Fuel EX Pro Set-up: Chris Eatough

Chris Eatough rode the Fuel EX to victory in the BC Bike Race this past July. Here's a quick  look at how he sets up his bike (NOTE: featured bike is regional rider Jeff Schalk's Fuel EX. Jeff and Chris rode together to victory in the BC Bike Race on nearly identical Fuel EX bikes)

My Fuel EX setup is basically an XC style setup (fast rolling tires and fairly lightweight parts), but the suspension quality is far superior to other XC bikes out there.

Rock Shox Reba Team, 120mm.  80psi in positive, 65 psi in negative chamber. Rebound set at one full rotation from the fastest setting.

Rock Shox MC 3 rear shock at 70psi.  Rebound set at 3 clicks from fastest setting.

I use a handlebar remote lockout for the front fork.  I lock it out for out of the saddle climbing or sprinting.I ride with the rear shock fully active most of the time.  I only use the motion control setting for extended climbing, and sprinting off the start line.

Stem: I use a Bontrager Race X Lite 105mm stem, 7 degree rise.

Tires: I use Bontrager Super X 2.2 Tubeless Ready Tires for just about all conditions. Front at 29psi, rear at 31psi.

Full Shimano XTR drivetrain and disc brakes.  Rapid Rise Dual Control shifters. For gearing, I usually use a fairly standard 22/32/44 chainring set with a 11-34 cassette.

For some race courses, I use a single front chainring, 34T.  This lets me shorten the chain for less chain slap and quicker shifting.  Also a bit lighter since no front shifter, cable and housing, and 2 less chainrings.  I keep the front derailleur on to keep the chain in place.

Overall, this is the perfect bike for covering serious distance on all day rides or races on rough mountain bike terrain.

ABP Explained

Alrighty, class. Welcome to Suspension 101. In today's lesson, we're going to go over what ABP is, what it does for you, and how it works. Ready? Let's jump in.

ABP: What is it?
The active brake pivot puts the rear suspension pivot concentric to the rear wheel axle, as opposed to Trek’s current design or the ‘Horst’ link where the pivot is located above (Trek) or Below (Horst) the rear axel.

What is the Benefit?
-The ABP keeps the suspension active and the rider in control while braking. Lock-up, or stiffening of the suspension under braking is virtually eliminated. Skidding is reduced; the tire stays in contact with the ground. Because the tire stays in contact with the ground, the brakes are more effective when they are used, and thus the time spent braking is reduced. Less braking also equals better handling and suspension by not loading the front fork.
Less time braking = more time going fast!
-Wide stance pivot bearings – same as the main pivot. Because the rear pivot bearings are spaced wider apart, the frame structure is torsionally stiffer.

How does it work?
The ABP allows the suspension to be active and independent of braking by separating the braking and drive-train components. The ABP allows the brake caliper to keep a near constant relationship to the brake rotor, so the caliper doesn’t rotate around the brake disk as the suspension moves through its range of travel.

What’s the science behind ABP?
Think that claim sounds too much like unsubstantiated marketing speak? Here’s the real deal, in-depth explanation (in other words, most of us will now tune out, and simply go riding and experience a ride like never before…)
The ABP allows the brake caliper to keep a near constant relationship to the brake rotor, so the caliper doesn’t rotate around the brake disk as the suspension moves through its range of travel.
Huh?
Brake force occurs between the ground and the tire. There is a contact patch on the bottom of the tire that is in contact with the ground. All modern, current suspension designs move the rear axel in an arcing motion. So when the brakes are applied, the wheel has to move in an arcing motion because it is fixed to the swing-arm. What this means is that the ground and the tire don’t exactly move together.
If you look at the bike with the suspension fully extended (bike completely un-weighted), there is a contact patch the tire has with the ground at 6 o’clock on the tire. With the wheel (and the tire) fixed to the swing-arm because of the brake being applied, when the suspension tries to move in the arc we described earlier, that original contact patch the tire had with ground moves.
However, because of friction between the tire and the ground, this contact patch doesn’t want to move. The rider feels this as “suspension stiffening” under braking, or a skidding, skipping feeling as the suspension bounces over bumps.
All suspension designs experience this to varying degrees, and all suspension designs can be analyzed to measure and quantify the amount of “contact patch rotation.” The lower or smaller the amount of rotation, the more active the suspension will be under braking.
ABP has the lowest rotation factor – lower than single pivot, lower than VPP, lower than FSR.
However, because the movement of the wheel is still based on our proven R1 design, all this active suspension comes without unwanted suspension movement. The bike is still highly efficient, bob-free, and without the need for suspension lock-outs.

