ORIGINAL: Diver944
17s will give a firmer ride because you have less rubber in the sidewall than a 16, and generally speaking the tyre sizes are wider as well. Some people don't like a firm ride and will tell you to stick with 16s but its all down to personal preference and you won't know what you prefer until you try them. If you do stick with the 17s make sure you have the latest castor mounts fitted to the back of your wishbones. The original version will be way past its best by now and also contains a lot more rubber than the updated version so you get a lot of tramlining. They are circa £50 each and easy to fit at home
I've had 17s on for the past 100,000 miles and they feel totally normal to me, however I'll be refitting some 16s with winter tyres next week so I'll probably come on here moaning that my car has gone all soft and wallowy like a saloon [

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Tyre brand and tread depth also makes a difference. I bought some secondhand weels with Pirelli P Zeros at 4mm some years ago and they felt horrible. When I replaced them with new budget Kumhos the ride was suddenly transformed [

] It was a world of difference from a tyre that cost a 3rd of the big brand