Tubeless Made Easy: Milkit System Review 5

Tubeless technologies have gotten much better over the years, but things can still get a bit messy from time to time when it comes to seating tires and manipulating sealants. Swiss company Milkit is on a mission to improve your tubeless life, and they’ve developed a whole system that makes adding, monitoring and replacing your sealant more convenient. They also have an excellent rim tape and a tubeless booster to make sure you can always get your tires seated. We’ve been using it all for a few months now, keep reading to find out how we’ve been getting along!

Company Background

The founders of Milkit, a couple of product developers and bike nerds working for a company doing development work for Scott and BMC in Switzerland, first stated thinking about how to make tubeless life better in 2013, when they ran into issue with their sealant during a bike trip to Moab. In 2014 they quit their jobs and started working on their idea in earnest. This led to the founding of Milkit in 2015, when they also undertook their first financing round to fund the tooling needed for the first products. In 2016 they were on the market with a sealant, with slow initial growth for the first couple of years. In 2019, the growth rate increased, and the launch of additional products set Milkit down the path of becoming “the tubeless company” as opposed to just “the sealant company”. The COVID bike boom proved highly beneficial for Milkit as well, with sales doubling each year over the past two years and a new, 1.5M Swiss Franc funding round secured to fuel further growth.

Milkit manufactures its products in Germany, although some components originate elsewhere in Europe – this has helped with keeping lead times under control during these times of industry-wide manufacturing delays, most notably in Asia. The main warehouse is in Europe, but the company has now opened a US warehouse too. Amazon and ShipBob are used to fulfil direct US orders, making for a much more convenient shopping experience stateside. A growing network of distributors and dealers ensures availability in many countries around the world now as well, and OE deals with Propain and Newmen as well as talks with other bike and component brands could lead to Milkit products popping up on more and more whole bike builds in the future. 

Initial Impressions

The heart of the Milkit system is the valve stem. By adding a set of rubber flaps to the tire side of the stem, Milkit has created a valve from which the core can be removed without causing the tire to lose any pressure. The flaps also prevent the tire sealant from reaching the valve core, which should help minimize the risk of clogged valves. This also means that the Presta valve core needs to be fitted with a small extra plunger of its own to help push open the flaps of the stem for deflating the tire.

To fill sealant via this special valve, you need a syringe and a small straw to push past the internal valve flaps. The Milkit syringe is equipped with a shut-off valve, which helps control the pressure in the system once the straw is pushed into the valve. There is also a backstop in the syringe itself, to prevent the plunger flying out and you getting covered in tubeless goo once the syringe is pressurized. This was actually an issue on previous iterations of the Milkit product, so we’re glad to see they’ve addressed it here.

Converting your tires to tubeless usually starts with the rim tape. Milkit tested a lot of different options before they settled on the final version – a strong tape that is just flexible enough to conform to the rim tape. To carry out the testing, the company developed a machine to test rim tape inhouse. The machine simulates a rim hole and applies increasing air pressure to the tape up to the point of failure. Milkit found a big variance in the strengths of different tapes available on the market. They also developed a pressure-sensitive glue that is particularly well suited to this application. 

One of the challenges of going tubeless is being able to seat a tire on a rim – a floor pump is often enough but will not deal with 100% of tire/rim combinations out there. Older and/or worn tires may also present an additional challenge. If you have access to a compressor this is never an issue, but many weekend warriors or even home mechanics do not. To provide a simple and in-expensive option, Milkit developed the Booster. It consists of a compact bottle equipped with a special two-way valve that can be pumped up to 160 psi of pressure using a regular floor pump. You then press the special nozzle of the Booster onto your valve stem to release a powerful surge of air that will seat the tire on the rim instantly. This idea is far from new, but Milkit has their own take on the concept: the Booster provides a very strong and fast surge to get that initial tire “pop” – oh and the bottle is sold with a regular cap as well, making it suitable to use for carrying drinking water when you don’t need it to seat your tires (the internal surface of the bottle features a food-grade coating).

To conclude this initial overview section, let’s take a look at the Milkit sealant. Based on a mix of synthetic latex and microfibers, it was designed specifically to stay homogenous and fresh for a long time (it will last for at least 5 years in the bottle, says the company). Aside from the economical and green aspect of not having to discard product too often, this also translates to the sealant staying functional in your tires for longer. The synthetic latex means there is no need for ammonia or other aggressive chemicals, and the water-based formula makes it easy to wash off as well. The company claims it coats the inside of the tire more evenly and that it will seal holes “up to 6 millimeters in diameter” – in temperatures ranging from -20° to +50° C (-4° – 122° F).

Milkit Tubeless System In Use

Taping up a pair of wheels using the Milkit rim tape was easy and straightforward. The tape is not super flexible, so it’s a little bit more difficult to apply than some others, but the glue is strong and we achieved a good seal on our first try with just one layer of tape. The same tape has been on the wheel for more than 6 months now, and has survived multiple tire changes without any issues.

