fork preload

[pigdog]

does anyone know if yamaha beefed up the fork springs for the 2013 fz8? with the forks fully extended i measured from the top of the seal to the bottom of the slider & came up with 150mm. with all my gear on i took another measurement but only compressed the spring 28mm. i even backed off the preload adjusters to within 3 flats of full seat. sag should be about 35mm. i weigh 158lb with all my gear. i used one of dave mosses tutorials on suspension set up. any ideas?

 

[Bajaedition]

As far as published they only added the adjustments, the spring rate is the same

 

[Banky2112]

I'll mention that I'm talking with racetech in Cali, they would like to do a fork setup for a 2013, but need a bike in shop.... I'm in VA so I can't do it......

 

[bikee4]

As far as published they only added the adjustments, the spring rate is the same

But compression and rebound and preload is adjustable, why are you making light of that fact?

 

[Bajaedition]

making light of what?

I states the fact that they claim not to have changed the spring rate, just made the preload adjustable thats all

 

[pigdog]

well preload is set soft. today i went for a spirited ride, took along a screwdriver & 1/4 in. open end box wrench. i added rebound until the forks stoped at the top of its stroke witout traveling down. i then i gradually backed off the compression screw 2 clicks. the bike turns into the corners better & doesn't bottom out with hard stops. now ill have to do this all over again when i get my modded stage 5 elka shock back from the factory.

 

[NoNine4me]

does anyone know if yamaha beefed up the fork springs for the 2013 fz8? with the forks fully extended i measured from the top of the seal to the bottom of the slider & came up with 150mm. with all my gear on i took another measurement but only compressed the spring 28mm. i even backed off the preload adjusters to within 3 flats of full seat. sag should be about 35mm. i weigh 158lb with all my gear. i used one of dave mosses tutorials on suspension set up. any ideas?

My bike is a stock 2012. I weigh a little less than you do and I'm right at 35mm on the fork sag. Appears that the preload adjusters may add a bit more preload in the standard position than the spacer in the '12. Spring rate may indeed be different but you can probably check that by looking at part numbers.

 

[pigdog]

im still fiddling with the fork adjusters, trying to use the info from the top suspension tuners on the net. first preload then rebound & compression damping.

 

[NoNine4me]

im still fiddling with the fork adjusters, trying to use the info from the top suspension tuners on the net. first preload then rebound & compression damping.

I have a 2012 with no adjusters. It just happened to be correct for my weight, luckily. I was thinking maybe the adjusters on the 2013 added more preload or changed something. What you could do is cut the spacers inside to a slightly shorter length and start over. That's quite a bit of work, you need to remove the handlebars and unscrew the fork caps (loosen upper pinchbolt or they will never unscrew). Then try removing no more than 5mm. You should have this done by a professional mechanic, at least the cutting part. Or try backing the adjusters all the way off. The stock springs are pretty stiff for anyone under 160 lbs. I will have to replace mine eventually, they are too stiff but the sag was right. They are .89 kg and I need a .85 kg. Try the Racetech.com website for more info. Good luck to you. Be careful with any of the work.

 

[Bajaedition]

preload and spring rate are 2 different things

setting the preload properly has nothing to do with the softness of the springs
as harsh springs do not help handling

racers are not trained to set suspensions, they are trained to tell mechanics exactly what they are feeling and the mechanic handles the suspension. 99 percent of street riders could not tell what was happening with damping as they do not know what to feel for or when to feel for it. What most guys claim is damping problems are spring issues and then they are adjusting the wrong thing compounding the issue.
Spring rates are chosen by manufacturers by the intended use of a bike, and it's paylaod rating, preload is so that the average payload can use that rate. Adjustable preload is so the [payload can change. in other words, so that a 200 pound rider and a 150 pound rider can have the bikes geometry set the same. If the manufacturer thinks the bike needs 55/45 then you set the proload to that according to your weight.
Trying to adjust the preload so that the bike preforms better is ludicrous. Once the bikes Preload is set, and you are having spring issues, then you need a different set of springs, not messing with the preload, and spacers do not help, all they do is limit the downward travel of a set of springs which compounds the issue again. (spacers help with preload, not spring rate.)
Damping is an issue that guys can really screw up the suspension of a bike as they do not know where they are feeling it's effect.
But that is for a different thread, what this thread is about is PRELOAD, and preload is set by bike. it is set so that the suspension of the bike can work in it's intended range, that is about it. Trying to use preload to help in handling changes the handling of the bike everywhere else because it changes the geometry of the bike everywhere else.
Set the preload so sag is correct, and leave it there.
If you want stiffer springs, get them, install them, then set the preload so you have the amount of sag you are suppose to have and then you can fiddle with preload trying to decide if it needs to be adjusted according to those springs to set the bike up to the bikes geometry.

