Spotted: EXT's New Air Shock
Earlier this year, keen-eyed Pinkbike users spotted an image of an air shock in the background of EXT's corporate video. Now, that shock has made it from the computer screen out into the real world, as the above photo illustrates.
Does that mean there's a review coming tomorrow? Not this time - according to EXT the official release dated is still over six months away. They had hoped to have the shock available by July/August, but the same supply chain and manufacturing delays that are affecting nearly every company in the bike industry caused that to be pushed back to October.
As for the details of the shock itself, it's based on the e-Storia/Arma MX hydraulic damper design, and has two positive air chambers, similar to what's found on the Era fork. The pressure in one chamber affects the beginning portion of the shock's stroke, and the pressure in the second chamber will handle the mid-stroke support and bottom out resistance, which should eliminate the need for volume spacers.
EXT's coil shocks are well-known for their level of adjustability, and the new air shock looks like it will be continuing the trend. The air valves for the positive chambers are visible above, as is the rebound dial at the rear of the shock, and the high- and low-speed compression adjustments, plus a lockout lever at the front.
The dials on the prototype are closer to what's found on EXT's current coil shock offerings rather than being the tool-free dials seen in this rendering.
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Could Nitrogen instead of air solve the pressure issue?
There, I've spoken about two things I know nothing about. Today's gonna be a good day.
If it's good enough for F1 cars or Trophy trucks and the temperatures they are subjected to, which are drastically more intense than even a harder ride at Whistler, you're going to be just fine charging the suspension with nitrogen on your MTB.
2. Temperature: this effect is more significant since (if you use the ideal gas law to model air) the pressure is proportional to the absolute temperature. So if you are going from +30°C to +20°C the absolute temperature would drop from 300K down to 290K which means you would loose 1/30 of your pressure. This would mean your pressure now would be 145psi/290psi, and the relation would still be exactly at 1/2, just everything is a bit softer. But this applies to a regular single positive chamber shock as well.
Example: if Temp goes up and everything else is held constant, pressure goes up. If Pressure goes up and everything else is held constant, Volume goes down. If Volume goes down and everything else is held constant, Temperature goes down. Etc.
A shock is an airtight metal cilinder that does not change it's volume as you gain or loose elevation, so neither does the pressure inside.
Where heat does come into play is the effect it has on oil viscosity- that is something even normal riders like you or I can feel. The claim is that an air shock insulates the oil in the shock more than a coil, so the oil heats up more. I doubt this is a real effect- a few years ago Minnaar's mechanic zip tied CPU heat sinks to Greg's rear shock as a joke- in his mind there is no measurable difference.
The reason why, in my opinion, that a dual chamber is worth it on a high end shock isn't for fine tuning the progression at a given weight. You don't change it from day to day riding. It allows for a "custom tune" for a wide variety of frames. Yeti's sb150 has like 14% progression, while YT often has 40% progression. This allows for you to get the same feel on both bikes. You can custom shim the compression to deal with different frame tunes, but most other air shocks rely on air volume spacers for a custom spring rate. Is having a 2nd chamber really harder than adding/removing spacers? It also helps with people on the extreme ends of the weight spectrum get a good tune.
Regarding altitude - the air spring in the shock is a closed system made of metal. Unless you're sending the shock into space or to the bottom of the Mariana trench (neither location being particularly known for its mountain biking) changes in external air pressure shouldn't affect anything.
Regarding temperature - I don't see why VP=nRT would apply differently when the gas in the positive and negative spring chambers of this shock is cooled.
Regarding altitude - changes in ambient pressure affect gauge pressure. Gauge pressure is what you are measuring on your shock pump. Gauge pressure is directly related to spring rate.
Regarding temperature - try checking your tire pressures with a digital gauge on a cold morning, then again later in the day after it's warmed up considerably. You'll see a 1-3 psi difference probably. I say tires because the air lost to the gauge in a tire is small relative to the total air volume when compared to a shock and shock pump, but the same applies.
Regarding people saying "no one can feel that" - get a digital shock gauge. Do back to back testing and change 2-3 psi in your fork or 3-5 psi in your shock. You will 100% notice the difference. Make sure to equalized the positive and negative springs my cycling a few times before removing the gauge, and lift the wheel off the ground to get an accurate reading
They buy their air from the same guy that sold Jack his beans
It does, however, lack the damping component of the air spring therefore you finally get to use those dials on your damper you paid good money for.
In a perfect world you design a bike with a certain shock in mind, but then again someone is gonna run a different shock or simply does not like this or that. As a manufacturer you need to say "works with all shocks" -and it can to some point, but on the other hand this will always be a compromise.
Seems like we have to agree to disagree there. The only bikes where you cannot run a coil instead of air are badly engineered with a complete lack of progression. In this case an air spring can cover up but not solve the problem.
