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Specialized Women’s RBX Comp Thermal Bib Knicker



Excellent comfort and warmth for days when full winter bibs are overkill, though the hem design won't appeal to all
Effective in cold weather
No bunching at front
Bunching behind knee

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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Specialized's Women's RBX Comp Thermal Bib Knickers are perfect for those days when there's zero chance temperatures will rise enough to make you want to peel off knee or leg warmers but full winter bibs would be overkill. The fabric is exceptionally effective at keeping the upper legs and knees protected from cold air, and the cut at the waist is great.

Despite their title, the knickers don't have a bib. They have a stretchy, well-proportioned folded panel at the front, and it's one of the most comfortable (waisted) pairs I have ridden with. At the rear there is a wide, elasticated band to help hold the knickers securely.

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I tested a medium; while my height put me in a large on Specialized's size chart, other measurements were at the bottom end of the medium range. The fit around the hips and waist felt great. I'd say allow hip and waist measurements to override height for these.

I found the leg length good – definitely shorter than some other 3/4s I've tested, which plays in their favour: there are no grippers at the leg ends to hold them in place, so less fabric to ride up.

2021 Specialized Womens RBX Comp Thermal Bib Knicker - knee detail.jpg

After 15-20 minutes in the saddle, they settle into a higher position, which doesn't look great but isn't uncomfortable, and a mesh panel behind the knee helps with heat regulation; the mesh is also soft and doesn't feel scratchy or irritate, even when the fabric starts to bunch up.

Specialized Women's RBX Comp Thermal Bib Knicker 2021 bunching behind knee.jpg

The lack of elastic or silicone and the inclusion of a dart in the lower hem means it's really easy to pull the leg ends down while on move, though it's a bit of a pointless exercise as they are going to ride up again in no time.

2021 Specialized Womens RBX Comp Thermal Bib Knicker - cuff.jpg

For this reason, I was thankful I hadn't opted to test the large that my height put me in – there would likely be more length to ride up and ultimately bunch at the knee.

The fit around the hips and waist was, as mentioned, spot on for me. I have tested very few waist shorts/knickers/tights that don't create some form of bunching at the groin, but the RBX Comp Thermals didn't bunch at all. Even better, there was no cutting in at the waist or marks left on my tummy after rides.

2021 Specialized Womens RBX Comp Thermal Bib Knicker - waist.jpg

The waist height is always a fine balance – teaming these with the shortest jersey I own was a no-no, but said jersey isn't compatible with all of the bib shorts I own either.

Recent conditions have been ideal for the Knickers; consistently cool weather. The fabric is surprisingly warm for something that is seemingly rather delicate and thin – in fact, anything above 14 degrees and I found these too much; the Action 210 fleece certainly seems more suited to single figure temperatures than double.

2021 Specialized Womens RBX Comp Thermal Bib Knicker - back.jpg

It's exceptionally soft against the skin, too, and super stretchy; it doesn't pinch and is very accommodating. I was also surprised that an outdoor coffee stop, sat on a wall, didn't causes any kind of threading or bobbling to the fabric. It's more robust than its touch might lead you to believe.

2021 Specialized Womens RBX Comp Thermal Bib Knicker - back detail.jpg

I found the Body Geometry 3D Contour Chamois to offer sufficient support for rides of up to four hours. I'd say that the variable density foam is firmer than average. It's a good length, too, just enough for efforts on the drops but not too much to add bulk if you are upright.

2021 Specialized Womens RBX Comp Thermal Bib Knicker - chamois.jpg


There aren't that many 3/4s out there, and those that do exist tend to also be bib-less, and around the same price as these RBX Comp Thermals.

> Buyer’s Guide: 8 of the best 3/4-length tights

Lara tested some from Fat Lad At the Back which are also £74.99. They are more colourful but the seams were an issue for Lara. She didn't rave about the cheaper (now £54.99) offering from Bontrager either.

Liv's Race Day Knickers are the same price, while its Mossa Knickers are cheaper at £49.99, but neither are thermal.

