CrankPump - the invisible bike pump
CrankPump - the invisible bike pump
Crankpump is a CO2 pump that lives in the hollow axle of Shimano cranks. Slot it in and forget about it
Crankpump is a CO2 pump that lives in the hollow axle of Shimano cranks. Slot it in and forget about it Read more
About this project
What is CrankPump?
Most new bicycles have a hollow axle between the pedal cranks. That hollow space is the perfect size for a bike pump. CrankPump is a CO2 pump for Shimano Hollowtech cranks. Simply unscrew the existing plastic bolt, screw in CrankPump, and forget about it until you need it.
Bike pumps are annoying. They live on a bracket that hangs off your bike getting ugly, dirty and lost, or they live in your back pocket beating up your kidneys. Sometimes they live forgotten in your drawer at home or on the road where they fell off. The pump and other stuff needed to repair a tyre hangs off your bike, making it look ugly and un-aerodynamic. CrankPump is a simple way to keep all that stuff from ruining the clean lines of your bike.
How it works
Shimano Hollowtech cranks have a plastic bolt that covers a hollow axle. CrankPump is a CO2 pump that is a simple screw-in replacement for that plastic bolt. CrankPump lives in the axle, hidden out of the way until you need it.
Fixing a flat tyre
When your tyre is flat, remove CrankPump from your crank, and screw it onto your tyre valve - instant inflation. It works for road and mountain bike valves. CrankPump is simple and tough, with no moving parts.
CrankPump also has a pair of TyreZip levers that work in a patent-pending new way to “unzip” your tyre from the rim. It’s a similar method to how a mechanic removes a car tyre.
TyreZip works in three simple steps:
1) roll the TyreZip under the tyre bead
2) pull a section of tyre bead over the rim
3) slide along the rim to unzip the tyre.
The TyreZips clip onto CrankPump for easy storage. When the TyreZips are clipped together in a locking arrangement, they stop the CO2 canister screwing all the way in and touching the piercer.
What do I get?
You get the CrankPump CO2 pump axle bolt, removable with just your fingers. The alloy part is made using high-quality CNC machined anodised aluminium, and a tempered steel cartridge piercer. The plastic part that screws in, is fibre-reinforced nylon. You get two TyreZip levers that click onto CrankPump.
You don’t get a CO2 canister, because it is illegal send them air freight. You can pick up CO2 canisters easily from your local bike store - just make sure you ask for a 12g threaded canister (a 12g canister can inflate a road tyre to 90PSI / 6.2 bar).
CrankPump comes in a package that also doubles as a tool to remove your cranks' plastic axle bolt.
You also get an anti-vibration foam insert, that prevents the CO2 cylinder from rattling inside the axle.
and you get a washer that lets you set the axle tension using the standard Shimano bolt, and then remove it after clamping the crank arm pinch bolts.
The first version of CrankPump fits Shimano Hollowtech II cranksets that have steel axles. It fits most recent Dura Ace, Ultegra, XTR, XT Shimano cranks. To check whether it will definitely fit your model of cranks, take a look in the FAQ.
What we've done so far
CrankPump started as one of those “aha!” moments, noticing that the hollow axle was exactly the right shape and size for a CO2 canister to pop in. Maybe you've had a few of those “aha” moments before too, and then kicked yourself when a couple of years later you see someone else bring that brilliant idea to market. Well with your help, it won't be like that this time…
When you slip a CO2 cartridge into a hollow axle, it all seems so obvious and simple. Keeping it that simple has been a lot of work.
There have been may design challenges, like how to make sure it still performs the tensioning function of the original plastic bolt? How to stop the canister rattling in the axle? How do you make it easy to tighten and remove, so it never jams? How to make sure your hands don’t freeze? How to stop the cylinder piercing while you ride? Most of all, how to do all that within the tiny space of a hollow axle? You can find details on many of these challenges in the FAQ section at the bottom.
CrankPump has gone through dozens of prototypes, trying to figure out what works well and what is strong enough.
For functional prototypes, we were fortunate that there are many CO2 pumps already around, so the basic problems of providing CO2 from a canister to a tyre are well understood. The problems of packing all that in a 20mm diameter axle were not so easy, and it has taken two years to get CrankPump to the point where it’s ready.
