Great suspension setup how-to link

[jaimev34]

Here's the link.

http://www.ehow.com/how_4602262_setup-suspension-sportbike-motorcycle.html

It actually talks about optimal free sag numbers, which is rare; most only mention rider sag. One site belonging to a moto mag (don't remember which one) actually had a chart for commonly used settings for each bike, which is utterly stupid since it doesn't take weight into account.

[Baileyrock]

Thanks, looks pretty good from what I glanced at! :goofy:

We have been trying to Hammer in the importance of FREE Sag to members here as most just look at Rider Sag which is basically meaningless to ID'ing proper spring Rates.

[Guest]

Thanks, looks pretty good from what I glanced at! :goofy:

We have been trying to Hammer in the importance of FREE Sag to members here as most just look at Rider Sag which is basically meaningless to ID'ing proper spring Rates.

Good post.

Plasma.

[Guest]

Not a bad post at all considering it comes form EHow. If you look at their references, they have some good ones. Andrew Trevitt wrote the series in Sport Rider magazine.

BTW, does anyone know how he is doing? I know he had a bad, bad wreck a year or so ago testing a bike for either Sport Rider or Motorcyclist.

[JamieDaugherty]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

[chris2992]

BTW, does anyone know how he is doing? I know he had a bad, bad wreck a year or so ago testing a bike for either Sport Rider or Motorcyclist.

There is an article on him in this months issue of "sport rider" talking about his return to the office. He is paralyzed from the waist down and obviously in a chair, he has a modified scion xb with hand controls so he can drive.

[jasonsmith]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

So in your opinion Jamie it's okay then to have the correct rider sag with the no free sag? Why does Trevitt incorporate free sag as a calculation factor when setting up sag? I'm so confused...

[jaimev34]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

So in your opinion Jamie it's okay then to have the correct rider sag with the no free sag? Why does Trevitt incorporate free sag as a calculation factor when setting up sag? I'm so confused...

Yes, Jamie, please explain. I understand that rider sag includes the free sag when it's measured, but what about the bike's effect on the suspension? Also, in all of these how-tos and instructional websites, there's never any mention of the fuel's effect on the sag. A full tank would increase the total weight by 30+ pounds, yet we're told to have all our gear on, which doesn't measure more than 5-7 pounds. I think half a tank is good for measuring sag since you're not at either extreme weight-wise, and the bike will be in this range or around it for the longest period.

[rdguy]

Andrew's blog.

I knew the Trevitts slightly back in the 70's (racing friends in common). I saw Andrew's first race in '78 (??) on a CB360 (also ??).

Glenn

Not a bad post at all considering it comes form EHow. If you look at their references, they have some good ones. Andrew Trevitt wrote the series in Sport Rider magazine.

BTW, does anyone know how he is doing? I know he had a bad, bad wreck a year or so ago testing a bike for either Sport Rider or Motorcyclist.

[Baileyrock]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

I completely disagree with you on this one Jamie! :angry: I'm focused almost completely on rear VFR sag & spring rates here.

W/O Free sag numbers you have No idea if you have correct springs rates! If you think all you need is a Spring Rate Calculator in order to find correct spring rates let me remind you that You Yourself used an erroneous Calculator for some time(maybe years)as have dozens of other Shops, builders & manufactures for the VFR. :ohmy:

Besides the many faulty rear VFR calculators out there providing most of our members with erroneous spring rate numbers, there's people who say all you need is Rider sag numbers.

ps: I think your new calculator also has errors in it.

How can you accurately determine correct spring rate numbers from a Rider Sag number(lets say 35mm) that can be achieved with spring rates from 800-1300 lbs on a VFR with the same rider on it? :huh:

I was able to get 35mm of rider sag on my VFR with both the stock 850 lb spring & the current 1100 lb spring. Which one is correct? W/O Free sag numbers as your check you have No idea what you have!

You also don't need a spring rate calculator at all if you use the trial & error method to achieve Manufactures desired Free & Rider sag numbers and several of us here have gone through that process!

Based on Ohlins or other manufactures recommendations which REQUIRE specific FREE SAG numbers along with Rider sag numbers you can Not achieve proper set-up w/o out Both Free & Rider sag numbers!

Rider Sag numbers are completely worthless w/o also having desired FREE Sag numbers!

This is NOT an attack on you Jamie, in fact I greatly appreciate your skills! But I just have to call BS on this one just to prevent Misinformation to our members! :rolleyes:

BR

[jasonsmith]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

I completely disagree with you on this one Jamie! :angry: I'm focused almost completely on rear VFR sag & spring rates here.

W/O Free sag numbers you have No idea if you have correct springs rates! If you think all you need is a Spring Rate Calculator in order to find correct spring rates let me remind you that You Yourself used an erroneous Calculator for some time(maybe years)as have dozens of other Shops, builders & manufactures for the VFR. :ohmy:

Besides the many faulty rear VFR calculators out there providing most of our members with erroneous spring rate numbers, there's people who say all you need is Rider sag numbers.

ps: I think your new calculator also has errors in it.

