Rod B.
Well-known member
Hello,
It's been a while since I've posted anything for the Orbea Forum. This will be a three part series on basic suspension and simple to perform suspension hacks that you might find interesting and helpful. If you have a "Simple" to perform suspension hack, post it to this thread so others can use it.
Part Two:
www.emtbforums.com
Part Three:
www.emtbforums.com
For those who don't know me yet, I'm 64 years old and I began riding mountain bikes in 2002. My Strava stats for the year 2022 , list 154 rides, 2,494 miles of travel, 346,083 feet of elevation gain and 310 hours in the saddle. While I occasionally enjoy a nice mellow flow ride through the woods, I especially love technical rock crawling on black to double black trails. I purchased my first eBike, an Orbea Rise M20 in 2021. I put 3,200 miles on the bike before selling it to my brother. I currently ride a Specialized Turbo Levo Carbon Comp. I've set the bike up with a ZEB 170mm fork, Fox X2 rear shock, SRAM AXS, TRP DH-R EVO brakes, and Zipp 3 Zero Moto wheels with DT Swiss 350 hubs. I do my own suspension, electrical, motor, brake and drivetrain work. I have nothing against bike shops, however a bike shop can't help you when your bike is broke down on the side of the trail. Get to know your bike, the knowledge you learn will save you, or a buddy from a long walk back to the trailhead.
The purpose of this article is to help provide a better understanding of how the "Air" suspension on your Rise operates, what the adjustments actually do and how you can improve your suspension. I realize there are some extremely good riders and mechanics on this forum who may already know much of what I'm about to discuss. I am writing this article for the newer riders who may not know, or who wish to know more about suspension. I will discuss only air suspension in this article. Lastly, I will use Fox suspension for illustration purposes. I have nothing against coil suspension. I have nothing against Rockshox, Ohlins, etc. The article will focus on air suspension and Fox because that's what comes stock on the Rise.
Okay, let's get into this....
Suspension Basics:
To understand suspension we first need to know Newton's Third Law: Action & Reaction. Newton's third law states that for every action (force) in nature, there is an equal and opposite reaction. FYI, Sir Issac Newton was a mountain biker at heart.
Despite all the suspension marketing hype, in truth mountain bike suspension does two very basic things. Your bike's suspension controls the rate of compression as the suspension collapses from the force of gravity and it controls the rate of expansion, also known as "Rebound" as the suspension component returns back to it's natural state of sag.
Air suspension, both fork and shock utilizes "Air" and "Oil" to control the forces of compression and rebound. This is accomplished through the use of a damper located on the right side of the fork and an air spring on the left side of the fork. Your Rear shock also utilizes a form of damper and air spring, however the design of the damper and air spring differs on a shock due to size constraints.
Note: When you hear the term "Air Spring" being referred to, this does not refer to an actual steel spring located inside the fork or shock. The air itself is the spring.
A suspension fork has four main components. They are the Upper Assembly, the Lower Leg Assembly, the damper and the Air Shaft. If you damage any of these components on your fork, they can be purchased as a separate replacement part.
Fox "Factory" 36 upper Assembly with Kashima coating
Fox 36 Lower Leg Assembly
Fox 36 Grip 2 damper
Fox 36 Air Shaft Assembly
Dampers:
Fox manufacturers several different types of dampers, i.e. FIT 4, Grip, and Grip 2. They all perform the same function, however dampers such as the GRIP 2 offer more user adjustment features which I'll cover below. All modern Fox dampers are self contained and sealed. The oil in the damper itself does not come into contact with the lubricating oils in the lower leg. This enables a longer service life since the damper's internals are not exposed to debris contamination from the lower leg oils.
Cut away view of a Fox 36 GRIP 2 damper mounted on the Fox upper. Lower leg assembly is missing.
Internal cut away view of a Fox 36 GRIP 2 Damper
Dampers can be owner serviced, however the process is very involved and requires special tools. If you are not confident in your mechanical skills, it's much better to have the damper serviced by a shop or Fox. Most "Good" bike shops have in-house suspension expects who can provide a damper service if needed. Fox also offers a damper service. You also have the option of purchasing a new damper or upgrading your old damper, i.e. switching from a "GRIP" damper to a "GRIP 2" damper and and installing the damper yourself. Switching dampers is an easy process and does not require special tools.