As you wrote the coilshock will have more midstroke support. Is it in your opinion plausible, that combined with a very progressive bike (again concerning midstroke) this harsh behaviour can occur?
And yes, the coil has more midstroke support but it may feel different due to the ton of lowspeed damping that occurs with the air spring. You have to crank a ton of damping into your coil shock to make it feel as damped as the air one. also air springs are speed sensitive, so the spring rate under fast acceleration is LOWER than during slow acceleration and yes, it is different going in and out of travel.
Basically all those air spring curves floating around are actually quite bollocks / bro science.
The guys using excel to calculate them deserve a special place in hell because those are flat out lying.
Tolerances seem to be pretty good and the bike -as i said - works really well, even compared to all the bikes i have owned i the last 25 years.
Now that you said it, i think i recall your aversion for alloy shortlinkbikes from the discussions about the IBC 2.0.
Also a lession learned from the last years is to test things. A lot of things that should on paper work, did not work and vice versa. For instance I have always been a big coil fan, but it did not really work on any of my last bikes.
Maybe you recall me being vocal about the IBC 1.0 because I had one of the very first frames and it was extremely misaligned and the replacement was so bad you would not believe, like dents with filler and the "raw" frame was suddenly white to cover the filler.
I only have a problem with dual short link bikes (short or long travel) because very often those frames are badly aligned, eat bearings, eat shocks and, eventually, eat wallets. Alloy frames are way worse in this regard since some manufacturers don´t machine their bearing seats after welding but before and then do their worst on alignment with the usual results. A 2mm shift on bearing position is "normal" with many welded frames. Just take Linkage, your favourite bike and move a pivot 2mm. See what happens...
However, I feel the need to clarify. Even a short link vpp style bike can be build with the tightest tolerances, look at banshee for example, they put all their pivots in one machined part, therefore ensuring high accuracy. Every design can be utilized in a good way, but many manufacturers compromise way to much for the sake of styling.
I am a member of the "old school horstlink plush suspension" crowd and will propably never leave my roots so yeah, even my opinion is tainted somewhat by personal preference.
MDE has been building shortlink bikes for 20 years now and cost and effort going into a frame has nothing to do with a mass produced frame, if anyone can make this system work its them. I say this not to justify my investment, infact my previous shortlinkbike a propain tyee was so bad i switched to a hardtail for over a year, same with my cotic or starling experiment, both bikes were very bad alinged and ate shocks and bearings.
I have owned pretty much every suspensionsystem in the last 25 years and the bikes i liked most were bikes with a fairly high antisquat and a constant and progressive leverage ratio. Antirise is never a big deal for me, so the system itself does not matter to me so much. I like bikes that sag under their own weight, but thats probably not so important while riding.
It's still better than the Float X2 I was riding before and IMO it has some of the positive qualities of an air shock anyway, the bike still feels poppy and engaging - it doesn't smother the trail like an Ohlins or Cane Creek might.
Like you, I saw this and just thought "why?".
Although being only slightly heavier than an X2 is impressive, considering the SDC is about 50% heavier.
Precisely the same for my 2019 Strive, which is fairly progressive. I had issues initially with the first tune but after having it tweaked I'm now in awe at the Storia. It's not making the trail disappear, the shock still gives a lot of feedback - it's the grip. This thing glues your back wheel at the ground, all the time. After riding it for months, going back to the original air shock my bike had before, made the bike feel like I had too much air on the rear wheel
Since having a family, most of my riding is at 5am. That early, once you get up past 8,000 feet, its in the high 40s, but by the time you get to the bottom its the low 60s 'cause the sun has come up and your 2500 feet lower. Tires are stiffer and less grippy in the cold.
blisterreview.com/podcasts/ext-founder-franco-fratton-on-a-lifetime-in-suspension-ep-110
He made a couple specific comments:
* They made an air fork first because they thought they could do better than their competitors and wanted to prove it to riders by making a similar system to how competitors make them
* Making a really good suspension fork is very very difficult
* He sounds interested in making a coil fork but had to make air first to prove they make quality products (àa
* Mountain bike riders are afraid of innovation if it looks too different so EXT needs to be careful with new products for them to be accepted
* If given his choice for a new fork design he would design an upside down design. However, he's cautious considering it has never been successful in sales on mountain bikes
* Funding development for a new product for mountain bikes is difficult compared to motorsports
* Expect something new late this year (late 2022 to early 2023)
* Their engineers have more ideas to improve the forks going forward
*shrug*
The Yeti two-piece eccentric ones are particularly weird though, I'm curious how much the shock shaft rotates relative to the body under high compression loads on those, being that the force vector through the bolt centre does not align with where the bearing is on each half of the link. It might be stiff enough that the answer is "an insignificant amount" or it might actually be pretty substantial.