My sister did a folding sliding set of timber doors. No tracks, no sliding mechanism, the entire set of doors supported by the hinges. Instead of the convential 2 hinge, I think she used 4. This design was advised by the timber door supplier. I think its 3 years, so far so good.

The RM21 psf sliding door is the light weight type.

The heavy duty sliding folding gate (means the entire opening is 'opened'), cost about RM80 to RM100 psf. This is usually supplied with thicker alum material, and the sliding mechanism is expensive. Some use taiwan type, one company uses henderson from UK.

I think if u get a alum door guy to come and 'recycle' your old set, it is not going to be cheap. I had a problem with my door (8') and a guy came to quote. If change the track only, RM500 but if the side frame has to change it came to RM1,500. Cost aside, to be green, it is worth to consider to recycle.