Zerofit Heatrub Ultimate Base Layer – Tested

The sign above the Zerofit stand at Motorcycle Live stated, “The World’s Warmest Base Layer”.

It is a bold claim. A quick search on SportBikeShop’s website for “Base Layers” offered me a choice of 598 products, including 12 body warmers, 70 jackets, 56 long-sleeve T-shirts and even a pair of MotoGP branded winter socks.

There is only one way to determine if Zerofit’s claim is valid … take the thermal liner out of my jacket, leave the Keis heated clothing in the garage, and go for a ride.

Base Layers

There are several different theories on how base layers work. Perhaps the most common is the tight-fitting compression style that uses thermal layers to trap your body heat. If totally sealed, there would be the problem of moisture build-up when you start to sweat, so most of the fabrics used in compression base layers allow moisture to escape through the weave while retaining the warmer air close to your body.

The science works and compression base layers are very popular. However, in those circumstances, our only source of heat is our own body. Physical exertion raises our body temperature, but riding a motorcycle is generally a passive activity.

Our colleague Carle expends a lot of energy picking his CRF out of the mud and hedges when off-roading, but we mortals that stick to tarmac roads tend to sit still on the bike … except for the odd bum shift when we spot an engaging corner.

Typically, staying warm while expending little physical energy requires an additional heat source – Keis Heated clothing is my preference. So, how does the Zerofit Heatrub base layer generate heat? The clue might be in the name.

Zerofit Heatrub Ultimate Base Layer

Whereas the Zerofit Base Layer being designed in Japan may be important to some, how the Zerofit works without me having to raise my body temperature intrigued me.

Stinging yourself with nettles was once a way of creating a feeling of warmth. Thankfully, stinging yourself is no longer required, although the woollen lining found in some base layers operates on the same principle. The wool irritates your skin, creating a reaction akin to warmth. It is the same reason we rub ourselves when cold.

Zerofit’s Heatrub is a modern take on the woollen base layer, most importantly, without the irritation. The threads inside the Zerofit base layer gently brush against your skin as you move, generating warmth through friction. The fluffy lining is soft to the touch – it is a blend of Acrylic, Nylon, Polyester, Wool and Polyurethane, making it easy to wash – and a pleasure to wear next to the skin.

The clever bit is that having generated the heat, the design of Zerofit’s base layer retains the heat better than any other base layer on the market, and from that comes their bold claim to be the best base layer available.

The Boken Institute – Japan’s leading textile testing organisation – measured the Heat Retention Rating of the Zerofit Heatrub Ultimate Base Layer at 0.78, which means nothing to me. However, the comparison data highlighted that a standard base layer has a rating of 0.1-0.14, while a sweater typically has a rating of around 0.3. The list of brands used to establish the comparison baseline is impressive. We are not talking cheap knock-offs from a sweatshop somewhere. There are some big brand names on the list.

The Heatrub base layer is so good at retaining heat that the neckline is designed to have a looser fit than you might expect. The concept of a wicking fabric does not align with the heat retention properties Zerofit wanted for the Heatrub Base Layer, so the excess heat (and moisture) needs an escape route, hence the loose-fitting neck.

On The Bike

Whereas the science is fascinating, and the results returned through testing are impressive, the true test is riding 50 miles for a sausage roll and a mug of tea in 2°C ambient air temperature, which will drop to an equivalent -8°C when I get to 60mph.

My only concern is that I’ll be sitting still on the bike, so there won’t be much movement to generate any heat.

Pushing the bike around in the garage and generally faffing about while getting ready, the Zerofit clothing is working as advertised. I’m toasty warm wearing the Zerofit base layer and the Heatrub Ultimate socks.

I still feel warm as I put the rest of my gear on and start the ride in the company of my colleague Roger, who is similarly attired.

With the Keis heated jacket, I can feel the heat it generates. With the Zerofit, I can’t, and whereas I’m not getting warmer as I ride, most importantly, I’m not getting colder.

My hands are missing the Keis heated gloves, even with the heated grips going flat out against the palms of my hands, and my feet – usually the first to feel the cold – are doing well.

Feet spend their motorcycling winter lives sticking out in a freezing 60mph breeze, and unless I’m wearing my electric socks, there is typically little hope for them. Today, though, is different. My feet are comfortably encased in Zerofit Heatrub Socks. They are so comfortable that I have to make a conscious effort to think about them. That is impressive.

With the first 50 miles completed, Roger and I opted to take a break and eat epic sausage rolls (they truly are epic) from Hel’s Kitchen in Caistor’s Marketplace. The route so far has taken just over an hour and mixes fast A roads and boring but functional dual carriageways. The ambient temperature has risen to 4°C in the weak winter sun, but neither of us is cold.

My feet are not complaining, and the slight chill I’d noticed on my upper body during the last few miles has disappeared, thanks to moving about. Refuelled and refreshed, we can’t be this close to the north end of the Caister High Road (B1225) and not enjoy its curves.

Another sixty miles later, Roger and I are drinking tea and comparing notes. Neither of us has been cold on the ride. Our feet have been the big winners, finding the Zerofit Heatrub Ultimate Base Layer socks warmer than any non-powered solution – even two pairs of “thermal” hiking socks.

The long-sleeved base layer has also done a cracking job, considering we gave it a hard time. At this time of year, we would usually have at least the thermal liner in our jackets and have considered putting a jumper on, but I went out wearing just the Zerofit and my Rev’it jacket.

The Bottom Line

The Zerofit base layer is both strange and wonderful. It is comfortable against the skin and, with a little movement, adds warmth to the comfortable feeling. Even when sitting largely stationary on a motorcycle, it toughs it out against the cold and turns a dull winter day into an enjoyable ride.

Keeping me warm in a 100-mile ride when the ambient temperatures didn’t rise above 4°C is a tough ask, but the Zerofit Heatrub worked as advertised.

And the cherry on top of being warm while riding in winter temperatures is that neither of us is sweaty. I appreciate that that is perhaps more information than you were looking for, but it is a factor.

Some of the winter clothing we have tested didn’t do a good enough job of giving the moisture a way out. Others did such a good job of removing the moisture from my skin that it became counterproductive, and the subsequent evaporation made me feel colder.

The Zerofit Heatrub base layer had none of those problems. My only issue is that Snr Management “borrowed” my Zerofit for one of her walks – for which read 8-mile hikes – and now it is missing from my collection of bike gear.

I’ll interpret that as an endorsement from Snr Management and buy some more.