I assume you meant stock size but aftermarket aluminum wheels??? You are limited on what you can squeeze under a 13" wheel. The Volvo calipers are bigger and heavier, but I'm not sure what rotors you would run with them. Volvo calipers also have a 3.5" spacing on the mounting holes where the TR has 3.25". You have to take the Volvo caliper and open up the holes to make them mount to our strut housings. It is a fairly common upgrade with the BMW 2002 and BMW 320i crowd because those models use the same uncommon 3.25" spread as the TR. Maybe a little searching over on the BMW2002faq site will help. Easiest solution without moving to larger wheels is to bolt on a set of TR8 calipers and rotor. You can score a set of used calipers for around $200, then buy new rotors at $100 a piece and then try and find decent pads. By the time your done, you've spent nearly as much as what I spend to install Willwood aluminum calipers and 300mm(11.75") rotors. Problem with that is you need at least 15" wheels.