 

[bikee4]

And compression and rebound damping. I agree that spring rate is constant, but if sag is achievable these adjustments can and do change the behaviour of the fork.

 

[9 Lives]

preload and spring rate are 2 different things

setting the preload properly has nothing to do with the softness of the springs
as harsh springs do not help handling

racers are not trained to set suspensions, they are trained to tell mechanics exactly what they are feeling and the mechanic handles the suspension. 99 percent of street riders could not tell what was happening with damping as they do not know what to feel for or when to feel for it. What most guys claim is damping problems are spring issues and then they are adjusting the wrong thing compounding the issue.
Spring rates are chosen by manufacturers by the intended use of a bike, and it's paylaod rating, preload is so that the average payload can use that rate. Adjustable preload is so the [payload can change. in other words, so that a 200 pound rider and a 150 pound rider can have the bikes geometry set the same. If the manufacturer thinks the bike needs 55/45 then you set the proload to that according to your weight.
Trying to adjust the preload so that the bike preforms better is ludicrous. Once the bikes Preload is set, and you are having spring issues, then you need a different set of springs, not messing with the preload, and spacers do not help, all they do is limit the downward travel of a set of springs which compounds the issue again. (spacers help with preload, not spring rate.)
Damping is an issue that guys can really screw up the suspension of a bike as they do not know where they are feeling it's effect.
But that is for a different thread, what this thread is about is PRELOAD, and preload is set by bike. it is set so that the suspension of the bike can work in it's intended range, that is about it. Trying to use preload to help in handling changes the handling of the bike everywhere else because it changes the geometry of the bike everywhere else.
Set the preload so sag is correct, and leave it there.
If you want stiffer springs, get them, install them, then set the preload so you have the amount of sag you are suppose to have and then you can fiddle with preload trying to decide if it needs to be adjusted according to those springs to set the bike up to the bikes geometry.

Excellent explanation, you hit the nail on the head.

 

[Bajaedition]

And compression and rebound damping. I agree that spring rate is constant, but if sag is achievable these adjustments can and do change the behaviour of the fork.

you are correct, and then at the same time it effects the way the rear shock works as it either loads or takes load off of that. Correct?
if we load more weight on the front we take weight off the rear. Correct?
now we need to adjust the rear. Correct?

What I mean is in order to the bike to work within it's geometry, we need the ratio, front to rear load to be correct. we adjust that with front fork sag.
by loading up the front end so the spring rate is stiffer we force it to absorb more of the duty intended for the rear of the bike and the rear suspension. in doing so we create a bike that will wash out easier in the front wheel because it has to handle more than it was intended to.
the correct way, and the safe way to do this, is to change out the forks and rear shock to units designed for what you want the bike to do. And when you do you will take away some of the UJM the FZ8 is designed to be and end up with a bike more like an R1 with less horsepower. I can get you that bike real easy and cheaper than doing all the mods to the FZ8, go buy a R6

 

[NoNine4me]

im still fiddling with the fork adjusters, trying to use the info from the top suspension tuners on the net. first preload then rebound & compression damping.

