I'm not very sure of the full context of the text, but this might be referring to bulges appearing in tyres upon passing over speed bumps at high speeds. Does this jive with the context of your text?

Google search for "tyre bulge": https://www.google.com.sg/#q=tyre bulge

Google search for "起包 轮胎": https://www.google.com.sg/search?q=起包 轮胎&biw=1366&bih=657&so...

http://iask.sina.com.cn/b/3ChCHceEHx.html

--------------------------------------------------
Note added at 15 mins (2016-04-21 10:21:08 GMT)
--------------------------------------------------

材质薄车身重<- I'm thinking that this might refer to the thin material used for tyres which is unable to take the heavy weight of the car body.