Words by: Liam Woods
Upgrading the suspension on your mountain bike is one of the best things you can do to breathe new life into your bike. Whether it is a fork or rear shock, you will be amazed at the technology these days in suspension, and how having a quality product gives you the confidence to shred harder than ever before. And let’s not forget to talk about the smile it can put on your face! When looking to upgrade the rear shock on your mountain bike, it may be overwhelming to know exactly what size shock you need, which kind of shock will fit on your bike, and also which shock will perform best on your specific bike. Here in this blog we are going to cover all of these questions and more.
Mountain bike rear shocks come in an array of different sizes and recently made the switch from the older “traditional” sizing measured in inches (8.5 x 2.5) to the newer modern sizing that is measured in millimeters (210mm x 55mm), AKA metric.
Now let’s break this down. A shock that measures 210 x 55 means that the shock is 210 millimeters long and uses a 55mm stroke. The length of the shock is measured from eyelet to eyelet, while the stroke of the shock is the amount the shock can physically compress. One thing to keep in mind here is that shocks that are the same eye to eye length may come with different stroke lengths. The most important thing is to make sure you get the correct length and stroke shock for your bike. It’s important to note that just because two different bikes have the same rear travel (150mm for example), doesn’t mean they always have the same stroke lengths. So what works for one bike might be very different on another bike.
Along with shock sizing from eye to eye and stroke length, you also need to know your frame mounting width, which is normally sized by shock hardware. Shock hardware adds another element to getting the new rear shock installed on your bike. For a rear shock, you have to match up the top and bottom for the shock mounting hardware. There are no standards and every brand chooses what they think works best with their design. So what’s usually best is to either look at the brand’s website or contact the manufacturer to get the correct shock hardware. If you are upgrading your shock but with the same brand, you can often use the same shock hardware as long as it's not super beat up or worn out. So Fox shock to new Fox shock, you can use the same hardware, and same with RockShox or other brands. There is also a Trunnion style shock mount, which normally does not use hardware on the top, but bolts directly to the bike. That is a certain type of shock and while you do not need hardware up top, you do need to get a Trunnion style shock if that is what your bike is designed around.
Each manufacturer and frame may use a different size shock and your bike is not guaranteed to function properly without using the correct size. To find out what size shock is correct for your mountain bike, either check the brand’s website for your model or call us at the shop and we will be more than happy to help!
When upgrading your rear shock, one major question is whether to get a coil shock or an air shock. While there is no simple answer to this question, hopefully this information will make it a little more clear.
Left: Fox Float X2 (Air) Right: Fox Float DHX2 (Coil)
First, think about what kind of terrain you are riding and also what terrain your bike is intended for. The majority of trail bikes out there today come stock with an air shock because they are lightweight, offer a range of tuning options, and can provide an efficient pedaling platform. For those cross country focused riders, an air shock will certainly do the trick. For those riders looking for a bit more downhill performance, or maybe even racing an enduro race, you may consider a coil option. In general, coil shocks handle the small bumps on the trail with more ease, giving the rider supple feedback and more traction. The negatives to using a coil shock are that your bike now weighs a little extra and they tend to be a little more difficult to tune, especially if you don’t get your spring rate correct.
It’s important to note that coil shocks tend to be more linear while air shocks provide a more progressive ramp up, so some bikes don't work well with coil shocks as you would bottom out very easily. So before you decide to get a coil shock, make sure it will work with your bike's suspension design.
+ Please ask one of our professionals whether you and your bike would be better suited with a coil shock or an air shock.
There is also the question of what brand and model shock to choose. Most people know the two dominant brands Fox and RockShox. Both of those brands have a full range of options from cross country shocks to downhill shocks. Fox has their lineup with DPS, Float X, Float X2, Float DHX and Float DHX2. That list starts with cross country and goes to enduro and downhill shocks, with both air and coil mixed in there. From RockShox, starting with cross country through downhill, you have SidLuxe, Deluxe, SuperDeluxe Air and SuperDeluxe Coil.
If you are looking for something a bit different other than the two big brands, there are a ton of cool small brands to look at. We carry Ohlins, DVO, Push Industries, Marzocchi, Cane Creek, and MRP. There are even more brands that we don't carry but we think are super cool like EXT, Intend, DT Swiss, more more!
There are pretty much three different questions you need to ask about a rear shock before you buy: What size? What’s my preference? And is it compatible? Compatibility is a huge factor. It’s important to get the correct stroke, although there are certain instances where you may be interested in over stroking your shock. If you do this though, you’ll sometimes have clearance issues on smaller travel bikes, as well as depending on whether you’re using coil or air that we briefly touched on.
