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Castelli Sanremo Thermosuit



Innovative all-weather all-in-one onesie takes winter clothing to another level

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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The Castelli Sanremo Thermosuit has been one of the most talked about pieces of cycle clothing since it launched last October. Why exactly all the buzz? Castelli have taken their Paris-Roubaix winning Speedsuit and turned into into a one-piece winter package that is one of the most innovative cold-weather garments we've seen in some time.

To briefly recap if you haven't been paying attention, the Sanremo Speedsuit was ridden to success in Paris-Roubaix by Johan Vansummeren in 2011. Its unique by virtue of combining the performance aero benefits of a skinsuit with the practicality of a jersey and bib short combination. To turn it into a insulation winter package, Castelli use warmer windproof materials.

Gore Windstopper X-Lite Plus fabric is found on the chest panels, while around the back and used for the tights is a lighter weight Thermoflex Core Due fabric. Gore Windstopper X-Lite Plus is the same water resistant 4-way stretch fabric they use in their highly acclaimed Gabba WS Rain jersey .

The Thermosuit is essentially a pair of tights and a long sleeve jersey stitched together at the waist around the back, with a full-length zip on the front. Pulling them on feels a bit odd, and straight away you notice the lack of bib straps, and how much more comfortable it is as a result - the Thermosuit is supported simply by the shoulders and arms. Don't worry, comfort breaks are easy, really easy. You don't need to remove the Thermosuit, the top section of the tights offers enough stretch to make toilet stops easier than regular bib tights.

You get three pockets around the back and, as is usual with Castelli jackets, they omit any sort of small zipped pocket for stashing your house keys. Fair enough on an item that is so clearly aimed at performance cyclists I guess, and perhaps not everyone feels the same way I do about zipped pockets for peace of mind? The pockets are large enough to allow you to comfortable stock up for a long ride, and a bonus of the one-piece design is that the pockets don't sag when fully loaded with food and supplies.

Other features include the zipped ankles with gripper tape, and generous reflective details. The high collar provides good coverage of the neck and the cutaway section ensures it's comfortable next to the skin.The elasticated cuffs are snug and prevent cold air seeping in through the arms.

Inside the shorts is a Progetto x2 air insert. It's super comfortable even for 4+ hours on the saddle. It's the same chamois Castelli fit to their £160 Sorpasso bib tights. It comprises two parts, a soft layer next to the skin and multi-density padding underneath, and the two layers can move independently. This design is what lends them their superb comfort.

One of the key design claims with the Speedsuit is its aerodynamic advantage over separates. There's no reason why you might not want such aero benefits through the winter, especially if you're a racing cyclist clocking up a lot of training miles during the week. However, as with most aero claims, it's a tad tricky for us to verifyso we can't pass verdict on them. I certainly felt fast wearing the Thermosuit...

Which could be on account of the mad fluoro yellow accents. It's been pointed out before that they're on the wrong side for UK roads, but let's remember Castelli is an Italian company and they drive on the wrong side of the road over there, so I'm prepared to let them off 'magnanimous' is my middle name. It's not something that ever bothered me during testing and it didn't make a blind bit of difference to my visibility to other road users. I'd like an all-black version personally, the yellow is a bit shouty for my tastes, but granted the visibility touches are spot on for a winter riding garment. There's plenty of reflective details too making it ideal for training in low light or at night.

It feels odd to pull on the Thermosuit at first. But out on the bike any concerns are banished as you enjoy how incredibly lightweight and unrestrictive it is. It feels very much like wearing summer weight clothing, there's none of the bulk that winter jackets usually come with.

Castelli claim it's good between 3 and 15 °C, but I found anything approaching the lower end of its limits just too cold to not require the addition of an extra layer in the shape of a jacket over the top. I do feel the cold easily it has to be said, and 3 °C would have me wrapping up in three long sleeve base layers. So I feel the Thermosuit hits the mark and is well suited to the most typical winter days. It's possible to adjust to different temperatures by careful selection of base layers, pick a heavier weight base layer on colder days and the Thermosuit offers good warmth. And a lightweight jacket that can be stashed in a pocket for cold early morning rides is a good way to combat the colder temperatures.

