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Old 07-27-2010, 11:31 PM   #1
randomwalk101
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suspension adjustment

Anyone here knows how to adjust suspension?
I just added the Intiminator & SSR preload adjustor to my 08 ninja 250 and cut the spacer about 20mm down. Stock spring & 5w fork oil for now as recommended by Ricor (Intiminator maker).
The stock 250's fork doesn't have any adjustment at all so right now with the preload adjustor added I'm just trying to get the right preload for my weight.
I cut the spacer 20mm because of 15mm taken up by Intiminator and about 10mm taken up by the SSR preload adjustor...I pick 20mm to be on the safe side..can always "cut" more if needed.

anyways, here are the initial measurements:

I measured from the dust seal to the lower fork clamp. One compression/bounce to free up fork before measurement.

(S1) No load on suspension (on tripple tree front stand): 13.5cm (135mm)
(S2) Bike load only: 11.0cm (110mm)
(S3) Bike + Rider load: 10.5cm (105mm)

Umm...so what's the sag? Is it in "range" ??

Is this how you calculate it?

Sag = S1 - [(S3+S2)/2]

If so it comes out to like 27.5mm... Is this too stiff & need to decrease preload? thanks.
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Old 07-28-2010, 12:37 AM   #2
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Old 07-28-2010, 01:37 AM   #3
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25-30 mm total for the street is about right. But seems like it is taking a bit much for just the bike weight. Normally it is just the opposite, 5-10 mm unloaded, add 15-20 with rider.

Are you taking the loaded weights with both wheels on the ground and a second person balancing the bike? Doing it on stands will give you incorrect numbers.
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Old 07-28-2010, 04:48 AM   #4
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Did it on rear stand :(
Will remeasure. Thanks
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Old 07-28-2010, 11:28 AM   #5
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Just did it again without rear stand for the front and included full gear for more accurate...got same number...so I guess the sag is 27.5mm...Dave Moss said it should be 35-40mm so I guess I'm on the stiff side. Need to decrease the preload a little.
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Old 07-28-2010, 12:03 PM   #6
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Quote:
Originally Posted by randomwalk101 View Post
Just did it again without rear stand for the front and included full gear for more accurate...got same number...so I guess the sag is 27.5mm...Dave Moss said it should be 35-40mm so I guess I'm on the stiff side. Need to decrease the preload a little.
depends what your needs are. for me, 27.5 sounds good for the track but for the street crusing i prefer 40; i guess i'm getting old...
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Old 07-28-2010, 01:14 PM   #7
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25% is a good starting point for the track, and 30% for the street (according to RaceTech). BUT... Pirelli race tires, for example, are said to like around 20% because it makes the tires work harder and stay hot. Nothing is set in stone.

Your actual measurements are difficult to get accurate (especially by yourself). "Sticktion" of the shock/fork seals will keep the shock/fork further up/down in its travel. Some people will sit on the bike and "jiggle" it side-to-side to get it to settle to its "natural" level.

Did any of that make sense?
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Old 07-28-2010, 01:18 PM   #8
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"Jiggling" side-to-side is an attempt to overcome the shock/fork's tendency to ride "high" in its travel WITHOUT actually compressing the shock/fork and causing it to ride "low" in its travel.
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Old 07-28-2010, 01:27 PM   #9
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I measured the front by myself today. I wrapped a ziptie around the fork and sat on the bike with gears and balanced the bike on peg for a second or two. The fork compressed and push the ziptie up. After dismounted, the fork extended leaving the ziptie in position...I then measured from the lower edge of the ziptie to the lower fork clamp...
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Old 07-28-2010, 01:46 PM   #10
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That method doesn't work very accurate. But, you could go ride it on some hard corners and braking, and see how far the zip tie moves. As long as it isn't bottoming it will be fine for the street. I usually fine tune mine after setting the static sag to make sure I am using the suspension in it's best range.
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Old 07-28-2010, 02:11 PM   #11
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Thanks. I'll leave the ziptie and ride around.
How do I know when/when the fork bottom out or not? Thanks
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Old 07-28-2010, 02:50 PM   #12
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I believe the issue of bottoming is one of compression damping. Someone correct me if I'm wrong.

