What's Cool In Road Cycling

Silca’s Eolo III Co2 Head: Instant Classic

Silca have been the benchmark inflation company for decades. Starting in 1917, they’ve made pumps and tools that have been in use for what seems to be the entire time… How many companies in cycling have been around long enough that you don’t remember “back when they started”? PEZ recently checked out their latest instant classic – the Eolo III Co2 Inflation Head.

Cycling product seems to have abandoned its classic roots to a large degree, while companies younger than several pairs of my socks are popping up with marketing guys looking for an old-school façade.

We all love the old school black and white pictures of our tire wearing, soiled and beaten heroes of the past and we’re all kinda sick of brand new companies using grainy black and white images of faux-euro hard men donning manicured-mud faces to hock overpriced kit made in China. It seems as if there’s been a mass manufacturing migration to the Far East, so it raises an eyebrow when a company nearly twice as old as classic brands like Colnago and Pinarello decides to go west.

Silca have designed, sourced materials and manufactured their latest CO2 inflation head, the Eolo III, from their new home in Indianapolis.


There’s no shortage of skilled labor in a place with a nickname like “The Racing Capitol of the World” and when the guy designing the products is the former head of Zipp’s Product development, there are also no shortages of raw materials and machining expertise to be found.

It seems like a tradition at Silca to build things that will be the last (…insert product name…) you’ll ever need to buy, the skill set and materials were simply not going to the lowest manufacturing bidder.

The main component pieces are the spool and body…


The Eolo III unit is machined from 6013 Aluminum sourced at Alcoa’s Lafayette Indiana location. Silca sourced 6013 because it has the strength / toughness of 2024 Alu but with far better corrosion resistance. It also makes for a better looking and more durable part by having a better response to anodizing.

It’s delivered in 12 foot long precision ground bars and the entire bar can be spun by a very cool and very high end machining mech, the Citizen Cincom L20x…

You can see it in operation here…


This machine is used because it allows for extremely high tolerance machining and it also allows for multiple steps to be performed that might otherwise be skipped due to cost. An example would be the extremely small o.5mm gas hole in the spool bore…


This hole sits in a channel and both the hole and the channel are designed to be small so that you have more air flow control (and so that temperature is better regulated because the gas can’t expand as much while still inside your inflator head).

There is an equally impressively teeny hole in the body unit that lets gas escape into the spool…


One of the tricks here is punching these holes and then going back through and cleaning the entry and exit of the holes punched (as well as the hole itself) so that the channel on the spool as well as the bores (the main tube sections that accept the gas cylinder and your inner tube valve) on both the spool and body are smooth and the hole is not blocked at all by material remaining after the initial hole punch.

Cheaper inflator units don’t typically have pathways this small and/ or don’t bother refinishing all of the surfaces, but then most of the cheaper units are not made from materials that will live as long as this unit will, so things like finish quality and tolerance don’t matter as much for the lesser blowers.

The spring is also exceptional material made with exceptional detail…


This is US wound stainless steel made by a spring maker that dates back before WWII where this same company made the springs for the Norden Bomb site (look it up, it’s kinda cool).


The springs have a flat wound end and are then precision ground so that they sit as evenly as possible within the unit much like better auto springs are manufactured. It’s for a similar reason as well. These steps make for a more consistent performing spring as well as extending the life of the spring.

The other Stainless part for the Eolo is the puncture pin.


Loads of manufacturers use a very crude spear that sits next to a hole in their spool. They puncture the cylinder seal and the gas has to escape past the torn seal into the hole next to it in order to get through the inflator head. While this method works, it means there is generally a lot more room for the gas to expand while still in the head, the hole gets clogged and corrosion will start to break down the entire area.

The Eolo machines a direct punch and hole in one that allows the gas to pass directly through a small hole without much room for expansion.

The material used for the puncture is 17-4 stainless PH (precipitation hardened) to ~50Rockwell C. That makes the part completely corrosion resistant and VERY hard. Hard enough that this unit will puncture cylinders in the thousands before it starts to lose its edge and will function for thousands more after that.

And after all of that, we get to a part that Silca very simply obsessed over because it may be the most important part for the unit…

The O rings.


Now most of us would just think “rubber”… Most manufacturers use a much cheaper option than Silca.
– The reddish ring is simple silicone. It’s inexpensive and is fairly good at handling temperature swings like going from a hot saddle bag to a freezing blast of CO2. But it’s just not tough enough to handle lots of rough threads.
– The light milky colored but cloudier ring is injection molded urethane. It also handles temp swings but it’s a very simple type of urethane that works well in injection, is still very inexpensive and while a bit more durable than silicone, it’s still not good enough for Silca.
– The clearest O ring is a special type of urethane that is vacuum cast.

That’s what Silca are using inside the Eolo because it handles temps well beyond what the unit will be required to do and it’s multiple times the durability of the others.

These will live through loads of use and held a Co2 charge for me for a week.

Silca actually used the other types for prototypes and very simply were not satisfied with the results after tearing down the units. They decided to hunt around in the tech world and found a US manufacturer that would make these to spec. And, like the rest of the parts, these are no place near relatively inexpensive… They’re multiple times the cost of the other two ring types used in what I previously considered to be the best Inflators on the market.

Of course there are a few other O rings in use, but these are a bit less critical in function.


