Originally Posted by Jonny

I ran a 275/35R18 up front and a 295/35R18 in the back. The springs were ordered with 14k up front and 8k in the rear. Going from 14k to 16k is on 8% stiffer. I was told that I can probably go up to 18k if needed but I only needed a slight adjustment. They have more than 5k miles but less than 9k miles. I do not daily my Z and I had them on for a little less than 2 years. I believe I had the new XR1's but I could be mistaken. I would have to go look for the invoice when I ordered them.