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CastelliFree Aero Race 4 Limited Edition Bib Short - Men's


Item # CSTZ7CK

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  • Black/Red, L ($199.95)
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Item # CSTZ7CK

Free Aero Race 4 Limited Edition Bib Short

Designed to cheat the wind, Castelli engineered its Free Aero Race 4 Limited Edition Bib Short as it's top-tier short before being bested by the Premio 2, however, the Free is still among one of our favorites and actually does a little better in the heat than the Premio. The Limited Edition designation pertains to the use of colors that distinguish it from the standard Frees. Comfort, aero benefits, and strikingly good looks, all in one package.

Castelli is one of the earliest adopters that we can think of adding aero elements to road clothing not necessarily used in Tri's and TT's. By now we're all familiar with aero clothing helping to reduce the power output needed to achieve the same speed and Castelli claims a savings of 10 watts at 50 kilometers an hour. It achieves this by streamlining the wind through the use of textures, particularly with the Vortex dimpled fabric across the bib's face fabric. Much like a golf ball and certain carbon rims, dimples better manage airflow, allowing it to stay attached to the surface for longer and become less turbulent which is a principal culprit of drag.

On the business end of the bibs, the excellent Progetto X2 Air chamois handle sitting duties and is pretty universally loved here at the office. Highlights include its seamless construction, four-way stretch, and impressive ventilation with its perforated foam layer. The perforated viscous comfort zone keeps your most sensitive areas comfortable for hours on end.

Comfort and aero duties aside, the Forza fabric on the inner legs contain 38% Lycra content to support hard-working muscles. The material also offers just the right amount of compression to aid in recovery and prevent premature fatigue over rougher terrain.

The bibs are quite open on the front, thanks to the Doppio V construction, allowing for excellent breathability without sacrificing support while the suspenders are mostly mesh and utilize lie-flat material on the shoulders. By lying flat, the fit is more refined and it creates a smoother silhouette under the jersey for improved aerodynamics. This is just one more detail proving that Castelli doesn't miss a beat.

For the leg openings, Castelli trusts its Giro 4 mesh-like grippers to keep the hem in place with improved tenacity over a larger area while remaining mostly impervious to the wind. Tan-lines everywhere just got a little sharper.

  • Aero and comfort racing bibs for performance-driven cyclist
  • Aerodynamic details net a claimed savings of 10 watts
  • Gently compressive material support muscles
  • Lie-flat grippers and suspenders are sleek and reduce drag
  • Progetto X2 Air chamois is supportive and comfortable
  • Castelli's construction and the fit is honed by its work with professionals

Tech Specs
Material[legs] Vortex, [inner thighs] Forza
Seasonspring, summer, fall
ChamoisProgetto X2 Air
Leg GripperGiro4
Recommended Useroad cycling
Manufacturer Warranty1 year


Men's Apparel




















































How to Measure:
For best results, take measurements over your underwear.
Measure under your arms, around the fullest part of your chest.
Measure around your natural waistline, keeping the tape a bit loose.
Measure around the fullest part of your body at the top of your legs.
Using pants that fit well, measure the crotch seam to the bottom of the leg.

What do you think about this product?


>Rating: 5

Nice shorts

I've used it several times
Runs small
Size Bought
5` 11"
152 lbs

I'm 5'11" and 152 lb. The mediums fit well except for the straps which were much too short. Returned for the large, which fits well. It could definitely accommodate a larger pair of legs. They are light but comfortable

>Rating: 2

Sadly, I had to send them back.

I returned this product before using it
Runs small

The graphic details around the cuffs and the grippers are super cool and more gray than bright white, but they really need to show you a side view. I was excited about the tech and style. I've rode a 2016 pair of black/gray/white Castelli bibs to death, but with the two-tone sides on these, it kind of looks like you’ve got a women’s bathing suit on over your bibs. That’s just my opinion, but my wife gave them the thumbs down too. From a technical standpoint, the chamois looks extremely plush, but the shoulder straps were way too short to “œlay flat” for me at 6’2” even in an XL.


two stars because you didn't like the side panel "look"? researching current castelli sizing would have indicated an XL at your stated weight. i'm still in my aeros after 2.5 seasons and my only complaint is the chamois has lost some but, the bibs are quality. the straps definitely run short if you are long in the torso.

>Rating: 5

Best bibs I've ever owned

I've put it through the wringer
True to size
Size Bought
6` 0"
210 lbs

I've ordered and worn out quite a few bibs over the years. The high-end Rosso Corsa Castelli bibs have always felt the best and lasted the longest. They are more expensive but given how long they last they are the most economical by far, not to mention the best performers. The Free Aero Race 4 bibs are the best yet. The straps are more comfortable than the other Castelli bibs I own. The chamois is very comfortable on long rides with plenty of ventilation. Castelli tends to run small but the XL was true-to-size, snug with no sagging anywhere but not so tight that they are constrictive.

>Rating: 5

Typical Castelli Quality

I've used it once or twice and have initial impressions
Size Bought
190 lbs

Simply a great overall bib. It's everything you expect from Castelli. The progetto chamois is super comfortable from any seating position, no odd or uncomfortable feeling from seams in the material, it's very supportive and great compression feel in the legs. My only gripe is that this version of the Aero race bib has a slightly tighter fit than the previous aero race kit versions. The kit version (size large) from 2016 was a perfect fit for me and this version truly feels like a "race fit." It's not so tight that is takes away any comfort or effectiveness, but takes me a bit longer to put on.

>Rating: 5

Super chamois!

I've used it once or twice and have initial impressions
True to size
Size Bought
6` 4"
208 lbs

The chamois in these bibs are great, I've always love Castelli's chamois, and how somehow it's even more comfortable. It magically sits in just the right place, isn't too think, and is insanely comfy on the longer rides compared to some of the other brand shorts I have. These are a "race" fit, so they're super snug, which I like, makes me feel fast and aero. As I'm probably never going to reach 50 kph, unless it's down a hill, the true aero benefits are probably lost on me, but they look fast and that's worth a couple watts right there! I went with XL and the straps feel a bit short. Not like they're digging into my shoulders short, but short to the point they don't lay nice and flat like Castelli intended. I went back and forth on ordering the XL and XXL, after looking at the sizing charts again I'm not sure it would have made any difference in the length of the shoulder straps. Just a heads up if you're a taller rider, that could be an issue you see. Otherwise I wouldn't let it stop you from owning these amazing bibs, especially if you wear a base layer, the strap tension is even less noticeable.