Deserves consideration, especially as it can be had half price online at the moment

Blackburn's Mars 4.0 rear light is a clever little light that comes with 3 different mounting options.

We really liked it when we reviewed its previous incarnation 4 years ago; though it's changed a bit since then, it's only got better.

It still has the amber side leds, but the 5 red LEDs on the Mars 3.0 have been upgraded and turned into one superbright 1 Watt LED, creating even more rear illumination. Whereas the model we reviewed then needed a screwdriver to undo the 3 screws that held the batteries in, the 4.0 unclips with a coin to change the 2 AAA batteries.

Not that you'll have to do that often, at 50 hrs runtime on full and a whopping 150 hrs on flashing.

As always with Blackburn stuff, the rear light is really well made, and the casing has stood up to the usual abuse and the wet weather we've been having over the winter. As with all their lights, this one too is covered with a lifetime warranty.

Apart from the overall goodness of this light, I was particularly impressed that it comes with a dedicated rack mounting bracket; something I usually have to DIY with other lights. It also comes with a tool-less seat post mount, and the light case itself has a belt clip which is what you clip into the bracket(s).

At 76 grams, it's not going to affect performance too much, and it will definitely get you seen in all but the brightest sunny weather.


Deserves consideration, especially as it can be had half price online at the moment.

If you're thinking of buying this product using a cashback deal why not use the road.cc Top Cashback page and get some top cashback while helping to support your favourite independent cycling website

road.cc test report

Make and model: Blackburn Mars 4.0 rear light

Size tested: n/a

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

* Blackburn's most powerful rear flasher

* 1 Watt ultra-bright red LED

* 2 Amber side LEDs for side visibility

* 50hr steady, 150hr flashing runtimes

* No tool battery installation

* 2 AAA batteries included

* 3 mounting options included: belt clip, seatpost clamp and reflector/rear rack mount

Rate the product for quality of construction:

The quality you've come to expect from Blackburn.

Rate the product for performance:

It really is quite bright for such a small light. The amber side lights help a lot, too.

Rate the product for durability:

These lights have a reputation for lasting a long time.

Rate the product for weight, if applicable:

76 grams, including batteries and seatpost mount. That's not a lot.

Rate the product for comfort, if applicable:

Once the mounting is in place, it's a doddle to use.

Rate the product for value:

Even at RRP it's value for money, let alone at half price currently available from Ribble.

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

It worked really well.

Tell us what you particularly liked about the product

It comes with a rack mount.

Tell us what you particularly disliked about the product


Did you enjoy using the product? Yes.

Would you consider buying the product? Yes.

Would you recommend the product to a friend? Yes.

Overall rating: 9/10

About the tester

Age: 32  Height: 1.78m  Weight: 76kg

I usually ride: All of them!  My best bike is: Cervelo Dual

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

I regularly do the following types of riding: time trialling, commuting, touring, club rides, fixed/singlespeed, Audax



matthewn5 [1063 posts] 6 years ago

Pity it's so unnecessarily ugly. All those angles! Time to hire a decent industrial designer, Blackburn.

caketaster [17 posts] 6 years ago

Ordered! and as I spent over 35 quid it was further reduced. and I'm in Japan so I don't pay any VAT.

Worth it for 8 pound 30p?  15

HLaB [106 posts] 6 years ago

Both mine have lost their teeth for the clip and been subject to water ingress (ones terminals corroded) but its a good bright light and if available at a good price its definitely worth considering.

paulfrank [93 posts] 6 years ago

I've had mine for over a year after the rough roads around Telford led to my old Cateye committing suicide. It is super bright and I usually have mine on flash for daylight running so there is no chance of the SMIDSY excuse for any driver approaching from the rear, and on for night. There is one downside to it being so bright; if you're riding at night in a group everyone will be asking you to switch it off or ride out back.

I got a bit of water in mine after 25 miles through some serious monsoon weather, dried it out, put a bit of vasoline around the seal, never had another problem.

Looking pretty indestructible so far.

stinch [1 post] 6 years ago

That little grey triangle on the top of the light is the power switch. It's tiny and a real pain to operate while wearing gloves, especially in the dark.

John_the_Monkey [438 posts] 6 years ago

I've had mine ages, replacing a Mars 3.0 that I gave to a friend. IME, a great light - mine lives in the light loop of my Carradice, and has survived everything the weather has thrown at it so far.

The only gripe I have is that both the rack mount and the post mount need a part that you only get one of; so mounting is an either/or choice, unless you buy another mounting kit (or another light - the Mars 1.0 is compatible and cheap, so I bought one of those). It's a small niggle, but if you've a racked bike, and another that you want to use the Mars 4.0 as well, a bit of a pain.

Joel [20 posts] 6 years ago

Have been using a pair of these for over 3 years now in all weather. Totally impressed with them, no faults or problems. Only gripe is that the batteries dont seem to last long, but I think that is reflective of the amount of use they get. Would buy again.

zzgavin [193 posts] 6 years ago

best bit of a mars 4.0 is the easy availability of cheap mountings to put it on other bikes. I ride with this on my Brompton and move it to my road bike. I had a lovely lezyne rear light (free with cycling plus iirc) bounced off on second ride and lost forever. £3 got my a mount for my CAAD10 and just one set of batteries / charging to think about...

bikelightsuk (not verified) [368 posts] 6 years ago

I've been using this one for over 9 months now. Rear lights did extremely well during the rains. There's lifetime warranty by I think I'm never gonna need that! I just wish there were more
bike light accessories available for this one.  105

Shades [344 posts] 5 years ago

Having gone through a variety of rear lights over the years, this is definitely the best by far.