Seating a tire and filling up the sealant is where the real fun of tubeless begins. With Milkit, the experience is a lot less messy than with a more traditional approach. Thanks to the Milkit valve stem and Booster bottle, you can mount and seat the tire without having to worry about adding the sealant. Pump up the Booster to 160 psi using your floor pump, then place the bottle’s nozzle over the valve stem and press down – this releases a strong surge of air into the tire which sees it pop up instantly on the rim. See it in action here:

The Booster bottle is quite compact and contains less air volume than some competitors. However, it delivers very high air flow when you activate it which ensures that the tire will seat instantly. The resulting tire air pressure after emptying the bottled air is about 15-20 psi, so you’ll need to use the floor pump afterwards to really seat the tire on the rim, but the hard part will have been done by then already (note that you need to remove the valve core before using the Booster bottle to achieve good enough air flow to push the tire onto the rim).

With the tire properly seated on the rim, drop the tire pressure to about 20 psi, and then remove the valve core again if you had previously put it back (remember, the tire will still stay inflated thanks to the special stem flaps). Now use the Milkit syringe to add the sealant. Close the valve on the syringe prior to pushing the straw through the valve stem, to help manage the sudden pressure build-up in the syringe (the backstop in the syringe body is effective in case you forget to close the valve – we tested at 30 psi tire pressure and the plunger stayed in the syringe). Replace the valve core, pump up the tire to the desired pressure, and you’re done.

Another somewhat tricky aspect of a tubeless set-up is the ability to manage your sealant over time. Thanks to the Milkit valve and syringe, it’s possible to check the state of your sealant at regular intervals, to understand if you need to add or replace your sealant altogether. To do this, simply remove the valve core, push the straw through the valve stem and all the way to the bottom of the tire, then open the valve on the syringe to allow the tire pressure to push the sealant remaining in the tire out into the syringe. This will give you the opportunity to see what state the sealant is in, and how much of it is actually left in the tire. You can now re-inject or discard the old sealant, and top up as needed. All this without having to un-seat your tire from the rim bead. It's easy to do, and it's pretty cool!

A final word on the Milkit tubeless sealant itself: it works really well, we had great results sealing off different tires while testing in very thorny areas. The sealant does work on bigger cuts as well, although we found we’d have to resort to the usual tubeless repair “worms” when dealing with rim-induced cuts (to be fair, we’ve yet to find a sealant that is actually able to deal with these – probably not going to ever happen if you take into account the high pressure and the size and location of these types of cuts). The sealant stays stay fresh and homogenous for a long time, even at higher temperatures. You don’t even need to shake the bottle before serving up a fresh dose.

Things That Could Be Improved

The system works very well on the whole. One thing we noted is that the valve stem reduces the airflow when using a regular pump quite a lot, slightly annoying when topping up air using a pocket pump on the trail for example. We also think the filling valve on the Booster bottle needs to be redesigned – it’s too conical and lacks any kind of grooves or threads for the floor pump nozzle to latch onto – ours would fly off at around 100 psi unless we held it in place with a counter-force of some kind. Another potential drawback of the concept in general is that you end up somewhat “locked in”, meaning that you always need access to the Milkit syringe (or something equivalent) to add sealant. This could turn into an issue if you visit a new riding destination and you forgot your syringe, for example – although we are kinda splitting hairs now to be fair. Worst case you can always unseat the tire and add sealant the old fashioned way.

What’s the Bottom Line?

All in all, the Milkit system does a really good job. From the rim tape to the sealant, all the products in the range are of high quality and they function as intended. The sealant in particular is one of the better ones we’ve tested. We don’t find it very hard to run tubeless the traditional way, but there are undeniable advantages to the Milkit approach, in particular when it comes to managing your sealant. Being able to measure and top up or replace your sealant over time without having to lose tire pressure and re-seat the tire bead each time is pretty cool, and something like the Booster bottle should have its place in every home mechanic’s and weekend warrior’s tool collection.

For more information, head on over to milkit.bike.

About The Reviewer

Johan Hjord - Age: 49 // Years Riding MTB: 17 // Weight: 190-pounds (87-kg) // Height: 6'0" (1.84m)

Johan loves bikes, which strangely doesn’t make him any better at riding them. After many years spent practicing falling off cliffs with his snowboard, he took up mountain biking in 2005. Ever since, he’s mostly been riding bikes with too much suspension travel to cover up his many flaws as a rider. His 200-pound body weight coupled with unique skill for poor line choice and clumsy landings make him an expert on durability - if parts survive Johan, they’re pretty much okay for anybody. Johan rides flat pedals with a riding style that he describes as "none" (when in actuality he rips!). Having found most trail features to be not to his liking, Johan uses much of his spare time building his own. Johan’s other accomplishments include surviving this far and helping keep the Vital Media Machine’s stoke dial firmly on 11.

Photos by Johan Hjord