Pearl Izumi isoTransition Shoes

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Manufacturer Description

Designed and developed with 2x IronMan World Champion Tim DeBoom, the new Men’s isoTransition was built to perform when it counts – on race day. The quick-pull lacing system and self-draining midsole are designed to help you shave valuable minutes for your next PR. The breathable, Seamless Upper provides such amazing out-of-the-box barefoot comfort; you’ll swear that someone is tickling your little piggies.


  • 1:1 Seamless Upper: creates an unparalleled fit with a seam-free interior
  • 1:1 360° Lacing: anatomically conforms to the foot for a tailored fit
  • Quick lacing system for easy entry and fast transition times
  • 1:1 Energy Foam: cushions the forefoot upon impact and then returns energy back to the runner
  • Blown rubber & high durability EVA outsole combine for great cushioning and weight savings
  • Quick draining Ortholite sock liner for amazing step-in comfort and long-lasting cushioning
  • Racing last
  • Measured size 9.5
    • Stack Height – 18 mm (Heel), 9 mm (Toe) 9 mm (drop)
    • Weight – 234 g (8.2 oz)
    • Forefoot Width – 98.4 mm (3.9 in)
  • Retail – $120

YMMV Review

I have now tested several items from Pearl Izumi, and this will be the third pair of shoes on the site. I can say that they are one of my favorite brands as they offer great technology at a good price. With the different levels, Pearl Izumi has offered a lineup for each type of consumer. Over the last couple years, Pearl Izumi has been putting a lot of effort into their running shoes. The isoTransition is the first shoe that has been classified as a triathlon shoe, a new category that has been growing as of late. Thanks to PI I was able to put a pair to the test during my training and early-season races.

Top View


The isoTransition is a road shoe. While it can be run off-road, it is better suited for the pavement. I have put in over 60 miles in the shoes and would say 95% have been on roads. My runs have varied from cold to hot and mostly dry weather unless you count dumping water on my head.

Design ★★★½☆

Appearance (20%) ★★★½☆

Construction (30%) ★★★★☆

Lacing (20%) ★★★★½

Sustainability (10%) ☆☆☆☆☆

Weight (20%) ★★★★☆

The Pearl Izumi isoTransition is made on a racing last. This is similar to the last of the Peak 2 that I tested a while back. The isoTransition was developed with the help of Tim DeBoom. DeBoom is a Pearl Izumi sponsored Triathlete, who has been the world champion at the Ironman distance. The racing last is a semi-curved last and is made to be neutral. The upper is a lightweight mesh that is seamless on the inside. The isoTransition is made to be worn without socks so you can have faster transition times in your races. Pearl Izumi calls it their 1:1 Seamless Race Upper and has designed it to have reduced irritation and better next to foot comfort. The sockliner is made by Ortholite and has long-lasting cushioning and drainage holes that line up with the holes that run the length of the shoe. The upper also has a small toe bumper for protection. The lacing consists of internal overlays at the midfoot to keep it secure and a bungee lacing system with a clip to secure the extra cord. There is no tongue as the upper is a complete unit for comfort and ease. Once the laces are set to your desired tightness the shoes should be able to be slipped on and off.

Mesh Upper

Most of the midsole is made out of EVA foam for durable cushioning. The isoTransition has 1:1 Energy Foam located under the forefoot. This foam is a responsive cushioning device that has been designed to give increased energy return. In the midsole, there is also a TPU Bridge located at the bottom of the midfoot. It is a thermoplastic unit intended to maintain forefoot and rearfoot torsional integrity. The outsole has a lot going on compared to other shoes. When looking at the sole you can see all the different materials used.  In the midfoot, you can see the silver TPU Bridge mentioned before. You can also see that much of the outsole is EVA foam that is unprotected or recessed so it will not contact the ground. This is the lime green colored material. The sole also uses what is known as high durability EVA Outsole material which is in the black color. The rest of the outsole, is made of a blown rubber for increased durability. These are strategically located in the highest wear spots and are blue.  It is nice that Pearl Izumi colors them all differently for easy identification. The other main feature of the sole is the water drainage holes that run the length of the shoe. These have an internal mesh guard to keep debris out while letting water pass through.

The isoTransition has been designed for fast transition times. This is made possible by the bungee lacing system as well as the shape of the shoe. It has a tall tongue that is easy to grab onto and a heel loop that can also be used to pull the shoes on quickly. None of the materials to my knowledge are from sustainable or green sources, which is a bummer. Pearl Izumi also can do a better job with their sustainable practices as I was not able to find out any information on them. If they do exist I will come back and fix this review.