Small bumps, big bumps, braking bumps, fast bumps – full time smooth, active, efficient suspension.

Here's how the Fuel EX compares to some of its competition. The first comparison is at the mid-stroke of the suspension, or at 50% travel. This is the most important measure because it's a bit past sag, and where the suspension is most likely to be during braking, and especially braking during high speed bumps.

Comparison of Contact Patch Rotational Factors – Mid-Stoke of Suspension Compression

2008 Fuel EX  -  2.3 degrees
2007 Stumpjumper  -  3.1 degrees
2007 Blur LT  -  4.5 degrees
2007 Mojo  -  4.0 degrees

Remember again, the lower the rotational number, the more active the suspension under braking.

Comparison of Contact Patch Rotational Factors – Full Suspension Compression

2008 Fuel EX  -  6.0 degrees
2007 Stumpjumper  -  7.3 degrees
2007 Blur LT  -  6.3 degrees
2007 Mojo  -  9.3 degrees

Full Floater Explained

Welocme again to Suspension 101. For this lesson, we're joined by Jose Gonzalez, as he can really explain how the Full Floater suspension really works, what its benefits are, and how it compares to the competition.

Full Floating Suspension - What is it?

The Full Floater works in conjunction with the EVO Link and the shock to create a suspension ride with unparalleled tuning and performance. Instead of simply mounting one end of the shock to the rocker link and one end to the frame, the shock is held in a suspended state between the rocker link and a mounting point attached to the swing-arm. The shock “floats” on two suspended attachment points.

What is the Benefit?
The Full Floating suspension design allows the suspension system to be tuned more highly than ever before. The suspension system is tuned to work in harmony with the specific shock spring technology (air or coil) through-out the entire range of suspension motion.
What this creates is a suspension that is incredibly supple and active on small bumps, has excellent control through the mid-stroke, and has a gentle progression at the end of the stroke to handle big hits and drops.
However, this progression has been very painstakingly tuned to get the perfect balance of allowing full travel, without blowing through the travel too easily.
All this comes without compromising the legendary ride of R1 – that is, comfort and efficiency all without pedal feedback, bob or brake-induced suspension stiffening – and all without the need for lockouts or other suspension inhibitors.

The Full Floating Suspension is not just more travel – it is BETTER travel!

How does it work?

The Full Floater allows the engineers and designers more control over the rates and tuning of the suspension than ever before. Because there are two moving mounts that can be controlled, the engineers can adjust the instantaneous ratios of the suspension system throughout its full travel range to do precisely what they want – keeping the suspension active over the small stuff, but with good control of the mid stroke, and precise end-stroke compression.

Want more info? The first graph shows the difference in the instantaneous leverage ratios of the 2007 Fuel EX (red curve) compared to the new 2008 Fuel EX (blue curve).

What you see is the 2008 red curve offers a “flatter” rising rate with a slight “hook” (digression) at the end of its stroke. This allows the system to have supple and active suspension over small bumps while maintaining a controlled mid stroke feel. However, due to the flatter pitch of the curve, the mid stroke offers a very fluid, smooth and controlling effect that does not have that firming feel (too progressive) and allows for better use of the available travel without rear suspension “wallow”.  The slight hook at the end adds a digression (falling rate) to the system which allows the suspension to continue to compress after most of the energy has already been absorbed and dissipated, as well as to counter the progressive nature of the air spring found on the shock. This gives the sensation that the bike has more travel than it really does, offering a bottomless feel and a higher quality travel (better use of the travel instead of just adding lower quality travel).

