I vote the sudsy water suggestion (Oren!) is tops. I would
concentrate the soap, liquid dish soap preferrably, so that it is more
creamy than sudsy water. Smear the whole tube, the inside of the tire
and rim. Works dandily on small wheel barrow tires, also.

Addendum: In trying to reinstall a large 250 lb pillar under a house
corner, after releveling the house, we 1) prepped/compacted the soil,
smooth, where the pillar was to go. 2) laid a large plastic trash bag
on the outside edge and up under the house corner. 3) smeared Dawn all
over the trash bag, 4) placed another trash bag over the first. 5)
placed the pillar on the top trash bag. 6) shoved the pillar right in
place. We had 1/8" clearance for negotiating that pillar. We would
have never wriggled that large pillar into place, with just that much
wriggle room, if we wouldn't have used the trashbag-dishsoap method.

Sonny