These are simply insulators that allow you to have a bit better grip on the head unit as it gets cold very quickly in use… The colors are just for fun, but they function all the same and make for personalizing your air rig.

And last but not least are Silca’s Air Cylinders.

Note Silca have changed the decal graphics which are now a nice grey/black/red

With zero prompting from Silca and having never read anything from them before using the first proto units, I noted these cylinders were a bit different.

Beyond that they have what I like to call a “Pro Fillactic” top that keeps the threads from wearing a hole in the spare inner tube (or anything else in your flat kit) while making sure nothing pierces the seal (which I have done while riding, causing me to nearly shit my pants), the cylinders just have more air.

While I hate overly general descriptions like “more”, it’s pretty much what my zero-budget-having-ass is stuck with. But here’s what I can tell you.

The first time I used one of these, I thought I was going to blow the tire off the rim. When Silca first had a prototype, it was a little to snug and sticky in the mechanism. Add that to an incredibly leak free seal and that I wasn’t pulling back on the air chuck and I’m VERY lucky I didn’t blow my rim.

I immediately let the air out of the tire in panic when what I should have done was grab a gauge, so I have no idea what the PSI was, but I can tell you that tire and rim beads should not make a creaking noise. [Silca have completely remedied the operating action by the way and there is little risk of a repeat unless you’re too stupid to use an Air Chuck in the first place.]

After calling to see what the hell kind of cylinder this was and or if it was poorly labeled or over-pressurized and learning that they were basically normal tanks, I did a little test.

– I grabbed a new Silca cylinder and used it with the Eolo on a 28 section tire and it filled it to 105 PSI. I did the same with a very popular (probably the most popular) brand cylinder and wound up with 90.

– Then I grabbed another brand of air chuck and attached a generic cylinder and got 85. A second generic with the other brand chuck got me 82. I also noted that I also felt a bit of leaking around the seal of what I always felt was a well-sealed unit.

– I tried the Eolo and another generic cylinder and got 88 psi.

– I finished by using the Eolo and another Silca Cylinder on the same 28 section tire and I wound up with 106.

Given Silca’s cylinders seem to be some place near the actual 16 grams on the label (while others seem to be in the 13-14 range) I wondered if they might make a 12 for folks using 23 section tires as a true 12 would do the job. But they’re going to stick with 16 though because it’s the market standard now.

I guess in the end, we all benefitted from shitty 12 gram cartridges not properly filling 23 section tires because now the industry is at 16 grams plus as a standard and that sits well with the trend to larger rubber.

This Eolo III is easily the best inflator head I’ve used to date.

When Silca sent me the first Proto, it sealed better than anything else I had used, but there was a little stickiness to the action. They went back to the drawing board, upgraded the sealing rings and made a small change to the machining to free up the action (when I say a “small change”, I mean that a basic hand caliper shows almost no change at all, a testament to the tolerances of their fabrication).

The production model landed with the changes made and it was/is fantastic.

Using the Eolo is very simple. You screw the Co2 Cylinder into the head unit and then either screw the head onto your valve and/or press it on a threadless valve extension.

Then you push it toward the valve to release the gas.

The differences to the other head units are easily notable as there are no air leaking / hissing sounds when you mount the cylinder and or attach it to your bike. There are also no leaks or blasts of cold air from the Eolo as you fill the tire (other than the air going into the inner tube itself).

With most inflators you have this kind of quick and panicky “PRESS-AND-PRAY” action where you put a giant blast of air in as fast as possible because the inflator head is leaking and the seal isn’t great. You have to hope you get the pressure right with a lot of inflators because there is very little modulation and if you pull off too soon, you lose the rest of the charge.

With the Eolo, you can put in a quick blast if you like, but it’s a smooth action and you can modulate the flow enough that you can put in air, let go of the inflator and use your hands to check the pressure. If you need a bit more, push lightly and let a little more air in until the feel is right.

It’s a calm situation compared to a lot of other inflators.

And if you’re running 23-25 section tires, the Eolo will hold the remaining gas for a while to allow for a freshen up blast later in the ride as compressed CO2 will make for a pressure drop after a bit more riding.

Silca’s goal is pretty simple
They want to make products that work very well and build them from materials that last for a very long time with solid base construction and materials and replaceable wear items. Putting that though to practice is the reason you see Silca pumps still in use (and working very well) after decades of regular action.

The goal didn’t change with the Eolo III and you can see and feel and hear the difference in use. This may be a simple part but it’s made fanatically well.

The SRP for the inflator head and 2 Cylinders is $46. A pair of replacement Co2 Cylinders will cost $11. While that may not be cheap, it’s a fraction of the cost of the dozen or so (functionally shitty) inflator heads I’ve thrown away over the past several years. And at the end of the day, it isn’t a lot of scratch for anything considered “high end / top line” when it comes to bike kit round here.


You can see the expanding product line from Silca at : SILCA.CC

You can pick them up at several retailers and they’re distributing to bike shops now.

Have Fun,
Charles Manantan
[email protected]

Note: if you have other experiences with gear, or something to add, drop us a line. We don’t claim to know everything (we just imply it at times). Give us a pat on the back if you like the review, or a slap in the head if you feel the need!

PezCycling News and the author ask that you contact the manufacturers before using any products you see here. Only the manufacturer can provide accurate and complete information on proper / safe use, handling, maintenance and or installation of products as well as any conditional information or product limitations.

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