Guide #2 Suspension: Selection, Setup, and Adjustment for Gravity Athletes
How to use this guide:
The goal of this guide is to help gravity athletes obtain a basic understanding of mountain bike suspension in terms of functionality, terminology, and tuning. We love the engineer types who can debate endlessly about shim stacks, valving, oil viscosities, internal temperatures, and spring rate curves, but we will save those topics for a more advanced guide. We will also devote a small section to products we think are interesting right now and a very brief discussion of where we think suspension and mountain bike tech is headed in the future.
Understanding mountain bike suspension the big picture:
We all get that suspension at high level is basically a spring designed to smooth out the bumps. A spring that is too soft doesn’t bounce back enough, a spring that is too hard is like not using a spring at all. A uncontrolled spring could be like riding on a pogo stick! The important thing to understand about mountain bike suspension is that there is no such thing as a perfect tune. The closest thing to optimization in mountain bike suspension is one racer on one course using a data analytics package to help determine the optimal settings for that suspension bike with that racer on that specific course. If you change any of the variables: the roughness/smoothness of the course, the weight, speed, or aggression of the rider this can push your tune out of balance which leads to sub-optimal performance. We here at rcycld.com emailed a German company once that was doing suspension data analytics for World Cup downhill teams because we heard they sold the data analytics software and hardware package. They responded that they wanted $20K USD for the kit! We think we will see one or more of the major suspension fork manufactures make a simplified data analytics package for mountain biking that is affordable. Until that kit is available, suspension tuning is a little bit of following the manufacturer's owner manual and a little bit of trial and error. Many suspension products have adjusters with anywhere from 6-50 clicks of adjustment. We have talked to more than one professional rider that will tell you they can’t feel a difference of a few clicks, and they can only feel a few more if they are on there local well known trail. Understanding that one setting can’t optimize a bike for every course or trail, even if the rider is the same, will lead you to the conclusion that suspension setup and tuning is really about finding the right balance. Balance can be found in the settings to make the most of your style of riding and typical trail format. Suspension setup and tuning is about finding the right general balance. Finding the right balance can make the ride much more enjoyable!
At this point we will cover some basic terminology that will be key to you finding the right balance in your suspension. This list is far from inclusive, but we think it covers the majority of what a gravity athlete needs to know about their mountain bike suspension.
Travel refers to the overall length of the stoke of the suspension fork or rear shock. It is generally quoted in inches or millimeters. When suspension first went mainstream for mountain bikes in the nineties 50-65mm (2-2.5”) was common for forks. We now have enduro forks settling at 160mm (6”+) and downhill forks at 203mm (8”). Todays rear shocks will have between 2-3” of travel that the suspension linkage leverages up to 6-8” of actual rear wheel travel. The extension of travel over time is a reflection of bikes being constructed better and more durably, efficient suspension platforms which make pedalling longer travel bikes more efficient, and to some degree riders’ increased confidence.
- Spring Rate & Air vs. Coil Springs
Spring Rate refers to how strong or soft your suspension is. A higher spring rate implies a heavier, faster, or both rider. Lower spring rates implies a lightweight, slower, or both rider. The manufacturer will usually make recommendations of spring rate based mainly on the rider’s weight. This info is ussually in the owner’s manual. The spring can be either a pressurized air chamber or a metal spring. A metal spring is usually made out of steel or if the rider can afford it titanium. If the suspension is air, the manufacturer will usually recommend a certain air pressure for a given rider’s weight. If the suspension uses metal springs for the fork, the manufacturer will usually offer several spring kits with recommended rider weight ranges such as soft,medium, firm, extra firm. We love the manufactures that include all the spring rate kits with the fork and wonder why they all don’t do this? The rear shock spring is usually quoted in lbs of force required to move the spring 1”. These springs will range from 200lbs for a lightweight rider to up to 450lbs for a heavy fast rider. We feel at this point it also worth mentioning the spring type can a significant effect of the bike’s weight and ride quality. Air springs are typically known for being lighter weight relative to metal springs, how much does air weigh again? The downside generally of going air is that many early air suspension products suffered from striction. Stiction is an effect that make suspension feel sticky or stepped. This is most likely to occur when seals dry out. Stiction is less of a problem today and most well made air forks today, you can’t tell the difference between air and coil, making air the best choice for most riders. Metal coil springs typically have been known for having a weight penalty but the benefit is they are generally known for having a nicer or “plusher” feeling stroke. I see many professional level racers that still prefer the feel and performance of a high quality titanium spring in their rear suspension. Marzocchi has positioned it’s top of the line forks around titanium springs this year (2015). Titanium springs are generally much lighter compared to comparable steel springs, but still heavier compared to air suspension. Titanium springs also tend to be significantly more expensive than steel springs. Most manufacturers sell their rear steel spring for $40, a comparable Ti spring would run you $200 approx.
