In reply to TMM:
> I am broadly in agreement with the other view here:
> Might be a bit late to change shoes
> Nowhere near as much need for cushioning or support with trail/off road shoes
> However...
> For me the decision would be based on the terrain for the race. If the trail is like a forestry access track, hard packed and fairly dry then your Kayanos may be fine. If the trail is on woodland paths or moorland then it is likely to very waterlogged and muddy now in which your Kayanos will offer you no grip, will be waterlogged and heavy, will require significantly more energy as you look to find traction and could cause you to slip/roll an ankle.
> I would research the course and think about an alternative shoe.
> For hard packed dry trails where the only water will from rain or small puddles the a Gore-Tex liner is nice but not necessary. If it is going to be wet and muddy and you are likely to be plunging into water that goes over the top of the shoe forget Gore-Tex and instead look for a light and free draining shoe.
Your second point is far more imporant in my eyes. You can easily adjust to a new pair of shoes in a few weeks - just go running in them. This can be made easier by getting a pair with a similar footbed profile and drop. In this instance, a suitable (i.e. off-road shoe) is essential - you WILL slip, slide and fall over on a trail in road shoes at the moment. That will be far slower and more likely to give you an injury than a not-quite-worn in shoe.