A friend of mine has the Toyo Proxes S/T on his 4.8is and I drove his car recently, they are the 275/315 standard 4.8is size. I have to say that I didn't really like them, in the dry at least.

Compared to the Michelin Diamaris the tread blocks of the Proxes extend all the way round the shoulder of the tyre and more noticeably the tyre has a virtually square sidewall compared to the round sidewall of the Diamaris. What this means in practice is that the dynamic camber and toe settings are altered by fitting these tyres. I suspect the X5 needs more toe-in at the front to compensate and perhaps less camber angle. When driving along a straight road the directional stability is poorer than with the Diamaris and bump steer is greater. Initial turn in to a corner is less linear (due to the square sidewalls) and with the tread blocks on the outer edge of the tyre this induces steering kick back at that point of turn-in, which further dilutes steering feel. Overall grip seemed higher than with the Diamaris which induces a feeling of confidence that is undermined somewhat by the corruption in steering feel.

I've suggested that he remove the Proxes for summer driving and put them back on for the winter. The alteration in the X5s handling and steering characteristics is so noticeable that I personally could not live with them all year round. Perhaps experimenting with tyre pressures and geometry settings may help, but I thought it worth warning you guys that althought the Proxes is an excellent cold weather tyre, it may not be the ideal solution to replace the OEM tyre for all year use.

Here are some pictures...

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