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CastelliFree Aero Race 4 Limited Edition Bib Short - Men's
Sale 35% Off$129.99 - $139.99

Item # CST00SU

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Item # CST00SU

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 SpecsSize
Tech Specs
[legs] Vortex dimpled fabric, [inner thighs] Forza fabric with 38% Lycra
spring, summer, fall
Progetto X2 Air
Leg Gripper
Giro 4
Recommended Use
gravel, road cycling
Manufacturer Warranty
1 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.

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Quite good EXCEPT the fit

  • Familiarity: I returned this product before using it
  • Fit: Runs small
  • Size Bought: large

I am usually a medium to a large. I got the large and it just doesn't fit. Going to try a larger size, otherwise the bibs are quite nice. Good looking and nice pad.

Unanswered Question

Hello there. Do you ship to New Zealand? thanks. Kieran

Great bib

  • Fit: Runs small
  • Size Bought: XL

Me, 5-11, 164lb, usually a Large fits me in Castelli, ordered the large, overall too small (quads, hips and strap length). Ordered the XL, all good, probably will lose some of the compression on the quads, but very happy with them. Typical day in the saddle for me 40-60 miles, 3-5k of climbing.

If there is one piece that concerns me,it's is the mesh straps, they seem delicate.

My favorite

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: Runs small
  • Size Bought: Xl

Very happy with these shorts. Does run small but not a big deal if you size up.


  • Familiarity: I've used it several times
  • Fit: Runs large
  • Size Bought: XL

Quite impressed by these bibs. Castelli's Free Aero Race shorts have always been a favorite and it looks like these will be at the top of the pile in my closet. Materials are excellent - the Progetto X2 Air chamois has padding in all the right places without excess bulk, the main fabric of the legs is compressive yet lightweight (I expect these will breathe well in summer), and the bib straps seem to lay especially well against my body and are once again quite airy. Usually I prefer seamless elastic bibs (like Giordana uses) but I have no complaints here. Even without the dimpled material on the legs I'm not winning races but it certainly makes me feel fast. Some of Castelli's lesser pieces have had occasional quality issues with the sewing of the seams but construction is excellent here. Lastly the leg grippers are wide and unobtrusive and the inseam length is perfect.

Once again, the fit is compressive to reduce muscle fatigue in hard efforts or on long days. If you're not familiar with Castelli, in general their apparel runs smaller than American brands and sometimes even a bit smaller than European brands. I wear a large bib in Assos, Giordana, and Pearl Izumi's PRO line, I went up to an XL in this for the strap length as Castelli's straps run short and dig into my shoulders in smaller sizes. The XL's straps are perfect and while I was worried that the body of the bib would be loose and baggy, that's not the case at all due to the compressive material. So if in doubt, size up!

The only difference between the Free Aero Race 4 LIMITED EDITION and Free Aero Race 4 is colors/graphics.

gray is blue

  • Familiarity: I returned this product before using it
  • Fit: Runs small
  • Size Bought: large

be advised, what appears gray in the images online actually ends up looking blue-ish when fabric is stretched. Not a big deal, unless you want your black bibs to match your black jersey.