suspension improvement and adjustment

[Sdaniels]

Anybody use the machined aluminum caps with the threaded compression adjustment that you can find on eBay and other places? Not sure I even need them, but I have some I may install someday.

Those are spring preload adjusters...it doesn't do anything with compression damping. Gary in NJ uses them.

 

[TownsendsFJR1300]

So no tapping but was the hole slightly smaller for a press fit or does the sealer do all the work?

No press fit. The sealer does the work...

Tolerances are as tight as possible and hammering/forcing the valve would likely damage it.. Just make sure you have enough Schrader valve sticking out and give the sealer time to set up.

JB weld would work fine as well too...

 

[Gary in NJ]

I've used the adjustable fork caps from ebay on a few bikes. I haven't had any problems with them and wouldn't hesitate to purchase again.

Regarding using air in the forks, the air acts as a secondary spring. In fact, with enough air pressure you could actually remove the spring (no one is advocating that...it's just a statement for illustration). Like a spring, air can be compressed and it acts in a linear fashion. So adding air to the forks is like adding a helper spring. What air doesn't do is improve the damping - you are still forcing oil through a few small holes at the bottom of the damping rod to create motion control.

So the air will help with fork dive, but it will not provide a plush ride.

 

[meadeam]

Those are spring preload adjusters...it doesn't do anything with compression damping. Gary in NJ uses them.

I didn't mean damping, but I see where I misused the term compression in this context.

I've used the adjustable fork caps from ebay on a few bikes. I haven't had any problems with them and wouldn't hesitate to purchase again.

Good to know, I'll try them out.

 

[Sdaniels]

I've used the adjustable fork caps from ebay on a few bikes. I haven't had any problems with them and wouldn't hesitate to purchase again.

Regarding using air in the forks, the air acts as a secondary spring. In fact, with enough air pressure you could actually remove the spring (no one is advocating that...it's just a statement for illustration). Like a spring, air can be compressed and it acts in a linear fashion. So adding air to the forks is like adding a helper spring. What air doesn't do is improve the damping - you are still forcing oil through a few small holes at the bottom of the damping rod to create motion control.

So the air will help with fork dive, but it will not provide a plush ride.

I'm still trying to figure out whether it's the spring rate, progressive springs or the damping that contributes to fork dive on hard braking. Stock springs are progressive on the FZ...initial rate is .75kg & it ramps up to 1.2kg. That soft, initial rate is there for slightly more than half the travel so that would be my first thought & makes a good argument for straight rate springs & the initial spring rate is too low. I ride a gen 2 vmax. Stock springs are straight rated but at .85kg. Race Tech suggests .85kg for the FZ with a 170lb rider so how does my vmax, which weighs another 230lb over the FZ, not dive with those springs? That suggests damping has a say in fork dive too but I've had other bikes where stiffer springs was the only change & it considerably reduced fork dive on hard braking.

 

[TownsendsFJR1300]

Just adding air DOES REDUCE dive and sag depending on how much you add.

Put in 30PSI and you have a SOLID front end...

And agreed, just adding air does not adjust dampening, changing the weight oil would help with that.

I added "air" after doing a fork oil change and am very content on how it operates on the street.
I don't see or do track days, just everyday riding and this set up works for me..

 

[Sdaniels]

Put in 30PSI and you have a SOLID front end...

My first bike was an early 80's 750 Maxim. Noticed the schrader valve on the forks once so I took a trip to the local garage, aired that joker up. Found out very quickly it does not take that much air...bike shot up almost instantly. The ride felt like a chopper with that wheel kicked out what felt like a mile! Turning was interesting & absolutely no compression, even with holding the front brake & bouncing on the handlebar. I find it comical reminiscing about it.

 

[Gary in NJ]

I'm still trying to figure out whether it's the spring rate, progressive springs or the damping that contributes to fork dive on hard braking. Stock springs are progressive on the FZ...initial rate is .75kg & it ramps up to 1.2kg. That soft, initial rate is there for slightly more than half the travel so that would be my first thought & makes a good argument for straight rate springs & the initial spring rate is too low. I ride a gen 2 vmax. Stock springs are straight rated but at .85kg. Race Tech suggests .85kg for the FZ with a 170lb rider so how does my vmax, which weighs another 230lb over the FZ, not dive with those springs? That suggests damping has a say in fork dive too but I've had other bikes where stiffer springs was the only change & it considerably reduced fork dive on hard braking.

