I know a great number of people fit 175 and even 185 section tyres but are they actually an improvement over the 5.50/155 x 13s that the car was designed for? Manufacturers spend huge sums of money to optimise all components and so unless the car is going to be used for something special why change from standard? You may say, there is a wider choice of H rated tyres but there is an H rated 155 80 13. We all know that the camber changes on the rear wheels don't favour wide tyres and on the front surely they just load up the steering; particularly true with a GT6. I ran my GT6 on 155 80 13s and never found them wanting in any department and the relatively light steering was much appreciated.
I've come across this great clip which presents the Lotus Elan and the benefits of narrow tyres and reduced unsprung weight.