How can you accurately determine correct spring rate numbers from a Rider Sag number(lets say 35mm) that can be achieved with spring rates from 800-1300 lbs on a VFR with the same rider on it? :huh:

I was able to get 35mm of rider sag on my VFR with both the stock 850 lb spring & the current 1100 lb spring. Which one is correct? W/O Free sag numbers as your check you have No idea what you have!

You also don't need a spring rate calculator at all if you use the trial & error method to achieve Manufactures desired Free & Rider sag numbers and several of us here have gone through that process!

Based on Ohlins or other manufactures recommendations which REQUIRE specific FREE SAG numbers along with Rider sag numbers you can Not achieve proper set-up w/o out Both Free & Rider sag numbers!

Rider Sag numbers are completely worthless w/o also having desired FREE Sag numbers!

This is NOT an attack on you, just on Misinformation to our members! :rolleyes:

BR

This is exactly why I am running and playing with my 1100# rather than my 1200# which I know will be closer to what I need. I'm building numbers that will proove that the 1100# is slightly on the soft side based on my free sag figures. When I put in my 1200# the change will obviously be in the right direction.

[creggur]

I know this info is here somewhere, but since we're on the subject what are the correct static and rider sag measurements front and rear for the VFR?

I have rider sag set at 35mm front and rear - didn't even check static - must have missed that part completely when I was tinkering with this stuff a couple of months ago. I do know that the bike handles worlds better now than with the factory settings...

[Guest]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

Jamie:

You can't be serious with that statement. :blink:

Pete

[Baileyrock]

Free sag (or static sag) truly is meaningless. When I have guys e-mail with a setup question that has them confused - and it's almost always because they are trying to measure and understand the static sag. This number has no significance what so ever, the rider sag is the only one that has bearing.

Jamie:

You can't be serious with that statement. :laugh:

Pete

Yes, I'm blown away with that statement also! :goofy:

No wonder his emailers are confused! Sorry Jamie, but you need to rethink or study much deeper on this subject.

The Only place this statement could be applied in any acceptable way would be for someone who has No plans to change or install the correct springs for their weight on there bike, which BTW(correct spring rates)is the foundation to building any decent suspension set-up.

Then yes, setting rider sag is all you have or as good as it gets with any stock suspension.

BR

[jaimev34]

I've been doing some searching for information about the importance of static sag and came across this article:

suspension setup.doc

It's got some good info concerning a three-pronged approach: static sag, rider sag (or the one G test, as he calls it), and suspension travel. Some of the measurment ranges are a bit large, but maybe using the three components makes up for this. Skip to parts 2-4 for the meat.

[Guest]

I've been doing some searching for information about the importance of static sag and came across this article:

suspension setup.doc

It's got some good info concerning a three-pronged approach: static sag, rider sag (or the one G test, as he calls it), and suspension travel. Some of the measurment ranges are a bit large, but maybe using the three components makes up for this. Skip to parts 2-4 for the meat.

Good article! Thanks for sharing it with the board.

[JamieDaugherty]

Yes, I am very serious. When establishing a correct spring rate for a motorcycle you will assume a certain amount (distance) of spring preload. Let's give an example:

Spring Preload = 16mm

That means, with the ideal spring rate for a given rider the spring will have a preload of 16mm. You change riders, the spring rate changes to get back to 16mm of preload. This is a very important concept to keep in mind during this discussion.

Case 1:

Rider = 130lb

Spring Rate = 1100lb/in (19.7kg/mm)

Preload = 16mm

Rider Sag = 36mm

Spring Compression at Rider Sag = 25mm

Spring Load at Rider Sag = 492.5kg

Spring Load at Full Extension = 315.2kg

Case 2:

Rider = 275lb

Spring Rate = 1300lb/in (23.3kg/mm)

Preload = 16mm

Rider Sag = 36mm

Spring Compression at Rider Sag = 25mm

Spring Load at Rider Sag = 582.5kg

Spring Load at Full Extension = 372.8kg

I've highlighted the values in question here in bold. For the lighter rider the static weight of the motorcycle only has to overcome 315.2kg of spring force (note: this is not motorcycle weight, this is the force the spring itself is producing). For the heavier rider the same motorcycle has to overcome almost 60kg more spring force. How can these two situations produce the same static sag? Answer: they can't.

Thus the conclusion that static sag will vary for each rider. If you focus on rider sag, which you should, then it has been proven to generate a motorcycle that handles well.

Bonus! The keen eye will have noticed that the crux of the assumptions is the 16mm spring preload number. This is not a magical number or anything, it's just that's about what the spring preload ends up being for most setups. Where does the 16mm number come from? You have to look at spring designs in depth to see that you should be careful to keep a spring in a range of 20-80% of it's total deflection. That means you should not have the spring "stoke" through the first 20% during operation and not beyond 80%. Because of that. when applying a spring to an application you need to look at it's maximum allowable deflection and establish the 20% mark for the initial preload. It just so happens that the springs used on motorcycle shocks are around 15mm-ish at the 20% deflection point.