Every Fox suspension component has a serial number or four digit code. If you visit Fox's "Tech Help" section on it's mountain bike website, you can run the four digit code or serial number. Doing so will provide you with useful information on the suspension component.
Below is an example of the Fox X2 on my Specialized Levo. My Levo came with a Fox Float X "Performance" model. I needed something with more cushioning because of my artificial right ankle. I purchased the Fox X2 shock as a new "Take Off" from my local bike shop, Pro Bike Supply in Newport Beach California. The shock originally came on an Ibis Ripmo.
The shock on your Rise will have something of a similar format. Run your shock and see what it says. You will note the description of my shock provides various numbers, codes, etc. You may be asking yourself...What the hell does all that mean? Well, it's a treasure map to the features and damper tuning that comes on the shock.
Author's Note: I am NOT a suspension specialist. My favorite method of suspension tuning consists of rubbing two chicken bones over my bike prior to setting out on a ride. If I screw up the interpretation below, please don't flame me, my heart's in the right place and well intentioned.
1. The first line is the shock's serial number.
2. The second line provides the part number for the exact shock itself.
3. The third line refers to the year of shock manufacture and also the shock model.
4. F-S refers to the shock series, i.e. Performance, Performance Elite, Factory. The Shock is a "Factory Shock."
5. "2 Pos-Adj." The shock has a blue lever on its side that allows me adjust High Speed Compression. The lever can be switched between "Firm" and "Open."
6. K refers to Kashima coating.
7. Ibis, Ripmo refers to the bike which the shock was originally installed on. Most bike manufacturers will request that Fox "Custom Tune" the rear shock's damper so that the damper's characteristics will enhance the bike's handling. I will cover tuning down below.
8. 210, 55, refers to the shock's overall length of 210mm, and stroke, 55mm. The Ibis Ripmo, and the Turbo Levo both use a 210mm x 55mm shock. The Orbea Rise also uses a 210mm x 55mm shock.
9. 0.3 Spacer x1 refers to the size of the air volume spacer installed by the factory on the shock, "0.3" "X1" refers to the amount of air volume spacers (X1=One) that comes stock on this particular X2 shock model. I removed the air volume spacer from my X2 shock. I will cover air volume spacers in detail below.
10. CL001 refers to the custom tune which Ibis had Fox do to the compression stack on the shock's main piston. The custom tune dictates how a shock's damper will perform during a compression cycle. If your shock came stock on your bike, it will typically come with some form of custom tune. The type of tune and code sequential will vary and depends on the shock, i.e. Fox Float DPS, Fox Float X, Fox DPX2, etc. If you bought your shock "On the Shelf" as a generic shock, it will come with a basic tune made to work for a wide "Bell Curve" range of bikes and rider weights. Once again, I will cover tuning and what it means down below.
11. ECR012 refers to the rebound stack tune on the shock. When you hear the term "Stack" in regards to suspension, this typically will refer to a "Stack" of shims which will vary in different size thickness. The shims in conjunction with piston porting and valving, will control the rate of oil flow through a shock upon compression or rebound. I will discuss shims down below.
12. REZI BV3 refers to a shock's "Lock Out" tune and or type of compression adjustment assembly. You will note that some shocks have a rigid lock out and other shocks will offer a more plush Lock Out. Some shocks will have a compression adjustment while others do not.
Example of the damper assembly on a Fox Float X
Example of a damper assembly on a Fox Float DPS
Compression
You may have heard the terms "High Speed Compression" and "Low Speed Compression." This is where the more expensive suspension components like Fox "Factory" and Fox "Performance Elite" earn their money. Both of these series of suspension components will have dampers that have separate High Speed Compression (HSC) and Low Speed Compression (LSC) adjustability. It should be noted that Fox "Performance" series forks and shocks do not have a separate High Speed Compression and Low Speed Compression. They instead will have a lever that allows the rider to adjust between Firm and Open compression. This concept was previously known as the F.I.T. 4 damper or better known as C.T.D., Climb, Trail, Descent.
GRIP 2 damper with it's High and Low Speed Compression adjustments
Fox FIT Grip damper with "Firm to Open" lever adjustment
Fox Float X Factory with it's separate Low Speed Compression (Blue Knob) and High Speed Compression (Blue Lever)
Below is depicted the Fox Float X "Performance" shock. You will note that the shock is missing the Low Speed Compression knob. A black plastic cap is installed in place of the blue LSC knob. Fox offers the Float X to the public in only "Factory" and "Performance Elite" specifications.
