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The new Castelli Sanremo 4.0 Speedsuit hasn't seen a massive redesign over the 3.0, more of a fettle to refine the details – but it works. After all, why mess with a classic? Make sure you go up a size though, as it's a much snugger fit than the majority of Castelli's range.
When I was time-trialling, Castelli's Body Paint Speedsuit was my clothing of choice. It was expensive, fragile and you couldn't stand up in it because it was designed in such a way that there wasn't a single wrinkle or piece of flapping material when you were stretched out on the aero bars. In fact it was so small and specifically designed that on the hanger it wouldn't look out of place in a toddler's clothing section. It was amazing, though, and the Sanremo takes a lot of its thinking and comfort but in a more real world application.
You still get the super-close fit, so when you are hammering along on the flat the material is stretched closely to the body, but although the shoulders may feel a little tight you can still walk around off the bike or stand up out of the saddle for a climb without the zip busting open.
It has all the practical benefits of wearing a pair of race shorts and jersey, but with the added aero benefits.
The lower portion of the suit is based on Castelli's Free Aero Race 4 bib shorts which use the Progetto X2 Air Seamless pad. This has a range of differing density foam across its layout but, like a lot of other pads we've seen lately, without any form of channelling between them for reducing pressure.
It's lovely to sit on – a really great balance of comfort and support for long rides, especially those where you are crouched in the saddle in one position, making yourself as aero as possible while smacking out the watts.
The only seam is the one that runs around the outside so there are no rubbing issues no matter how long you are riding for.
Aerodynamics is key here so Castelli has used computational fluid dynamics (CFD), software to mimic airflow, at the design stage to perfect the Sanremo, so you'll find that all of the fabric choices and seam layouts are positioned to achieve the best possible outcomes. We are talking tiny parameters here, mind, especially in the real world.
Castelli has used its Vortex fabric on the legs, which has a dimpled finish for an aero performance, while on the inside of the thighs it's gone for Forza – a material that has a high 38% Lycra content for a really close and supportive fit.
Keeping everything in situ are Giro4 leg grippers. They are quite tall to spread the compressive load, and on the whole are quite comfortable.
Up top, the jersey uses Velocity Rev2 fabric on the front and sleeves for a close and aerodynamic fit, while the rear is made of a lighter mesh style fabric to aid breathability. It's a good combination that allows you to ride hard without getting overwhelmed in sweat, doing a really good job of keeping you dry.
Castelli has changed the pocket layout on the 4.0 to give you better access on the fly. Feedback was that the three narrow pockets were a bit of a faff to reach into at times, so this new edition has just the two but much wider.
They are still deep and taut enough to keep things secure when riding in a crouched, flat back position, and I did find it easy to reach back to grab a snack or my phone without issue.
As I've mentioned, the fit of this skinsuit is supposed to be close, but a word of warning: Castelli has a single size guide for all of its products. I'm usually a medium in its clothing if I want a snug fit, but I'm glad I had the large in the Sanremo. It fitted well, though I would say I was right at the upper limit of what is acceptable, so you'll definitely need to size up by at least one.
Now, value. At first glimpse the price looks mental at £240, and while many of you will still shake your heads and mutter under your breath while I have a go at justifying it, bear with me.
The Free Aero Race 4 bib shorts that these are based on are £150 on their own, and while Castelli doesn't base the jersey on anything specific in the range, the Aero Race 6.0 Jersey FZ is pretty similar and that'll cost you £110. So while the Sanremo isn't a bargain, you are getting a bit of a discount.
A cheaper option, though, is the Endura Pro SL Roadsuit for £179.99. The Castelli has the better fit and what feel to be better materials in terms of comfort, but the Endura does have a very good pad plus you'll have 60 sheets in your back pocket so it's definitely a contender.
Overall, the Sanremo has lost none of its edge over the competition. It's a very well made piece of kit that performs well, and as long as you bear the sizing in mind there is little to dislike.
A well-executed compromise between an aero skinsuit and a jersey/short combination – a quality piece of kit for racers
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road.cc test report
Make and model: Castelli Sanremo 4.0 Speed Suit
Size tested: Large
Tell us what the product is for
Castelli says, "The Sanremo Speed Suit revolutionized the way pro riders dress when we invented it back in 2011 and we're still surprised that every other manufacturer has simply copied the Sanremo front opening rather than trying to come up with something original.
"While the front opening is the most visible part, we've worked on every other detail to make this the perfect race suit. It's aero thanks to our CFD based seaming and wind-tunnel selected fabrics. It's comfortable thanks to the body fabrics that will keep you dryer and cooler than some of the simple Lycra fabrics used by some other companies. The lower portion of the suit is our Free Aero Race 4 bibshort, our most comfortable suit for your longest, toughest race days.
"Besides the new fabrics and seam placement we've also worked on the pockets to make them better for racing. They're somewhat narrower for better aerodynamics but there are now 2 big pockets instead of 3 small ones, so they're easier to access in racing."
Tell us some more about the technical aspects of the product?
CFD-based fabric placement and seam construction.
Engineered for aero efficiency at 30 to 55 km/h.
Airflow shoulder construction.
Velocity Rev2 fabric on front and sleeve.
3D mesh back for breathability.
Elbow-length stretch sleeves with raw-cut edge.
YKK® Vislon® zipper.
2 pockets with floating design for more space in pockets.
Vortex fabric on legs for aero performance.
Forza fabric on inner legs with 38% Lycra® content for perfect fit.
Giro4 leg gripper elastic for better grip distributed over larger area
Doppio V construction in front for increased support and comfort.
Progetto X2 Air Seamless seat pad.
Get the right size and the fit is great.
You definitely need to go up a size compared to Castelli's size guide.
How easy is the product to care for? How did it respond to being washed?
No issues at all with washing it on a cool 30 degrees wash.
Tell us how the product performed overall when used for its designed purpose
For those who want the aerodynamics of a skinsuit but without the impracticality, the Sanremo is a good compromise.
Tell us what you particularly liked about the product
The pad is excellent.
Tell us what you particularly disliked about the product
Make sure you get the sizing right...
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
There are a few other options out there that are cheaper and nearly as close in performance.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your overall score
For those who want to be aero while still being comfortable at all times on the bike, the Sanremo is hard to fault, although there are some cheaper alternatives out there.
About the tester
I usually ride: This month's test bike My best bike is: B'Twin Ultra CF draped in the latest bling test components
I've been riding for: Over 20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed
As part of the Tech Hub here at F-At Digital, our senior product reviewer Stu uses the knowledge gained from putting well over a 1,000 products through their paces (including hundreds of bikes) to write in-depth reviews of a huge range of kit. After first throwing his leg over a race bike back in 2000, Stu's ridden more than 160,000 miles on road, time-trial, track, and gravel bikes, and while he's put his racing days behind him he still likes to smash the pedals rather than take things easy. Although, as he spends a fair bit of his time reviewing ebikes these days he's becoming an expert in letting the motor take the strain. He's also waiting for 23mm race tyres to make a comeback!