Gloworm XSV LED light review

The updated Gloworm XSV is packed with features but how does it perform on the trail?

Gloworm XSV Light
(Image: © Guy Kesteven)

Bike Perfect Verdict

Gloworm’s latest light is a powerful and super versatile performance package


  • +

    Impressive power for size and excellent wireless control

  • +

    Compact head units with multiple mount options

  • +

    Interchangeable optics and switchable output menus


  • -

    The battery can slide around

  • -

    Charge gauge slightly awkward to see

Why trust BikePerfect Our cycling experts have decades of testing experience. We\'ll always share our unbiased opinions on bikes and gear. Find out more about how we test.

The latest evolution of Gloworm’s XSV light gets 30 per cent more power but keeps its impressively comprehensive range of configuration and customisation options. Remote syncing means it’s even better as a double act with the X2 headlamp, too.


The latest XSV hasn’t changed structurally but having used the design for years that’s fine by us. Three Cree XHP LEDs sit in a CNC machined head behind three separate optic cones. It comes fitted with two spot optics and a central honeycomb diffusion optic as standard. Extra spot and honeycomb optics plus a wide optic are supplied in the box though and switching them is super easy.

Switching modes (low-, med-high in ‘Trail’ or low, high flash in ‘Commute') can be done with the button on the back of the head but syncing the wireless remote only takes seconds when you plug light and battery together. The same remote can also connect to a second Gloworm headlight for perfectly choreographed output and run-time control.

Gloworm XSV Light

The remote allows easy changing between light modes even when using a pair of headlights (Image credit: Guy Kesteven)

Mount options are very comprehensive. It comes with a 31.8mm quick-release bar mount that offsets the light centrally over the stem. While there’s the option to add a 35mm bar mount you can also use a GoPro-compatible tab onto the bottom as well. This syncs with a clip-in mount for a strapped helmet shoe (all provided) but you can use it with any existing ‘action camera’ mount.

All bolts are stainless steel so there are no concerns about corrosion no matter how salty things get if you’re commuting with them. Gloworm even provides the 3 and 1.5mm Allen keys needed for all changes. Old cable-to-head issues were sorted with a super solid overhaul a few seasons back and the IP67 watertight connectors and hard case batteries have proved bombproof ever since.

The rectangular hard case battery has a 6800 mAH capacity, with an elasticated Velcro strap and weighs 246g. The head unit and bar mount weigh 150g making it a comparatively light combo for its 3400 lumens (measured not claimed*) output.

To maximise the gains from the wireless remote, the 105g twin LED X2 produces 1700 lumens and comes with the same arsenal of accessories for £225/$265/€269. The X2 Adventure twins the same light with a 142g 2 cell rather than 4 cell battery for a 20 per cent cost reduction.


While a lot of lights claim their lumens from the maximum theoretical output these calculations don't account for various losses in the circuitry and optics which results in massively over-optimistic numbers. The 3400-lumen figures for the XSV are obviously real as soon as you fire it up. Even with the honeycomb centre optic spreading out light to soften the edges, there’s a ton of punch down the trail for flat out commitment. In fact, most of the time we ran it in the medium mode and never struggled to see what was coming. The flat three LED arrangement also gives more stereoscopic depth to judge detail so you’ve got a better sense of surface detail which can often get ‘bleached out’ with a single light source. Having the different optics obviously lets you tweak output/spread and you can also change the preset power outputs if they don’t suit.

While the light seems to swivel easily on the sidebar mount even when bolted up tight, centralised weight balance and the sandwiched O rings in the mount actually keep it impressively stable and on target even when thrapping down big steps or hitting nocturnal jump lines.

Gloworm XSV Light

Depending on your frame's tube shapes you may need to do a little home customisation to keep the battery secure (Image credit: Guy Kesteven)

The only thing that does move about is the battery, particularly on curved or tapered frames. That’s certainly not a unique issue to Gloworm but the stretchy wrap-over strap makes it hard to really cinch down tight. The stick-on rubber ‘grip strip’ is very small and relatively slippery, too. We’d suggest you add a section of inner tube or grip tape between strap/battery and frame to keep it better anchored and protect your paint at the same time.

While the deep recessed indicator LEDs make seeing remaining charge a bit awkward, lower levels are clearly communicated with colour change and an eventual light flash after around an hour and 40 minutes at full power even in cold conditions. Toggling through low and medium settings via the bar remote is so easy that doubling that run time is easy without compromising your ability to see even on continuously technical trails. The flash mode is great for commuting and road use, and props to Gloworm for putting it on a separate menu so that you don’t accidentally go ‘disco’ just as you drop into a sketchy section.

As previously mentioned, reliability has been consistently excellent on every recent Gloworm we’ve used and pricing is reasonable considering the care package provided. Recharge times are really short too, which is a big bonus for forgetful riders.

Gloworm XSV Light

The headlight features a durable CNC construction and at 150g is light enough to comfortably mount to a helmet (Image credit: Guy Kesteven)


Once you’ve worked out how to get the battery settled securely, Gloworm’s XSV is an outstandingly versatile and practical light package with an impressive, widely tuneable performance. Excellent reliability, super-comprehensive accessories package, custom tuning options and the neat wireless remote control make it very user friendly on the trail and over the long term, too. We’d definitely team it with one of the X2 options to really maximise the Gloworm system advantage though. 

Tech Specs

  • Lumens: 3500 
  • Weight: 332g (claimed) 
  • Battery life: 1.5hr at maximum power
  • Price:  £289 / $320 / €330  
Guy Kesteven

Guy has been working on Bike Perfect since launch in 2019. He started writing and testing for bike mags in 1996. Since then he’s written several million words about several thousand test bikes and a ridiculous amount of riding gear. To make sure he rarely sleeps and to fund his custom tandem habit, he’s also penned a handful of bike-related books and talks to a GoPro for YouTube, too.

Current rides: Cervelo ZFS-5, Specialized Chisel, custom Nicolai enduro tandem, Landescape/Swallow custom gravel tandem

Height: 180cm

Weight: 69kg