Stiff sliding aluminium patio door

[randers]

Hi. I have aluminium sliding patio (well...onto a small balcony really) door which is really heavy and stiff to slide open. I've cleaned & lubricated all I can get at but with very little effect. They must be about 25-30 years old, there is no product name on them that I can see.
They look as if they will lift up and then sideways to get them off the runner for access to the underside, but the weight is far too much for a non-Mr Universe type to control them on a small balcony and not see them topple over & drop 2 storeys. Guess it might scratch them a bit.
Does anyone know what might typically cause this kind of problem (I thought seized or broken roller wheels probably), if spares are likely to be available if I got friends to help lift them off and found that eg new roller wheels or whatever were needed, or if there are other ways to access the sort of workings which would likely cause this problem, or know of anyone good & not over-expensive in Edinburgh to do this kind of thing? Guess I'm asking for any help/knowledge you have really? Thanks!

 

[Gazman16]

Most likely the bearings in the wheels have worn away.
The door will have to come off and be layed down flat to check what sizes wheels you need. You will also most likely have to take the whole bottom rail off the door as the wheels tend to be screwed in from behind the glass.

Once you have a set of wheels out you can check for any names and codes or failing that just take very accurate sizes and get some ordered in.
The wheels are fairly cheap (about £15-20 for a pair) but its the risk of damaging the rail or the glass when taking them off that's the scary part (especially a few floors up).

You may want to get some quotes from double glazing company's first just to see what they would charge.