Competitor Comparison

So how does this compare with the competition’s systems? The following graph shows the 2008 Fuel EX compared with some of the most notable suspension designs used by its competitors:

The Ibis Mojo with DW-Link and VPP bikes fall victim to their very small links – they simply cannot provide the control needed due to the dramatic swing amount and radius it covers during use. But they differ slightly in effect as follows:

Mojo with DW-Link – This curve has a pretty steep progressive rate initially that flattens out in mid stroke and quickly goes to a digressive rate for the last half of its travel. This curve makes it almost impossible to optimize the tuning of the shock as the first part of the curve requires that the shock have light spring force and damping but the second part of the stroke requires the opposite. If you set this system up to have decent small bump performance, it will blow through its travel, giving the bike a wallow feel and will bottom out easily. It is almost impossible to optimize the shock tuning to this curve due to its contradicting requirements and huge swing.

VPP – This curve has a steep, digressive rate for the first 1/3 of its travel and then goes to a steep progressive rate for the last 2/3 of its travel. Due to the nature of the design and the rear wheel path this system has, the digressive rate at the beginning of the stroke helps to mask the inherent lack of small bump performance this design has. It allows for a lot of suspension movement for a smaller bump. But that also creates a wallow effect. The steep progressive rate after mid stroke creates a very firm shock effect and does not complement an air spring curve (too much progression effect when combined). As with the Mojo with DW Link, it’s very difficult to tune a shock to this curve. On both the VPP and Mojo with DW-Link, these curves become more of an issue as travel is increased (meaning that it’s easier to get a 4” bike to function than a longer travel application). Keep in mind that the original multi-link designs, that these bikes are based on, were conceived when downhill bikes were using under 6” of travel!

The FSR bike, while it does have a pretty good curve, the overall ratio is much higher than the EX. This means that it will require higher shocks pressures, creating more stiction and producing higher forces on the system, and requires heavier compression damping effect to control rider input (chassis stability). This is why Specialized bikes require some platform, inertia or lockout feature for efficiency and pedaling. The higher initial pressure needed also means the spring curve of the air shock itself will ramp up much more, which combined with progressive rate of the system, gives it a firmer overall feel and does not offer as fluid of a suspension feel or use.

All the while, the R1i design allows the weight of the frame to be kept and low and centered, with easy rider access to all shock adjusters and air valves.
By centralizing the weight over the BB (referred to as Mass Centralization-as important as Center of Gravity), the Center of Gravity is brought to the middle of the bike, under the rider, where the rider feels it much less when throwing the bike around (in line with his own weight and point of moment). Although lowering the weight helps, just lowering weight doesn’t do as much.

By keeping the shock low and centered, we’re also able to keep it in front of the seat tube. This keeps the shock and all its seals and bushings well protected from mud, rocks and other debris that gets thrown off the rear tire. And giving the rider easy access to the adjustment knobs and air valves – well, that’s pretty self-explanatory.

This design further allows room for a water bottle, and a full seat tube, allowing the rider a large range of seat height adjustment depending on the terrain and rider preference. Seat tube adjustment and protection of the shock are major benefits over other designs that don’t provide for this.

Well, that certainly is a lot of information. Everyone still with us? Good. How 'bout a ride?

Hey, you in the back! Wake up! It's time to ride now!

This post was modified on 8/22/07.  References to  “DW Link” have been changed to “Mojo with DW Link.”

Travis Brown's Fuel EX setup tips

When you get a new suspension bike, there's nothing more important than dialing the bike in to fit your specific needs. One person on the Trek testing staff who's spent the most time trying out different bikes and varying setups is Travis Brown.

Since he was instrumental in developing the Fuel EX, we only thought it proper to bring you some setup tips from the man himself:

Sag:
Trail bikes in the travel range around 120 mm to 130 mm... I like to set up 20 - 30 % of the total travel in sag.  Setting up more sag will give you a more plush feel and give you better small bump compliance but at the same time you will be sacrificing usable compression travel for hitting that big hit so keep in mind that you can go to far with sag even when pedaling isn't a primary concern.