Let’s dive a little deeper into the over stroke topic. When metric shocks came out I quickly realized that the small steps with the shock stroke would allow for lots of tuning and mods. For reference, a Yeti SB130 comes stock with a 210x52.5 rear shock, meaning there is 52.5mm of rear stroke. I wanted to see if I put on a shock with the same 210mm eye to eye but with a 55mm stroke if the frame would clear on bottom out causing frame on frame contact or tire on frame contact. I found out that Yeti was already making these small modifications in stroke length. They had something called the SB130 Lunch Ride where the rear shock is extended to the full 55mm stroke length. So the SB130 is a bike where the manufacturer has said you can change that stroke and not void the frame warranty. Other times you might be going against what the manufacturer recommends, so be careful and err on the more reserved side if looking to change your shock stroke.
Left: RockShox Super Deluxe on a Santa Cruz, which is designed to take a coil but a tight fit. Right: Ohlins Coil on Specialized Demo that has very tight clearance to the frame
Moving into clearance issues, there are two clearances you should look for. One is the frame/shock clearance, which you might see a little more often with smaller travel bikes when you are looking to add a larger shock (i.e. moving from Fox DPS to Fox Float X). The piggyback reservoir might be a tight fit or not clear certain bikes. On some other bikes like the Santa Cruz Hightower and similar designs, the shock runs through the seat tube in a “tunnel” so there is a size max width. The Hightower does not allow for larger shocks like the Fox Float X, Cane Creek DBair or most coil shocks, so make sure your frame will clear a larger air can or piggyback shock if you are looking to upgrade your shock in that way. The other clearance to watch out for is simply making sure nothing hits. Normally if the seat stays have a brace, it could hit the seat tube if you over stroke the shock. Also to watch out for with over stroking the shock is the rear tire hitting the frame. On a Revel Rascal, for example, you cannot over stroke the shock as on bottom out the tire will hit the seat tube. You might think well it's only 2.5mm of stroke, and I have over 5mm of clearance, but the reality is that the 2.5mm of stroke is a ratio. For example, the bike has 130mm of rear travel with 52.5mm stroke, but when taking the shock stroke to 55mm the rear end gets about 136-137mm rear travel at the back wheel, making those clearance measurements hard to predict. So it's best to err on the safe side, or at the very least check with the manufacturer before going to a larger shock or a longer stroke.
Coil versus Air, the forever topic that we here at Worldwide Cyclery still go back and forth about. Coil versus air is about half preference and half what your bike is designed around. We have a full blog going way into detail so we will keep it light here. If your bike does not work well with a coil shock, you are kinda stuck with an air shock. There’s also the fact that some suspension designs that have a yoke, shock extender or clevis put too much side load on a coil shock and are also not recommended. So if that is the case, it doesn't really matter about your preference since you are sticking with air.
Left: Fox Float X (Air) Right: Fox DHX2 (Right)
Next is preference, and some riders definitely have one they like over the other. Coil gives a very smooth, very consistent feeling and once you ride coil and are not a weight-weenie or care about max pedaling efficiency, you might stick with coil. If you are jumping a lot or like a progressive suspension feeling, the air might be what you like. Like I said, we go back and forth, depending on riding style, trails, and season. Coil might be fun for six months then you suddenly want to jump back to air. If you are more of a straight line smash type of rider, you might have a preference for coil shocks more. The traction and small bump the rear shock gives you really cannot be beaten. If you like to jump around, take all the side hits, or ride a huge range of different trails the air shock might be more your style. Having the ability to add air pressure or add tokens to tune makes the air shock a more versatile tool.
Some of our favorite shocks come from brands like Fox, Rockshox, Marzocchi, Cane Creek, Push Industries, and DVO. While each has its advantages and disadvantages, finding a shock with good tunability and reliability will improve your riding experience on the trail. Personally, one of my favorites for a smaller travel bike is the new RockShox SidLuxe rear shock. For how small the shock is, its performance is insane, so smooth and works perfectly. If you’re looking for a bigger travel air shock, the Fox Float X2 and RockShox Super Deluxe are some top picks you will find on our bikes. And last but certainly not least is the Push Industries ElevenSix rear coil shock, tuned and made specifically for each model bike it goes on. It's a work of art that is also a top performing shock in its class.
So when looking to upgrade your rear shock, there are so many things to consider and look at for rear shocks, from finding information to what feeling you want and how you would like your suspension to handle or change the way your bike rides. Below is a list of information you should look for and questions you should answer before looking to upgrade.
Remember to never hesitate to call us at the shop with any questions. We give recommendations on rear shock upgrades all the time! Mountain bikes are our passion and we love assisting our customers with anything cycling related. Feel free to send us a picture of your bike, use our live chat on our website or bring your bike into the shop. We are here to help!
This article was written / authored by Liam Woods. Liam has been in the bicycle industry for over 10 years as a racer, professional mechanic, service manager and as of late, media and content creator. Liam has ridden thousands of different bikes, ridden countless components, tested endless MTB apparel of all kinds and written reviews on it all. He's a key piece to the Worldwide Cyclery "All Things MTB" content creation puzzle. He also makes consistent appearances on the Worldwide Cyclery YouTube channel and Instagram.