Where abouts are they growing: temperate climate, sub-tropical, tropical; what's the soil like, acidic, alkaline, well drained, clayee? How often are they watered? A rough guess might suggest a soil deficiency. More info. would help!

Thanks Funnelweb.

1. Cold climate
2. Haven't done a PH test on the soil. The ground is clay. I dug a sizeable hole and placed a garden mix in when I planted them. They've grown quite a bit since then, it's a possibility the roots have grown down into the clay.
3. Drainage is poor. The ground is level, and I believe my neighbours yard slopes toward these trees.

Cold climate should be ok, I grew 2 ornamental pears in Sydney, pyrus pashia (from a seed I nicked from the Syd. Bot Gdns. many years ago) and p. ussuriensis. Both grew to maturity and flowered magnificently every winter. They were on typical Sydney soil, free draining, neutral ph. They are regarded as pretty hardy in cool to temperate climates and like an ample supply of water. From the look of the leaves in your pic. I'm inclined to think it could be drainage and either too much or too little water. Can you improve the drainage? Alternatively looks like it might be pretty close to what looks like a garage door - colourbond steel-work. Any reflected heat from that? Those crinkled leaves could be the result of burning; other leaves in the picture seem to be unaffected. If it is too close and if the tree isn't too big you might consider moving it during the winter dormant period.

The trees are 600mm off a colourbond fence with a North/South orientation. In the afternoon the fence cops the full brunt of the hot Western sun. Unfortunately, the garden bed is bounded by a brick edging which has been mortared in. It would be a massive task to shift both the trees and the edging. If they die I'll replace them with something that can handle the heat.

As far as drainage goes, the only thing I could really do would be to build up the garden bed level. The neighbours block slopes toward the fence, I'm probably copping his stormwater run off.

Yep, I reckon it's leaf burn from the reflected heat off the fence. In my opinion your only option is to move them to where they can get better air circulation otherwise they'll continue to struggle until eventually they give up the ghost. Depending on how big they are, you could risk cutting the roots that extend out beyond the edging - no shorter than you have to - during the dormant period in winter. I'd also reduce the top growth accordingly to reduce stress on the tree(s) when the sap again begins to rise and new growth appears. That's standard bonsai practice, done with caution they should cope ok.