Great suspension setup how-to link

[JamieDaugherty]

Sure, many sources will discuss static sag, but if you look at their spring rate suggestions and back out the static sag you will find that number to vary with rider weight. This is not a constant. Once again, static sag is not part of most suspension tuners approach to setting correct spring rate. Just discussing a simple, straighforward approach does not make for a very good article in a magazine! Yet, the reality is that it's not too complicated providing that you get close with the spring rate.

One of the problems is that starting with the VFR800 some people switched from a performance approach to a 'sort of' performance approach. For example, if you look at the 3rd gen VFR750 suggested spring rate for a 130lb rider in the Penske information (I'm assuming you'll trust this more than me) it shows 1100 lb/in. The same rider on a 5th gen VFR800 it shows a suggested 1000 lb/in. Looking at the motorcycle weight and linkage ratio all factors would point to a spring rate that is higher for the 5th gens than the 3rd, yet they went lower. I believe this to be a function of perception that the bike moved more toward touring and away from sport. My guess would be that it's the same reason the RaceTech values are low (I think we are in agreement on that point).

The initial spring preload is defined as the compression on the spring as installed on the shock. This would be the same measurement as with the suspension fully extended. The linkage ratio on the VFR800 is about 4:1, meaning for every 4mm of travel at the wheel the shock compresses 1mm. For a rider sag of 36mm that would give you 9mm of shock compression.

jasonsmith - I'm sure there is no way you have only 4mm of spring preload with an 1100 lb/in spring. Maybe you can clarify your definition of this measurement? Remember, spring rates are pounds per inch, there is no correlation between the spring rate number and rider weight. A 100lb increase in rider weight does not translate to 100 lb/in increase in spring rate.

I will mention this again: there is no magic here - just approaches that been proven to work well. Every rider will want something different. I have worked with my calculations for several years and adjusted them as I've seen necessary. I feel that what I have now is good. We have also only been looking at full extension and 20% travel (where the ~35mm sag number comes from). What about the other 75%, what happens at 100% travel? That's where approaches differ.

Kevin, for my benefit why don't you run through your approach for 130lb and 275lb riders so we can see how they differ? I'd be very intersted to understand what you are doing and why you believe it is better.

[jasonsmith]

.... Maybe JD is combining that number with the actual user applied pre-load?? I don't think I have 12mm of install pre-load though...

jasonsmith - I'm sure there is no way you have only 4mm of spring preload with an 1100 lb/in spring. Maybe you can clarify your definition of this measurement? Remember, spring rates are pounds per inch, there is no correlation between the spring rate number and rider weight. A 100lb increase in rider weight does not translate to 100 lb/in increase in spring rate.

Jamie I initially said 4mm because that is how much pre-load I have added via my hyd adjuster visible at my pre-load ring. Now I see that you are using the total pre-load, installation and user added.

I'll check my total spring length with the wheel off the ground and see what it is, can I assume that a 6" spring is actually 6" when not compressed?

[jasonsmith]

Wow JD, assuming that my spring (1100#) was exactly 6" prior to installation I have exactly 16mm of total pre-load right now to get my 35mm of rider sag.

:rolleyes:

Is it possible that your 16mm method will also produce the correct Free Sag giving us two different ways to achieve the same goal??

[JamieDaugherty]

Wow JD, assuming that my spring (1100#) was exactly 6" prior to installation I have exactly 16mm of total pre-load right now to get my 35mm of rider sag.

:rolleyes:

Is it possible that your 16mm method will also produce the correct Free Sag giving us two different ways to achieve the same goal??

Questions:

- What spring are using (brand)?

- What is your installed height in mm?

6" springs are normally 153mm free length.

[jasonsmith]

Wow JD, assuming that my spring (1100#) was exactly 6" prior to installation I have exactly 16mm of total pre-load right now to get my 35mm of rider sag.

:rolleyes:

Is it possible that your 16mm method will also produce the correct Free Sag giving us two different ways to achieve the same goal??