The Float X Performance is an OEM bike manufacturer specific shock. Manufacturers like this shock because it saves them money on bike builds. They can specify a "Bling" item such as Fox in the bike build specification. You just don't get all the bells and whistles.
The Fox Float X Performance shock can only be purchased as a "Take Off." The Fox Float X performance can usually be purchased for about $300 cheaper than the Factory and Performance Elite shock. Here's the cool thing. Later in this post, I will show you how to modify the Float X Performance shock for $30 and literally turn it into a Performance Elite shock.
Okay, lets get real....I need a show of hands here. How many of you think Low Speed Compression and High Speed Compression refers to how fast you are going when you compress the suspension???? As a side note, I'm raising my hand.
In truth, LSC and HSC refers to the speed of the force, which causes the fork or shock to go into a state of compression. As an example, say you are riding down the trail and you run over a small branch laying on the trail. You bounce over the branch and the action causes your fork and shock to slowly compress a little. That my friends is a Low Speed Compression. Lets say you are getting rowdy and decide to hit a six foot vertical drop on your Rise. You send it off the drop and stick the landing. The force of impact upon landing quickly compresses the suspension. This would be a High Speed Compression.
Do you really need both a High Speed and Low Speed Compression adjustment? It depends. If you are a legit rider and pushing your bike and it's suspension to it's limits, then having the ability to adjust LSC and HSC is worth it. If you are a basic rider and not pushing the envelope on the trail, then paying extra for LSC may not be money well spent.
How your Suspension Works:
Let use your fork as an example. Remember, your shock acts in a similar manner. The principles of adjustment and tuning are identical for both.
Located within the fork's left stanchion is the air shaft and the negative and positive air chambers. The air shaft serves two purposes. It determines what the travel will be for the fork and allows the air spring to be regulated via air pressure.
Fox does not make numerous types of Fox 36 or Fox 38 forks, each with different travel. Fox instead makes one fork and uses the air shaft to determine what the travel of the fork will be. If you have a 150mm Fox 36 fork and you want to change the travel from 150mm to 160mm, you simply replace the air shaft. It's easy to do and doesn't require a host of special tools. Note that Fox does limit the amount of a fork's travel based on the diameter of the stanchion, i.e. if you have a Fox 34, you can't install a 170mm air shaft in it. The leverage on an overly extended Fox 34 fork would quickly break it.
Negative Air chamber, Positive air chamber, the Yin and the Yang. The Negative Air chamber on a fork serves to assist with small bump compliance. All suspension components have some form of "Stiction." Stiction is the friction between stationary surfaces at rest. If all your fork had was a positive air chamber and you hit a bump, it would take considerable force to get the suspension moving. The ride would be harsh and jarring. The Negative air chamber serves as a negative air spring, it pulls so to speak and is used to slightly overcome the positive side of the air chamber. When you hit a bump, the fork will break free from stiction much more easily.
Some fork models tend to ride harsh on the top end due to stiction and the design of the fork. I've always felt the Fox 36 seemed to ride a bit harsh on the top end of the suspension when encountering small wash boarded trail. My hands would hurt. There are companies like Vorsprung Suspension which manufactures a negative air piston modification for the Fox 36 and other forks. It's called the Luftkappe Negative Air Piston. The Luftkappe turns the first 20-30% of the suspension into a coil fork like feel. The ride is extremely plush and your front wheel will tend to track true over wash boarded trail and not walk sideways offline. With the Luftkappe installed, once the fork has reached 30% travel, it will revert to normal air spring rate of compression. Only the first 30% rides plush.
www.vorsprungsuspension.com
The purpose of the positive side of the air chamber on a fork provides resistance from compression. If we take it to extremes, imagine inflating your fork's air chamber to 500 psi. Besides sending it and you to the moon when it exploded, you wouldn't be able to compress the fork. If we take it to an extreme in the opposite direction and only pumped 40 psi into the fork's positive air chamber, you could compress the fork with one finger. Were you to try and ride you bike, you would bottom out the suspension.
When you adjust and tune the air side of your suspension, you are seeking an even balance to the Yin of compression and yang of rebound. When things are out of balance, bad things can happen. When the fork's air chamber is overly inflated, your fork will ride very harsh on the top end, your front wheel will want to walk sideways when you encounter ripples in the trail at high speed. This will prevent you from holding a line on a trail. You'll literally feel the bike bounce and walk sideways. With the air system is adjusted properly, the front wheel will remain planted to the ground and not bounce erratically, the ride will be smooth. More importantly, you'll be able to hold a line through the chunk at speed.
