Deosn't tire pressure increase upfront reduce the contact patch and thus reduce grip, ineffect increasing front slip or understeer!? It does increase stiffness and make for a firmer ride but I dont know about better grip. I must admit I have limited experience on road-car setup. Just go karts which are a whole different animal.

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2003 BMW X5 3.0i Steptronic, Sport, Prem, Rear Climate, Xenon