Questions:

- What spring are using (brand)?

- What is your installed height in mm?

6" springs are normally 153mm free length.

Eibach 0600.225.1100

Total install height is 137mm that's including my 4mm of dialed in pre-load.

So "Install" would be 141mm?

[JamieDaugherty]

Eibach 0600.225.1100

Total install height is 137mm that's including my 4mm of dialed in pre-load.

So "Install" would be 141mm?

Your installed height is 137mm. The preload adjuster changes the installed height of the spring. Installed height is the spring length when the shock is at it's longest length.

I'm surprised that you are getting only 35mm of rider sag. My experiences are for riders of you size it's taken a higher spring rate to get 35mm with that amount of preload. You are measuring the difference from fully extended to with rider, correct?

[jasonsmith]

Eibach 0600.225.1100

Total install height is 137mm that's including my 4mm of dialed in pre-load.

So "Install" would be 141mm?

Your installed height is 137mm. The preload adjuster changes the installed height of the spring. Installed height is the spring length when the shock is at it's longest length.

I'm surprised that you are getting only 35mm of rider sag. My experiences are for riders of you size it's taken a higher spring rate to get 35mm with that amount of preload. You are measuring the difference from fully extended to with rider, correct?

Jamie I'm not "only" getting 35mm rider sag, I could probably get down to about 30mm before losing my Free Sag. Right now I have 35m Rider and 9mm Free. I could probably get down to 25mm or so if I didn't care about the Free Sag. And yep I'm measuring correctly.

[JamieDaugherty]

When I've tried to use a spring in that range for a rider like yourself I've gotten 40+mm of rider sag with the target spring compression (15mm). That's why I said "only", I'm surprised it's that low, I would have expected the sag to be more.

So tell me, what you do think the free sag is doing for you? From your wording it sounds like you are suggesting that having no free sag is a bad thing ("before losing my Free Sag"). I'm curious to know why you are viewing it this way.

[jasonsmith]

When I've tried to use a spring in that range for a rider like yourself I've gotten 40+mm of rider sag with the target spring compression (15mm). That's why I said "only", I'm surprised it's that low, I would have expected the sag to be more.

So does that mean your calculator is broken....?

So tell me, what you do think the free sag is doing for you? From your wording it sounds like you are suggesting that having no free sag is a bad thing ("before losing my Free Sag"). I'm curious to know why you are viewing it this way.

I like Free Sag because everywhere I've looked, everything I have read and all that I have spoken with state that Free Sag is an important factor in suspension tuning. I understand that Free Sag is not your thing, but since everything I have read states otherwise, maybe you can tell me why you think it's not. Convincing me though is kind of a waste of time since I'm learning from you guys, I would like to see this difference in tuning style debated with the 4 out of 5 dentists who believe that Free Sag is a must.

[Guest]

Jason:

Spring numbering methods do have some logic to them - I know RaceTech's do.

Right now you are running an Eibach 0600.225.1100.

That means it's a 6" spring, 2.25" I.D., with a spring rate of 1100#/in. Ever wonder why "foreign" springs have oddish numbers for their spring rates (17.28, 16.39, etc) - it's because they're using an American spring rated in #/inch and converting the numbers over to metric. If metric spring rates were the standard, you could buy 15.00, 15.50, 16.00, etc springs.

I've got two Hyperco springs sitting on my work bench right now. A 6" x 2.25" ID x 1050# and a 6" x 2.25" I.D. x 1400#. I can tell you they are both dead on exactly 6" long when they are off the shock.

I agree with you about loosing your Free Sag. To me (and others) if you have 0.00" of Free Sag, you have too much preload on the spring. Free Sag isn't a necessity for riding per se, it is a necessity for determining whether or not you have the correct spring on the bike.

IMO, if you're not on the money with what you have now, you are getting very, very close. 9 & 35 are good numbers for street riding. I tend to go 30 mm Rider Sag due to my aggressive style of riding. I like to have 5-10 mm Free Sag.