Under inflating a fork is equally bad. An under inflated fork will cause you to crash. The best way to describe this is to picture yourself dropping off of a small two foot ledge by rolling it. As your front wheel hits the lower ground, the fork begins to compress as gravity takes over. A properly adjusted fork will allow the fork to compress to a certain point at which point the air spring overcomes gravity and begins to push back via rebound. An under inflated fork will instead continue to compress until the fork bottoms out. When the fork cannot cannot compress further, your body will begin to compress downwards due to gravity. Because you are moving downwards on the drop, your compressing body will move forward and over the handlebars you go. A properly adjusted air spring is essential to your safety.
This will conclude Part One of the suspension series. I realize this is an odd place to conclude the article. I promised you tuning. Unfortunately, eMTB forum limits posting word counts to 2,000 words. I have to end it here my friends.
Part Two will continue with how suspension operates, suspension damper tuning, suspension hacks on the Float X Performance, and things that I do on a routine basis to achieve perfect suspension. Because I'm not a suspension expert, it's highly likely I've made a mistake. Please let me know if I've done so and I'll make the correction. I do not take offense at being corrected, we're all here to learn and we all dig mountain biking. Attempting to place into words what my understanding of suspension is and how it operates is extremely difficult. I would ask that you have a understanding of this difficulty and not call "Bullshit" too harshly on my mistakes. Wahoo!
I hope you've enjoyed Part One and find it helpful and useful.
Be safe,
Rod
It's been a while since I've posted anything for the Orbea Forum. This will be a three part series on basic suspension and simple to perform suspension hacks that you might find interesting and helpful. If you have a "Simple" to perform suspension hack, post it to this thread so others can use it.
Part Two:
Technical Article, Part # 2: Suspension, The Ups, The Downs, The Hacks
This is Part Two in a three part series on suspension, tuning, hacks and tips. I've always enjoyed the people on the Orbea forum and I've met a lot of good people and many new ride partners through this forum. If you're looking for new ride partners, I encourage you to reach out to other members...
www.emtbforums.com
Part Three:
Technical Article, Part # 3: Suspension, The Ups, The Downs, The Hacks
Greetings, This will be the third installment in a three part series on suspension. This third installment will cover hacking a Fox Float X Performance shock and other small performance tips that you can do to improve your suspension. You can find read the first two installments via the...
www.emtbforums.com
For those who don't know me yet, I'm 64 years old and I began riding mountain bikes in 2002. My Strava stats for the year 2022 , list 154 rides, 2,494 miles of travel, 346,083 feet of elevation gain and 310 hours in the saddle. While I occasionally enjoy a nice mellow flow ride through the woods, I especially love technical rock crawling on black to double black trails. I purchased my first eBike, an Orbea Rise M20 in 2021. I put 3,200 miles on the bike before selling it to my brother. I currently ride a Specialized Turbo Levo Carbon Comp. I've set the bike up with a ZEB 170mm fork, Fox X2 rear shock, SRAM AXS, TRP DH-R EVO brakes, and Zipp 3 Zero Moto wheels with DT Swiss 350 hubs. I do my own suspension, electrical, motor, brake and drivetrain work. I have nothing against bike shops, however a bike shop can't help you when your bike is broke down on the side of the trail. Get to know your bike, the knowledge you learn will save you, or a buddy from a long walk back to the trailhead.
The purpose of this article is to help provide a better understanding of how the "Air" suspension on your Rise operates, what the adjustments actually do and how you can improve your suspension. I realize there are some extremely good riders and mechanics on this forum who may already know much of what I'm about to discuss. I am writing this article for the newer riders who may not know, or who wish to know more about suspension. I will discuss only air suspension in this article. Lastly, I will use Fox suspension for illustration purposes. I have nothing against coil suspension. I have nothing against Rockshox, Ohlins, etc. The article will focus on air suspension and Fox because that's what comes stock on the Rise.
Okay, let's get into this....
Suspension Basics:
To understand suspension we first need to know Newton's Third Law: Action & Reaction. Newton's third law states that for every action (force) in nature, there is an equal and opposite reaction. FYI, Sir Issac Newton was a mountain biker at heart.
