It's NOT preload!

[HaulinAshe]

I don't care what it's called in the Yamaha manual. I don't care how many times it's been referred to that way. That adjuster on the front forks, up top, the 17mm hex with the lines...

IT'S NOT PRELOAD!!!

Preload is the tension/pressure that's applied to the fork springs as everything is assembled. Think of preload as the amount of squish pre-applied to the fork springs. It resembles compressing that spring in a retractable writing pen as you screw the two parts together.

On FJR forks, the fork spring preload is a function of the length of the spacer tubes that slide down against the upper spring washer and butt up against the jam nuts for the dampener rods/fork caps. If you make that spacer tube longer, you get more spring squish, hence more PRELOAD. If you make the spacer tube shorter, you get less squish, hence less PRELOAD. Preload is measured as the difference in the spring length after assembly, versus the free length of the spring laying on your shop floor.

The 17mm hex adjuster in the center of the fork cap(s), MOVES THE ENTIRE SPRING/CARTRIDGE ASSEMBLY UP/DOWN. It changes FRONT RIDE HEIGHT which has the most effect on turn-in response. Raise the front ride height and the steering becomes less responsive, or "pushes" with the light application of brakes in a sweeping turn. Lower the front ride height and the steering becomes more responsive or "tucks" with a light application of brakes in a sweeping turn. Get it just right, and a smoking hot Goldilocks will jump on the back and say "Ride me baby".

It should go without saying but... Correct ride height is a balance from front-to-back. Therefore, if you change payload, change rear spring range (Soft/Hard on stock shock, preload on aftermarket shocks), add/remove bags, eat a big BBQ lunch, anything of that nature can and will change the ride height balance. Fortunately, the FJR geometry is very tolerant. Once you get the bike set for your typical payload situation, changing the adjusters mid-ride is almost never required. But that's why Yamaha put them there, for you to experiment and tweak the bike to your body size and typical payload.

GOT IT!!!???

 

[Pterodactyl]

Gee, do you feel better now?

Now I need to adjust my front fork preload.

 

[bluesdog]

Can I please have more hot sauce for my BBQ ribs?

 

[MrZappo]

Unfortunately, the body size they used as a reference is a 5 foot 2 inch Japanese test dude that weighs 92 pounds with gear on.

I dare say that is a far cry from the traditional FJR rider.

So, if we assume that everything you said is correct, there is minimal chance of it doing much good anyways.

The FJR is tolerant though as you said. Most of them (if someone made an effort to adjust the crappy suspension anyways), are dialed way up. And still, probably not enough spring for a proper setting.

 

[HaulinAshe]

I do feel better now. And now you know that there's yet another (internal) adjustment on the FJR forks to putz around with.

Here's a tip...

If you want to play around with the actual preload, slice off two 5mm slices of the spacer tube. Then you can stack them on or take them off to vary the preload. Buy an extra spacer tube and use it to make 5mm additional spacers to increase the preload over stock config. You can typically go 10mm either side of the stock setting without getting into other issues.

 

[RaYzerman19]

Ashe, too much hot sauce? The bottom part of the cartridge is a fixed length tube (spacer if you will) attached to the bottom of the fork. The bottom end of the spring rests on it, can't move. The top cap has the 17 adjuster to press the top end of the spacer/spring down, and since the bottom end of the spring can't move, you are adding preload, sorry to say.

Ride height is the height of the forks in the triple tree. When you add preload, you just are adding resistance to the fork compressing, which is your sag. Your sag is a ride height of sorts, but not really, it is the end result of compressed fork length for your weight. To adjust ride height, you would have to raise or lower the forks in the triple tree.

Same goes for rear, except some shocks have an actual ride height adjustment, normally part of the lower mount that is an adjustable length.

 

[HaulinAshe]

Ashe, too much hot sauce? The bottom part of the cartridge is a fixed length tube (spacer if you will) attached to the bottom of the fork. The bottom end of the spring rests on it, can't move. The top cap has the 17 adjuster to press the top end of the spacer/spring down, and since the bottom end of the spring can't move, you are adding preload, sorry to say.
Ride height is the height of the forks in the triple tree. When you add preload, you just are adding resistance to the fork compressing, which is your sag. Your sag is a ride height of sorts, but not really, it is the end result of compressed fork length for your weight. To adjust ride height, you would have to raise or lower the forks in the triple tree.

Same goes for rear, except some shocks have an actual ride height adjustment, normally part of the lower mount that is an adjustable length.

Your overall description is correct. But this portion is not "The top cap has the 17 adjuster to press the top end of the spacer/spring down". The adjuster portion is locked on the dampner rod with a jam nut. You really can't study the diagrams and see it. You must take the fork apart to see how it works. The diagrams are deceiving.

Under a load, meaning the bike not on the center stand, adjusting the 17mm hex does NOT change the amount/length the spring is compressed. It effectively does exactly the same thing as raising or lowering the forks in the triple clamps. Trust me, look again. Take the forks apart and look. Once the adjuster penetrates below flush with the bottom of the outer portion of the fork cap (only a couple mm's down), it changes ride height and does not alter preload.

 

[LKLD]

Would a measurement from floor to frame, or triple tree, confirm this? Using all of the adjustment length of course (max-min).

 

[redneckj]

So if you compress the front spring with a 1/2 inch spacer, that IS preload. But if you compress the front spring with the adjuster cap by screwing in down by 1/2 inch, that is NOT preload. Even though they do they do the same thing. Thanks for clearing that up. Now go drink a beer and chill.