Warning: Long post to a simple question!

The FZ6 comes equipped with dual rate progressive springs from the factory. This type of spring is typical for conventional damping rod forks because a damping rod with fixed orifices, in and of itself, have no means of adjusting the speed of movement (compression and rebound). It can only provide a fixed amount of motion control, also known as damping. A progressive spring requires additive amounts of force to compress; this allows for fast movement in the early part of the fork stroke and as the fork compresses the spring requires additional force to achieve the additional movement.

The damping rod is a tube with an opening on the top and a pair of small holes on the lower portion of the tube. The damping rod has a seal and acts as a piston as the slider moves up and down the fork tube. As the fork is compressed the piston moves and forces oil through the damping rod from the top of the tube through the smaller holes on the bottom. This creates resistance inside the fork itself. This resistance to movement is called damping; compression damping as the fork compresses and rebound damping as the spring in the fork seeks its static or neutral position.

How did Yamaha select the rate of the spring and the size of the holes in the damping rod? They estimate an “average rider” across their vast market. In this case a rider who weighs around 150 pounds. If this is you, your springs have been designed with you in mind. If this is not you, your bike is most likely under-sprung for you.

The only job of the fork spring (or shock spring for that matter) is to support the bike and rider through the full range of travel. We measure the effectiveness of the chosen rate of the spring through sag measurements - and we confirm this with real world performance. The amount of force required to compress a spring is expressed as its rate. As noted above, the FZ6 uses a dual-rate (progressive) spring from the factory. Progressive rate springs are typically used in damping rod forks in an effort to provide a sense of...well...progressiveness to the movement of the fork/shock. Small impacts and movements are absorbed through the lower of the two rates available whereas harsh/fast movements are absorbed through the higher rate portion of the spring. Unfortunately, in order to make use of the higher rate portion of the spring, you need to use most of the lower rate portion. This is where the forks/shocks become harsh with excessive movement (example, brake dive).

A spring will always seek its static position. When you open up a box with a fresh new spring, it is in its static position. When you compress the spring and then allow it to rebound, it will seek its static position as quickly as able. When installed in our motorcycles we preload the spring. When this happens there is an ocilation of the spring as it seeks its static position. Spring damping is a secondary force on the spring that is used to 1) slow the rate of movement of the spring and 2) reduce the amplitude and frequency of the oscillation as the spring seeks its static position. In motorcycle forks and shocks we use oil and air (nitrogen) to create and control damping.

What follows is a write up I did for another forum that I participate. While it is specific to RaceTech Gold Valve Emulators, it give an overview of how the moving parts of the suspension work together. Enjoy!

______________________________________________________

The suspension on a motorcycle is a system. The forks and shocks have to work in balance for good performance and a comfortable ride. This article is focused on forks that use RaceTech Gold Valve Emulators (GVE). By using GVE you have greater ability to adjust and tune the performance of the forks to suit your needs. GVE allow you to adjust compression damping and rebound damping. But before we get to that, let’s understand what it is that we are trying to balance. We can break this down into four elements:

1. Unsprung Weight – The weight of the wheels, tires and brake components
2. Sprung Weight – The weight of the bike (excluding unsprung weight) and the rider
3. Springs – The part of the suspension that supports the sprung weight
4. Damping – The aspect of the suspension that controls how fast the suspension moves (compresses and rebounds).

In sentence structure, the springs support the sprung weight of the bike and rider and damping controls how fast the suspension compresses and rebounds. Simple, right?

There are five different adjustable elements to understand to properly tune your forks so they suit your riding style and weight.

1. Fork Springs

What do they do?
They support the sprung weight of the bike and rider. A spring has a neutral position when unladen (sitting in the box), a static position (installed and preloaded for the bike and rider) and a dynamic position (moving while riding due to road irregularities, braking and acceleration). When in a dynamic position the spring will always be seeking its static position.