Despite all the suspension marketing hype, in truth mountain bike suspension does two very basic things. Your bike's suspension controls the rate of compression as the suspension collapses from the force of gravity and it controls the rate of expansion, also known as "Rebound" as the suspension component returns back to it's natural state of sag.
Air suspension, both fork and shock utilizes "Air" and "Oil" to control the forces of compression and rebound. This is accomplished through the use of a damper located on the right side of the fork and an air spring on the left side of the fork. Your Rear shock also utilizes a form of damper and air spring, however the design of the damper and air spring differs on a shock due to size constraints.
Note: When you hear the term "Air Spring" being referred to, this does not refer to an actual steel spring located inside the fork or shock. The air itself is the spring.
A suspension fork has four main components. They are the Upper Assembly, the Lower Leg Assembly, the damper and the Air Shaft. If you damage any of these components on your fork, they can be purchased as a separate replacement part.
Fox "Factory" 36 upper Assembly with Kashima coating
Fox 36 Lower Leg Assembly
Fox 36 Grip 2 damper
Fox 36 Air Shaft Assembly
Dampers:
Fox manufacturers several different types of dampers, i.e. FIT 4, Grip, and Grip 2. They all perform the same function, however dampers such as the GRIP 2 offer more user adjustment features which I'll cover below. All modern Fox dampers are self contained and sealed. The oil in the damper itself does not come into contact with the lubricating oils in the lower leg. This enables a longer service life since the damper's internals are not exposed to debris contamination from the lower leg oils.
Cut away view of a Fox 36 GRIP 2 damper mounted on the Fox upper. Lower leg assembly is missing.
Internal cut away view of a Fox 36 GRIP 2 Damper
Dampers can be owner serviced, however the process is very involved and requires special tools. If you are not confident in your mechanical skills, it's much better to have the damper serviced by a shop or Fox. Most "Good" bike shops have in-house suspension expects who can provide a damper service if needed. Fox also offers a damper service. You also have the option of purchasing a new damper or upgrading your old damper, i.e. switching from a "GRIP" damper to a "GRIP 2" damper and and installing the damper yourself. Switching dampers is an easy process and does not require special tools.
Every Fox suspension component has a serial number or four digit code. If you visit Fox's "Tech Help" section on it's mountain bike website, you can run the four digit code or serial number. Doing so will provide you with useful information on the suspension component.
Below is an example of the Fox X2 on my Specialized Levo. My Levo came with a Fox Float X "Performance" model. I needed something with more cushioning because of my artificial right ankle. I purchased the Fox X2 shock as a new "Take Off" from my local bike shop, Pro Bike Supply in Newport Beach California. The shock originally came on an Ibis Ripmo.
The shock on your Rise will have something of a similar format. Run your shock and see what it says. You will note the description of my shock provides various numbers, codes, etc. You may be asking yourself...What the hell does all that mean? Well, it's a treasure map to the features and damper tuning that comes on the shock.
Author's Note: I am NOT a suspension specialist. My favorite method of suspension tuning consists of rubbing two chicken bones over my bike prior to setting out on a ride. If I screw up the interpretation below, please don't flame me, my heart's in the right place and well intentioned.
1. The first line is the shock's serial number.
2. The second line provides the part number for the exact shock itself.
3. The third line refers to the year of shock manufacture and also the shock model.
4. F-S refers to the shock series, i.e. Performance, Performance Elite, Factory. The Shock is a "Factory Shock."
5. "2 Pos-Adj." The shock has a blue lever on its side that allows me adjust High Speed Compression. The lever can be switched between "Firm" and "Open."
6. K refers to Kashima coating.
7. Ibis, Ripmo refers to the bike which the shock was originally installed on. Most bike manufacturers will request that Fox "Custom Tune" the rear shock's damper so that the damper's characteristics will enhance the bike's handling. I will cover tuning down below.
8. 210, 55, refers to the shock's overall length of 210mm, and stroke, 55mm. The Ibis Ripmo, and the Turbo Levo both use a 210mm x 55mm shock. The Orbea Rise also uses a 210mm x 55mm shock.
9. 0.3 Spacer x1 refers to the size of the air volume spacer installed by the factory on the shock, "0.3" "X1" refers to the amount of air volume spacers (X1=One) that comes stock on this particular X2 shock model. I removed the air volume spacer from my X2 shock. I will cover air volume spacers in detail below.