It's like bajaedition said. But you are starting out right with getting your sag set properly. However to do it really right, you gotta find out what spring rate is right for your weight/riding style/etc and replace the springs if necessary. Stock is a 0.89. Racetech's website has a nice little calculator. THEN after you replace the springs you will want to set the preload to achieve the correct sag. After you do that you set the damping adjusters at the baseline recommended in the manual, whatever it is, and just ride the bike a while. Also your tires have a huge effect on handling. Often changing to a different tire can solve many suspension/handling issues; or create new ones.

So you have to train yourself to tell the tuner what's happening when you ride, for example "the bars are trying get torn out of my hands whilst I'm leaned over and run through a rough section of pavement" or "the ass end is bouncing all over the place".

Those are highly technical terms that take years to learn.

 

[NoNine4me]

And compression and rebound damping. I agree that spring rate is constant, but if sag is achievable these adjustments can and do change the behaviour of the fork.

Spring rate is not constant. It is dynamic and changes based on the amount the spring is compressed. "Progressively" wound springs are designed to maintain a more predictable and constant behaviour. We can see this as we look at the spring. Part is wound tightly, part is wound more openly. The tightly wound portion (less space betwixt each coil) is the softer, more easily compressed portion.

The spring rating is just a starting, baseline number. Every spring manufacturer uses their own way of winding a spring so the performance is going to be different between stock, Progressive, White Power, Works Performance, Racetech, Ohlins, and so on.

 

[NoNine4me]

you are correct, and then at the same time it effects the way the rear shock works as it either loads or takes load off of that. Correct?
if we load more weight on the front we take weight off the rear. Correct?
now we need to adjust the rear. Correct?

What I mean is in order to the bike to work within it's geometry, we need the ratio, front to rear load to be correct. we adjust that with front fork sag.
by loading up the front end so the spring rate is stiffer we force it to absorb more of the duty intended for the rear of the bike and the rear suspension. in doing so we create a bike that will wash out easier in the front wheel because it has to handle more than it was intended to.
the correct way, and the safe way to do this, is to change out the forks and rear shock to units designed for what you want the bike to do. And when you do you will take away some of the UJM the FZ8 is designed to be and end up with a bike more like an R1 with less horsepower. I can get you that bike real easy and cheaper than doing all the mods to the FZ8, go buy a R6

Pay attention to this guys, he is right. You want awesome suspension and speed, get a GSX-R, R1, what have you. The FZ8 is an awesome platform and far, far better than the FZ-09 as a starting point for a UJM or streetfighter but when you get into the area where the sportbikes start to shine the FZ8 and the like are going to get dropped like flies. We start throwing money away at that point. However the FZ8 can benefit from thoughtful improvements and a moderate investment in suspension can be a good investment.

I say get your preload and sag where it's supposed to be (~35mm), put on a set of good tires (Q3s, SuperCorsas, something sporty and compliant and grippy), and work from there.

Of course we also have tire pressure to consider, rider smoothness...this can and does go on forever and ever.

BTW the difference between one bicycle tire and another is even more noticeable than between brands of motorcycle tire. I'm talking the high-performance road bicycles like Lance rides. Even a 5% difference in rolling resistance and compliance can be easily felt by a good rider. So we are not alone in seeking perfection.

 

[Banky2112]

Dang, it's like I'm playing a different sport here lol.

I'm putting 08 r1 suspension on my fz8 with an eye to eye adapter for the rear. So that I have components that were supposed to be together anyways. I'm doing it JUST to do it.
I don't actually know if it will help the bike....

At VIR trackdays they have tire mounting services seriously cheap and they have guys that can help you adjust your suspension correctly for a small fee. I think for me to learn this I gotta have a guy show me and help me understand it.

Sorry if I thread jacked........

But this seems like good stuff.

 

[skooter65]

Spring rate is not constant. It is dynamic and changes based on the amount the spring is compressed. "Progressively" wound springs are designed to maintain a more predictable and constant behaviour...

Just a slight correction here as I think you have your explanations backwards. Standard wound springs have a constant rate (Also known as the spring rate or spring constant; See Hooke's Law). The force, or "preload", is a function of the amount of compression on the spring: Force = Spring Constant X Amount of Compression.

