Arcee (Prime) - Transformers Wiki

All of the Autobots in Prime change size between alternate modes, but it’s way more noticeable with Arcee’s transformation from a vehicle the size of a human to a robot the same general size as the rest of the Autobots. Her tires do not change size when she transforms. One can see a little regular-sized tire in her back, and small half-tires on her calves.

watching arcee transform is like watching prime’s trailer roll offscreen in g1.  it’s ridiculous, but she’s rad, so whatevs.