I bought the FELT IAx expecting speed, but I underestimated the work it would take to make the bike fit me. On the same course, I averaged 32 km/h using roughly 20 W less power than on my road bike. Before I could appreciate that difference, I broke two front derailleur cables and made several visits to the workshop. The biggest improvement in how the bike felt came from a professional bike fit rather than another new component. After several months, I know what makes this bike rewarding and which compromises I still have to accept.
Why I chose the FELT IAx
The FELT IAx Advanced 105 had been on my sporting wish list for years. I loved its distinctive shape and its focus on time trials and triathlon. For anyone new to this type of bike, the key difference is the riding position: I rest my forearms on pads and reach forward along the extensions, allowing me to lower my upper body.
This review covers my own bike over several months, including setup changes, training and racing. I swapped the wheels early on, so my later impressions describe my modified setup rather than a completely standard bike.
Watch my video review
In the video, I show the bike and explain what worked, what needed attention and how the fit changed my experience. The spoken commentary is in Polish.
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Delivery was the start of the setup process
My bike arrived partially assembled. Everything appeared to be in place, but the first rides made it clear that the gears needed adjustment and other parts needed checking. In my case, taking delivery did not mean the bike was ready for uninterrupted training.
I cannot judge every IAx from my own example. What I can say is that setup was a meaningful part of my ownership experience. If I were starting again, I would allow time for an inspection, adjustments and a proper fit from the outset.
Berg wheels and the first brake complication
The original wheels impressed me less than the frame. Almost immediately, I transferred my Berg PRO SL AERO wheels from my road bike and fitted TPU inner tubes. With that setup, the FELT looked and felt much closer to the triathlon bike I had imagined owning.
I do not have an isolated before-and-after measurement for the wheels. I cannot assign them a specific watt saving or separate their effect from my riding position and the rest of the setup.
The carbon rims also meant fitting suitable brake pads. I managed to set up the front brake, but at the rear I struggled to open the caliper far enough to accommodate the wheel. I resorted to filing the pads as a temporary workaround. I do not recommend copying that approach: a few days later, the bike went to a workshop and the issue was resolved properly.
On the flat courses I have ridden, the rim brakes have worked well. They have also handled the hard braking situations I have encountered. The awkward part was adjusting them around a wheel change. That is the compromise I remember most clearly; my experience is not a controlled comparison of braking systems in all conditions.
The bike fit changed everything
Initially, the front end was much too low for me while I needed the saddle relatively high. To see the road, I had to tilt my head back considerably. I felt uncomfortable, breathing felt harder and the position was difficult to settle into.
A professional bike fit — adjusting the bike to my body and riding needs — made a substantial difference. Afterwards, the position felt more natural, I could hold it for longer and I found it easier to produce power effectively. That was when I began to enjoy what the FELT could offer.
My personal lesson is straightforward: a triathlon bike budget needs to include fitting. An aggressive-looking position is of little use to me if I cannot see ahead comfortably or stay on the forearm supports for a meaningful length of time.
Risers offered adjustment, with some extra work
The supplied risers, which lift the aerobar supports, gave me scope to adjust the front-end height. However, I did not have the bolt lengths needed for my chosen setup and had to source them separately.
I also struggled to achieve a rigid assembly with two risers combined. After spending time trying to resolve it myself, I returned to the workshop. I value the adjustment options, but getting my particular setup right took more than simply rearranging a few spacers.
Shimano 105 and two broken cables
Once adjusted, my mechanical Shimano 105 R7000 drivetrain worked very well. Here, “mechanical” means the shifters operate the derailleurs through cables rather than an electronic system. Unfortunately, the front derailleur cable broke twice within two weeks.
On the second visit, the workshop removed the upper cable adjuster. The problem did not return during the period covered by this review. I do not have a confirmed diagnosis of why both cables broke, so I would not use my experience to claim a fault with the entire Shimano 105 groupset.
Electronic shifting is now high on my list of possible upgrades. I want more convenient operation in my triathlon position. It remains a plan, not part of the tested configuration or a measured time saving.
Was the FELT actually more efficient for me?
On ordinary easy rides, I noticed an increase in average speed of roughly 2 km/h. The more interesting comparison for me came from the power needed to average the same speed on the Enea Bydgoszcz Triathlon course.
| My ride | Average speed | Average power |
|---|---|---|
| FELT IAx in the setup described here | 32 km/h | 171 W |
| My road bike on the same course | 32 km/h | approximately 192 W |
Those figures give a difference of approximately 21 W, or roughly 20 W less at the same average speed. Watts describe the power I was producing on the bike. What interests me is the possibility of maintaining a given pace with less power, particularly when I still have to run afterwards.
This is a comparison of my rides, not a controlled aerodynamic test. I do not have enough information to equalise weather, traffic, pacing and every equipment detail. I therefore cannot attribute the full difference to the frame or promise the same result to another rider. For me, it is an encouraging observation about the complete setup I used.
I describe the event itself in my Enea Bydgoszcz Triathlon 2026 race report.
What about the run afterwards?
In the video, I also compare two races. In 2021, the roughly 22 km run took me more than two hours and included a serious low point. In 2026, I covered that distance in around one hour and 37 minutes. The difference in my experience was substantial.
I cannot calculate how much of that improvement came from the bike. The races were years apart, rather than an experiment changing just one variable. The FELT gives me a sense of riding more efficiently, but my run results alone do not establish how many minutes the bike saved.
Storage that earns its place
The rear storage box takes two spare tubes, tools and a CO₂ cartridge in my setup. I use the top-tube box for gels and recently fitted four inside. These are simple conveniences that I appreciate on longer rides and race day.
I also fitted Favero Assioma UNO power-meter pedals and plan to upgrade to DUO. There is a hydration system between the aerobar extensions as well. I intend to cover that separately, because training and racing have already given me specific observations to discuss.
What still needs attention?
Even after the bike fit, I have not completely resolved the width of the forearm supports. They are set as wide as the current adjustment allows, yet my elbows still feel too close together. On longer rides, I notice tension around my shoulder blades. That remains an area to work on.
The bar tape is another disappointment. It was already lifting in places when the bike arrived, and the outer layer later began to peel. On my bike, it quickly became an item on the replacement list.
As the equipment issues have been addressed, my focus has shifted towards training. Over the coming months, I want to build the power and endurance needed for a full-distance Ironman.
My verdict: I would buy it again, with a realistic setup budget
Yes — after several months, I am still very happy with the FELT. I enjoy riding it, and I see the frame as a strong foundation for future changes. I have already swapped the wheels, I am considering electronic shifting and I am still refining the cockpit setup.
However, this was not a purchase that let me focus exclusively on training straight out of the box. I needed adjustments, fitting and workshop help. When considering a similar bike, I would look closely at brake condition, drivetrain operation, the parts needed for cockpit adjustment and whether I could achieve a suitable riding position.
For me, the balance is positive. I fulfilled a long-standing sporting ambition and now have a bike I want to use towards my next goal. The biggest opportunity I see now is in my own training. You can follow the wider story in my Road to Ironman 2027 series.