Sole with Drainage Holes

Fit ★★★½☆

Comfort Next to Skin (25%) ★★★½☆

Foot Length (10%) ★★½☆☆

Foot Volume (15%) ★★★½☆

Heel Width (15%) ★★★☆☆

Midfoot Width (15%) ★★★☆☆

Toe Box Width (15%) ★★★★☆

I ended up testing a size 9.5 in the isoTransition after the sizing challenges I had with the Peak 2. Even though they use the same last I actually had plenty of room in the 9.5 when the Peak 2 ended up being tight. I do think these run slightly small as I am normally a size 9, but they are not nearly as small as the Peak 2 which ran about ¾ of a size small. First thing you will notice is how easy these are to put on. The stretchy laces and easy grab points make it easy to get into the shoes. I did my first run with socks on and then could go sockless for all the rest of my runs. The only time I had an issue with the inside of the shoes was during the REV3 Triathlon. On that day, I was dumping about three glasses of water on myself every mile and my shoes were quite wet form all the water. This caused them to rub my instep a little on my left foot and gave me a little blister. This seems to be my most prone spot for blisters as it has happened with quite a few shoes. I am not sure if it was just because of the wetness because on all other runs without socks these have felt great.

Bungee Laces

I found the shoes had a good amount a room in the forefoot, and it was a medium width through the rest of the shoe. The bungee laces do not tighten up the shoes too tight, so they feel a bit like slippers when you have them on. I really liked how they fit. The one piece upper is very comfortable and even with the taller tongue in the front it was completely comfortable the whole time. On occasion, I would get poked by rocks and other objects up through the holes. The holes are also noticeable under you r feet because they are also in the insole. This is a different feeling that sometimes felt weird, but for the most part, I did not pay attention to it.

Performance ★★★½☆

Breathability (15%) ★★★½☆

Cushioning/Ground Feel (20%) ★★★½☆

Drying Speed (15%) ★★★☆☆

Durability (10%) ★★★☆☆

Moisture Transport (20%) ★★★½☆

Quick On/Off (15%) ★★★★☆

Traction (5%) ★★½☆☆

The isoTransition definitely made my transitions faster. I really liked not having to tie the laces; the bungee laces worked great for a quick change. The clip for securing the excess cord is also a genius solution. While the shoes do not ever feel super snug, they were enough to stay snug and with the flexibility in the shoes I did not have any issues with excessive foot movement. The upper on the isoTransition is very breathable; you can even feel the air coming through the holes in the sole.  Since the upper is mesh it will not be water resistant in any way. If you are running in the rain or it s hot enough that you are dumping water on your head like I did at REV3 Portland, the water will get into the shoes. Pearl Izumi has thought of this and added the holes in the sole to help drain this water. In the race, I dumped a whole lot of water on myself and never felt like I was sloshing around in the shoes. Were they wet, yes. Were they water logged, no. The upper also seems to dry fairly quickly. That was more difficult to ascertain as I was dumping 3+ cups of water on myself every mile. Afterwards, they did seem to be dry before I had everything packed up.

Drainage Holes

The isoTransition is a racing shoe. It is very lightweight and even when wet it still felt light. The shoe is very flexible since much of the sole is made of EVA foam. This makes for a shoe that has a decent amount of cushioning but also maintains a little ground feel. In triathlons, I normally appreciate a bit more cushioning than my normal runs as my form is not as precise due to the other disciplines. The isoTransition has a stack height of 9mm, which is more than I prefer. I have found that I really like shoes that are in the 0-4mm range, and I wish these were in there. Nonetheless, the isoTransition still runs very well and felt fast. Some of my brick runs in these were my best runs of the season thus far. Unfortunately, the REV3 race did not go as well, but it was not the shoes fault. On occasion, I would notice that debris would poke my foot through the holes, and from time to time rocks would get stuck in there. Sometimes they would fall out on their own, and I even had to stop to remove a rock on a couple training runs. Since the isoTransition is mainly a road shoe, there is not much traction nor does there need to be. I had no issues with the traction. After 60 miles, the shoes are still looking like new, as race shoes their lifespan is most likely going to be about 400 miles.

Very Comfortable Inside

Overall ★★★½☆

Overall, I liked the isoTransition. I am glad I sized up a half a size as the 9.5 fits me perfectly. The shoes are comfortable without socks and very easy to get on and off. This is great for having faster transition times and therefore, higher finishing places. The holes in the soles do a good job allowing water to pass through the shoes but do sometimes feel weird underfoot. The isoTransition is a good mix of cushioning and flexibility. I do wish they were a slightly lower drop for my tastes, but others will be happy to find them at 9mm. I am also a big fan of the Blue and Lime green color scheme, but if you do not like that they have others as well. The isoTransition retails for $120, which is on the higher side. You do get a high quality lightweight racer. As always, your mileage may vary.

Pros [field name=iFrame]

  • Lightweight, even when wet
  • Breathes well
  • Lets water pass through and out the sole
  • Lacing system is comfortable and easy to use
  • Can wear sockless


  • A bit more stack height than I prefer
  • Can feel the holes in the insole form time to time

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About the Author

I am an avid runner, cyclist, swimmer, hiker, climber, skier and many other activities that would make this list too long. I started Your Mileage May Vary Reviews in Early 2011 to combine two of my passions: sports and gear.

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