Looking at this whole sag thing from a completely different angle for a minute. It's a cheap tuner's trick to make a bike handle better by jacking up the rear end using either spacers, an adjustable shock, etc. What is happening is that the person is making up for the weakness of a spring by doing that. The rear spring is so weak the suspension is over compressing (especially coming out of turns) and wants to run wide. Jacking up the rear end takes care of that. If the bike had the proper shock spring it wouldn't squat so much in the first place. And it would handle and ride better to boot!

I've used every suspension tuner in the world - Traxxion Dynamics, Phil Douglas, Jim Lindemann, Ken Soignet at CompuTrack. I have had the best luck since I became an Andrew Trevitt & Andy Ibbott disciple than with any one else. Traxxion Dynamics set my original VFR shock up with 0 mm of free sag. Just about broke my back. Sent it up to PA to Shane Sweigert with Penske and he got it all straightened out. I think due to a non-competition agreement with their dealers Penske doesn't advertise their motorcycle division that much, but they do have one. Great guys to work with. Shane just moved the nitrogen fill valve on my ST1300 shock for the cost of parts only - no charge for any labor. Penske's Motorcycle Division in one of the best kept secrets in the motorcycle world.

Read, learn, experiment - teach yourself. Old BR might be the third runner up in the Billy Bob Thornton Look-a-like contest, but he has years of experimentation and experience under his belt. The guy knows his stuff.

Did y'all know that Kevin won his class one year at Pike's Peak? He's been around.

Pete

[jaimev34]

One question I have that was mentioned by BR or Jason earlier in the thread is why would free sag not be an important component of suspension tuning if a 35mm rider sag can be attained with the stock 850#/in spring or a 1200#/in spring? Obviously, one shock will be maxed out on preload and will have no free sag, while the other will require much less preload and will have a higher free sag. I like the approach that the document I posted had: a three-pronged approach - free sag, rider sag, and suspension travel.

[Guest]

One question I have that was mentioned by BR or Jason earlier in the thread is why would free sag not be an important component of suspension tuning if a 35mm rider sag can be attained with the stock 850#/in spring or a 1200#/in spring? Obviously, one shock will be maxed out on preload and will have no free sag, while the other will require much less preload and will have a higher free sag. I like the approach that the document I posted had: a three-pronged approach - free sag, rider sag, and suspension travel.

You're on the right track with that article - free sag is an important part of the equation. It's critical in determining whether you have the correct spring on the bike for your weight.

[Guest]

You know Dave at GP Suspension gave me the same kinda answer when I quizzed him about Sag, free sag and spring calculators ect... He said he has his own data base based on real world applications. The one thing I haven't seen mention is "sticton" that alone can account for 10mm difference in the #'s which might just change you free sag quite a bit...BTW I thought Dave was off his med when he put a .95 front fork springs in my bike for a 251 pound rider.. But low an behold my free sag and rider sag are right on with 7mm of sticton.. There seems to be more than one way to skin a horse..

Dan

[Guest]

I do everything I can to get my stiction down to as small an amount as possible.

When I service my forks, I take the fork tubes, thouroughly clean all the bugs and road tar off with lacquer thinner, and then buff them for about a half hour each with Simichrome and an orbital buffer. Then wash them again in lacquer thinner prior to installation. In the rear, make sure everything is greased properly, there is no binding, no burrs on the hardware, no corrosion, etc. It all adds up. I go so far with my shocks as making some Delrin "washers" that sit on each side of the upper heim fitting (Penske shock) to prevent the shock body from rotating more than a degree or so. I want everything straight and the eyes of the top and bottom nice and parallel. Paying attention to the little things pays off.

One thing that needs to be mentioned concerning sag (both rider and free): You should have all of your damping adjustments backed off as far as possible. You don't want any interference from the damping mechanisms to influence the sag when you're in the adjusting/correct spring selection phase of suspension setup.

[Baileyrock]

I don't understand the need for all this Fancy talk!

