John, hope you solved your problem after taking JohnG's advice. If not, I've had similar problems with my set-up. My van came with a factory fitted Al-Ko spare wheel carrier and jack and I've been moaning for nearly 12 months on how impractical it is to use. However, after talking to Al-Ko things are a lot better and the answer to the problem in my case was to make sure that the jack is extended to it's full height. The spare wheel on mine finishes up under the chassis when pulled out but it's fairly easy to remove it from the carrier with the ground clearance provided by the jack. Also, as JohnG says, make sure the spare wheel sits on the carrier as close to the chassis as possible (or blown air ducting in my case) but not so close that it stops you pulling the carrier off it's retaining stud. I know JohnG says you may need to drop the jockey wheel to aid wheel removal but for safety reasons Al-Ko recommend leaving the van hitched to the car. After removing my spare a couple of days ago I must say that it's good advice from Al-Ko as when the van is lifted to the full height on the jack it looks rather precarious. Hope this helps if you haven't sorted it already. P.S. you say that you can pull the whole unit off the guide rails. On mine it's not possible to do this as there are stops which prevent the telescopic tubes pulling apart.