Saddle setback, sag and chassis pitch:
Setting consistent saddle setback is relatively easy on a rigid MTB or road bike, but the dynamic position of full suspension bike adds a new dimension to this part of setup.   First of all it is important to consider that your pedalling setback should be measured on the bike with full weight.  If you set the same amount of sag front and rear this won't change but most riders set a bit less sag in the fork than in the rear shock and in this case a riders position behind the bottom bracket increases when the bike is under full rider weight.  Another thing to consider is chassis pitch.  While climbing because of a rearward weight bias the rear suspension will sag more an the front less.  Visa verse on descending.  For trial riding, since most of your pedalling will be done climbing, a rider should consider a level sagged setback that is slightly less than they would have on a rigid bike so that the climbing setback will more closely approximate the
true saddle setback and achieve the most comfortable and powerful position where most of your crucial pedalling will be done.

Rear shock rebound and compression:

The Fox RP23 is specifically tuned for the rates and ratios or our frame design.  I set exactly half of the rebound damping which is four clicks.  This is a great place to start with your own tuning.  If you desire a bit more control of the suspension movement add a few  clicks of rebound damping.  If you are looking for a bit more "lively" feel to the suspension back off a few clicks. For an Alpine style course, I use the 3 Pro Pedal compression damping setting for climbing and open for descending.   On a course with shorter climbs and many transitions I will usually leave the shock in the 1 or 2 setting for the entire race.  I like to run the shock on one or two for trail riding also so that I don' have to think about switching during the ride.

Fork tuning:
I like to set almost equal front suspension sag to rear.  Many riders run less sag in the front to have a controlled feeling but with the sophistication of today's forks there are ways to have a controlled
fork action and still have a fair amount of sag to achieve suppleness. On the Fox RLC forks that have both slow speed compression adjustment and bump threshold adjustment it is very easy to set up a fork that
has both very controlled and very plush travel.  The slow speed compression allows you to tune out slow fork movements such as movement from the pedaling cycle.  Higher slow speed compression also
can keep the fork from diving in switchbacks and slow speed drop offs.  I run about 6 clicks of slow speed compression for most types of terrain.  This also allows me to back off the bump threshold adjustment from full lockout an have a very firm pedalling platform that will also move if I hit something with the fork "locked".   I will run about nine clicks for normal conditions.  Experiment with these as base settings for your local conditions and personal riding style.

Cockpit:
I usually run 100 mm stem with a handlebar that has 12 degrees of sweep.  Keep in mind that a bar with more sweep considerably shortens your reach.  For example when I run a bar with 16 degrees of sweep I
lengthen the stem 5 to 10 mm to get the same reach to the bars and with a 5 degree bar I would use a 90 mm stem.  If you need to go much longer than 100 mm to get the proper length rider compartment consider one size larger frame.

Fuel EX Suspension Set-Up - Intro

This and the following few posts come directly from our SoCal Suspension R&D Lab. These set-up steps were written by Jose Gonzalez and Greg Buhl. Most people already know who Jose is (our Director of Suspension Development - check this site and the EX site for more info). Jose knows so much about suspension, he's forgotten more than most of us will ever know. Greg is the new Suspension Tech Engineer working with Jose. Greg's been at Trek for a few years, but recently decided he simply couldn't take the Wisconsin winters any more.

Be sure to check out the 3 following posts - even though it's not complicated, there's a lot of info here!

Trek’s Suspension R&D Lab 2008 Fuel EX Suspension Set-Up Tips

The 2008 Fuel EX’s R1i suspension system is a highly engineered and refined suspension design. To reach its full potential, and to enjoy the designed performance levels, it’s imperative that a rider takes the time to properly set up the rear shock settings. Although the Fox Float RP2 and RP23 rear shocks used on the 2008 Fuel EX are custom tuned ( both compression and rebound) to match the specific performance requirements of the R1i suspension system, it is necessary for each individual rider to set it up to their weight (most important),  riding style and terrain. 