- Preload & Sag
Preload was the original adjuster that fork manufactures offered. Preload is essential a dial that compresses down on a metal spring “preloading” the spring to attempt to have the effect of increases the spring’s rate. Most coil forks still have preload adjusters. We think preloading is ok for small adjustments but should not be used a substitute for getting the right spring kit or spring rate. We see preload get overused on low end forks and when the owner can’t justify the cost of a spring kit. In the long run this overstresses the spring and doesn’t provide a great level of ride quality. Preload is not an issue with air suspension because you can easily adjust the spring rate by changing the air pressure in the main air chamber. Sag is the amount of suspension compression you get when you just sit down on the bike. Now for gravity athletes sag should be set while standing on the bike. Generally you set sag in whatever riding position you will use most. Sag is expressed in a percentage of travel. Fork sag is generally set 10-15% of total fork travel and 15-25% of rear wheel travel. Preload adjusters can be used to set sag on coil suspension and air suspension it is adjusted with air pressure just like setting the spring rate. Sag can be tilted to adjust for riding style or to balance out mismatched suspension. For example if your bike really needs 140mm fork to balance nicely, but you have a 160mm fork, you could take the 160mm fork and run it a little softer than normal so it sags to the same height as the 140mm fork. In this example you will get a little negative travel (-20mm) so the fork will drop in to holes, some riders like this effect and feel it causes straighter tracking, but it has the overall effect of finding suspension balance on a bike that is mismatched (experiment here at your own risk- generally we like following manufacturer’s recommended settings). If the rear is run with excess sag it is important to be aware that that could slack out your bike’s angles and give you less usable travel.
- Tuning and Adjusters:
Tuning and adjusting the your suspension is where the magic happens. A good tune can help you bike disappear under your feet and help you get zen when you're shredding your favorite trail. A bad tune can make a ride uncomfortable and painful for the rider and perhaps even make the bike awkward handling and potentially unsafe to ride. Tuning is calibrated with our overall suspension philosophy of finding the best balance for most situation, not optimization or seeking perfection. Here will we cover the most common adjusters found on mountain bike suspension and what they really mean for the gravity athlete.
At one point in time when the industry was still young, a quality fork manufacturer only offered two adjustments preload and rebound. Rebound adjusters are typically dials that turn the head of a shaft and piston that either frees or restricts the flow of oil threw the fork. This occurs as the fork extends to full extension after taking a hit on the trail and has little if any effect on the compression stroke while taking a hit. We think of rebond as the true workhorse of the suspension component’s internals. Suspension lacking rebound would feel like riding a pogo stick. The rebound adjuster allows you to adjust the speed of the after compression re-extension. If you run the adjuster full open you might not have enough rebound control and you're in pogo stick territory again which could get dangerous. If you run full closed you could find that the suspension “stacks” up or it takes too many hits because it can’t setup for the next hit fast enough. Setting your rebound is about finding the right balance. We suggest gravity athlete run it as open as they can while still feeling in control and non-jarring (pogo sticking).
Compression adjustment is usually a dial that adjusts the speed and flow of oil moving through the fork for the impact stoke. Compression is arguable less important than rebond if the spring rate is set well, but it does allow some tuning to occur. if you set compression full open generally you feel just the spring rate. If you set compression full closed you could cause the fork to feel near rigid. We think using compression adjustment is about finding the right balance for most situations and can be handy for fine tuning the stroke resistance if your riding someplace different from your normal set of trails or fine tuning for a specific trail.