What we need from Kickstarter
We've been building and testing CrankPump prototypes for two years. As you can see in the video, the prototypes are working well.
Now that the patents have been filed, our next step is to prepare tooling. CrankPump uses a fibre-reinforced nylon bolt, designed so it threads accurately into the axle. Producing the mouldings to cast plastics is expensive - many thousands of pounds. If you’re spending that sort of money, you’d like to make sure a few other people want to have a CrankPump.
We need your support and orders.
Timeline / When we will deliver
CrankPump has a simple timeline: There’s a short sample run that gets tested to iron out any kinks, then production.
We’ll give you give you a regular update at each stage, on the status of everything.
CrankPump isn't just a guy in a workshop in London - CrankPump is based at the Royal College of Art’s InnovationRCA business incubator. That means there has been some serious coaching that you don’t have to pay for, so your money will be spent on making CrankPump high quality.
CrankPump will be well made - it is designed by Damon Millar, an ex-Formula 1 engineer, avid cyclist and industrial designer from London's Royal College of Art, who has started a few successful companies, but prefers to be in the workshop.
Here's how you can get involved with CrankPump:
Risks and challenges
CrankPump has no moving parts, so the risks and challenges are pretty straightforward. But if you’re risking your money, you’ll want to know that all the challenges have been considered, so read on.
First, there’s a risk that CrankPump won’t be good to use. To mitigate that risk, we’ve taken expert advice, done lots of prototype testing, and have scheduled in another round of testing for a month with the samples, when they arrive. Any issues we see with the samples will be fixed before production tooling begins.
Then, there’s a risk that some part can’t be manufactured in the way we expect. To mitigate that risk, we’ve had manufacturers quote on detailed engineering drawings and CAD files. They are happy that the parts can be made.
Finally, there’s a risk that some part won’t be made well. To mitigate this risk, we’re paying more money to deal with high-end manufacturers, and we are only using manufacturers that people we know have previously made successful products with.
CrankPump has fitted every steel Shimano Hollowtech II axle we have tried, and Shimano's UK distributer has in stock.
Here is a list of what is known about compatibility:
Sora 3500 (uses same cap as another tested crank)
Sora 3550 TESTED
Tiagra 4600 TESTED
RS-500 500 TESTED
105 5700 TESTED
Ultegra 6600 not tested, but probably ok
Ultegra 6700 TESTED
Ultegra 6800 TESTED
DuraAce 7800 not tested, but probably ok
DuraAce 7900 not tested, but probably ok
DuraAce 9000 TESTED
Alfine s500 (Aluminium axle)
Sora 3450 (Aluminium axle)
Tiagra 4500 (Aluminium axle)
105 5600 (Aluminium axle)
Ultegra 6600 (Aluminium axle)
Deore M530 (uses same cap as another tested crank)
Deore M540 (uses same cap as another tested crank)
Deore M550 (uses same cap as another tested crank)
LX M580 (uses same cap as another tested crank)
LX M590 (uses same cap as another tested crank)
Deore M590 TESTED
Deore M615 TESTED
Zee M640 TESTED
SLX M660 (uses same cap as another tested crank)
SLX M670 (uses same cap as another tested crank)
XT M760 (uses same cap as another tested crank)
XT M770 (uses same cap as another tested crank)
XT M780 TESTED
Saint M800 probably OK
Saint M805 probably OK
Saint M810 (uses same cap as another tested crank)
Saint M815 (uses same cap as another tested crank)
Saint M820 TESTED
Saint M825 (uses same cap as another tested crank)
XTR M970 probably OK
XTR M980 (uses same cap as another tested crank)
LX M580 (Aluminium axle)
Hone M600 (Aluminium axle)
XTR M960 probably NOT okay
XTR M970 probably NOT okay
Bike mechanics and Shimano's UK distributors tell us that if your bike has steel Shimano Hollowtech II cranks, CrankPump will probably fit. Be warned though: if your Shimano cranks have an aluminium hollow axle, square-taper or Octolink axles, then CrankPump won’t fit.