Just ride the damn things!

btw I use Penske's , Ohlins & Trevitt's guidelines for my set-ups, an't got no fancy formula ta eyeply! :laugh:

[JamieDaugherty]

btw I use Penske's , Ohlins & Trevitt's guidelines for my set-ups, an't got no fancy formula ta eyeply! :laugh:

Ok, now I'm confused. You have criticized me for having a scientific approach that you disagree with, yet you claim to not have an approach of your own? Am I missing something?

As Wistrick mentions, most (dare I say, all?) professional suspension tuners pay zero attention to static sag. After reading through this and trying to understand the various opinions and points of view, I am convinced that when it all settles out the net result is very similar. Be it a scientific approach or a trial-and-error approach I think you still end up with a spring that is in the ballpark which you can fine tune to get the desired results. Are we really discussing large fundamental differences or just small details?

[jasonsmith]

btw I use Penske's , Ohlins & Trevitt's guidelines for my set-ups, an't got no fancy formula ta eyeply! :laugh:

Ok, now I'm confused. You have criticized me for having a scientific approach that you disagree with, yet you claim to not have an approach of your own? Am I missing something?

As Wistrick mentions, most (dare I say, all?) professional suspension tuners pay zero attention to static sag. After reading through this and trying to understand the various opinions and points of view, I am convinced that when it all settles out the net result is very similar. Be it a scientific approach or a trial-and-error approach I think you still end up with a spring that is in the ballpark which you can fine tune to get the desired results. Are we really discussing large fundamental differences or just small details?

Bottom line we need a way to figure out what the correct spring "actually" is for a bike with it's rider. There is the "Free Sag" method and your method JD. Surprising both those methods have confirmed that I at least have the correct spring installed, give or take a tiny bit. The only thing that concerns me about your method is that 16mm number, where does it come from and why do my results not match your experience? I'm all for multiple ways to skin a cat providing it gets fully skinned, not half or 3/4 but fully. So how does the best suspension guru in the whole wide world determine what is the correct spring? How do the MotoGP guys do it? I imagine it couldn't be any more critcal there? Maybe the correct ONE spring doesn't exist... maybe it's fine balance between the bike and the rider style.

[Guest]

... maybe it's fine balance between the bike and the rider style.

Congratulations! You have just figured out the correct and final answer. :goofy:

[Baileyrock]

btw I use Penske's , Ohlins & Trevitt's guidelines for my set-ups, an't got no fancy formula ta eyeply! :biggrin:

Ok, now I'm confused. You have criticized me for having a scientific approach that you disagree with, yet you claim to not have an approach of your own? Am I missing something?

As Wistrick mentions, most (dare I say, all?) professional suspension tuners pay zero attention to static sag. After reading through this and trying to understand the various opinions and points of view, I am convinced that when it all settles out the net result is very similar. Be it a scientific approach or a trial-and-error approach I think you still end up with a spring that is in the ballpark which you can fine tune to get the desired results. Are we really discussing large fundamental differences or just small details?

I have no issue with your method if it gives accurate results JD, and if your 15mm preload method actually provides the correct spring rate for a specific bike/rider combo than I guarantee that that set-up Will Have Free/Static sag in the range of the manufactures recommendations and all manufactures seem to want Free sag in their set-ups.

Free/Static recommendations vary depending on intended use just like Rider sag does.

Point 1: Just about every tuner & all manufactures recommend Free sag and you say it's meaningless?

Point 2: You recently posted up spring rate recommendations for our VFR's based on your New rate calculator formula and in one range it actually is very similar or identical to what others here like Pete, Jason & myself have found using the Free/Static method and that is the one 220 lb rider range.

The remainder of your suggested rates especially on the lower rider weight range seem radically HIGH! :goofy:

Please reprint those suggested numbers here again so that I don't misquote, but I seem to remember that it suggests a spring rate for a 120 lb riders several hundred lbs heavier than the stock VFR set-up. I think your (example A) was from that chart in a previous post.

