I've been to a truck show over the weekend, and although my resulting truck photos are quite uninspiring, just as we were about to leave, about 8 or so classic cars pulled into the park. On the day the sky was overcast. Shooting in such conditions and also shooting man made objects, means you should shoot bracketed shots for post processing using HDR software. The image below is of a 1961 or thereabouts, Ford Thunderbird.
To comment on the Tamron, it again did me proud by showing off its versatility. It really is handy to have one lens do the job of two kit lenses. A real time saver if you ask me.
Canon 600D, Tamron 18-270mm f3.5-6.3 Di II VC PZD. Focal length 33mm, Exposure 1/160sec at f8 +2/3EV, ISO 400, Focus auto, VC on, Flash none, Filter none, 3 shots bracketed at +-2EV.