hi
i have owned a gs300 sport for almost ten years, do not lower the suspension any lower, i cant see how you can theres not much clearance under the front arches now and u will have a ride even harder and noisier .You will not be able to adjust geometry correctly and if you think the tyres wear fast now think again.The creaking noise mention is not caused by broken springs, my car had the same noise but the springs where not broken, they all have it even from new, you would have thought lexus could have sorted it by now considering they had a recall on it in 99.The car looks nice lowered with big wheels ect but i was more for comfort so i had the springs changed back to normal gs300 and 16" gold alloys.The tyres now last at least 20,000 miles and now can get out of it after a long journey without being shaken to pieces.ah and since i have not kerbed it once, dont know why i was always kerbing the big wheels.the big alloys also buckled very easily.all this sporty stuff very pretty but pretty useless when it comes to praticability.unless you drive like a madman and need strait line cornering the normal set up seems good enough .one more thing, those skinny fat tyres dammage easily on pot holes ect and do not cushion the impact from the road to the wheels ect causing buckling and bearing dammage. one word of caution do not drive over 60-70 mph in heavy rain with those wide tyres,even with good thread because they are so wide the weight of the car is spread over a wider area of the tyre surface causing it to run lighter on the road.thus the tyres are unable to move the water away fast enough and causes aquaplaneing, trust me i know it happend to me quite often,scares the **** out of you. Never happened with normal tyres.
hope this could be of any use to you, regards alan