Cyl/Head o-rings why so small

[Treesmacker]

My question is why are the cylinder o-rings on the GasGas undersized compared to the o-ring groove?? They need to be stretched alot to fit into the groove, resulting in a smaller cross section. Are they undersized for thermal expansion?? http://catalog.precisionassoc.com/pr...lication-data?

I'm a mold designer and spec out o-ring grooves all the time.
When we size a o-ring groove we match either the outside or inside of the o-ring to the groove, depending on if it has internal or external pressure. The groove is designed so that the o-ring protrudes above the surface but is wide
enough to accomadate the o-rings cross sectional area.
Bob in MN
2 weeks till the Wudi!