure when at operating temp (about 15 minutes or so constant road driving) the reasonable pressure difference between the cold and hot pressure should be around 4psi - any more (excessive - like 15psi) means that the tyre is underinflated and excessive heat is building in the tyre carcass. Most bias ply tyres do have a heavier carcass so they will be hotter than normal radials, but like I said, excessive pressure difference is what you have to avoid. Overinflation will result in the tyre wearing in the crown area of the tyre and the associated uneven wearing of the tyre overall. this can usually be seen, but it will be harder with a heavy bias carcass.
I run 20 psi on the road in the Camolux on JT2's, around 35psi on the Mav wagon with JT2's, to give you an idea of weight difference and pressure.