Here is a few simple steps to replace your old bad rubber tire for the new one:
1. Unscrew your pinch roller from your deck and remove the cap
2. Use sharp knife to cut out the old bad rubber from the metal core
3. Use an acetone thinner to clean off the rest of the rubber from your core
4. Use a drop of any detergent to help slide the new rubber tire over your metal core and than push down firmly until you make it flat on front sides
Be careful removing the original caps, sometimes they get stuck on the core almost bonded together, use very sharp painters spatula to remove those. Wash them carefully but don't use acetone at this point that would cause the plastic to go soft. You might wanna use an alcohol or oil based thinner instead.