Interval Straining: What Actually Happens if You Don’t Regularly Service Your Bicycle Suspension?


Interval Straining: What Actually Happens if You Don’t Regularly Service Your Bicycle Suspension?

If you own a car, you change your oil. And not just because it’s part of adulting. Even if you know nothing about engines, you probably know what can happen if you push it too far. Debris will eventually build up, viscosity will eventually break down, and the more miles your car travels in that condition, the fewer miles it will last. But if you own bicycle suspension, the specific reasons for performing regular service may not be quite so clear.

Travis Engel knows a lot more about shocks and forks than he does about rods and pistons, but he doesn’t know exactly what happens when he blows past the manufacturer-recommended 50- and 200-hour service intervals. And like many riders, he pretty much always blows past them. So, he did some research and is here to tell us what we are (and aren’t) risking when we ignore the proverbial sticker in the upper left corner of our suspension’s proverbial windshield.


Peek behind the Flash-animated marketing curtain of your favorite suspension brand’s website, and somewhere you’ll find a “service” tab. Amid the multilingual manuals and exploded drawings, there will be an outline of how often you should perform various types of maintenance. The tasks range from a post-ride wipe-down to a nuts-and-bolts rebuild. The frequency with which we’re expected to do them will also vary, but I’ve always felt brands go a little overboard. Some want you to perform a fork lower-leg service and a rear-shock air-can service after every 50 riding hours. During my peak season, that might be every two or three weeks. But at least those are relatively easy tasks to do at home, and they don’t require too many special tools.

Really, it’s the much more involved damper overhauls that got me asking the question at the heart of this story. According to most brands, a damper service is supposed to be performed on both front and rear suspension every 150 to 200 riding hours. Usually by a professional, and usually costing about $100 to $200 respectively.

But even though suspension manufacturers are asking us to pour up to $400 a year into our bikes—not to mention the cost of parts and oil required for those 50-hour services—I’m going to take a non-cynical look at this issue. After all, these brands have good reasons for wanting us to have a problem-free experience with their products. And I trust they want that experience to last us many years. But at the same time, they don’t want to scare away customers with unnecessarily excessive maintenance. So, that means these intervals must not be arbitrary. Something must be happening inside our suspension after those 200-hour and 50-hour benchmarks that we should be trying to prevent.

But unfortunately, there isn’t much information about exactly what that is. And not all of it is obvious or intuitive, like replacing our tire sealant as it dries out or even replacing our chains as they stretch. I’d be a lot more motivated to do costly and time-consuming suspension maintenance if I knew what was at risk if I skipped it. So, I reached out to SRAM / RockShox’s Chris Mandell and asked for some brand-agnostic details on what specifically is going on inside our suspension as we approach, and pass, our service intervals.

Every ride: Fork and shock stanchion wipe-down

This step is an interesting starting point because it both seems like common sense, but is also commonly overlooked. It’s simply a quick wipe-down of fork and shock stanchions after every ride, especially rides when you may have encountered mud or moisture. By “stanchion,” I mean the smooth tubes that slide into and out of your fork or shock as the suspension moves. On the topic of vocabulary, since we’re just starting out, maybe let’s take a quick pause to cover a few more terms. Those front or rear stanchions initially slide into “wiper seals.” Up front, those seals are held in the fork “lowers” and in the rear, they’re part of the shock “air can” or “air sleeve.” And when we’re talking about air suspension, there’s an “air spring,” which is the pressurized chamber along with all of its accompanying pistons and seals. Acting in parallel to the air spring is the “damper,” which is an oil-filled chamber that controls speed of compression and rebound. But we’ll get to that. First, back to stanchion-wiping.

The reason for this task isn’t as much about damage or corrosion if you let wet dirt slowly dry on your wiper seal and stanchions. It’s about the fact that, once that dirt has dried onto your stanchion, it can potentially make it past the wiper seal and damage your fork or shock internals on your next ride. As Mandell puts it, “Dry, hardened mud on your upper tube is going to be more difficult for your wiper seals to deal with than dynamic, wet and loose dirt.”

The outermost seals on our forks and shocks were specifically designed to deal with that “dynamic” wet and loose dirt. They do it thousands of times every ride, and are often called “dust wipers” for that reason. But if even a small piece of dirt manages to cling hard enough to the stanchion that it sneaks past them, it’s now grinding against your suspension’s soft, tender insides. Again, common sense, and #1 on many suspension brands’ recommended maintenance regimens, but I rarely took this step seriously until someone spelled this out for me.

Every 50 hours: Fork lower-leg and shock air-sleeve service

First, I’ll briefly cover what these procedures entail. Very briefly, because this isn’t a how-to. Your suspension’s website will be a much better place to find that. Anyway, the details will vary for each manufacturer. But basically, fork lower-leg service involves removing the fork lowers so you can clean the internals, re-lubricate the surfaces and components, and replace the small quantities of oil that slosh around in there. The empty spaces you’ll access during this process are really just that: empty spaces.

On the fork, this is not where the damping control or spring force comes from, so it’s not fiddly work and doesn’t require special tools. It’s pretty similar to the rear shock air-can service. My story about volume spacers covers part of the process. During fork air-can service, you’re releasing the air pressure and unthreading the “body” of the shock to access the insides. But unlike fork lower-leg service, most shock brands also recommend you replace all of the wiper seals and O-rings that make the air spring work. It’s a simpler, slightly cleaner, process than a fork lower-leg service, but those rear shock seal kits usually cost $20 to $50. So, that’s a big ask if you’re doing it every 50 hours.