How are they adjusted?
The first adjustment is choosing the correct spring for bike and rider. Once you’ve confirmed that you are using the correct straight-rate spring, the way to fine tune the spring is through preloading. You preload (pre compress) the springs by adjusting the length of the spring stack (GVE, spring, spacer, washers and cap) by adding or removing shims (washers) that are placed between the fork cap and the spacer. If you have adjustable fork caps you can make the adjustments very easily without disassembling the forks by turning the adjusting rod in the fork cap.

How do I know when it’s right?
There are two types of sag settings that you need to set; static sag; the amount the spring compresses under the load of the bike, and race (also known as total) sag; the amount the spring compresses with the rider on the bike, in a riding position. You want about 10mm of static sag and 25% to 30% of your suspension travel for total sag. This equates to 32mm to 38mm of sag for our 127mm of travel.

2. Compression Damping via Gold Valve Emulator (GVE)

What is it?
Compression Damping controls the rate (or speed) that the forks can compress. We know that the spring is always seeking its static position. Without damping the spring will seek this position as fast as it can and the inertia of the bike and rider will cause the spring to overshoot its movement towards the static position. Without damping the bike will feel as though you are riding in a rodeo. Too little compression damping results in a fork that goes through its initial stroke too quickly (and feels mushy) and too much compression results in a fork that feels stiff/harsh.

How is it adjusted?
The GVE is adjusted by selecting the correct spring (yellow, blue or silver) and then preloading it so the valve opens under the right circumstances. For this application the #40 blue spring is used with a baseline preload of 2-1/2 turns out. Increasing the preload increase the damping (stiffer) and decreasing the preload decreases the damping.

How do I know when it’s right?
You’re gonna hate this answer, but it’s the truth – you’ll know when it’s right when you like it. If the forks are harsh, reduce the preload on the GVE by 1/2 a turn. If they then feel soft, add back in an additional 1/4 turn of preload. This is an iterative process.

3. Rebound Damping

What is it?
Rebound damping controls (slows) the speed at which the spring seeks its static position from a compressed position. Rebound is the intersection between ride and handling. Too little rebound and the forks will wallow like a 1970’s Cadillac. Too much rebound and the forks will feel darty/twitchy.

How is it adjusted?
On forks using GVE rebound is adjusted via the weight of the fork oil. The baseline is 15wt with an air gap of 140mm. Going to a higher viscosity oil increases rebound (slows the rate at which the spring seeks its static position) and a lower viscosity decreases the rate at which the springs seek its static position. An important note on fork oils – there is little commonality between manufacturers of fork oil. So if you are going to go from 15wt oil to 10wt, choose the same manufacturer otherwise you may go from 15wt to 15wt…or 5wt – there’s no way to know.

How do I know when it’s right?
When the forks provide a comfortable and controlled ride, and the handling feels linear and natural, the rebound damping is correct.

4. Oil Height

What is it?
The amount of oil in the fork. You are actually measuring the AIR GAP. It is measured from the top of the slider tube to the top of the oil with the fork compressed, GVE in place and the spring out. The baseline air gap is 140mm.

How is it adjusted?
This one is easy…remove or add oil as needed. It is usually added/removed in 10mm increments for tuning and then as required for fine tuning.

To change the oil height just remove a fork cap (one at a time - if you remove both fork caps your bike will sag to its stops and you’ll probably make quite a mess) and insert a hose into the forks and attach it to a syringe to extract or add a measured amount of oil.

How do I know when it’s right?
If the final 1/3 of travel is too soft and bottoms, add oil in 10cc increments. Do the opposite if you can’t use 85-90% of all fork travel.

5. Stroke

What is it?
It’s the amount of available fork travel used. It’s determined by the combined effect of spring selection, preload, damping and oil height. As a general rule of thumb, the first 1/3 of fork travel is controlled by the spring and is used mostly for race sag. The next 1/3 of travel is controlled by compression valving via the GVE. The final 1/3 of travel is affected by oil height (air chamber). Ideally you want to use 85-90% of available fork travel; 60-65% for normal riding and 85-90% under heavy compression (like an emergency stop).