> Read more reviews of women’s cycling clothing here

Morvelo's Stormshields do have a bib, but they have the same issue with the legs riding up as the Specialized knickers, despite being elasticated with silicone, and are now £115.


Justifying buying 3/4s isn't always easy when you could invest in some quality knee warmers to team with any pair of shorts that you own. However, the warmth that these Specialized knickers offer certainly beats all of the shorts I own.

While the legs riding up isn't a great look, neither are the sausage legs that knee warmers can sometimes cause. I'd say it's a matter of personal preference here. The quality, warmth and fit at the hips justify the £75 price tag. For me, they are the most comfortable and effective 3/4s I've ever used.


Excellent comfort and warmth for days when full winter bibs are overkill, though the hem design won't appeal to all test report

Make and model: Specialized Women's RBX Comp Thermal Bib Knicker

Size tested: Medium

Tell us what the product is for

Specialized says: 'Cold legs make for bad rides, and bad rides are no fun. Lucky for you, the RBX Comp Thermal Bib Knickers keep your legs toasty on chilly days. And to top off the comfort, we've used our Body Geometry 3D Contour Chamois with a variable density design that places support and padding where you need it, not where you don't.'

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

Specialized lists:

Fully made of soft and stretchy Action 210 fleece.

Front waist construction has folded fabric band, which offers freedom of movement while riding, and rear inner soft elastic band.

Fabric Content: 70% Polyamide

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

Brilliant in cool to cold conditions.

Rate the product for durability:

Fabric surprisingly resistant to snags.

Rate the product for fit:
Rate the product for sizing:
Rate the product for weight:
Rate the product for comfort:

While the legs ride up, the hems aren't elasticated and have no silicone grippers, so they don't really cause any discomfort.

Rate the product for value:

How easy is the product to care for? How did it respond to being washed?

No problems in a standard 30 degree cycle.

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

Excellent protection and comfort in typical autumn conditions.

Tell us what you particularly liked about the product

Comfortable waist with no bunching at the groin. Warmth.

Tell us what you particularly disliked about the product

Nothing really. Yes, it'd be better if the legs didn't ride up, but without an elastic gripper and silicone, which themselves can be aggressive and cause bagging at the knee, I wasn't bothered by the gathering.

How does the price compare to that of similar products in the market, including ones recently tested on

They're cheaper than Morvelo's £115 Stealth Stormshields, though they do have a bib, and the same price as others from Fat Lad At The Back and Liv, though they're not thermal.

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

The warmth, comfort and quality of the Knickers overshadow the issues with the legs for me. Although they do ride up, it never felt uncomfortable since there is no elastic or silicone, so the fabric doesn't pull around the knee; it's soft and giving.

Overall rating: 8/10

About the tester

Age: 42  Height: 173cm  Weight: 64kg

I usually ride: Road  My best bike is: Carbon road.

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Expert

I regularly do the following types of riding: commuting, touring, club rides, general fitness riding, Getting to grips with off roading too!

Emma’s first encounters with a road bike were in between swimming and running. Soon after competing for GB in the World Age Group Triathlon Championships in Edmonton in 2001 she saw the light and decided to focus on cycling. 

After a couple of half decent UK road seasons racing for Leisure Lakes, she went out to Belgium to sample the racing there and spent two years with Lotto-Belisol Ladies team, racing alongside the likes of Sara Carrigan, Grace Verbeke, Rochelle Gilmore and Lizzie Deignan. Emma moved from Lotto-Belisol to Dutch team Redsun, then a new Belgian team of primarily developing riders, where there was less pressure, an opportunity to share her experience and help build a whole new team; a nice way to spend her final years of professional racing. 

Since retiring Emma has returned to teaching. When not coercing kids to do maths, she is invariably out on two wheels. In addition to the daily commute, Emma still enjoys getting out on her road bike and having her legs ripped off on the local club rides and chain gangs. She has also developed an addiction to touring, with destinations including Iceland, Georgia and Albania, to mention just a few. There have also been rare sightings of Emma off-road on a mountain bike…

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