 

[Enn]

I had not ridden the FJR for few weeks as I mainly ride Vstrom in a city commute. A couple of days ago I took FJR to work. Strange enough, in low speed turns (on roundabouts) it wanted to turn the front wheel more into the curve than needed and I had to use quite some force in order to keep it up. That does not happen on Vstrom. I wonder if this "preload" adjustment has any effect on that behavior of my FJR? I had just changed the front wheel to new ( Dunlop Roadsmart II), but I do not think that is the cause.

 

[Old Guy]

Would a measurement from floor to frame, or triple tree, confirm this? Using all of the adjustment length of course (max-min).

To further confuse the issue, what if you adjust one side to maximum preload height and the other side to the minimum, would the fork assembly no longer be a rectangle? Would the axle no longer be parallel with the floor when the bike's level?

 

[mcatrophy]

I had not ridden the FJR for few weeks as I mainly ride Vstrom in a city commute. A couple of days ago I took FJR to work. Strange enough, in low speed turns (on roundabouts) it wanted to turn the front wheel more into the curve than needed and I had to use quite some force in order to keep it up. That does not happen on Vstrom. I wonder if this "preload" adjustment has any effect on that behavior of my FJR? I had just changed the front wheel to new ( Dunlop Roadsmart II), but I do not think that is the cause.

Tyres are off topic, but I'd suggest it would do that. The FJR is very sensitive to its tyres, particularly the front. Try experimenting with the tyre pressure in the range 35-42 psi (2.4-2.9 bar). Then swap the tyre for something more suited to the FJR, see the tyre poll thread for suggestions, my personal favourite is the BT023.

 

[Old Guy]

I had not ridden the FJR for few weeks as I mainly ride Vstrom in a city commute. A couple of days ago I took FJR to work. Strange enough, in low speed turns (on roundabouts) it wanted to turn the front wheel more into the curve than needed and I had to use quite some force in order to keep it up. That does not happen on Vstrom. I wonder if this "preload" adjustment has any effect on that behavior of my FJR? I had just changed the front wheel to new ( Dunlop Roadsmart II), but I do not think that is the cause.

I would expect that the new tire is the difference. Mine turns in more easily with new tires even of the same type and takes a few miles for me to reacquaint myself with the feel.

 

[Geezer]

If the total length of each fork leg remains the same as I turn the adjuster on top of each tube, then I believe I am adjusting preload because I am changing the compression of the spring. If the adjustment alters the length of each leg, then the adjustment would be ride height.

 

[RaYzerman19]

I've had a lot of FJR forks apart, so lemme try again...... If you back the preload adjuster right off, remove cartridge assembly from the fork, measure overall length to a reference point on the fork cap itself, say the top. Screw in the preload adjuster...... the spring will be compressed shorter the more you turn it in. That's preload.

Sag is when you put the fork back together, and add weight (of the bike and rider) and the spring compresses even more. Adjusting preload will alter the sag.

 

[Redfish Hunter]

Great! This means I can load one sidecase completely full and leave the other empty and then just use the adjustment on the fork caps to compensate. Kind of like trim tabs on a boat.

 

[yamafitter]

You need to understand what is happening when you turn the 17mm adjuster. Next time you have your forks apart turn the adjuster and look what is happening. The fork cap has an inner and outer section. The outer section threads into the fork tube and therefore relative to the fork tube does not move. The inner section is threaded into the outer section of the fork cap and therefore moves up and down relative to the fork tube.

When you turn the "preload" adjuster in (less lines showing) the distance between the top of the cartridge and the bottom of the fork cap is decreased. The only way this can happen since the preload spacer position is fixed relative to the cap is for the spring to compress. This by definition is increasing preload.

All other things being equal when preload is increased the spring pushes back against the top spring washer and since everything is fixed above the washer the fork tube will extend slightly which reduces sag.

Sorry for the long winded explanation but I wanted to be as clear as possible.

 

[MCRIDER007]

If the total length of each fork leg remains the same as I turn the adjuster on top of each tube, then I believe I am adjusting preload because I am changing the compression of the spring. If the adjustment alters the length of each leg, then the adjustment would be ride height.

This is what happens when the fork is off the bike and no weight is being applied. The adjuster is pushing down on the main spring but it is also lifting up on the fork tube, the bottom of which is making contact with the top out springs (those short springs on the outside of the cartridge). The weaker of the 2 springs is going to compress and how much it compresses will be determined by the relative strength of the 2 springs. The fork will get longer as long as the top out spring is the one compressing, once it reaches a point where it has more resistance than the main spring, then the main spring will start to compress and that will be spring preload.

However, this is what happens only when no weight is being applied to the forks. When the forks are on the bike and the bike is off the center stand, everything changes. The main spring compresses from the weight of the bike and the bottom of the fork tubes drop below the top out springs so when the adjuster is applied all the force of the adjuster is being applied to the main spring.....but the main spring is not going to further compress as long as the fork tube is free to lift and extend....which it can easily do since the bottom of the fork tube is no longer making contact with the top out springs. What Ashe describes in Post #7 is correct.

Preload is always a back door way to achieve a desired ride height and obtain/maintain steering geometry. Preload does not change the spring rate, it doesn't even change the portion of the spring that is used when riding because the TOTAL amount that a spring is compressed with any given weight is NOT effected by preload, preload only changes the amount the spring compresses AFTER the weight is applied. Increasing preload will decrease the spring's compression after weight is applied, however the spring's total compression will always be the same, and that is why the fork's adjuster's are not going to further compress (preload) the main spring after weight is applied. The only way to compress the fork's main spring after weight is applied is to add more weight.

 

[LKLD]

Well, I'm glad we cleared that up.