My concern here is that before you and I discussed rear spring rate issues in PM's just last year you were using a calculator and suggesting spring rates to our members that were extremely LOW. Now you have reworked that same formula because you said you found an error in it(at the time you said it was the same calculator that many shops were using). You've recently reworked the numbers in it and now suggest spring rates that are extremely High IMO, except in the highest range of rider weights.

My point all along is that for Years our members have been getting erroneous rear spring rates suggested to them and have even bought new shocks from manufactures that installed the wrong springs on them and w/o and control or check method there was no way for most of our members to know what they had. Like I've mentioned before there are 190 lb members here who have had suspension Pro's suggest spring rates to them from as low as 800 lbs to as high as 1200 lbs, who's right, who's wrong or is a 400 lb range close enough. Unlike any other method, using the manufactured suggested Free(static)& Rider sag numbers method at least gives you 2 control points. Saying 35mm Rider sag is all you need is an Uncheckable reference, now if you added a second check like say your 15mm of preload equal 35mm Rider sag as you suggest then that also works, if it's true throughout the rider range! :goofy:

Hell if I remember correctly Elka just slapped 850 lb springs on most of their shipped shocks because I guess they basically used the stock spring rate or used the same error-ed calculator you once used. :goofy:

So for most of use who don't have or can't find shops, tuners or manufactures who can provide accurate Rear spring rate suggestions for our VFR's then using the Static/Free Sag numbers are our Only control along with Rider sag numbers.

I am no expert and I don't need to be right, I am just trying to find and suggest a control method that any VFRD member can use to calculate if in fact they have the correct spring rate, instead of just being told a number that for the most part have been proven wrong from everything I can tell so far.

The entire idea is to benefit our DIY members and the more checks you have the more accurate the results.

BR

[Guest]

[jaimev34]

Gonna hijack a thread I started for a little bit.

Back in December, I sent my forks to Racetech to have springs, valves, and oil installed. They installed .90 kg/mm springs, which is what the calculator suggested. When I got the forks back from RT, I installed them and measured the sag. Back then, I used a much lower sag number (~32mm) and payed no attention to the free sag. Well, I checked my rider and free sag today, as well as my suspension travel. With the preload backed out all the way and with a half tank of gas, I was able to get a maximum of ~35mm rider sag. My free sag was somewhere around 23-25 mm. After riding around all day with a zip tie attached to my right fork, I know that I've got about 1 inch left of travel. Well, my rider sag and susp. travel are ok, but my free sag is too high as a result of not using any preload to achieve a decent rider sag number. I weigh about 185-190 lbs with gear on, which is heavier than I was when I sent the forks to RT.

What do you guys think of my numbers??

[vfrcapn]

Gonna hijack a thread I started for a little bit.

Back in December, I sent my forks to Racetech to have springs, valves, and oil installed. They installed .90 kg/mm springs, which is what the calculator suggested. When I got the forks back from RT, I installed them and measured the sag. Back then, I used a much lower sag number (~32mm) and payed no attention to the free sag. Well, I checked my rider and free sag today, as well as my suspension travel. With the preload backed out all the way and with a half tank of gas, I was able to get a maximum of ~35mm rider sag. My free sag was somewhere around 23-25 mm. After riding around all day with a zip tie attached to my right fork, I know that I've got about 1 inch left of travel. Well, my rider sag and susp. travel are ok, but my free sag is too high as a result of not using any preload to achieve a decent rider sag number. I weigh about 185-190 lbs with gear on, which is heavier than I was when I sent the forks to RT.

What do you guys think of my numbers??

I would double check the preload spacer they installed. Racetech cuts new spacers to use with their springs and in my experience they install/recommend them to be way too long.

[Guest]

Gonna hijack a thread I started for a little bit.

