Assos Thermobooster Foil

The Assos ThermoBooster Foil is today's version of a solution cyclists have been using for generations: stuffing a newspaper under your jersey to combat cold on a long descent from a mountain pass. While it certainly shares similarities with the good old newspaper, the most important one being its windproofness, the ThermoBooster Foil is also waterproof, softly padded and made to be used hundreds of times.

It is deliberately not a gilet but, rather, a thin panel that you place against your chest, beneath the bib straps of your cycling shorts or longs, so it stays in place without needing to be zipped up. Thus, you can put it on in 20 seconds at the top of a climb and fold it away again just as quickly once you are back down.

Who is it for? For riders who get warm going uphill and cold going downhill. For cyclists who love Alpine rides and long descents, and who want added protection for unexpected rain showers or a chilly morning start. Assos positions the ThermoBooster Foil as emergency insulation for such times, and ensures that it folds flat so you can keep it in a back pocket all year round.

That said, if you want protection on both your chest and back, or are looking for a separate layer to wear over your cycling jersey, take a look at the Assos Mille GT Wind Vest S11. This is a full-featured wind vest with a two-way zip, available in sizes S to XXL, designed for temperatures of 15 degrees and above. While it is windproof, it is not waterproof, whereas the ThermoBooster Foil is. So, many cyclists end up owning both – the vest for the whole ride, and the Foil for the descents.

HYPERPLUSH three-layer softshell fabric

Assos combines three layers here, each of which serves its own purpose. On the outside is a fully storm-proof barrier that keeps out wind and water; behind that is a layer that wicks sweat away; and on the inside is a lining that Assos calls its softest ever. This combination is why you can wear the panel close to your body without it chafing during a 20-minute descent.

Secure fit under your bib straps

The ThermoBooster Foil has no zip, Velcro or elastic. You simply put it under the bib straps of your cycling shorts or longs, which hold it in place while you are leaning over the handlebars. This saves weight and eliminates seams that might cause irritation, and it means you can put it on without having to take your jersey or jacket off completely.

Compatible with:

• Bib shorts or tights – the bib straps keep the panel in place.
• Any Assos layering system, from the close-fitting RacingFit RS range to the GT series for long distances.
• Cycling jerseys from any brand – as you wear the Foil underneath, the fit of the jersey doesn’t matter.
• Any body type – it has a one-size-fits-all design.

Not compatible with:

• Cycling shorts or tights without bib straps – without those shoulder straps, the panel will not stay in place.
• Use as a wind vest over your cycling jersey – as the Foil has no fastening or back panel, you must always wear it under your jersey.
• Use as protection for your back or arms.

Not sure? Here’s how to check:

Put on the bib short or bib tight you usually wear and check whether its bib straps go over your shoulders. If so, the ThermoBooster Foil will work. Hold the panel flat against your chest, slide the bib straps over it, close your jersey and bend forwards. If the panel feels secure enough not to slip, it is fitted correctly.

Included as standard:

• 1x Assos ThermoBooster Foil in the blackSeries, one size, 200 grams

Not included, but necessary or useful:

• A bib short or bib tight – you need bib straps to keep the panel in place.
• Pockets – the design is flat for an easy fit under cycling clothing, and ultra-compact for easy storage in a back pocket of your jersey.
• A base layer – if you prefer a layer between the panel and your skin.
• Assos Active Wear Cleanser – for best care of the panel itself and its wind- and waterproof properties.

• Fold it flat rather than stuffing it. The tighter you fold it, the smaller it is, and the longer the softshell will stay in good condition.
• Wash the panel at a maximum of 30 degrees using Assos Active Wear Cleanser. Do not use fabric softener because it closes the pores of the fabric, reducing its breathability.
• Let the Foil air-dry – never use a tumble dryer or put the Foil on a heater, as heat will damage the storm-proof layer.
• Take it with you on rides where you are not yet familiar with the descent(s) – weighing just 200 grams, it is hardly noticeable yet offers great comfort and protection when you need it.