Special pliars and bolt cutters are used to set up chains to size. Farm boy methods to open the cross bars are to drive a drift punch into the end crows while the chain is in a vise. They are driven back shut with a hammer and a block or anvil. Shortening the side chain can be done with bolt cutters or a hack saw hammer and chisel etc. The easiest way I have used to narrow cross bars to make larger chains fit a smaller tire is the cut the piece to make it shorter from the center of the cross bar with a torch or a chop saw, then weld them back togather. You can remove the crows from the end of each cross bar then cut the length you want out and put the crow back on. To shorten side chain to fit just cut off the excess with a torch or saw and use. Truck tire chains are fairly heavy chains unless you are talking about say a F150 sized truck. Even those are plenty big and heavy. The lawn is go-ing to suffer from those chains, and you are going to have to keep them checked over and tight. I would look into some different tires before I used chains on soft lawns.