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Suspension and You (How to set up your suspension)
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Suspension and You (How to set up your suspension) - August 2, 2011, 11:00 AM

Here's some reading on suspension. If you ride a bike without your suspension setup properly, it is like trying to fuck with a limp deck. Sure you have the tools to perform, but you need some fine tuning ,maybe a fluffer, and it befits you more to make adjustments. Hope this suspension guide and links help. Vote for sticky if you like.

-Adrian
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Sag Setup

The first step to setting up any bike is to set the spring sag and determine if you have the correct-rate springs. Spring sag is the amount the springs compress between fully topped out and fully loaded with the rider on board in riding position.

REAR END

Step 1: Extend the suspension completely by getting the wheel off the ground. It helps to have a few friends around. On bikes with sidestands the bike can usually be carefully rocked up on the stand to unload the suspension. Most race stands will not work because the suspension will still be loaded by resting on the swingarm rather than the wheel. Measure the distance from the axle vertically to some point on the chassis (metric figures are easiest and more precise; Figure 1). Mark this reference point because you'll need to refer to it again. This measurement is L1. If the measurement is not exactly vertical the sag numbers will be inaccurate (too low).

Step 2: Take the bike off the stand and put the rider on board in riding position. Have a third person balance the bike from the front. If accuracy is important to you, you must take friction of the linkage into account. This is where our procedure is different: We take two additional measurements. First, push down on the rear end about 25mm (1") and let it extend very slowly.
Where it stops, measure the distance between the axle and the mark on chassis again. If there were no drag in the linkage the bike would come up a little further. It's important that you do not bounce! This measurement is L2.

Step 3: Have your assistant lift up on the rear of the bike about 25mm and let it down very slowly. Where it stops, measure it. If there were no drag it would drop a little further. Remember, don't bounce! This measurement it L3.

Step 4: The spring sag is in the middle of these two measurements. In fact, if there were no drag in the linkage, L2 and L3 would be the same. To get the actual sag figure you find the midpoint by averaging the two numbers and subtracting them from the fully extended measurement L1: static spring sag=L1 -[(L2 + L3) / 2].

Step 5: Adjust the preload with whatever method applies to your bike. Spring collars are common, and some benefit from the use of special tools. In a pinch you can use a blunt chisel to unlock the collars and turn the main adjusting collar. If you have too much sag you need more preload; if you have too little sag you need less preload. For road race bikes, rear sag is typically 25 to 30mm. Street riders usually use 30 to 35mm. Bikes set up for the track are compromise when ridden on the street. The firmer settings commonly used on the tract are generally not recommended (or desirable) for road work.

You might notice the Sag Master measuring tool (available from Race Tech) in the pictures. It's a special tool made to assist you in measuring sag by allowing you to read sag directly without subtracting. It can also be used as a standard tape measure.
Measuring front-end sag is very similar to the rear. However, it' much more critical to take seal drag into account on the front end because it is more pronounced.

FRONT END

Step 1: Extend the fork completely and measure from the wiper (the dust seal atop the slider) to the bottom of the triple clamp (or lower fork casting on inverted forks; Figure 2). This measurement is L1.

Step 2: Take the bike off the sidestand, and put the rider on board in riding position. Get and assistant to balance the bike from the rear, then push down on the front end and let it extend very slowly.


Where it stops, measure the distance between the wiper and the bottom of the triple clamp again. Do not bounce. This measurement is L2.

Step 3: Lift up on the front end and let it drop very slowly. Where it stops, measure again. Don't bounce. This measurement is L3. Once again, L2 and L3 are different due to stiction or drag in the seals and bushings, which is particularly high for telescopic front ends.

Step 4: Just as with the front, halfway between L2 and L3 is where the sag would be with no drag or stiction. Therefore L2 and L3 must be averaged and subtracted from L1 to calculate true spring sag: static spring sag=L1 - [l2 + l3) / 2].

Step 5: To adjust sag use the preload adjusters, if available, or vary the length of the preload spaces inside the fork.
Street bikes run between 25 and 33 percent of their total travel, which equates to 30 to 35mm. Roadrace bikes usually run between 25 and 30mm.

This method of checking sag and taking stiction into account also allows you to check the drag of the linkage and seals. It follows that the greater the difference between the measurements (pushing down and pulling up), the worse the stiction. A good linkage (rear sag) has less than 3mm (0.12") difference, and a bad one has more than 10mm (0.39"). Good forks have less than 15mm difference, and we've seen forks with more than 50mm. (Gee, I wonder why they're harsh?)

It's important to stress that there is no magic number. If you like the feel of the bike with less or more sag than these guidelines, great. Your personal sag and front-to-rear sag bias will depend on chassis geometry, track or road conditions, tire selection and rider weight and riding preference.