Progressive springs are just that, progressive. The Spring rate of each section of coil winding is different.

Continue on, great topic for a thread!

 

[Bajaedition]

look at this guys

you dial in preload, the spring is compressed, in order to do that we made the area the spring can work in smaller, now the total distance it works in is less

we did not change the spring rate in any way, the rate is still the same, it just starts loaded up.

it still has the same rate as it had in the beginning only now it has less area to travel

ok, so we want it to feel stiffer and we put in 1 inch spacers, again we are not making the spring rate any stiffer, we are just loading up the spring more and giving it less room to move. The spring rate is still the same

now, the loaded rate of the spring changes proportional to its change in length. but that does not effect the spring until compressed there for a spring with a stiffer rate would have the same change when compressed.
I have studied the formulas in college but as of now it is not in the head.
anyway, so preloading the spring, it still has the rate of the spring multiplied by the formula for change of length, as such as a stiffer spring would also.

seeing that, you start to realise, replacing the spring and retaining the suspension travel to use all the spring is the answer, to compress the spring to get a stiffer spring limits the travel and will never end up with the end ratio you want from the stiffer spring anyway.

Hookes law, thats it, F=-kx, F is displacement, X is rate and k is resulting force

so spring one is rated at z, and compressed to the end it is r
so spring two is rated at x, and compressed to the end it is q

if compressed and we change F on either spring, we will never get kx to be the same on the other spring anywhere along the travel that is the same

so

the rate does not change as it is already a constant at any point set by the original rate of the spring
in other words, at any point of the travel, you will never get that spring to do what a stiffer spring will do, al you have done is changed the preload and shortened how much area the spring has to perform in.

in order to get a stiffer rate, you have to change the spring

using hooks law, at any time during

so preloading does not change the rate, it changes the rate times Hook's formula. but the starting rate is constant and that is what you need to consider, IF I set the spring rate for a 1000 pound rider, how much suspension travel would I have? and is that enough for the curves I want to hit? Of I changed the spring for a spring that would be designed to have the rate at the amt of compression I wanted, and got on the bike, without having to load up the bike so much, do I not end up with a spring I can use during full suspension travel?

we do not need the springs super stiff, if we did why even use the springs just go rigid. What we need is a spring that can help control the movement of the suspension as we load it up and work the corner. going in we want it to be able to compress at a rate our tire can not wash out as it loads up. that means it compresses, once it stops compressing the tire starts to slip. in other words the spring is part of the traction formula. Now as we transition into leaving the curve we use damping more than spring rate and once leaving we want the spring to expand at a rate that again we keep traction during. We do not want it to POGO.
Pogo is a bad thing. A spring with to much preload will have the tendency to POGO when exiting a curve. A spring of the proper rate will be in the range it is intended to be in at that point.

that is why different bikes have different springs
the need to adjust damping on a touring bike is not there, they will never push a curve like that, but a SS needs the damping to control the spring during hard turns.
As it needs a spring of different rate as a UJM.
PS, I think most springs now days are progressive.

is that clear?

 

[Bajaedition]

Dang, it's like I'm playing a different sport here lol.

I'm putting 08 r1 suspension on my fz8 with an eye to eye adapter for the rear. So that I have components that were supposed to be together anyways. I'm doing it JUST to do it.
I don't actually know if it will help the bike....

At VIR trackdays they have tire mounting services seriously cheap and they have guys that can help you adjust your suspension correctly for a small fee. I think for me to learn this I gotta have a guy show me and help me understand it.

Sorry if I thread jacked........

But this seems like good stuff.

Banky what you are doing is the way to approach it
you are not trying to get the perfornace of the stock spring to work like a R1 spring, you are replacing the entire unit and gaining damping with that. that is great, you are also redoing the great so it is designed to do what you want
want it to do also. Great
When you finish, you will have suspension parts more designed for track work, but less designed for UJM work.
What I am talking about here is trying to make the stock stuff work, it is not designed to

Do you think the AMA superbike team from Yamaha uses stock R1 springs in those bikes and just dial up the preload?