By Brandon Bilyeu
F-XX II: 
Hot!
- Full carbon sole with top-end stiffness at mid-range price
- Above average toe box width
- Atop dials work great and easily snug the uppers
- Great fit and comfort
- Excellent durability and easy to clean
- Reflective details at front and rear of shoe
Not!
- No half sizes available
- Non-replaceable heel/toe pads
Cost: $220
How obtained: review sample
Available: online, retail
Colors: White, Black
Website: FLR F-XX
RBR Sponsor: no
Tested: 70+ hours
Sizing: 39-47 (no half sizes!)
Pop Quiz – What shoes propelled Alex Howes to the 2019 USA Road Title?
I had never heard of FLR until I read a story about Alex Howes’ 2019 USA National Road Championship, which he won wearing FLR’s F-XX shoes. A little research turned up a few more World Tour riders wearing FLRs, but what really caught my attention was the value proposition of the top-end F-XX shoes. The shoes cost $220 and you get a full carbon sole with World Tour level stiffness. For perspective, most $220 shoes are mid-range and would typically have a nylon or mid-range carbon sole with lower stiffness. Range-topping shoes from the major manufacturers are often double that price.
FLR was kind enough to send over a pair for testing and after a delivery delay because of current events, I went to work doing my best Alex Howes impression. After months of testing, I can say that these shoes are the real deal, albeit with a couple minor compromises.
Rick’s Shoe Criteria
Recently Rick Shultz wrote the article How to Choose Cycling Shoes and I’ll quickly run through his three checks on the F-XX shoes for reference:
- Slotted Cleat Mounting Holes – like most cycling shoes, the F-XX shoes have fixed mounting holes so available adjustment falls solely to the cleat slots. Hole placement seems consistent to its peers as relative cleat location seems to match all my other shoes.
- Twist Test – the F-XX has a full carbon sole, and I only observe the slightest twist under the full force of my cyclist arms. Feeling on the bike is of ungiving stiffness and great power transfer.
- Width Test – the F-XX carbon sole measures 94mm wide at the metatarsals for my size 44. This 94mm is the widest in my closet (the smallest shoe I measured is 86mm) and I appreciate the extra width.
Full Carbon Sole – Stiffness Rating of 14
Admittedly, there is no standard stiffness rating index so the numbers different brands tout cannot be meaningfully compared, but in general a rating of 14 means super stiff. And after lots of sprinting and hill climbing my perception is that the F-XX soles do not waste any watts. Under power there is a rock-solid connection to the pedals. A minor side effect of this stiffness is a bit of a harsh ride on rougher roads, but while road buzz was noticeable, I would not describe it as uncomfortable.
As noted above, the cleat mounting holes are fixed and surrounded by grid lines to help with cleat placement. The three holes are standard for road shoes and will fit all major brand road cleats. After cleat installation I had zero movement issues with my SPD-SL cleats.
To save weight the toe/heel pads are permanently bonded to the sole. So far, I do not see any significant wear on either pad, but I do not spend much time walking in road shoes (no coffee and cake stops for me) and have never personally worn out a pad. If you have worn out pads on other shoes, this might not be the best choice for you.
Atop Dials Lock It Down
In a market dominated by Boa, FLR uses Atop dials for shoe retention. Each shoe utilizes two dials, one for the ankle and one for the forefoot. Turning the dials forward tightens the synthetic wire in small increments with audible and tactile clicks. Turning the opposite direction, nothing happens until one-quarter turn when the wire is released, allowing the shoes to be fully loosened.
While on the bike, tightening is quick and easy with light dial action. But releasing a little tension takes a bit longer. A quarter turn unclamps the wire releasing all pressure, in my case it was equivalent to about three to four ‘clicks’ of loosening. Then you must start tightening again and stop at the new looser setting (or go too far and have to start over again). While not as easy to adjust as a Boa IP1 dial, I found the Atops worked well and I never had any issues quickly dialing in the tightness. If you adjust your shoe tightness constantly on rides, then this might be a bigger issue for you.
I found the overall fit to be very good. The above average 94mm sole width leads to good forefoot volume and the Atop dials quickly snug everything into place. The tongue is thick enough to eliminate any pressure points from the wires, but doesn’t slide well under the uppers during tightening. This meant I usually had to massage the tongue a little bit to smooth out bumps and creases. The heel cup is relatively deep and holds my heels in place well. There are gripper dots at the heel, but they do not seem very aggressive and thankfully are not really needed. There is no arch support built into the sole or insole so after market insoles are a must if you need any amount of arch support. The provided insoles are basic low profile, 2mm thick foam.
Coupled with the carbon sole, the no-stretch uppers feel great when pounding the pedals. There is simply no movement of the foot which leads to great stability and power transfer. And the single piece microfiber upper construction leaves no seams to cause any irritation.
Good, but not Great Venting
There is one air vent in the sole at the toes, and the rest of the venting comes from the uppers. Four mesh inserts over the toes do a good job of letting air in and a fifth insert is located on the outside edge of each shoe. A row of small holes on each side finish out the air-conditioning system. I’ve ridden in temperatures of 90+ F (32+ C) and didn’t have any problem with overheating, but I would like to see rear vents in the soles and more small holes to help the air flow better front-to-back through the shoe.
Those vents also do a great job of letting in water during epic downpours, several of which I was lucky enough to ride through during testing. Another good reason to add another sole vent is to help get water out. This was a great test of how easy the white shoes were to clean, and I was very impressed at how the grime just wiped off with a wet rag. Grease and rubber from toe rub were a bit more effort to remove, but after all this time the white still looks almost new.
Sizing Might Not Work for Everyone
The biggest drawback of the FLR shoes is that they only come in full sizes increments. Since sizing down is not really an option with shoes, this means the fit is either going to be spot on or a little big. The size chart lists standard sizes as well as the measurement in centimeters (cm). The length difference between sizes is not huge at 0.7 cm (7mm or 0.28 inches), but note that if you currently have your cleats set all the way back and you have to size up for the F-XX your cleats will be impossible to get in the correct position.
Bottom Line
For maximum sole stiffness on a budget, it is tough to beat the FLR F-XX shoes. I found them to be great as everyday riding shoes that are both comfortable and high performance. From centuries to Wednesday Worlds sprints, they were up to the task. I think these are a great option for race shoes that provide all the stiffness but will not break the bank to replace if damaged in a crash. Just be aware of the sizing and its possible effect on your cleat placement.
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