Due to the efficiency and suspension performance engineered into the R1i rear suspension system, the Fuel EX does not rely on firm damping settings and higher spring pressures to have an efficient ride. This enables us to focus more on tuning the rear shock for the bump performance qualities, optimizing the performance in rough terrain. This allows for the use of the more efficient ProPedal setting in tight, rough singletrack and during technical climbing. Because of this inherent efficiency in the suspension system, it’s very important that the spring pressure is set properly for a given rider, which is 25-30% sag when the bike is static.

Spring force and rebound are the key two elements that need to be tweaked for individual proper set-up. Although this is a simple process to do by following these steps & tips, its simplicity belies its importance.  There is nothing you can do that can enhance your ride more than setting your suspension properly.

Fuel EX Suspension Set-Up - Part 1: Setting Spring Pressure

Step 1 - Setting Air Spring Pressure

Although Trek offers recommended spring pressure baselines, these are just starting baselines to get a rider in the “ballpark”. To truly achieve the ideal spring pressure for each individual rider, it is necessary to adjust your spring pressure by using sag as the indicator. Sag is the amount of shock compression with rider static on bike. The easiest way to do this is with the o-ring that’s installed on the shock’s damper body. This is pretty easy to get with the following tips:

1. When checking sag and setting spring pressure, make sure that the ProPedal is in the open position. Otherwise you will have excessive sag when using the ProPedal open position.

 

2. ACG tip for setting sag - With a permanent ink marker and measuring tape, measure 12mm (25% sag) & 16mm (30% sag) below the lower air canister seal and make two marks with the ink marker on the damper body. This is the sag range you need your o-ring to end up in. If you prefer a more of a longer travel, All-Mountain suspension feel, run the sag closer to the 16mm mark.

 

3. Start by setting your air pressure to the body weight recommendations shown on the 2008 Trek Suspension Set-Up Card. This will get you in the ballpark to check sag.

 

4. Push the o-ring up against the upper air canister wiper.

5. Have a friend hold your bike up for you, and get a stool placed next to the bike (you can also use the wall as shown).  Sit on the bike, putting your full weight on the saddle with your feet on the pedals.  Be careful getting on and off the bike, as you do not want to push the suspension artificially further into the travel.

6. The o-ring that you previously pushed up against the air canister, should be12-16mm below the upper air canister wiper after the rider has sat on the bike static. If it’s more than that, you need more pressure and if it’s less than that you’ll need less pressure. Change the pressure by 10psi each time until you get to the proper sag.

Keep in mind that with most shock pumps you will read a lower pressure than what was in the shock when re-installing the pump. This is due to the pump having to fill itself up with pressure upon installation onto the pressurized shock. Although this varies with pumps, it’s usually about a 10psi change.

7. Once you’ve set your sag, just jot down your pressure and check it every 1-2 week to make sure you have optimum performance every time you ride.

About Spring Pressure
Setting your spring pressure is the first step. It’s common for many riders to have the spring pressure set too high, greatly diminishing the performance of the rear suspension. When the spring pressure is set too high, the small bump performance is compromised and it feels like the suspension ramps up too much in the middle of the travel. The rider also will not get the full benefit of all of the travel designed into the system (you should reach full travel at least once or twice during a trail ride). On the other hand, if you’re spring pressure is too low the bike will ride harsh on small bumps (yes, that’s not a typo) and bottoms out on big stuff. This is due to the engineered leverage ratio and rate that changes as the system is compressed (think position sensitive here).

The R1i is designed with a rising rate or progressive leverage ratio that gets firmer as the rear suspension is compressed. If your spring pressure is too low for your weight, you will be sitting into a firmer part of that leverage ratio for a given bump (especially small bumps) which will make it feel too firm. At the same time, you will bottom out on big bumps.

