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CastelliFree Aero Race 4 Bib Short - Men's

Item # CST00RY

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Item # CST00RY

Free Aero Race 4 Bib Short

The Free Aero Race 4 Bib Short from Castelli is built using extensive feedback from the professionals on Team Sky. Its general consensus is the existing Free Bibshort was already pretty well dialed and the only requests were the addition of a loop in the bib to hold a race radio microphone and one rider wanting his chamois shifted back a bit. Team Sky isn't the only one who likes it, in fact, the Free Aero Race Bibshort is the best-selling Castelli short of all time, so it knew that when it was time for an update, it wanted to make it better but not change the shorts too drastically.

First up is a new leg gripper that still features a lie-flat, raw-cut edge but now has vertical silicone stripes to hold it comfortably in place without restricting stretch. Next is a new fabric that allows for better print quality and Castelli updated the seams to improve the fit and looks. It also re-engineered the bib straps with new fabrics and construction so they help you stay cooler, lie flat, and are more durable. Finally, it also receives the updated Progetto X2 Air seamless seat insert featuring one of the softest surfaces we've ever felt in a chamois.

  • Castelli's most popular bib short, newly updated
  • Vortex dimpled fabric on the legs boost aero performance
  • Forza fabric on the inner legs stretches for a perfect fit
  • Stripe mesh engineered minimalist bib construction keeps you cool
  • Giro4 leg gripper elastic distributes the grip over a larger area
  • Doppio V construction up front increases support and comfort
  • Flat-lock stitching reduces irritation
  • Progetto X2 Air Seamless seat insert cushions against road chatter
Tech SpecsSize
Tech Specs
[legs] Vortex dimpled fabric, [inner thighs] Forza fabric with 38% Lycra
spring, summer, fall
Progetto X2 Air
Leg Gripper
Giro4 elastic
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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Gigantic leap in quality

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: M

I used to have a fleet of bibs. Giordana for long rides, Castelli for trainer and shorter rides. a few sponsored bibs for charity rides and team events. Now I only wear this pair if I can get away with it. The old version of Free Aero rubbed my private parts after an hour or two, so I kept rides to 2 hours or less. The new pair has a different cut that solves that problem. The chamois has all the padding I need, without feeling like a diaper. They don't look that different, but they feel perfect once they're on.

Great Fit

  • Fit: Runs small
  • Size Bought: XXL

The blue bibs appear to be a faded blue in the photo but are really grey. Ordered a size up from my typical bibs and tried them on right out of the bag, should have ordered two sizes up. The fit is excellent and the fabric i very comfortable but the sizes run very small.

Odd sizing but probably OK if they fit

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

I have several Castelli skin suits that fit OK in size small but for some reason their shorts never quite fit right. I could wear these bibs in size Small ... except that the straps are so short they put too much pressure on my shoulders. The size Medium fit a little better but the straps were still too short for comfort and the grippers on the legs were too large. I guess they made them for short guys with tree trunk legs.

I am 5' 7" and weight 142lbs. and the medium shorts fit me perfect.

I have virtually the same general specs as Michael C. though his inseam to upper body ratio unknown. For the sake of confirmation for others looking to try the brand I would concur - Medium in most Castelli bottoms fits great - straps ARE a bit tighter than I would ideally like, but after on bike a minute I forget how they felt. Jerseys and jackets can be a mixed bag - med in some and large in others.

Comfy AF

  • Familiarity: I've put it through the wringer
  • Fit: Runs small

These bibs fit great and are easily one of the most comfortable bibs I've worn.The fabrics offer great compression complimented by an updated leg gripper that allows it to lie flat, stay in place, without the discomfort of having the silicone grips right at the edge.

Castelli also updated the straps to this short which I found to be a huge plus from their previous models. The new bib staps have mesh allowing better ventilation but most importantly they don't roll and seem like they will hold up to stretching a bit longer.

The reason Castelli keeps us coming back though is the chamois. Am I right or am i right? The Progetto x2 Air chamois is their best chamois yet and I was truly impressed. I've used these on my longer rides and it's so plush. The new top layer is even softer and more flexible giving you confidence that you can move around the saddle, adjust riding pistions, etc.. and still be comfy AF.

One thing to note with Castelli sizing is often if you've never tried their apparel before you will likely need to go up a size from what you are used to. For more precise help though with sizing, fit, etc please feel free to reach out to me and I'd be more than happy to help.

Stylish but uncomfortable

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: True to size
  • Size Bought: XXL

This is a great bib if you prefer style over comfort. I wore these for about 2 hours and the chamois did nothing to alleviate the discomfort of my perineum. It was a relief to stand up in the saddle when I could. I will say that I did like the leg grippers and the look of the bib. They also fit pretty well, but every rider is different and these just didn't do it for me.

Way better than last year's version.

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

I've always got on good with castelli bibs but the pad usaully only last a season. The new pad seems to be made out of a different material so hopefully they last a little longer .the leg length is also longer then last year's. over all great improvement . Glad I stuck with castelli . A steal on sale .

Amazing looks and comfort

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

I originally bought the size small but they were extremely tight, went up to a medium and i am glad i did. Just did a 60 mile ride this weekend and the bibs practically disappeared. These look great and the chamois is even better (and it is softer than my other Assos and Castelli Bibs). Keep in mind that the blue is actually more of a grey but they still look amazing. I am 5'8" and 152lbs for reference.

Race Ready

  • Familiarity: I've used it several times
  • Fit: Runs small
  • Size Bought: Large

These are actually my first Castelli bibs and they certainly won't be my last! The Progetto X2 Air chamois is quite comfortable for longer days in the saddle. These are a quality product thru and thru. As far as sizing, be sure to size up. I am a size Medium in most other bibs but these Free Aero's in size large feel like a snugger medium to me.

A New Favorite

  • Familiarity: I've used it several times
  • Fit: Runs small
  • 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!

Great Bibs!

  • Familiarity: I've used it several times
  • Fit: True to size
  • Size Bought: Small

These bibs are really nice. Much better than the previous version. They are more durable and they are super comfortable. The material is a bit stronger, so they will last. They are quiet comfortable for those long days in the saddle. The material of the bibs is also super comfortable. Well worth it!