October 6th @8pm saw the start of the One night in Thetford 12hr MTB race. It was also the first race outing for me using PTN - pepi's tyre noodles. The bike is an Orange stage4. the wheels have 35mm wide rims (29mm internal width). The tyres I use are IRC Mythos 29x2.1". On these rims they inflate to 54mm wide at 20 psi. The course was typical Thetford, dirt single track. With the small sized PTN fitted which was not too difficult and the normal load of sealant I was able to run 15 psi front and 18 psi rear which diffcultly. I normally run 22psi front and 24 psi rear. I did raise the pressure later in the race to 20 psi front and rear to see what that was like. I think I preferred the higher pressure on this terrain but the bike felt more stable than it does normally without PTN. Inserts work best if they fill a big proportion of the tyre volume like PTN does. Not only are the tyre sidewalls better supported allowing lower pressures to be run, the spring rate vs displacement is changed. The result are tyres that stay in more contact with the ground. You notice this more in ruts. Ruts with a tubeless setup without PTN can throw you off and down to the ground quite easily if you catch them wrong. With the insert if you catch the rut edge you can just ride up and over without issue. Essentially PTN makes it feel like you riding wider tyres. 

Which PTN?

There are three models now.

Race line, Rokkline and Revolution. They rank in order of stiffness with revolution being the stiffest. 

Revolution is therefore suited to gravity, enduro XC and CX use. The last is important. A small tyre need a firm insert so the air pressure does not squish to nothing. Revolution is the most impact reistant as well. It suits heavier riders  and E bike user more than the other two. Revolution has the best runflat potential and like most insert stops burping. Revolution allows the lowest tyre pressures.

Rokkline is the most versitile. Given its construction and material used it has excellent damping abilities and is impact resistant. It is diifuclt to break or tear it. It allows you to run your tyres flat with control and stops burping. It is well suited to XC riding as well as enduro riding. The stiff insert allows the rider to tune the feel of the bike with a wide variety of air pressures. Rokkline is the choice when the trails get narly. Its allow you to be faster than raceline over this sort of terrain. 

Raceline is the lisghtest but the least impact reistant of the three. The larger sizes are robust and suitable for enduro use but the rokkline or revolution will allow lower tyre pressures. Therefore Raceline I think is best suited to XC use and are East Anglia its all I need.

https://thecycleclinic.co.uk/products/pepis-tyre-noodles-ptn