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03 Jan

Tyre pressuree

Posted by Bold Apps

Well what you think you know is probably wrong. Let's start there.

Let's start with a manufacturers recommended tyre pressure. These are not to used. The standards organisation has an approved test using a steel rim to se when a tyre blows off. Half that pressure is the recommended tyre pressure. It's a range due to variability but it's also way too high. 

Back in 2015 when I got my first IRC tubeless RBCC tyres myself and others noted at 90 psi for a 25mm tyres (that sat at 27.5nm on a 19mm internal width rim) the tyre felt faster. What was described is zing however that road buzz is exactly what you dont want. 

Road buzz is energy lost. You get this with wheels when manufacturers build a wheel that has zing. Smoothness is better. Smoothness is less energy lost. That's faster.

There is no relationship that works between rider weight and pressure as it far too dependent on road surfaces.

So to work out for a tubular  tubeless or tubed clincher the correct pressure find a typical loop. Pick a starting pressure for a tubeless road tyre that's no more than 80 psi try it out. Your looking for smoothness I.e no buzz. Continue dropping until you feel tyre squirm in the bends

 Squirm or pedal bob means the pressure is too low. The point at which there is no squirm and you have no road buzz that your min pressure and possibly the lowest rolling resistance. Your max pressure is just below the point where you start to feel road buzz. Rolling resistance

between these two points should not be that different but on most U.K road surfaces lower seems to be better.

This works for road, MTB, gravel or CX tyres of all types. The physics is the same. 

For IRC road tyres and me 80 psi seems to be the point at which road buzz starts to become noticeable is 80 psi for a 28mm Formula Pro RBCC tyre. At 30 psi I cant really feel squirm but can bottom the tyre out. So 40 psi seems to be the minimum. 50to 60 psi is what I normally use now. With panniers I may push it up a bit. I am nearly 90kg kitted up and generally ride road biked 9 to 14kg in weight without extra load in panniers. 

 




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