Using different sag front and rear will have huge effect on steering characteristics. More sag on the front or less sag on the rear will make the bike turn more slowly. Increasing sag will also decrease bottoming resistance, though spring rate has a bigger effect than sag. Racers often use less sag to keep the bike clearance, and since roadraces work greater than we see on the street, they require a stiffer setup. Of course, setting spring sag is only first step of dialing in your suspension, so stay tuned for future articles on spring rates and damping.

Race Tech - Setting Sag
---------------------

Motorcycle Suspension Tuning

Sport Riderís Motorcycle Suspension section showcases articles about how to setup and tune your motorcycle suspension. Learn the correct settings for motorcycle shocks, damping rod and cartridge forks, fork spring rate and preload, high speed vs. low speed rebound damping and more.

Read more: Motorcycle Suspension Tuning, Sport Bike Suspension Settings & Setup at Sport Rider

--------------------------

Rear rebound: Use just barely enough to prevent wallowing in high speed sweepers.

I like to leave it just a teeny teeny bit "shy", so I always know I'm "right there". If it ever feels "totally" under control, I back off the damping a click.

That prevents the dreaded "over damped" rebound situation, where the suspension "packs down" in multiple ripples.

Front rebound: Use just enough rebound to keep the front end from topping out and drifting wide when exiting low speed corners at full throttle.

Same deal as the rear, I like it "ever so slightly" shy of totally controlled.

Compression damping, front and rear: The goal is to use as little as possible. Use the proper, perhaps heavier than stock spring to do the major work during non-braking mode riding - but never use a front spring that is stiff enough to be stronger than and mismatched than the required rear spring.
Use compression damping to trim if necessary and only if required.

Excessive dive under braking: Use increased oil level to firm the front end under hard braking. 5mm is a significant change in modern forks.

Goals are to always use the softest rear spring that works within "sag" range limit.

Use just enough rebound damping to control the springs.

Use as little compression damping as possible and only when required. Not everybody has a supply of alternate fork and shock springs, so you will probably have to improvise and use a bit of extra preload or a bit more compression damping to compensate for too soft of a spring.

------------------------------

Shock Rebound

On shocks, the typical location for the rebound adjuster is on the shaft at the bottom of the shock. Increase the rebound damping by turning the adjuster clockwise looking at the bottom of the shock. Normally, the set point is fully in. Gently wind the adjuster all the way up until it just stops; do not force it. Begin turning it back counterclockwise and count the clicks; the first position (all the way in) does not count as a click. Some shocks have screw-type adjusters that are similar to the common compression adjusters. (See the section on compression-damping adjustment for the details.) On the fork, the rebound adjuster is found on the fork caps.





Shock Compression

This is a Soqi shock, with a click-type compression adjuster adjacent to the integral reservoir. It controls low-speed compression damping only. To find the baseline, use a good flat-head screwdriver and run the adjuster all the way in clockwise. Gently, please. When it stops, turn the adjuster back (counterclockwise) the specified number of clicks. As with rebound adjusters, the compression side is often not linear. That is, you may be changing damping force by, say, half a percent per click near the maximum, or fully in settings, but probably aren't making a quarter or even an eighth of that difference as the adjuster moves farther out.





Fork Rebound

Most rebound adjusters for the fork are located on the fork cap. Note that Showa components often use stepless adjusters, indicated by the punch marks, one on the adjuster and another adjacent. To find the baseline settings, run the adjuster all the way clockwise and then turn outthe specified amount. On most new Hondas, the baseline setting is found by turning the adjuster all the way in and then back out until the punch marks align, and then out a farther full turn. Useful increments for this type of fork are often a quarter or an eighth turn. Incidentally, the word "ten" on the label has nothing to do with the number of adjustments; it signifies "tension," which is just another way of describing rebound damping.





Fork Compression

Front-end compression clickers are almost always found on the bottom of the fork leg. Showa 's compression setup is stepless (as with rebound), and the baseline setting is often all the way in plus one turn beyond the first alignment of the punch marks.



Read more: How to Adjust your Motorcycle Suspension - Motorcyclist Online

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August 2, 2011, 11:01 AM

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August 2, 2011, 11:05 AM

Great older article that will never go out of style. Sticky.


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August 2, 2011, 11:12 AM

i used to have a guide up that I thought was better, but I think it got purged
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August 2, 2011, 11:22 AM

Good stuff. However is the following quote a typo? I would think the opposite would be true, no?

Quote:
More sag on the front or less sag on the rear will make the bike turn more slowly.
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August 2, 2011, 11:26 AM

Quote:
Originally Posted by windblown View Post
Good stuff. However is the following quote a typo? I would think the opposite would be true, no?

No it is not. The bike uses the rear tire to really turn. Hence the definition of counter steering.

My best explanation is. Too much sag on the front causes the front to dive excessively causing you to go wide and making it more difficult to turn. Not enough sag in the rear makes the rear too stiff to allow the bike to turn.
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August 2, 2011, 11:27 AM

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Originally Posted by Sportbike2 View Post
No it is not. The bike uses the rear tire to really turn. Hence the definition of counter steering.

