Depends on how far out they stick out. Every inch you lower the car, the wheels will produce some negative camber which would be bad for tyre wear, but will bring it closer under the guards. Seeing as you already run fairly thin tyres, if they stick out too much as it is, then the you have 3 options:
1. Replace wheels with correct offset and clears calipers
2. Do not lower your car
3. Lower the car and roll your guards
Spacers are illegal and would void ur insurance if u were involved in an acco, not to mention if the cops spot it...prepare lube.