VorsprungSuspension

@jwestenhoff: servicing your fork, using good lubricants, removing sources of friction entirely (eg replacing the air spring with a coil). And I guess you could probably find ways to increase friction but I don't think that's what you're asking :)

@L0rdTom: my theory on the lack of compression damping in current dampers is that it comes about as a result of 4 things: 1. Air forks have more friction than (older) coil forks. This is equivalent to LSC in some sense, because it has a disproportionate effect at very low speeds. Running very soft compression valving reduces total resistance, and can make the fork feel more "plush'. 2. Air springs have a thermal damping effect. Some of the energy in the compressed air turns into heat during fast compressions, which increases the pressure further, but it very quickly bleeds off into the surrounding stanchion, so the spring rate on return is a bit lower than during compression. Effectively, you get a certain amount of compression damping from the air spring, and to achieve a given "total" amount of speed-sensitive compression resistance (ie damping), you need less damping to come from the hydraulic cartridge if using an air spring than if you're using a coil spring. 3. There is a certain datalogger out there that seems to push users (many of whom are reputable people within the industry) towards lighter and lighter damped setups in both compression and rebound. It does this because it chases numbers that I believe are fundamentally irrelevant. Check out the Pinkbike reviews of the Ibis "traction tune" bikes and you'll see what I am on about. 4. Internet forums. About 8 years ago, a handful of people started posting that their forks were overdamped (which is very often misdiagnosed from some other issue, such as friction, poor spring curve, excessive progression etc), spread that idea online, other people picked it up and reiterated it, and as a result it became a contagious concept that "everything is overdamped". But because reducing the compression damping does make the fork feel a bit better, when people revalve the damper lighter, they do find it moves more freely, so they assume that they have correctly diagnosed the issue because they successfully made some improvement. Get enough people on the internet to repeat it, and eventually people at the big companies start taking notice. To answer your second question, it's not really related to friction - rebound dampers always generate way more force than the compression side, they are where most of the energy gets dissipated. Typical rebound damping forces are 3-4x that of the compression curve at any given speed. This is partly because the peak rebound speeds are way lower than peak compression speeds (8m/s in compression happens now and then, 8m/s in rebound and you're going to jump about 10ft in the air), so the damping power (force x velocity) requires more force because there's less velocity. The rebound damping force subtracts from the spring force, whereas the compression damping adds to the spring force.

While I'd agree that getting spring rate/curve and rebound sorted are a higher priority than compression tunes, I'd suggest that your experience with HSC settings not making any difference may come from time spent on products where the HSC adjuster just isn't very effective, because changes to the damping characteristic can definitely have pretty significant effects on how the bike rides. Riders definitely do adapt to their bike though, and for a lot of people what feels "good" is often just what feels familiar. We actually did a bunch of testing like this years and years ago (like 2011 or so) using a Freelap system. Rider was not told what the compression damping changes were, and timed over a short (~50 second) section of trail that the rider was very familiar with, on several different trails. We ran through three "extremes" of settings (basically minimum, midrange, maximum) on both LSC and HSC, fork and shock. The settings were cycled through several times, so you'd do several non-consecutive laps on each setting, so that fatigue and "learning the trail" effects would not affect the results. Any laps with major mistakes (crashing or running off track) were re-run. The conclusion was, in that particular case, that the firmest setting was consistently measurably faster (about 2-3%) on the segments we tested on. However, it also beat the rider up noticeably more, and might not have been faster on a longer (5-15 minute) trail. But that was also testing on a thoroughly tuned 40RC2 and DHX RC2, which both had very effective compression adjusters, not the current crop of stock forks with generally ineffective compression adjusters.