10. CL001 refers to the custom tune which Ibis had Fox do to the compression stack on the shock's main piston. The custom tune dictates how a shock's damper will perform during a compression cycle. If your shock came stock on your bike, it will typically come with some form of custom tune. The type of tune and code sequential will vary and depends on the shock, i.e. Fox Float DPS, Fox Float X, Fox DPX2, etc. If you bought your shock "On the Shelf" as a generic shock, it will come with a basic tune made to work for a wide "Bell Curve" range of bikes and rider weights. Once again, I will cover tuning and what it means down below.
11. ECR012 refers to the rebound stack tune on the shock. When you hear the term "Stack" in regards to suspension, this typically will refer to a "Stack" of shims which will vary in different size thickness. The shims in conjunction with piston porting and valving, will control the rate of oil flow through a shock upon compression or rebound. I will discuss shims down below.
12. REZI BV3 refers to a shock's "Lock Out" tune and or type of compression adjustment assembly. You will note that some shocks have a rigid lock out and other shocks will offer a more plush Lock Out. Some shocks will have a compression adjustment while others do not.
Example of the damper assembly on a Fox Float X
Example of a damper assembly on a Fox Float DPS
Compression
You may have heard the terms "High Speed Compression" and "Low Speed Compression." This is where the more expensive suspension components like Fox "Factory" and Fox "Performance Elite" earn their money. Both of these series of suspension components will have dampers that have separate High Speed Compression (HSC) and Low Speed Compression (LSC) adjustability. It should be noted that Fox "Performance" series forks and shocks do not have a separate High Speed Compression and Low Speed Compression. They instead will have a lever that allows the rider to adjust between Firm and Open compression. This concept was previously known as the F.I.T. 4 damper or better known as C.T.D., Climb, Trail, Descent.
GRIP 2 damper with it's High and Low Speed Compression adjustments
Fox FIT Grip damper with "Firm to Open" lever adjustment
Fox Float X Factory with it's separate Low Speed Compression (Blue Knob) and High Speed Compression (Blue Lever)
Below is depicted the Fox Float X "Performance" shock. You will note that the shock is missing the Low Speed Compression knob. A black plastic cap is installed in place of the blue LSC knob. Fox offers the Float X to the public in only "Factory" and "Performance Elite" specifications.
The Float X Performance is an OEM bike manufacturer specific shock. Manufacturers like this shock because it saves them money on bike builds. They can specify a "Bling" item such as Fox in the bike build specification. You just don't get all the bells and whistles.
The Fox Float X Performance shock can only be purchased as a "Take Off." The Fox Float X performance can usually be purchased for about $300 cheaper than the Factory and Performance Elite shock. Here's the cool thing. Later in this post, I will show you how to modify the Float X Performance shock for $30 and literally turn it into a Performance Elite shock.
Okay, lets get real....I need a show of hands here. How many of you think Low Speed Compression and High Speed Compression refers to how fast you are going when you compress the suspension???? As a side note, I'm raising my hand.
In truth, LSC and HSC refers to the speed of the force, which causes the fork or shock to go into a state of compression. As an example, say you are riding down the trail and you run over a small branch laying on the trail. You bounce over the branch and the action causes your fork and shock to slowly compress a little. That my friends is a Low Speed Compression. Lets say you are getting rowdy and decide to hit a six foot vertical drop on your Rise. You send it off the drop and stick the landing. The force of impact upon landing quickly compresses the suspension. This would be a High Speed Compression.
Do you really need both a High Speed and Low Speed Compression adjustment? It depends. If you are a legit rider and pushing your bike and it's suspension to it's limits, then having the ability to adjust LSC and HSC is worth it. If you are a basic rider and not pushing the envelope on the trail, then paying extra for LSC may not be money well spent.
How your Suspension Works:
Let use your fork as an example. Remember, your shock acts in a similar manner. The principles of adjustment and tuning are identical for both.
Located within the fork's left stanchion is the air shaft and the negative and positive air chambers. The air shaft serves two purposes. It determines what the travel will be for the fork and allows the air spring to be regulated via air pressure.
