I'm nor a layer, nor a tire expert.
Over-inflating between placard and sidewall is in safety limits given by constructor and manufacturer.
Over-inflating over sidewall is certainly dangerous under unexperienced people's hands, but can be safely used by experienced people :
Driving Under Pressure (full article) - CleanMPG Forums
Denis.
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Save money & CO2 at home :
http://ecorenovator.org/ 
Created and managed by the creators of
http://ecomodder.com/ 
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Earth and health are priceless, so are kilotank and AT-PZEV
Best Mégane tank: 1268.9mi @ 77.847 MPG(US)
2008/06-2011/10 saving:
- 5725.5 kg CO2 (5342.6+382.9)
- Diesel / Money: 42.17% = 2446.25€ = 3357.26$
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megane :
thread -
kill switch.