How is it adjusted?
Since it’s the combined effect of everything…it’s everything noted above. With that said, try to only change one element at a time. Fork tuning can be confusing at times. If you change too many things at a time, you have no way of knowing what gave you the desired (or undesired) effect and how to minimize or maximize the change.

How do I know when it’s right?
You don’t know…until you make a change. If you make changes and like the results…you’re not done. If your changes take you further from where you want to be…then you’re done. Always remember. The forks and shocks work as a system. A change at one end of the bike will likely result in a change at the other end.

 

[Gary in NJ]

I ride a gen 2 vmax. Stock springs are straight rated but at .85kg. Race Tech suggests .85kg for the FZ with a 170lb rider so how does my vmax, which weighs another 230lb over the FZ, not dive with those springs?

I realized that I didn't answer this question

The answer is weight distribution. Sport bikes (which the FZ is close to being) carry their weight primarily over the front axle while cruisers (which is close to what the V-Max is close to being) carry their weight primarily over the rear axle. Add a rider and the sport bike gets closer to a 50:50 weight distribution, whereas a cruiser goes further towards the rear axle.

That is why a database like RaceTech's is so useful, it looks at the rider weight, bike weight and total weight distribution, and calculates a spring rate based on riding style and experience. Want to lower the suspension...yep it compensates for that as well (but I don't think it always gets that one correct).

 

[Sdaniels]

I realized that I didn't answer this question

The answer is weight distribution. Sport bikes (which the FZ is close to being) carry their weight primarily over the front axle while cruisers (which is close to what the V-Max is close to being) carry their weight primarily over the rear axle. Add a rider and the sport bike gets closer to a 50:50 weight distribution, whereas a cruiser goes further towards the rear axle.

That is why a database like RaceTech's is so useful, it looks at the rider weight, bike weight and total weight distribution, and calculates a spring rate based on riding style and experience. Want to lower the suspension...yep it compensates for that as well (but I don't think it always gets that one correct).

Yeah, the vmax is a cruiser...even if it isn't marketed that way. I have no idea what the ratio is but I'd guess close to 40/60 front/back. Still seems like a light spring for it's weight. It's got a pretty relaxed rake...31 degrees. I'm guessing that has input into what rate spring they picked. Comparatively, a Honda VTX 1300 has a 32 degree rake but it most definitely is a cruiser. I like the RT site too...typically I've found the recommended settings to be just a bit stiffer than I prefer. But ride quality is subjective so I don't fault them. It just means I adjust things a bit lighter which is what their product allows for.

 

[DeepBarney]

I've heard of Ricor's from other bike forums. It's definitely inviting being able to toss them in without anything other than spring removal. Some of the guys described it having a vague, gliding sensation compared to the emulators. Most of those comments came from the guys that leaned more towards sportbike handling than cruiser handling. Correct me if I'm wrong but I don't think they suggest changing springs, they don't specify a heavier suspension oil & they don't have adjustments...no ability to tailor settings. I think they appeal to the cruiser folks. Something improves ride quality with minimal wrenching & no adjustments is a good deal for some.

Spring the bike to your weight to get the correct sag (if necessary, which for me at 160lbs it wasn't). They do specify a fork oil weight but I don't remember what off hand. No changes are necessary, though some folks will want to trim their spacer depending on where their sag ends up. You're also right in that you really can't adjust them. Though based on how they work I don't see much reason you'd want them adjustable. I've never ridden a great cartridge damped bike, so I can't compare to that, but I can say they made a noticeable difference in how planted my Bonneville feels in a corner. I can definitely push it harder than before and not have it upset by the mid corner bumps like used to be the case (always a bit wallowy and shakey). Also brake dive is greatly mitigated. For that bike and how I use it, a set it and forget it approach was the best route for me.

The Ricor essentially has a check valve that opens or remains closed depending on whether the bike is diving (ie braking) or the wheel is traveling upwards (didn't see that bump in the road).

Definitely a lot of cruisers that are using them, but I also found a fair number of positive reviews by folks that used them on dual sport bikes (KLR's, DR650's, and BMW 650's mostly). They do a good job of dampening sharp hits and keeping the front compliant.

Btw, I had a Kawasaki KLR250 that had factory Schrader valves on the forks. Like others have said, bit of air went a long way in stiffening them up.