AND... to find out where your true bottom is, measure downwards from the fork's fully extended posistion. You MAY find your forks travel (lets say 120mm) is still 5 or 10mm from where it LOOKS like the bottom of the stroke would be.
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Old 07-28-2010, 03:24 PM   #13
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Fork fully extended = measurement of fork when bike on tripple tree stand?

But I thought it bottoms out when bike hits a bump, fork compresses to max = bottom out? If so, why measure fork max extention?

Last edited by randomwalk101; 07-28-2010 at 03:26 PM.
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Old 07-28-2010, 04:13 PM   #14
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Quote:
Originally Posted by randomwalk101 View Post
Fork fully extended = measurement of fork when bike on tripple tree stand? Yeah, its fully extended when its on a tripple tree stand.

But I thought it bottoms out when bike hits a bump, fork compresses to max = bottom out? If so, why measure fork max extention? Lets say your suspension (forks or shock) has 120mm of travel. That means it CAN move 120mm from the fully extended posistion, but it doesn't have to. Heck, when you sit on it and set the sag, it uses 25-30% of that 120mm. If you hit a small bump, it will compress some more, and a bigger bump will compress it even more. Guys that go to the track use zip ties to determine fork travel, and adjust as needed. Ideally, under the very hardest braking, you'll want your forks to be CLOSE to bottoming, but not quite bottomed-out.
Make sense at all?
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Old 07-28-2010, 04:20 PM   #15
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Sag adjustments are for your weight.

Compression adjustments are for your style of riding (track, aggressive street, cruising, etc...)
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Old 07-28-2010, 04:23 PM   #16
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Oem 250 fork has no adjustment at all. I added preload adjustor to only allow doing just that. To change compression/rebound etc prob have to mod fork's internal.

I found this little segment which answered my question:

Your Bike Bottoms Out
****Symptoms: When you brake hard into a turn or at a stoplight the front end seems to dive down or bottoms out. You accelerate hard and the front of the bike raises up and the back squats down, like a boat. Entering a turn at speed the back or front of the bike feels like it drops significantly and then becomes unstable when get back on the gas. When you hit a bump the you get an extreme double bounce from the front and then the back.
*** Solution: You need more preload. If you notice the symptoms on the front increase the front preload, if the rear, rear preload. Do one at a time and then test it out. One out of adjustment can give the feel of both being out. When you change the preload adjustments you will also be affecting the bikes ride height, which will affect the handling. So if you stiffen the front preload and not the back, the front of your bike will raise. This will cause you to notice that the bike doesn't turn into the turns as easily as before. To correct this and keep the same rear preload adjust the rear ride height or lower the front by raising the fork tubes in the triple clamps. Adjusting the front ride height by the triple clamps can be tricky and needs to be done in very small increment, 4mm at a time or so.
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Old 07-28-2010, 04:30 PM   #17
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Sorry dood, forgot it has no damping adjustments. And you have right-side-up forks, too. I made things way too complicated... again, sorry!

Stick a zip tie around the bottom of the shiny part of your fork. Ride around, brake hard, hit some bumps, etc. and measure. Adjust as needed (turn preload adjuster clockwise for less travel, counterclockwise for more travel).

Unless you're fairly heavy and/or super aggressive, I doubt you'll be bottoming out.

Last edited by Pre-K; 07-28-2010 at 04:32 PM.
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Old 07-28-2010, 04:39 PM   #18
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I appreciate the help as always.
This is the first time trying to adjust it myself. Fun but confusing as

So from what I've gathered, these are the steps for dummy (ziptie method).

1)Lower preload and drive around with ziptie and do some hard braking to bottom out (nose dive at braking as above). Mark this as max travel distance (bottom out mark).
2) increase preload and do the same as step one. If ziptie moves to about 10mm below bottom out mark, you're done....

Is this it??
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Old 07-29-2010, 12:42 AM   #19
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I would just try what you got, see how it feels, and adjust from there to get the fork working in mid travel.

Basic idea of setting sag is to put the ride height in the mid stroke area for most riding, based on rider weight. You don't want it topping out or bottoming out. Plus the internal valving works the best in the mid stroke areas, and the geometry of the bike is designed to work correctly at the specified sag settings.
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