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The Bontrager MIK Utility Trunk Bag is a tidy way of carrying gear and knick-knacks and keeping them all organised and able to be quickly popped on and off your bike.
If you're an organised type, Bontrager has you covered with the MIK Utility Trunk Bag. It has the obvious large main compartment, plus four side pockets (each side has an expandable large pocket with a smaller flat pocket outboard of it). On top there's a soft-lined pocket for your sunglasses and an elastic cord for a jacket, plus there's a mesh pocket inside the lid.
Mounting the MIK Utility Trunk Bag to a compatible rack is a doddle: you just slide the bag into place on a MIK-compatible rack until it clicks. To release it, you use the included MIK stick to push the latch open. You don't even need the stick; you can just reach under the bag and push the catch open.
Pull the bag off the bike and there's a built-in handle to carry it around, and Bontrager throws in a shoulder strap that clips into D-rings on the bag for a comfier, hands-free carry.
Once the MIK Utility Trunk Bag is in place, it's not going anywhere. The mechanism's grip on the rack is tenacious and the bag is very stable as a result.
The Bontrager MIK Utility Trunk Bag swallows a lot of stuff for its nominal 13-litre capacity. Jackets, spares, food, other clothing and more all vanished into its TARDIS-like interior. It helps that the large side pockets are very flexible so can really be crammed with extra stuff if necessary.
It's also fairly water-resistant, though in theory water could get in from underneath through the holes in the base where the attachment hardware fits. Unlike its stablemate the MIK Commuter Boot Bag, it doesn't have an internal waterproof liner, so if keeping your kit dry is your absolute priority, that's the bag to go for. If it's tipping down there's a waterproof rain cover tucked into a front pocket.
Perhaps the MIK Utility Trunk Bag's biggest disadvantage is that there isn't quite enough room inside it for a large U-lock. If you want to carry, say, a 30cm Abus Granit XPlus you'll have to take the lock housing off the shackle. This is irritating because if the main compartment were just a little bit bigger the lock would pop straight in.
Over time the Trunk Bag's side pockets have gotten a bit saggy. It doesn't affect the use at all, especially if you stuff it with clothes or whatever so the shape is supported, it just looks a bit off.
Let's take a broader look at the MIK attachment system here. It isn't proprietary to Bontrager but was developed by Netherlands bike luggage company Basil and Taiwanese accessory maker Massload as a quick and easy-to-use method of mounting bags, baskets and crates on top of a rack. Very much a niche application but one that previously involved tedious faffing with Velcro straps; MIK (it stands for Mounting Is Key) is a definite improvement.
The danger with a system like this is that the manufacturer will stop making it and you'll be left with a bag you can't replace. Basil has been using MIK for several years now so it seems likely to stick around.
If you already have a rack that's not MIK-compatible, you can get a MIK Carrier Plate for £17. Note that this is NOT the same as the MIK Adapter Plate which you use to convert an existing bag, basket, crate or box to the MIK system.
Bontrager says that the MIK system 'locks your bags to your rack to prevent theft'. Yeah... no. It's so trivially easy to release a MIK bag from the rack even without the MIK stick that this claim is just silly. In fact on its page for the MIK stick, Basil says: 'The MIK stick ... does not protect the accessories against theft.'
In fact, rather than carry the MIK stick around separately or leave it in place and risk it falling out, I tightened the 3mm hex key grub screw in the latch to mount the stick permanently in place.
With a MIK bag in place on a standard MIK rack like the Bontrager BackRack MIK, you can't really use your rack's top bars to carry a pannier. Bontrager makes a rack – the BackRack Deluxe MIK – with an extra bar to hook your panniers on, so if you're going to start with the MIK system, buy that one. Alternatively, with a non-MIK rack and the MIK Carrier Plate you can fit MIK Pannier Bag Tubes to take panniers.
I like the MIK system as a way of quickly fitting and removing a top bag, but it's a pity Basil and Massload didn't think a bit more about making it a complete system to accommodate panniers as efficiently as it accommodates a top bag.
There are several click-on-to-rack systems vying for your top-bag money. Topeak's long-established MTX system offers the MTX TrunkBag DX, which is very good and quite a bit cheaper than the Bontrager bag. The Racktime system from Germany also includes top-bags for less money than this one, and Basil offers the Trunk Bag MIK for £91, though you can get it for £68.
This is a very good bag for cyclists who need to carry a moderate amount of stuff and want to be able to quickly and easily fit and detach a bag from the bike. That's a pretty big range of use cases: commuter and other utility cyclists, countryside explorers, touring-style day trippers, and audax riders.