Back in December, I sent my forks to Racetech to have springs, valves, and oil installed. They installed .90 kg/mm springs, which is what the calculator suggested. When I got the forks back from RT, I installed them and measured the sag. Back then, I used a much lower sag number (~32mm) and payed no attention to the free sag. Well, I checked my rider and free sag today, as well as my suspension travel. With the preload backed out all the way and with a half tank of gas, I was able to get a maximum of ~35mm rider sag. My free sag was somewhere around 23-25 mm. After riding around all day with a zip tie attached to my right fork, I know that I've got about 1 inch left of travel. Well, my rider sag and susp. travel are ok, but my free sag is too high as a result of not using any preload to achieve a decent rider sag number. I weigh about 185-190 lbs with gear on, which is heavier than I was when I sent the forks to RT.

What do you guys think of my numbers??

I think you may have a tad stiff spring. The same rules/numbers for Free Sag and Rider Sag don't apply to forks that apply to the rear (shock).

Per Keith Code & Andy Ibbott: Front Static (Free) Sag for a road bike: 30-40 mm

Front Rider Sag for a road bike: 35-50 mm

The fact that you're not using all of your front fork travel also reinforces my thoughts. You shouldn't be bottoming out at any time, but under hard braking into a corner or an emergency stop, you should use up just about every mm of travel available in your forks.

One of my critiques of many suspension shops (including RaceTech) is that they are so racing oriented that they don't always adjust properly for the street rider.

Hate to say it but it's just a fact of getting suspension dialed in - you may have to purchase/swap for another set of springs and do some experimenting. It is next to impossible to get the suspension spot on with the first try. I would suggest trying to borrow some 0.85 springs so you can swap them out and compare them to the 0.90's.

[jasonsmith]

I also think that maybe .85kg would be closer unless you plan on approaching the 200# mark (lots of donuts). I'm using .95kg's for my 220# with just small amount of preload. When I built my forks I made sure my package length (spring + spacer) was the same as stock. My forks are purrrrfect.

[vfrcapn]

Gonna hijack a thread I started for a little bit.

Back in December, I sent my forks to Racetech to have springs, valves, and oil installed. They installed .90 kg/mm springs, which is what the calculator suggested. When I got the forks back from RT, I installed them and measured the sag. Back then, I used a much lower sag number (~32mm) and payed no attention to the free sag. Well, I checked my rider and free sag today, as well as my suspension travel. With the preload backed out all the way and with a half tank of gas, I was able to get a maximum of ~35mm rider sag. My free sag was somewhere around 23-25 mm. After riding around all day with a zip tie attached to my right fork, I know that I've got about 1 inch left of travel. Well, my rider sag and susp. travel are ok, but my free sag is too high as a result of not using any preload to achieve a decent rider sag number. I weigh about 185-190 lbs with gear on, which is heavier than I was when I sent the forks to RT.

What do you guys think of my numbers??

I think you may have a tad stiff spring. The same rules/numbers for Free Sag and Rider Sag don't apply to forks that apply to the rear (shock).

Per Keith Code & Andy Ibbott: Front Static (Free) Sag for a road bike: 30-40 mm

Front Rider Sag for a road bike: 35-50 mm

The fact that you're not using all of your front fork travel also reinforces my thoughts. You shouldn't be bottoming out at any time, but under hard braking into a corner or an emergency stop, you should use up just about every mm of travel available in your forks.

One of my critiques of many suspension shops (including RaceTech) is that they are so racing oriented that they don't always adjust properly for the street rider.

Hate to say it but it's just a fact of getting suspension dialed in - you may have to purchase/swap for another set of springs and do some experimenting. It is next to impossible to get the suspension spot on with the first try. I would suggest trying to borrow some 0.85 springs so you can swap them out and compare them to the 0.90's.

That doesn't seem to leave very much dynamic sag? Ohlins recommends (front) 15-30mm static & 35-50mm dynamic.

Travel can be affected by fluid height also, how much did RT put in? Cutting out 10-15mm of the preload spacer should get you right about in the right range, I'd do it in 5mm increments though and test after each cut. Your numbers seem ok, it's just your preload adjuster is at the end of the range. I would doubt you need new springs, too many things to check and dial in first.