- High/low speed compression and stable platforms
Early performance mountain bike suspension suffered greatly from “pedal bob” or the effect of the athlete's pedaling causing the bike to “bob” up and down which wasted a lot of energy that could have been used to push the bike forward. The industry responded to this problem by offering “platform” suspension products that allowed the rider to tune their suspension to have firm early stroke resistance. Progressive Suspension’s SPV (Stable Platform Valve), Manitou’s licensed SPV, Romic, and Fox’ ProPedal are all examples of this technology. Rider’s with a motocross background understood platform suspension was a form of low speed compression damping. The basic idea behind suspension platforms or low speed compression damping is that the suspension resists movements caused by low speed impacts (or low speed pressure to compress caused by the rider’s pedalling forces). High speed hits cross the threshold set by the low speed compression tune and pass through the low speed resistance to still allow the fork to absorb the high speed hit. When this setup works well it can give the rider the best of both worlds, it climbs with minimal “bobbing” effect but still offers all the benefits of suspension, such as better handling ride, increased comfort, and increased traction. Adjustable platform and low speed compression tuning allows the athlete to adjust the amount of force required to bypass the low speed resistance and move forward to the high speed resistance. The trade off here is a full close setting on low speed compression or platform will climb very efficiently but may give up small bump sensitivity. The loss of small bump sensitivity could lead to a less supple ride quality and more hand fatigue. Many manufacturers offer a switch to allow the low speed or platform suspension feature to be toggled off and on. We feel the switch offers a good solution. You keep the platform on for your climbs and then switch it off to get maximum suppleness for your descents!
- High/low rebound
Low speed rebound is a relatively new feature in the history of performance mountain bike suspension. Low speed rebound is similar to low speed compression in that it breaks the stroke direction into two circuits inside the suspension chamber. The same way you're able to use low speed compression adjusters to tune the resistance to early stage hits in the impact stroke, low speed rebound adjustment allows you to tune the resistance levels of early stage extension speed of the post extension stroke. Proponents of of low speed compression damping argue that given the heavy use of platform and low speed compression in mountain biking to counter pedaling forces a separate circuit is needed for low speed rebound to complement platform settings for better suspension performance and feel. We feel that low speed rebound damping adjusters hold promise and plan to spend more time using products with this feature. We think Cane Creek’s double barrel products are a nice example of this tech and they also do a nice job of explaining the benifits here: www.canecreek.com
- Stable platforms and lockouts
A lockout is a another way suspension can address the problem of pedal “bob”. A lock out adjuster is usually a dial or lever that when utilized completely disables the suspension of the fork, rear, or both turning the bike rigid. The thinking here is the lockout is used mostly for climbing which occurs at lower speeds where the rider can use his arms and legs to absorb bumps and pedal “bob” free. We think the fork lockout is a good ideas when you have a “earn your turns” ride or when your going to be climbing for an extended period of time and then descending in later sections. This model also fits enduro stage races where you are doing climbing sections and descending sections. We do feel that low speed compression is better than a lockout for the rear wheel because the ability for the shock to cross the low speed threshold and remain active offers a lot of traction benefits while climbing and still offers a good amount of pedal feedback resistance.
We feel a concept worth mentioning at this point is unsprung weight and we will discuss briefly why we feel it matters. Unsprung weight is the mass of the parts of the bike that are not suspended. On a full suspension bike this is generally the fork lowers, the swingarm, the wheels and brakes. The sprung weight is the mass of the bike parts and rider that are suspended or everything else. The reason that unsprung weight matters is generally the lighter weight the unsprung components, the easier it is for the suspension to be active. This leads to increased suppleness in the feel of the suspension and traction benefits in the bike’s handling. One area where you see intense debate over unsprung weight is the argument for and against inverted suspension forks. Inverted designs are forks such as the Manitou’s Dorado, MRP’s Groove, or DVO’s Emerald. Proponents of inverted designs argue they offer lower unsprung weight. The argument against inverted forks is they are not a laterally as stiff or as straight tracking. We think there is a place in the market for both designs, but we are also excited for new products like the DVO Emerald that has a stiffening slider guard or X-Fusion’s forthcoming single crown the Revel with internal sliding tracks to prevent stanchion twisting. We think unsprung weight is a concept worth understanding and should be considered when choosing components.