Fox does not make numerous types of Fox 36 or Fox 38 forks, each with different travel. Fox instead makes one fork and uses the air shaft to determine what the travel of the fork will be. If you have a 150mm Fox 36 fork and you want to change the travel from 150mm to 160mm, you simply replace the air shaft. It's easy to do and doesn't require a host of special tools. Note that Fox does limit the amount of a fork's travel based on the diameter of the stanchion, i.e. if you have a Fox 34, you can't install a 170mm air shaft in it. The leverage on an overly extended Fox 34 fork would quickly break it.
Negative Air chamber, Positive air chamber, the Yin and the Yang. The Negative Air chamber on a fork serves to assist with small bump compliance. All suspension components have some form of "Stiction." Stiction is the friction between stationary surfaces at rest. If all your fork had was a positive air chamber and you hit a bump, it would take considerable force to get the suspension moving. The ride would be harsh and jarring. The Negative air chamber serves as a negative air spring, it pulls so to speak and is used to slightly overcome the positive side of the air chamber. When you hit a bump, the fork will break free from stiction much more easily.
Some fork models tend to ride harsh on the top end due to stiction and the design of the fork. I've always felt the Fox 36 seemed to ride a bit harsh on the top end of the suspension when encountering small wash boarded trail. My hands would hurt. There are companies like Vorsprung Suspension which manufactures a negative air piston modification for the Fox 36 and other forks. It's called the Luftkappe Negative Air Piston. The Luftkappe turns the first 20-30% of the suspension into a coil fork like feel. The ride is extremely plush and your front wheel will tend to track true over wash boarded trail and not walk sideways offline. With the Luftkappe installed, once the fork has reached 30% travel, it will revert to normal air spring rate of compression. Only the first 30% rides plush.
Luftkappe Air Piston Kit - Fox & Rockshox Forks
Enhance Your MTB Suspension with the Luftkappe Air Piston Kit for Fox & Rockshox Forks Unlock peak performance with our Luftkappe Air Piston Kit, designed for avid MTB enthusiasts seeking precision tuning. Elevate your riding experience with expertly calibrated adjustments tailored for Fox and...
www.vorsprungsuspension.com
The purpose of the positive side of the air chamber on a fork provides resistance from compression. If we take it to extremes, imagine inflating your fork's air chamber to 500 psi. Besides sending it and you to the moon when it exploded, you wouldn't be able to compress the fork. If we take it to an extreme in the opposite direction and only pumped 40 psi into the fork's positive air chamber, you could compress the fork with one finger. Were you to try and ride you bike, you would bottom out the suspension.
When you adjust and tune the air side of your suspension, you are seeking an even balance to the Yin of compression and yang of rebound. When things are out of balance, bad things can happen. When the fork's air chamber is overly inflated, your fork will ride very harsh on the top end, your front wheel will want to walk sideways when you encounter ripples in the trail at high speed. This will prevent you from holding a line on a trail. You'll literally feel the bike bounce and walk sideways. With the air system is adjusted properly, the front wheel will remain planted to the ground and not bounce erratically, the ride will be smooth. More importantly, you'll be able to hold a line through the chunk at speed.
Under inflating a fork is equally bad. An under inflated fork will cause you to crash. The best way to describe this is to picture yourself dropping off of a small two foot ledge by rolling it. As your front wheel hits the lower ground, the fork begins to compress as gravity takes over. A properly adjusted fork will allow the fork to compress to a certain point at which point the air spring overcomes gravity and begins to push back via rebound. An under inflated fork will instead continue to compress until the fork bottoms out. When the fork cannot cannot compress further, your body will begin to compress downwards due to gravity. Because you are moving downwards on the drop, your compressing body will move forward and over the handlebars you go. A properly adjusted air spring is essential to your safety.
This will conclude Part One of the suspension series. I realize this is an odd place to conclude the article. I promised you tuning. Unfortunately, eMTB forum limits posting word counts to 2,000 words. I have to end it here my friends.
Part Two will continue with how suspension operates, suspension damper tuning, suspension hacks on the Float X Performance, and things that I do on a routine basis to achieve perfect suspension. Because I'm not a suspension expert, it's highly likely I've made a mistake. Please let me know if I've done so and I'll make the correction. I do not take offense at being corrected, we're all here to learn and we all dig mountain biking. Attempting to place into words what my understanding of suspension is and how it operates is extremely difficult. I would ask that you have a understanding of this difficulty and not call "Bullshit" too harshly on my mistakes. Wahoo!
I hope you've enjoyed Part One and find it helpful and useful.
Be safe,
Rod
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