When I started back seriously into running in 2011, I gravitated towards "minimalist" shoes. As a natural forefoot striker, I've always felt uncomfortable running in shoes with a large heel, since for me such a shoe configuration does little more than get in my way. I started running in Nike Free 3.0s, but once those wore out, I switched to New Balance Minimuses. I found that those shoes wore out for me really quickly, so when I started training for my first marathon, I switched to Merrell Road Gloves. However, after 1 Marathon and accompanying mileage, me feet simply hurt all the time, so I looked into shoes with a bit thicker sole. Enter the Merrell Bare Access.
Merrell Bare Access 1: My first experience with the Bare Access line was the Bare Access 1. With a 15mm forefoot cushion, this shoe felt wonderful (especially in comparison to the Road Glove). However, this shoe's sole was about 70% soft foam rubber, and only about 30% hard rubber vibram. I wear out shoes quickly, but these were ridiculously fragile, and running on Texas roads (which consist of asphalt and crushed basalt) really shreds shoes. I think that they lasted me all of three weeks (or about 100 miles at that time). My wife was running in Altra Instincts at the time, so I switched to those.
I was never really happy with the construction of the uppers in the Altra Instinct 1.0 or 1.5 - they seemed to me to be prone to tearing and wear a lot faster than other shoes. So I was pleased when I saw that Merrell was reintroducing its Bare Access in a completely remodeled shoe.
Merrell Bare Access 2: The new iteration of the Bare Access shoe consisted of a more stylish upper and sole made up of 98% vibram, making them much longer lasting. I trained for and ran 3 marathons ("The Gusher", The Missoula Marathon, and Marathon 2 Marathon) in these shoes before they were replaced by the Bare Access 3. Of the Bare Access line, the Bare Access 2 seemed to have the most breathable uppers. I no longer have any for comparison, but I didn't see much difference in the soles between the Bare Access 2 and 3 (photos of Bare Access 3s at right). Mine lasted me on average about 200 miles of training (3-4 weeks at 60-70 miles), which for me is about average for a shoe on my local roads. I only switched to Bare Access 3s because they replaced the 2s.
Merrell Bare Access 3: I didn't see much difference in this shoe and the previous version. The upper was slightly less breathable, the reflective piece on the toe was different, and the design on the side changed slightly, but otherwise this was the same shoe as the Bare Access 2. I ran the Louisiana Marathon, the Boston Marathon (2x), the Shiprock Marathon, the Jacksonville Bank Marathon, the Fiesta Half-marathon, and the Spicewoods Vineyards Half Marathon in these (probably going through a dozen pairs or so).
Merrell Bare Access 3 - trail: During this time frame, I bought a pair of Merrell Bare Access 3 Trails shoes. Fit and uppers were essentially the same as the Bare Access 3s, except that these shoes lack the heel loop. The sole is the first in the line with 100% vibram sole. I don't think that this makes the shoes noticeably stiffer - they feel essentially the same on my feet. The soles are a bit more aggressively lugged than the road version, but I found them to be too thin for the local rocky trails. If I were running trails on sand or clay, I think this shoe would be just about perfect.
Merrell Bare Access Ultra: Supposedly this is a hybrid road/trail shoe, but in my opinion, its a pure road shoe. I expected this one to be simply a replacement of the Bare Access 3. It lacks the heel loop, and has a slightly different sole configuration from the Bare Access 3. The upper isn't quite as rigid. I don't find much wrong with this shoe, except its sole wears out just a little faster than the Bare Access 3. I ran the Mississippi River Marathon in these, and will run the Tucson Marathon in them next weekend.
Merrell Bare Access 4: The uppers on these and the Bare Access 3 are essentially the same, minus the heel loop. The soles are slightly different, with a little different vibram portion (inconsequential difference), and with deep grooves between the vibram section. This causes the shoes to wear out a LOT faster for me, as the leading edge of the vibram behind those deep groove catch on the crushed basalt gravel of the local roads. These shoes feel just fine, but I regard them as a step back from the Bare Access 3s. I ran Marathon 2 Marathon in 2015 in these.
At this point, I try to buy either Bare Access 3s or Ultras, whichever I can find for sale more cheaply. I'm hoping that Merrell will correct the problem with the soles of the 4s in the next iteration and before online stores run out of the older shoes that I prefer. Otherwise, I may have to look for something that I like in another shoe design - the 4s wear out that fast for me.
Merrell Bare Access Ultras
Merrell Bare Access 3 - trails, with 100% vibram soles
Merrell Bare Access 4 (top) and Bare Access 3 (bottom) - the Bare Access 3s are the best of the line
Merrell Bare Access 4s
Merrell Bare Access 3 (top) and 4 (bottom) showing difference in soles
Merrell Bare Access 4 (top) has a wider groove and more vertical vibram piece than the Bare Access 3 (bottom) - this causes the leading edge of the vibram behind the grooves catches on gravel in the road, and for me, it separates after only about 10-15 miles
Running in Bare Access Ultras at Mississippi River in 2015
Running in Bare Access 4s at Marathon 2 Marathon in 2015