My best explanation is. Too much sag on the front causes the front to dive excessively causing you to go wide and making it more difficult to turn. Not enough sag in the rear makes the rear too stiff to allow the bike to turn.
Exactly. Windblown, you're thinking ride height.


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August 2, 2011, 11:43 AM

Please understand I'm not trying to play devils advocate, I am no suspension guru, hell barely rate a suspension noob, but I am trying to learn, and to learn I gotta understand.

So lowering the front by raising the forks in the triples makes a bike turn faster but lowering the front by increasing front end sag has the opposite affect?

Damn, no wonder suspension tuning makes my head hurt!
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August 2, 2011, 11:46 AM

Ride height has nothing to do with sag or suspension. You are mixing the 2 up as one.

Lowering the front makes the bike more agressive. Sag is how much the shock travels up and down freely.
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August 2, 2011, 02:08 PM

Quote:
Originally Posted by Sportbike2 View Post
Lowering the front makes the bike more agressive. Sag is how much the shock travels up and down freely.
My head just exploded, haha. I appreciate the input. I'm obviously too obtuse and missing something.

I get that changing sag would would change the relationship between how much extension versus how much compression distance was available with the rider on the bike. More sag = less travel before the forks bottom, less sag = less travel until the forks top out. I assumed that was the primary purpose of sag adjustment. To get the suspension with rider weight on it set to the "sweet" spot where there was a proper amount of compression and extention is availible to let the suspension do it's job.

I wasn't advocating using sag to adjust geometry, simply looking at the physical affect of increasing sag on the front which does lower ride hieght as sag is increased.

So what I'm getting now is that even though increasing sag will lower the front of the bike at rest apparently under power and in motion there is a dynamic I'm missing that causes the opposite affect. I don't doubt the statement - two of you with much more knowledge than I have have stated this is the case.

Ah well, it's a good thing I don't make a living adjusting suspensions, I'd starve. I need a really good in depth MC suspension/geometry book. Any suggestions?
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August 2, 2011, 02:24 PM

Quote:
Originally Posted by windblown View Post
My head just exploded, haha. I appreciate the input. I'm obviously too obtuse and missing something.

I get that changing sag would would change the relationship between how much extension versus how much compression distance was available with the rider on the bike. More sag = less travel before the forks bottom, less sag = less travel until the forks top out. I assumed that was the primary purpose of sag adjustment. To get the suspension with rider weight on it set to the "sweet" spot where there was a proper amount of compression and extention is availible to let the suspension do it's job.

I wasn't advocating using sag to adjust geometry, simply looking at the physical affect of increasing sag on the front which does lower ride hieght as sag is increased.

So what I'm getting now is that even though increasing sag will lower the front of the bike at rest apparently under power and in motion there is a dynamic I'm missing that causes the opposite affect. I don't doubt the statement - two of you with much more knowledge than I have have stated this is the case.

Ah well, it's a good thing I don't make a living adjusting suspensions, I'd starve. I need a really good in depth MC suspension/geometry book. Any suggestions?
Amazon.com: Race Tech's Motorcycle Suspension Bible (Motorbooks Workshop) (9780760331408): Paul Thede, Lee Parks: Books Amazon.com: Race Tech's Motorcycle Suspension Bible (Motorbooks Workshop) (9780760331408): Paul Thede, Lee Parks: Books
Amazon.com: Race Tech's Motorcycle Suspension Bible (Motorbooks Workshop) (9780760331408): Paul Thede, Lee Parks: BooksAmazon.com: Race Tech's Motorcycle Suspension Bible (Motorbooks Workshop) (9780760331408): Paul Thede, Lee Parks: Books
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August 2, 2011, 03:57 PM

Man, I'm with windblown on this one. I've tried reading about suspension before and it just hurts. I'll have to try that book out when I get a chance.

Good post
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August 2, 2011, 05:23 PM

Do the "Days of Thunder" method. Change a setting drastically and ride your bike down a road. Feel what is happening and then change it the opposite and run down that same road. Read the first post after you stop and you will learn very quickly about suspension.
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Quote:
Originally Posted by badguy View Post
Man, I'm with windblown on this one. I've tried reading about suspension before and it just hurts. I'll have to try that book out when I get a chance.

Good post
I've got that book and it is AWESOME! There is more info in that book than most of us will ever need to know. I definitely give it two thumbs up.


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August 4, 2011, 10:54 AM

Here is a link to my post in 2006 that also explains suspension.
Your Suspension and You.

Check it out if it makes your head explode. The more you know about your suspension the better rider you will become.

It took me about a full year to grasp it properly through trying various settings.

I have ridden people track bikes on the track and helped them set up their suspension. I am willing to help anyone out with their suspension. All you need to do is ask.
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