At about 50 or so hours of riding is when most brands conclude that enough grit has made its way inside to start to do damage. To be fair, it’s not the same for all riders. “Our service intervals are based on worst-case scenarios,” Mandell says. Some conditions and riding styles just aren’t that abusive. Dusty and muddy conditions are more likely to coat the stanchion with fine, invasive particles, and the more active the suspension is, the more opportunities those particles have to work their way past the wiper seals and into the system. But even in the gentlest use cases, lubricants are still migrating, moving from where they should be to where they shouldn’t.

This issue of oil movement will become more important in the damper section, but that oil that’s sloshing around to keep things slick doesn’t stay there forever. It slowly creeps past seals into places it is less useful. Like, for instance, out of the positive air spring and into the negative. Or, out of the foam reservoir rings under the fork wipers and into the lowers.

Bottom line, the 50-ish-hour service procedures are meant to replace potentially dirty lubricant with clean lubricant and put it back where it belongs to limit friction and protect surfaces from premature wear. Fork and rear shock stanchions are not cheap to replace. And the bushings they slide on are not possible to replace. I mean, some bushings used to be replaceable. And hell, maybe there are a few gurus out there still doing it. It’s just not the way things are normally done anymore. Anyway, the whole idea here is how to avoid that scenario in the first place, but feel free to @ me if you know a bushing expert with old-world knowledge.

Every 150-200 hours: Damper rebuilds and fork air-spring service

Most otherwise tech-savvy DIY-ers aren’t rebuilding their fork or rear shock dampers. I’m sure not going inside there. Fork dampers aren’t too crazy, but most require a number of special tools, a potpourri of tiny spacers and O-rings, and a strict order of operations that wouldn’t feel intuitive until I’d gone through the process a few times. And rear shocks generally have the added complication of pressurized nitrogen. So, I’ve always left those 200-hour tasks for the professionals.

Fork air-spring service is the only 200-ish-hour service I’m happy to do myself. Especially because I’ve had an air spring fail on me, leaving me to finish a ride completely bottomed-out. So, that experience taught me what can happen if I go too far past that deadline. But what about the dampers? Do I really need to spend that $100 to $200 when I don’t yet sense any problems?

A quick education on dampers first. Though designs vary widely, they all rely on some sort of valved piston being pushed and pulled through a sealed chamber of oil as the shock compresses and rebounds. As the shaft that pushes that piston is introduced into that chamber, it displaces oil. Oil that has nowhere else to go.

There have been experiments with thru-shaft shocks and forks, where a dummy shaft exits opposite the damper shaft, keeping the volume constant. Trek went all-in on it with their highest-end bikes for a while, but eventually changed course. Alternatively, some brands solve this with a flexible bladder. But most systems include something called an internal floating piston, or IFP. This is a small pressurized chamber that is separated from the damper with a simple seal that allows the system volume to change slightly as the damper shaft slides in and out, while also maintaining pressure on the system.

When that damper shaft is “out,” it’s still somewhere, ideally getting splashed with a small amount of lubricant like what you’re replacing in those 50-hour services. But as Mandell explains, that can present a problem over time. “Some of that lubricant is not going to get scraped off by the scraper seal and is going to end up inside that damper.” We’re not talking about surfaces that are ever directly exposed to the elements. Indirectly, maybe, but this isn’t about debris and damage. It’s about suspension behavior. “You could run into problems if you ingest a lot of lower leg fluid and your IFP ends up in the wrong spot.” The IFP is designed to keep the system at a specific pressure to keep the damper working properly.

Mandell made sure to mention that RockShox’s new Charger 3 fork damper has a system to purge this excess oil and keep things working better longer, but the point is that things are slowly changing inside of our suspension dampers.


So, does it matter?

I get the benefits of the every-ride wipe-down. And I’m going to be better about doing my 50-hour lower-leg service, though on the rear shock, I might wait for every two or three cycles to replace all the seals. But those are all ways to keep me from slowly ruining my expensive suspension bits. So, a lot like changing the oil in my 2006 Tacoma, I’ll be motivated to perform those services semi-regularly. The 200-hour damper service is more complicated.

Even Mandell admitted that something would have to be very obviously wrong for a very long time before you’d do structural damage by postponing it. “If you run the damper out of oil to the point where the piston is going up and down on a dry damper tube—though I can’t imagine a scenario where that would happen—that would be bad,” he says. “But realistically, you’re never going to get to the point where you’re hurting anything.” Again, this is not referring to everything done in a 200-hour service. The fork air-spring service is important, and of course, you’d probably have those 50-hour services done at the same time. But I think maybe it’s missing the point to approach suspension maintenance only in terms of preserving longevity. It’s also about preserving performance.

When the IFP slips from its optimal position, it means the pressure inside the damper is off. And that can lead to things like gaps in the damping and a fun little word called “cavitation.” I won’t get into the weeds about exactly what these things mean, but they can all result from a damper that has gone out of whack.

You’re not being irresponsible if you continue to ride when the clock strikes 200 hours. Or maybe even 300. As long as you’re keeping things clean in there, you can probably go well beyond that. But gradually, your bike will lose its edge. You won’t be getting as much traction as you were. You won’t be getting as much support or as much tuning control. So, after spending several hundreds of dollars (or more) on your suspension, and then putting several hours of elbow grease and regular grease into keeping it healthy, maybe it’s worth making sure you’re getting the most out of it.