Suppleness, vibration, and hand fatigue
When suspension forks first hit the market many proponents argued the traction and tracking benefits but the true benefit of adding a suspension fork to a hardtail was that it made it far easier to keep your hand on the handlebar over rough terrain and at speed. Since that time suspension travel and quality has increased significantly and we do see a lot of tracking and traction benefits from suspension, but the comfort and fatigue benefits should not be underestimated. Having suspension that is supple, well suited for your trails, and style of riding can give you significantly less hand fatigue and beat you up less over a day of riding. This is essentially an argument for getting the best suspension you can, setting it up well, and also considering a vibration damping handlebar if it’s in the budget. We think carbon fiber handlebars and products such as Spank’s Vibracore bar offer vibration damping characteristics that serve as inactive suspension that can go a long way in increasing comfort and decreasing fatigue.
Suspension selection, setup, and tuning is a balancing act!
The gravity athlete should be thinking about finding the right balance for the following factors:
- riding style
- rider weight
- rider aggression
- rider speed
- trail & course style
Today’s gravity athlete should understand suspension adjusters and their proper useage:
- Spring rate
- Preload & Sag
- Rebound damping
- Compression damping
- Low speed compression and platforms
- Low speed rebound
Here at Rcycld.com we like to think we are ahead of the curve and we also have an eye for the future. We will cover here three products we are excited about and are looking forward to riding this year. We will also will share trends we see for the future close and far.
DVO’s OTT adjuster
The first technology is DVO’s OTT adjuster. OTT (Off The Top) is an adjuster that allows you to fine tune the suppleness of the first 70mm of travel on DVO’s Emerald downhill fork. We think this feature is a response to overuse of low speed compression and platform damping in many products. It allows the rider to have a fork that is very responsive to small bumps and decrease hand fatigue. We think this could be used to push the low speed compression a little higher in the stroke and find a better balance between plushness and efficiency. Judging by the success of the DVO fork we can’t be the only ones thinking this. We will be selling DVO this year and we are taking pre-orders for the highly anticipated Diamond enduro fork which also will have the OTT adjuster. You can read more about the tech here:
MRP’s Ramp Control & Magnetic Valving
MRP started in our home state of Oregon before moving to Colorado. We think MRP has really stepped up it’s game by jumping from the chainguide market into the suspension fork market. We will be selling MRP forks this year and we think the Stage fork is one of the best values in the crowded 160mm enduro fork market. The Stage forks has two technologies we find interesting and we are excited to ride. The technologies are MRP’s Ramp Control & Magnetic Valving. Magnetic technologies use magnetic energy to effect valving or oil viscosity. These technologies have been used successfully in the high end automotive suspension market. This is the first mountain bike application we are aware of using this tech. The basic ideas is is that a oil port in the fork has a magnetized valve to create a platform effect. The second technology is the Ramp Control adjuster. The idea on this one is that the adjuster allows you to tune how progressively the resistance ramps up threw the compression stroke. This allows you to go from very linear ramp up to a very progressive ramp. You can read more about the two technologies here:
We feel Push Industries’ (http://www.pushindustries.com) new Elevensix rear shock is the single most exciting product in mountain bike suspension right now. The big picture here is that in addition to very high quality production processes, production controls, and attention to detail, Push adds in personalized attention to customer’s needs with a rear shock that has two low speed compression circuits. Overall the shock is customized for the rider and bike, but having two low speed circuits and the ability to switch off allows the rider to have a lot of versatility. Having the rider set these circuits means the rider can move beyond just having a “climb” mode and “descend” mode, and can customer tune two modes for whatever type of riding is most important to them. We feel this is a very creative solution. If you feel like nerding out on the details (don’t worry we nerd out sometimes too) check out Vitalmtb.com’s excellent audio presentation here:
(we have no affiliation with vitalmtb.com)
The future for mountain bike technology looks bright. Here are four trends we see either deepening or happening in the future. We see more suspension products that will alter bike geometry and they will be first electronically controlled and then computer controlled. We will see the birth of what we are calling the “on bike computer” or OBC. The OBC will be similar to Raspberry Pi, but optimized for performance bicycles. It will acquire and process data to give actionable outputs in real time. The OBC will go a step further than suspension and integrate with shifting, and a wide range of other systems. The OBC will also gather data for meaningful analysis. In the closer future we see suspension data acquisition systems to be more available and economical for the consumer market. We predict that more magnetic technologies will trickle down from the automotive industry to mountain biking. These trends will lead to a mountain bike that adjusts itself to optimize ride performance, safety, comfort, and training effectiveness. The consumer will also have better suspension and more tools to analyze suspension and ride performance.