Fuel EX Suspension Set-Up - Part 2: Setting Rebound Damping

Step 2 - Setting Rebound Damping

To set the proper rebound for your spring settings and weight, use the 2008 Trek Suspension Set-Up Card (click on the image at left) as the starting point. Make sure you set spring pressure and sag first.  Look on the chart for the spring pressure you ended up using to get proper sag and set rebound to the recommended clicks for that spring pressure.

 

ACG tip for checking rebound - A general way to gauge rebound is to ride off a street curb size drop at slow speed while seated. The rear suspension will compress and extend, and should settle after the first compression and extension. If it does not and wants to compress and extend a second time, rebound is set too fast. If it feels like the rear end lags in returning back up, speed it up. You can get a feel for the differences by setting the shock at both extremes of the adjuster range and doing this exercise.

 

About Rebound Damping
Rebound damping has two circuits inside the shock. One is adjustable and the other is a tuned valve. The adjustable circuit controls how much oil can bypass the tuned valve. Depending on where the adjuster is set, at some point in the extension process, the bypass pathway is too small to accommodate the speed of fluid transfer and the valve takes over.

In general, the bypass adjustable pathway influences small to medium bump rebound, as well as in rider influence/chassis stability. It also is felt on rolling G-outs and the face of a jump where the shock is slowly and gradually compressed. The valve controls mid to end stroke (extension after full bottom) rebound/extension. This is felt on more severe impacts such as at full compression from a jump or big G-out.

Rebound adds stability and control to the bike by eliminating oscillation and maintaining traction. Ideally, rebound should be tuned so that the shock responds to a bump and extends quick enough to be ready for the next impact and track the ground for traction, but without extending so quick that the system oscillates.

Fuel EX Suspension Set-Up - Part 3: Pro Pedal

Step 3 - Setting ProPedal RP2 and RP23

On the RP23, you have three levels of platform that you can choose from. You can gauge which platform level is best for you by using the following recommendations. Remember, the open mode (shown at left) is identical regardless of which platform setting you choose as you are only changing the close mode:

Platform #1 – You ride a lot of rolling terrain that is fairly rough that doesn’t give you time to switch modes or you spend a lot of time on flatter, mildly rough single-track. This allows for more efficiency than the open mode but with good bump compliance. Riding in the #1 setting reduces the need to flip from open to close on rougher terrain.

Platform #2 -  Our favorite setting for terrain that has more extended climbing and with longer descending which gives time to switch modes. The close mode also works well on flat, flowy single track that’s not very rough. In the close mode, it offers just enough bump absorption with outstanding efficiency.

Platform #3 – This setting is for optimum efficiency on a long, smoother climb and for fire road riding. It’s slightly firmer than #2 and is intended to be used as an on and off mode.

About ProPedal
The Fox Float RP2 and RP23 both utilize a very sophisticated valve system that is highly tuned. Both shocks have an open and closed mode. The closed mode is tuned to allow use in real-world off road conditions, offering efficiency with some bump compliance. The close mode allows for a firm feeling rear suspension that still maintains traction and stability, and with some level of bump compliance. In the open mode it’s all about suspension performance and making the bumps disappear.

2008 Fuel EX Geometry

We've had a lot of questions about the geometry of the new EX. The basic geometry and handling of the 2007 EX has been carried over to this new bike. We went through a lot of iterations and testing to get that bike dialed as far as the geometry and handling was concerned, so we didn't feel a need to change what was working so well.

The effective top tube length and overall cocpit area is something we've had worked out for quite a while, going back to the original Fuel bikes. It gives you a good amount of room to stretch out and keeps your weight centered in the bike, but still allows you to very easily weight the bike forward or back depending on the terrain (trail obstacles, or big descents for instance).

The BB height was something we experimented with quite a bit. What we finally settled on was an excellent balance of keeping your weight as low as possible for stability and the ability to really rail corners, but at the same time, keeping it high enough to avoid bashing chain-rings into logs and rocks.

We really put a lot of effort into the steering geometry. Here our objective, and what we attained, was a very balanced handling - responsive handling to keep things sharp in tight, twisty trails, but stable enough to be able to really open it up on big descents.