The 12g canister will inflate most bike tyres enough to get you home:
23mm road bike tyre: 90PSI / 6.2bar
28mm touring bike tyre: 60PSI / 4.1bar
26 inch by 2 inch mountain bike tyre: 30PSI / 2.1bar
CO2 cannisters aren't allowed to be shipped by mail. We could ship them by courier, but that would double the price, and do you really want to pay all that shipping money when your local bike store probably has CO2 canisters for a pound/dollar/euro?
That thing on the end of CrankPump's packaging is a tool for removing the Shimano crank tension bolt. CrankPump comes with instructions, but they are pretty simple:
- loosen off the crank arm pinch bolts with a 5mm allen key (every bike tool has one)
- unscrew Shimano's plastic bolt, put the supplied washer on and tension it as normal
- tighten up the pinch bolts, to clamp the tension
- unscrew Shimano's plastic bolt and screw in CrankPump into the axle, Job done.
Shimano's plastic bolt is there to preload the the axle, so your axle doesn't slide side-to-side. CrankPump is made of the same glass fibre reinforced Nylon material as Shinmano's preload bolt. Shimano recommends the preload bolt is tightened to between 0.7 to 1 NM. Once the pinch bolts have been tightened, the axle tension is firmly clamped, and you can remove the Shimano preload bolt (CrankPump includes a washer to make it easy to remove). You can screw in and remove CrankPump (by hand) when you need to fix a flat tyre. To ensure CrankPump can be removed without loosening the pinch bolts, its flange is a slightly smaller diameter than the original preload bolt, so CrankPump doesn't get clamped in place.
No. CrankPump is an independently made product, not related to Shimano. The terms “Shimano” and “Hollowtech” are trademarks of Shimano, so when we use them here, we are referring to products that Shimano makes.
We made CrankPump for Shimano cranks because they are so popular (Shimano makes great cranks). Shimano has more than half of the crank market, so it makes sense to go there first. If the Shimano version sells well, it would be great to make a version of CrankPump that fits other hollow cranks, like FSA and SRAM.
No. CrankPump includes a small cylinder of foam, that you drop into your axle the first time you install CrankPump. This foam supports the end of the canister, and prevents it from rattling.
If you have road cranks, the drive-side end of the axle is closed, so the foam stays in the axle when you remove CrankPump, and you’ll not have to think about it again. If you have mountain-bike cranks, Shimano leaves the drive-side end of the axle open, so you need to give the foam cylinder a push every time you remove CrankPump, to secure it.
CrankPump lives in the exact middle of your cranks, so it makes negligible difference to your cranks inertia. Inertia is a product of mass * distance from the axis of rotation, so things that are in the middle the axle have a tiny effect on inertia.
CrankPump also improves the total weight of bike + rider: it weighs a bit less than most other CO2 pumps, because it doesn't use a flow-control lever.
CO2 cannisters get cold when they empty themselves into a tyre. After a few seconds, the cannister will end up with a thin covering of ice. All CO2 pumps do this, and it takes about 10 seconds for the cylinder to become freezing cold, after the cannister is pierced. Just let go of the cylinder as soon as you see your tire start to inflate, and you will be fine.
We recommend you wear your cycle gloves while piercing a canister, in case it gets cold quicker than you realise.
CrankPump has a plastic collar, so you don't need to touch the cannister to remove it once your tyre is full. By holding the plastic part, it is easy to unscrew CrankPump from your tyre, and screw it back into your cranks without touching the canister.
If you normally carry a CO2 pump in your back pocket, then it’s nice not to have it beating up your kidneys when you go over a bump, or in your laundry basket beating up your washing machine when it should be on the road with you.
If you normally carry a CO2 pump in your saddle-bag, then it’s nice to be able to use a smaller saddle bag (or even go “commando” and carry no saddle bag for short rides).
And why not? If you are going to carry a CO2 pump anyway, it’s pretty cool to have one you never need to think about.
For a slow leak, a shot of CO2 might get you home. Most often though, you’re going to need a spare inner tube. Many people jam a spare tube under their seat, or even shove it down their seat tube.
