[The Freebairn wheel you mention were truly the bees knees weren't they? In loose or heavy going they made a massive difference to how horses got to the line.]
The advantages of the Freebairn Singles: Very light. Excellent hub. large tyre (44 mm) great for soft tracks which were best for horses. Tyres had the lowest hysteresis (deformation) losses of any tyre ever used in harness racing. So all up, the most energy-efficient harness racing wheels ever made. DISADVANTAGES: The 15g spokes were the lightest and weakest ever used in a harness racing wheel. Frequent spoke failures. The wooden rims were VERY fragile, a strike from a hoof would shatter them. The tyres were equally fragile, easily punctured, with the result that the flat tyre would often wind around the hub and lead to the catastrophic failure of the whole wheel. It was these disadvantages that caused R.J. Walsh & Son never to go that route. That said, nothing could match the Freebairn Singles for over-all efficiency.
Cheers,