Anything I'd change? Well I felt the overlap between the front panel and the top of the tights wasn't generous enough, and would like to see a couple more inches added to the top of the tights. And I had a few comments about an apparent transparency of the fabric when riding with others. It's not something I was aware of myself, for obvious reasons, but slightly disconcerting that I might be exposing just a little too much for fellow riders.

That aside, they delivered impressive comfort on the bike and fantastic performance in a range of conditions. I didn't feel they provided enough insulation when riding close to sub zero degrees, but that's nothing a jacket over the top doesn't take care off. It really is the most comfortable cycle clothing I have ever worn in the winter. At first it feels you're not wearing enough, like you've dared to step outside in a skin suit, but the insulation is there to keep the chill at bay on training rides. The slim fit and onesie design also means there's none of that flapping of excess material that can occur even on the best winter jackets.

Which just leaves the price. £250 is top-end money, but here's another way of looking at it. You could buy the Sorpasso bib tights, £160, and the Trasparente Due Wind Jersey, £145, on their own (the Thermosuit essentially blends key elements of these two garments), but you do the maths. The Thermosuit can actually be considered good value. You do lose out a bit in versatility and size compared to the separates, but you gain so much more in other areas (fit, comfort, aero) that makes it an appealing package.

A upside of the separates however is the ability to choose different sizes top and bottom, you can't do that with the Thermosuit. I'm a large on the legs but a medium up top. Unless Castelli starting offering mixed sizes, you might find the size a compromise. So make sure you try one before you buy. Castelli clothing comes up nice and slim anyway so it's not as big an issue at it might be.


Innovative winter all-in-one offers unsurpassed levels of comfort, temperature regulation and none of the bulk of other winter clothing. And it looks great too. If you like fluoro yello

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Make and model: Castelli Sanremo Thermosuit

Size tested: Large

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

With the product concept of the SanRemo SpeedSuit in mind, Castelli engineers created a new way to dress warm and light for winter riding. There are no bib straps to restrict breathing, the seat pad is as good as the one in your best shorts, and the materials don't feel bulky or restrictive. By joining the jacket and the tight together, the Sanremo Thermosuit prevents cold air from entering, keeping you warmer and dryer with lighter-weight fabrics.

Tell us some more about the technical aspects of the product?

Sorpasso tight lower portion combined with trasparente jersey upper portion

Jacket: windstopper® x-lite plus stretch fabric on front is windproof and splash resistant

Thermoflex core due fabric on back for high breathability

Long ykk® camlock zipper with overlapping front opening

3 rear pockets with limited-stretch back to keep pockets in place

Rear reflective tabs

Tight: thermoflex and thermoflex core due fabric

Progetto x2 air seat pad for comfort and improved airflow

Giro3 ankle grippers position the tight and seal around shoecover

Ykk® ankle camlock zippers with reflective tape for high visibility

Rate the product for quality of construction:
Rate the product for performance:

One of the best winter cycling garments I've ever used. It is lightweight and lacks any restriction making it superbly comfortable for winter training rides

Rate the product for durability:
Rate the product for comfort, if applicable:

The lack of bib straps is perhaps the biggest contributor to their comfort, no straps digging into the shoulders. The chamois is one of the best on the market too

Rate the product for value:

It's a lot of money yes, but it's cheaper than individually buying the top and tights it's essentially based on

Tell us how the product performed overall when used for its designed purpose

Takes winter clothing to another level

Tell us what you particularly liked about the product

The comfort and lightness

Tell us what you particularly disliked about the product

The fluoro yellow is a bit bold, so other colour options (all black please) would be nice to see added to the range. I'd like the top of the tights to rise a bit higher to provide a large overlap with the jersey

Did you enjoy using the product? Yes

Would you consider buying the product? Yes

Would you recommend the product to a friend? Yes

Anything further to say about the product in conclusion?

Innovative all-weather all-in-one onesie takes winter clothing to another level

Overall rating: 8/10

About the tester

Age: 31  Height: 180  Weight: 67

I usually ride:   My best bike is:

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo cross, commuting, touring, mtb,


David worked on the tech team from 2012-2020. Previously he was editor of and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds, and you can now find him over on his own YouTube channel David Arthur - Just Ride Bikes

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