@freeridejerk888: The range of the Grip2 rebound damper is very wide, but the range of the compression damper (VVC, 2021+) is pretty tiny actually. For anyone wanting more support, it just isn't able to do that - the maximum force it can generate is really very low. With HSC and LSC maxed out (ie fully firm), it can only generate about 15kgf (33lbs) at 2.5m/s (this is a mid to high speed rock strike or a very sudden compression at the bottom of a rock roll), and about 25kgf (55lbs) at 4m/s, which is a heavy landing or a square edge at very high speed. A combined bike/rider load through the fork (for an 80kg/175lbs rider), when heavily loading up the front wheel, can be about 160kgf (350lbs) without bottoming out. Does the compression damper do anything in these situations? Yes, but not much. These numbers are giving the damper the benefit of the doubt too, by using really high velocities rather than typical this-happens-every-impact-on-the-trail velocities. And again, this is with both adjusters fully closed. If you spend the $400CAD or so to change out the Grip for the Grip2 damper, and run it wide open like many people do, it has negligible difference to the Grip in any practical sense. At 2.5m/s fully open, it's generating less damping force (8kgf/17lbs) than the fork chassis is generating in friction (approx 9kg/20lbs depending on how recently it was serviced, of which between 30-50% can come from the air spring). Depending on the size of the impact, it's very common for the fork to have more thermopneumatic damping (damping from air temperature change during compression/rebound) than actual hydraulic damping. During "dive" events like sudden hard braking into a compression at around 0.75m/s, the Grip2 damper itself (again at fully firm HSC/LSC) is generating about 5kgf/11lbs. This is about the same force difference generated by compressing the spring another 5mm/0.2", so at maximum we could suggest that the fork would ride around 5mm higher than if it had no compression damper at all (in practice, the difference is usually much smaller with such low damping forces because the peak spring & peak damping forces don't happen simultaneously and the total energy dissipation is very small). The term "placebo dial" has some merit here, and it's not limited to Fox, the Rockshox adjustments are pretty similar in their range. Why should anyone care about this? Because even small changes to the spring characteristic or fork friction make way more of a difference than that - there's a reason we focus more on improving the springs than the damper. If you want to make the biggest possible improvements to your fork, look at friction, spring curve/rate and then damping, in that order.

@Brasher: The "Ohlins" TTX25 is actually a rebadged CCDB coil, made by Cane Creek. It was made available a couple of years after the Double Barrel - https://www.ohlinsusa.com/files/files/TTX25%20MKII%20-%20Base%20Assembly%202014%20Service%20_rev12_Page_1.jpg note the logos.

You've clearly been riding bikes a good while! The Romic wasn't a recirculating TTX-style design despite having two tubes, it was effectively a single tube where the reservoir/piggyback was concentric to the damper tube which was a smart layout (albeit with a few drawbacks, such as eye to eye length vs stroke). Cane Creek's claim is correct in the TTX/recirculating sense of the design.

@onawalk: I guess it depends what your criteria for "better" actually is. If you mean fastest around a given circuit, vehicles prone to understeer usually comes last. If you mean most fun to slide around in the snow or on dirt, understeer definitely comes last. But if by "best" you mean safest, then it depends to some extent on the driver, but for solidly 99% of drivers, understeer comes first. Also worth considering that for most drivers who never (deliberately) approach the limits of grip, under/oversteer has zero bearing on how well they feel the car handles, because until one axle or the other is significantly slipping, there is no under/oversteer anyway. If you want to go for a moderately spirited drive (you know, the average moderately wealthy 50yr old in a "sports" car that's just a family car with a spoiler on it) on a clear sealed road, it doesn't actually have any relevance because the wheels are gripping not slipping (yes, they're always technically slipping, but slip ratio 0.2 or slip angle 5deg means they're effectively gripping). If you're racing (or pretending to), it's an entirely different story, understeer doesn't do anything good there.

@onawalk: I don't think anybody has said understeer tendency is "better for handling", you seem to be shadow boxing there. I also prefer vehicles with a neutral or oversteer tendency, especially in the snow, but only for the sake of fun not safety, and most people don't even know what terms like understeer and oversteer even mean. Is an understeer tendency better as an end product if safety is your first priority though? Unquestionably yes (and fair enough if safety isn't your first priority when choosing a vehicle for handling, but you're in the minority if so). There are people out there with 50+ years driving experience who, pragmatically, we just are not going to be able to retrain to deal with a car sliding. And even if we did manage that, it's worth pointing out that despite having more degrees of control over oversteer, in slippery conditions it's extremely easy to loop out and have a (much more dangerous) crash where you hit something side-on or roll the car, especially given that most vehicles with automatic transmissions have a massive lag between the pedal and the wheel. Yeah, there are situations where understeer can cause a crash that a neutral or oversteering vehicle might have been able to avoid IF the driver was highly skilled, but there's unquestionably a far greater number of times that understeer prevented lethal rollover or side intrusion than the number of lethal crashes caused by the understeer itself. Education and training are great but by the time anyone managed to get any significant percentage of the population trained in how to handle an oversteering car consistently and safely on icy surfaces, we'd all be in self-driving cars anyway. Training isn't actually a statistically viable proposition as an alternative to just building a car that's harder for the average person to kill themselves in.

This made me 11/10 want to ride.

@onawalk: understeer is built into most road-going cars as a default response to emergency maneuvers (ie hard braking and steering, or swerving on slippery surfaces like snow). The reason is that you have a lot of crumple zone in front of you, not much beside you, and almost nothing above you, so in combination with the fact that it's relatively easy to roll a car sideways and extremely difficult to do that end-over-end, it's a lot safer to leave the road or hit something traveling basically forwards rather than sideways. It's not better for high-performance handling as such, but for the general population it's safer in the sense that less people die.