Brooks Adrenaline has been the exact same shoe version after version since the GTS 6. Now however, they have changed not only the version number (8 vs. 9) but also the shoe.
- The Adrenaline 8 is much narrower in both forefoot width and throatline opening which is identified by arrows below. If you have a tendency toward heel slippage, than the wider throatline as found in the 9 will be more difficult to secure snugly.
- Width – Overall, GTS 9 is wider than GTS 8. Again this will be a problem if you are counting on the GTS 9 to be a good match for a narrow foot.
- Toebox depth – The GTS 8 was very shallow in the toebox, while the GTS 9 is not. This shoe fails the pinch test https://drshoe.wordpress.com/2008/01/15/pinch-test-shoe-toebox/ for someone having a shallow forefoot.
If you have a narrow foot and found the perfect fitting running shoe in Adrenaline GTS 8 , you will be disappointed with the extra volume found in GTS 9. In fact you may want to try Asics 2140 in narrow width instead. If you hve a wide foot, however you will like the changes GTS 9 provides.
Here is my Adrenaline GTS 10 post https://drshoe.wordpress.com/2009/11/05/shoe-review-brooks-adrenaline-gts-10/