Tired of tyres

Mandai, 35 km. I have three pairs of tyres. Slicks: the brand I use is prone to cuts and punctures (seems endemic to this brand, when I compared notes with world wheelchair racing champ William Tan). Semi-slicks: can't blame it for loss of traction in certain trail conditions. Knobbies: 13 years old and tough, but heavy. The last time I used it - and my Camelbak (which came out literally from cold storage) - was Apr 06 (both work fine despite the 2-year break). Also heavy on my mind: this weekend's race. Usually, I train several times a week for 2-3 months. This race, I barely have two nights to train. I do some urban off-road to build up tenacity and lacerate my arm against a bush. At least, weather and work permit me to cycle tonight.