Overall, if you're willing to commit to the MIK system, this is a very handy bag that'll swallow everything you need for a day ride, and can be removed and fitted easily and quickly.
Excellent rack-top bag for the MIK click-on mounting system
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road.cc test report
Make and model: Bontrager MIK Utility Trunk Bag
Size tested: One size: 800 cu in (13L)
Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
A bag for riders who want to carry a moderate amount of stuff on top of a rack in a very convenient and stable system.
Make errands more fun
The MIK Utility Trunk Bag offers simple and secure on-bike storage that's easy to install and remove without the need for tools. It has multiple pockets to keep you organised, a durable design with reflective materials and built-in rain cover to keep you and your gear safe and secure in all conditions.
MIK mounting system provides secure, integrated mounting with compatible racks
Front and rear black reflective materials enhance visibility with a stylish finish
Stay organised with internal mesh pocket and two side pockets, each with a smaller internal pocket
Zipped pocket with soft lining provides secure phone storage accessible from top of bag
Be ready for weather with an integrated rain bag securely stowed in rear pocket
Light loop for easy rear light mounting
Adjustable carrying strap for convenient off-bike use
Function, performance and style
Bontrager City Utility bags, Bontrager City Shopping Boot bags and Bontrager Panniers turn any bike into a stylish utility ride. High-end fabrics and thoughtful finishing materials deliver the perfect balance of great looks and great function.
MIK: Mounting is Key
MIK racks and bags feature a keyed install system that secures your bags to your rack but still makes it easy to remove them when you need to.
How MIK works
Slide the MIK bag onto the MIK rack. Once you hear a click, the installation is complete. If you want to remove the bag, simply insert the key and press. Once pressed the bag can be removed.
Our bags and racks are designed as one complete system that's easy to install and remove and made keep to your precious cargo safe.
Integrated light mounting
You'll find a dedicated spot to mount your light on racks and bags for better all-hours visibility.
Tell us some more about the technical aspects of the product?
The specs are:
Cargo capacity: 800 cu in (13 l)
Bag type: Trunk Bags
Dimensions: 35cm (l) x 20cm (w) x 20cm (h)
Fibre content: 35% Poly 600 PU Coating / 30% Poly 840 PU Coating / 15% 3M Silver Reflective Mesh / 11% Nylon Mesh / 9% Poly Super Nylex Mesh
Weight: 860g claimed
Tidy, fine stitching all round.
Plenty of space, very stable and generally easy to use.
After a year of weekly use it's still looking, great though the side pockets have sagged a little.
A recent price rise from £80 to £115 has left it looking very expensive compared with similar bags like the Topeak MTX TrunkBag DX or bags for the Racktime SnapIt 2.0 system.
Tell us how the product performed overall when used for its designed purpose
Tell us what you particularly liked about the product
Ease of fitting and removal, attention to detail, organisation.
Tell us what you particularly disliked about the product
Its appearance is a bit dull; a splash of colour wouldn't go amiss!
How does the price compare to that of similar products in the market, including ones recently tested on road.cc?
It's expensive compared with other system bags like the Topeak MTX TrunkBag DX, which is nominally £89.99 but you can find for £70-£80, or Racktime top bags at similar prices to the Topeak.
Did you enjoy using the product? Yes
Would you consider buying the product? Probably not, but only because it doesn't quite fit any of my use cases.
Would you recommend the product to a friend? Yes
Use this box to explain your overall score
This is a really good, stable and well-thought-out bag but the price is a bit ouchy compared with its rivals.
About the tester
I usually ride: Scapin Style My best bike is:
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, mtb,
John has been writing about bikes and cycling for over 30 years since discovering that people were mug enough to pay him for it rather than expecting him to do an honest day's work.
He was heavily involved in the mountain bike boom of the late 1980s as a racer, team manager and race promoter, and that led to writing for Mountain Biking UK magazine shortly after its inception. He got the gig by phoning up the editor and telling him the magazine was rubbish and he could do better. Rather than telling him to get lost, MBUK editor Tym Manley called John’s bluff and the rest is history.
Since then he has worked on MTB Pro magazine and was editor of Maximum Mountain Bike and Australian Mountain Bike magazines, before switching to the web in 2000 to work for CyclingNews.com. Along with road.cc founder Tony Farrelly, John was on the launch team for BikeRadar.com and subsequently became editor in chief of Future Publishing’s group of cycling magazines and websites, including Cycling Plus, MBUK, What Mountain Bike and Procycling.
John has also written for Cyclist magazine, edited the BikeMagic website and was founding editor of TotalWomensCycling.com before handing over to someone far more representative of the site's main audience.
He joined road.cc in 2013. He lives in Cambridge where the lack of hills is more than made up for by the headwinds.