Not really. Unscrewing CrankPump takes about 10 seconds, and it’s priced about the same as most other CO2 pumps.
Yes, anyone can use CrankPump. The only tool you'll need to install it is a 5mm allen key, which every bike tool has.
Yes, Shimano's road and mountain bike Hollowtech 2 cranksets use the same thread on their plastic bolts, so Crankpump fits both. CrankPump is compatible with Presta (road) and Schreader (mountain bike) valves. No need to change anything to fit.
12g threaded cannisters. That's the biggest CO2 canister that will fit into the axle. It’s a common CO2 canister size, that many pumps use, so it shouldn’t be hard to find. It’s worth noting that the most popular size canisters are 14g, which are too big to fit in the axle. A 12g cannister is enough to completely inflate a 23mm road tyre, and partially inflate every other tyre enough to get you home.
CrankPump will be available in only red colour at first, because with injection moulding each colour is a new run, and we need a minimum order quantity to get a decent price. As you can tell from the images, we’ve made prototypes in red and yellow. We chose red for the first production run, to match the CrankPump logo, and because it looks nice.
The “Test Pilot” edition of CrankPump will be purple.
The outer part of CrankPump is made from glass fibre reinforced nylon, the same material that Shimano make their tension bolt from. This ensures it is tough enough not to break, accurate enough to thread easily, and insulative enough that your fingers don’t get cold when you unscrew it after inflating your tyre
The inner part of CrankPump is made from CNC-machined, anodised alloy, to keep it strong enough to withstand the CO2 pressure, durable enough to use many hundred times, and light.
The piercer that punctures the CO2 canister is made from hardened, tempered steel. Hardening makes the steel tip hard enough to pierce canisters without becoming blunt, and tempering makes it tough enough that it won’t crack.
Using up a CO2 cartridge creates waste, which sucks. Calling someone to pick you up because you forgot to bring a pump creates more waste and sucks more. CO2 cannisters are recyclable steel, and CrankPump lets you stow the canister cold, making it easy to take your empties home for recycling. CrankPump is an emergency tool, so you're not going to use it often. Overall the waste is minimal - the waste in the few canisters you will use is probably only a little bit more than the waste in making a bike pump.
Producing CO2 can also make waste. A 12 gram CO2 cylinder has about the same amount of CO2 found in a one liter bottle of soda. Good CO2 canister manufacturers advertise that their CO2 doesn’t come from the burning of fossil fuels, but instead reuses the by-product of factories whose CO2 would otherwise have been exhausted into the atmosphere.
CrankPump is rated to last many more inflations than you are likely to have punctures. There are no moving parts, so there's not much to wear out. The threads and piercer are rated to hundreds of cycles. Maybe in 10 years time you might want to change the O-rings (which are standard sizes)
Normal tyre levers must be strong and have long levers because they use your strength to stretch the tyre over the rim. If you've ever seen a car tyre being removed, you know that you don't have to do it that way - they use a shaped tool like a zipper, to "unzip" the tyre bead from the rim.
In a similar way, CrankPump has a patent pending new way to get a tyre off the rim, called a "TyreZip". TyreZip is smaller and faster than traditional tyre levers. Rather than poking levers under the tyre and working your way around in steps, the TyreZip unzips your tyre from the rim in one continuous motion, to peel the tyre off it.
You can also use TyreZips to mount the tyre back on the rim.
TyreZip is simple, but there is a knack to it. You might want to practice it at home. We’ll give you some instructions with your CrankPump.
“xpyknn” by DRIV3. Check it out on
If the design is improved or changed as a result of the test phase, will the Test Pilots have replacement purple final versions sent out?
It's only fair that if anything significant changes for the production version, our Test Pilots will also be sent the production version.
It's possible that if we send you an extra production version might not be purple - the production run is red and it's really expensive to change colour in plastic casting. We will see what can be done, and keep you posted. If we have to give you a red one, we'll refund you the £35 extra you paid to be a Test Pilot.
Yes, you only pay for international postage once, even if you buy more than one CrankPump. If you are an international buyer who buys two CrankPumps, you would just increase your pledge to £40 and send us a message that you wanted more than one CrankPump.
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