It's important to reiterate that an approach is only as good as it's results. I've done a lot of research and experimentation over the years and have found that what I spell out above is consistent with what most suspension tuners agree to be a "correct" approach. Is it the only approach? Maybe not. Is it perfect? No, but for the 99% of riders this will generate a spring rate that gets you very close and you can dial-in from there.

[JamieDaugherty]

Sorry Jamie, but you need to rethink or study much deeper on this subject.

See above. I've got many years of of study on this topic!

[jaimev34]

I'm confused.

And wouldn't an 1100 #/in spring be too stiff for a 130# rider? Maybe you were merely using it as an example and not a real life pairing.

[Guest]

Jamie:

I feel you have a flaw in your logic there. Let's say for the sake of conversation that the spring must exert 315.2 kg of force to maintain a certain Free Sag. For a 1100# spring, that might mean 16 mm of spring preload. For a 1300# spring, you would only need 13.53 mm of preload to obtain the same 315.2 kg of force.

The amount of preload (if measured in mm of compression of the spring) will vary for each strength of spring.

Pete

[jasonsmith]

Ever since I got into tweaking my suspension I have read everything that I could find including Trevitt's book which I am looking at right now. I have found countless articles online and chatted with many people online and in the industry. The one thing I have noticed is that not all the information that I found was the same BUT it was all kinda close with a tweak here and tweak there. Most of what I would call "good" articles mention "Free Sag". Even Elka, Racetech, Ohlins, RMR and others have mentioned "Free Sag" to me as a factor.

The one thing I have noticed JD is that your spring numbers and now methods are different from everyone that I have spoken too and everything that I have read. You may be correct and the information that I have read may be wrong. Now I mean no offense by any of this, after all you are the one with many years of study on the subject and I only have knowledge gathered from people like yourself. I just find it difficult to be able to swallow your info since it is so far off from industry standard.

Needless to say I would like to figure out where you are coming from rather than just discounting your info... so a few questions if I may:

1. Is the 16mm pre-load distance figure based on the total travel of a typical MC spring?

2. Is your Case 1 scenario just that or is that a real "Case"? 1100# for 130# rider sounds crazy. A spread of only 200# spring rate vs an extra 145# of rider weight sounds even worse.

3. I currently have an 1100# spring and I am 220#. I have 4mm of pre-load distance with 35mm Rider Sag. Are you suggesting that I need to go to a softer spring to be able to achieve 16mm pre-load distance? I'm guessing if I attempted 16mm of pre-load distance with my shock I would be around <10mm rider sag.

Elka has stated that anything more than 15mm of pre-load requires a stiffer spring. In actuality I think 15mm of pre-load is the max available on my shock.

4. Am I correct to assume that your method abandons "Free Sag" as a determining factor and uses pre-load distance instead, yielding completely different results?

Sorry man, I'm trust trying to figure this out... :biggrin:

[Guest]

Jason:

That's interesting that Elka makes the statement that more than 15 mm preload indicates a stronger spring is required. I've never heard that particular number before. However, it has been my experience that once you get the correct spring on a bike it doesn't require a lot of preloading.

Your preload of 4 mm certainly seems to verify my experiences.

Pete

[jasonsmith]

Jason:

That's interesting that Elka makes the statement that more than 15 mm preload indicates a stronger spring is required. I've never heard that particular number before. However, it has been my experience that once you get the correct spring on a bike it doesn't require a lot of preloading.

Your preload of 4 mm certainly seems to verify my experiences.

Pete

Pete the one thing I haven't measured yet is how much pre-load is placed on the spring for basic static installation into the shock, you by any chance know? Is the top ring just snugged down enough to hold the spring in and stop it from rotating or is there a number? 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...

[Guest]

Jason:

To tell you the truth, I've never measured it. I just know if the preload ring on my Penske has to make 6 or more rotations after it begins to touch the spring, I'm too soft on my spring.

The correct spring thing will blow your mind. It is amazing once you hit on it, it all comes together. Little preload, Free Sag and Rider Sag on the money, and a nice handling rear end.

I'm a big boy (heck, I weighed 11 lbs and 13 oz at birth) and every one of my bikes takes a fairly stiff spring. 1100# on my Duke II, 1300# on my VFR, and 1400# on my ST1300.

Pete

[Baileyrock]

2. Is your Case 1 scenario just that or is that a real "Case"? 1100# for 130# rider sounds crazy. A spread of only 200# spring rate vs an extra 145# of rider weight sounds even worse.

I'm pretty sure that 1100 lb spring for a 130# rider is from his recently posted recommendation chart for our VFR's! Can't find it at the moment but looking! :unsure: If you followed the logic/formula used the stock VFR is sprung for a 10# rider at most! :unsure:

I asked for an explanation but have yet to get one.

Again not trying to trash Jamie here, just the formula/logic used. :rolleyes: I've actually sent/recommended many members to Jamie for help, but I've never agreed with the rear spring rates he comes up with! The front end stuff he did for me was great!

BR