# Tyres on the right pressure

Depending if you look in the Owners manual or the Workshop manual tyres need different pressures. Surprising, isn’t it? It even looks like the conversion between psi and bar is drifting away from science.

From the available literature:

 18” tyres Owners manual Workshop manual Solo psi kg/cm² psi kg/cm² Front 20 1,41 18 1,24 Rear 30 2,11 28 1,93 With pillion Front 22 1,55 20 1,38 Rear 32 2,25 30 2,07

psi means pound per square inch. 1 psi = 6894,757 N/m² = 0,06894757 bar,  and: 1 bar = 1 kg/cm²

When you drive a 19” tyre, the pressure might be increased by 2 psi (= 0,14 kg/cm²) for a solo rider and 3 psi (= 0,21 kg/cm²) with a pillion.

TIP: on the road you simply withhold: 100 psi = 7 kg/cm² (= 7 bar)

Driving with too low pressure in the tyre can have dramatic consequences. A lot of stories about this are circling around, but I always will remind the following ones, as I can couple them to some technical truth.

A too low pressure might provoke some slippage of the tyre over the wheel. As the inner tyre has a lot of surface in touch with the outer tyre, he will follow the movement of the latest. However the valve, fitted on the inner tyre will remain fixed to the wheel. Too low tyre pressure might make the tyre valve ripped from the inner tyre. The tyre looses it’s pressure in only seconds.

With too low pressure, the bead heel is not firmly  pressed against the edge of the rim. During turns a lot of forces are trying to push the tyre towards the inner side of the rim. If this happens, the inner part of the rim having a lower diameter, there is place for the tyre to run of the rim. I would not like to experience this.

Hearing around at the Royal Association France, the Bullet Club in New Delhi and checking the web, …, following table might be a good lead for you:

 Solo Front 2,0 kg/cm² 29 psi Rear 2,2 kg/cm² 32 psi With Pillion Front 2,2 kg/cm² 32 psi Rear 2,4 kg/cm² 35 psi

Quite some differences, especially on the front tyre. This might be due to climate differences between Europe and India, but I have no proof for that.
So, although the latest table gives you the pressures commonly used by our French friends, I would like you to be a bit careful with the front tyre.

It definitely can be useful to share your experience with tyre pressure. Please send your opinion on: refriends.be@gmail.com