I started building Tamiyas new Humvee a while ago, and was going to resume building it this weekend. But when I look at the tyres, they are all dried up and cracked. Anyone else that have encountered this?

Have built a lot of car kits from Tamiya and never had any problem with these tyres.

And what options is there to replace these???

Never had the problem either. You can contact Tamiya for replacements. They are great about replacing damaged parts.

Thomas, they cracked as a result of being vinyl. I had ther same results with several of my kits in the pat. Since I figured out how to cast my bown parts, I take the kit tires and cast resin ones as soon as posssible. I'd suggest looking into Blast models new tires for the Hummer. A little narrow, but they have the correct tread pattern of the radial tires in use now compared with the bias ply that Tamiya provides in the kit. HTH "Q"