 

[Sdaniels]

Want to lower the suspension...yep it compensates for that as well (but I don't think it always gets that one correct).

Do you think it over or undercompensates? My son is on the ball of his feet with the rear shock on it's lowest setting. We'll be doing the springs/emulators later in the month & an Ohlin's is probably not too far down the road. He may opt for lowering the forks about an inch.

 

[Gary in NJ]

Do you think it over or undercompensates? My son is on the ball of his feet with the rear shock on it's lowest setting. We'll be doing the springs/emulators later in the month & an Ohlin's is probably not too far down the road. He may opt for lowering the forks about an inch.

If the calculator suggests a rate that is between available rates, choose the lower rate. RT suggests to use the higher rate, but I have found that the lower rate always is more compliant.

For example, if the calculator suggests a rate of 0.83kg/m and 0.80 and 0.85 are available, use the 0.80kg/m.

 

[Sdaniels]

If the calculator suggests a rate that is between available rates, choose the lower rate. RT suggests to use the higher rate, but I have found that the lower rate always is more compliant.

For example, if the calculator suggests a rate of 0.83kg/m and 0.80 and 0.85 are available, use the 0.80kg/m.

The calculation for my son calls for a .80 kg spring but the lowest rate they offer is .85 kg. I've already got the .85 spring so I'm trying to make them work. When picking the 1" lowered option, the rate jumps up to 1.02 kg, a .22 kg difference. RT doesn't list it, but I'm wondering if lowering by 1/2 an inch would effectively call for a .10 kg increase (.90 kg) & get him closer to the .85 spring. I just think .85 unlowered is going to be too stiff him.

 

[Gary in NJ]

Call them. RaceTech can provide you with a custom rate spring. I’ve done it before on my DRZ street tracker (lowered 2 inches) and I think the cost was an extra $10.

You can also choose a spring that has 1mm less diameter. Lastly, you can choose a spring that is slightly longer or shorter. If you download their spring catalog you’ll likely find a perfect alternative.

 

[Sdaniels]

Call them. RaceTech can provide you with a custom rate spring. I’ve done it before on my DRZ street tracker (lowered 2 inches) and I think the cost was an extra $10.

You can also choose a spring that has 1mm less diameter. Lastly, you can choose a spring that is slightly longer or shorter. If you download their spring catalog you’ll likely find a perfect alternative.

Well apparently I won't have to do anything...seems my boy is about 20 pounds heavier than I thought so springs are right on the money . We've got spring preload adjustable fork caps coming. RT suggests 10mm preload...if I put the preloaders at minimum setting, can I go with 2 or 3 mm preload?

 

[Gary in NJ]

I usually cut my spacers so the top of the stack-up is even with the top of the extended fork tube. Most fork caps will provide approximately 15mm of pre-load, so if you need less you can always shorten the stack-up (spacer). That's the nice thing about adjustable fork caps...doesn't matter (too much).

 

[Sdaniels]

I usually cut my spacers so the top of the stack-up is even with the top of the extended fork tube. Most fork caps will provide approximately 15mm of pre-load, so if you need less you can always shorten the stack-up (spacer). That's the nice thing about adjustable fork caps...doesn't matter (too much).

Gotcha....I was mainly thinking to give him the softest ride on the minimum setting. He can always adjust to stiffer...and I've got to have some preload to keep the emulator in place. Think I'll put them at 5mm preload.

 

[Sdaniels]

Gary, can you tell me about your Ohlins shock? I find a street version with preload & rebound adjustments but there's one with all 3 adjustments with a remote reservoir.

 

[Gary in NJ]

The spring does not determine ride plushness/firmness. Ride quality is handled by the rebound and compression damping. The springs only job is to properly suspend the bike and rider. Yes, too stiff a spring will result in a harsh ride that can't be adjusted away, and the same is true for too soft of a spring. Ride control is not adjusted via pre-load - sag is adjusted via preload.

The Ohlins shock with the remote reservoir is one of the holy grail shocks. If you have found one at a good price, buy it. And if you don't buy it, post it here so someone else can. My shock is the one with the screw-type preload adjustment and rebound control.