@ ABBB: Milo is a purebred AmStaff, mostly White Rock Line and a little Woods Forrest. @davidfitness: yes, chains are better for the reasons you've mentioned. another reason for chains is that they very hard get stuck to roots, sticks, etc. that happens much easier with a tire. but if you see that your dogs starts limping every time you train wp nomatter how little weight he pulls, you will have to find another training method. and as i sayed, do send in those x-rays because we can only guess how his hip status is.