We see more bikes from top manufacturers with suspension designed to optimize the mountain bike’s geometry such as Scott’s TwinLoc and Rocky Mountain’s Ride9. We will see more electronics in suspension such as Fox’s IRD. Further out into the future we see the OBC governing these suspension systems. The electronics will control suspension tuning and ride heights that affect the bike’s overall geometry. OBCs will sense changing trail conditions and adjust the suspension in real time on the trail. For example, right now with this new crop of geometry adjusting suspension bikes, if you go into a climb, you flip a switch that changes the suspension. Now the bike’s fork travel drops down, stiffens up, and the head angle steepens. The rear end extends slightly giving you more uphill traction. You reach the peak elevation and hit the switch again before you begin your descent. Now the bike extends the travel to 120% the bottom bracket raises up to give you more clearance and the head angel slacks out several degree for a higher speed descent. Now imagine the OBC is making these changes for you. The OCB uses sensors to tell if your climbing or descending or sense how the trail is changing and it adjusts your bike’s suspension and geometry automatically in real time. Once you get home, the OBC links wirelessly with your PC, tablet, or maybe hologram device and you see all the data acquired on the day’s ride. Furthermore, that data it analyzed for you to give you meaningful insights into your ride, race training progress, and(or) fitness goals. Pretty cool future right?
The incorporation of data and electronic systems will continue for a long time into the future. We see more mountain bikes with electronic controls such as Shimano’s electronic XTR. We also see more data monitoring technologies trickling down from the road racing bicycle segment such as integrated power meters and heart rate monitors. I saw my first downhill crank with a power meter this year. We think the trend of electronically controlled and integrated mountain bike systems will continue. It’s easy to follow this idea or argument to its end. When you do you envision a mountain bike where the OBC in addition to managing the suspension and geometry of the bike is also processing shifting, heart rate monitoring, power output monitoring, as well as a wide range of other functions. The OBC will take all of this data and give the athlete actionable outputs in real time on the trail. The athlete can make manual changes or set the bike to adjust automatically to the situation. The OBC would gather and process a wide range of data from a wide range of sensors. The on-bike sensors could be designed to read anything. The OBC could access distance, speed, trail conditions, rates of change, moisture levels, trail conditions, altimeter data, a barometer, a heart rate monitor (HRM), other rider health sensors that track sweat and hydration levels, a power meter, as well as the traditional sensors for speed, distance, cadence, gear ratios, and suspension performance. The OBC would compile and process this data into outputs like optimal gear ratios, suspension settings, adjustable bike geometries, target wattage output, and displays the data in a HUD that would make a fighter pilot happy.
We see more trickle down in mountain bike suspension of magnetic technologies form the auto industry. We mentioned earlier in this guide MRP’s magnetic valve. Top auto manufacturers including Ferrari are using magnetic technologies to change suspension oil’s viscosity. This allows the vechical to control how fast oil can flow through the suspension. The iron in the oil stacks up when charged electrically to change the viscosity. This allows you to electronically change suspension settings on the fly. You can see a nice summary of this technology here:
- Magnetized valves or fluid that can be electrically charged on and off for different properties
We think a trend we will see in nearer future is more data acquisition packages for consumers. The hardware will be bolted and zip tied onto your bike so you can do a half dozen runs on your favorite trail. The data will be downloaded from your device onto a pc and analyzed in Microsoft Excel. This will give racers and performance oriented riders insights into suspension setup. Data acquisition for suspension is not anything new. In a recent interview with orginal downhill champion Myles Rockwell, he describes some of the benefits we derived from working with a suspension data analytics expert in the early 90’s. We are excited to see this type of analysis become more readily available. We enjoy seeing the articles in supercross and motocross magazines showing the data acquisition packages that that factory bikes run. When will this come to mountain biking? We think soon.
That concludes our guide #2 Suspension - We hope you found it useful or interesting. If you missed it check out guide #1 Parts here:
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