How are the 30mm spacer designed? Are the spacer bolted to the hub first with one set of bolts, then your wheels are attached to the spacer with a 2nd set of bolts? Or does one set of bolts go all the way through from the wheel all the way to the hub squeezing the spacer in between? If it's the former, then I believed that using the OEM bolts should be fine. But if it's the latter design type, then I would definitely agree with Hayaku that your OEM bolts are too short for the application. What's the model number of the H&R spacer?