Trying to understand static sag

[needsprayer]

I have a XR650R '01. Suspension is stock and at factory settings.
Static sag = 2"
Race sag is = 3.75"


If I understand what I have been reading, when I add preload (shorten the rear spring) I will decrease both static and race sag.

I don't know if the spring is a straight or progressive rate spring.

Questions:

1) Is there a 1:1 change in both static and race sag when I change the spring length (add preload)?
2) How much can compression and rebound settings compensate for static sag if it is greater than the ideal measurement of 1"?

Comment: I see that the flame forum is gone. Great improvement for DRN.

Thanks

 

[Jaybird]

When you have your race sag set with the spring pre-load, then you can check your static sag, or sag that the bike alone yields. If your static sag is within the spec at that point, you probably have the correct spring. If it has no static sag after race sag adjustment it means you probably have too light a spring in and had to tighten the pre-load to a point that the weight of the bike alone can't overcome it and the bike shows no sag. Since you are showing a sag of 2" and spec is 1", then your spring is too stiff for you. To obtain the race sag, you had to back it off so much the bike's weight could make it sag further. Are you a smaller guy on that beast?
The clickers effect the suspension when it's in operation so they won't effect your static sags.

 

[needsprayer]

Rider size and other considerations

" Are you a smaller guy on that beast? "

Jaybird,

I am 200 lbs with gear on. I have lowered the front clamps 30mm down the forks from stock position (helps a 5'-8" person get better footing). This lowering of the front end has redistributed the weight and may account for some of the 2'" of static sag. I am still curious about rear shock spring adjustment and how it relates to sag change. Will a 1" change in preload (compressed spring length) result in a 1" change in static sag? Is there a 1:1 correspondence?

Thanks for your reply

 

[Shaw520]

One inch of preload will not equal one inch less of sag, it is not a 1:1 ratio. Spring rate and your weight will determine what the sag will be. Adjust according to Jaybirds instructions above.

 

[yota]

sounds like you are confusing front and rear. sag is measured in the rear.

30mm is way too much to raise your forks in the triple clamps in my opinion. you are way upsetting the balance of the bike. I am also 5' 8" tall. I wouldn't go more than 5 to 8 mm. set your rear sag to spec sitting on the bike in attack position with all your gear on. Get someone to help if you can. measure from the rear axle to the seat bolt or other point which is easy to line a tape measure up on. measure first with the bike on a stand and no one on the bike and write down the number. take the bike off the stand and sit on the bike in your gear, bounce up and down a few times and adjust the shock spring preload until you are at spec. get off the bike, leave it off the stand and bounce the seat up and down. measure the sag now without rider, this is static sag. if you have too much the spring is too soft for your weight, if you don't have enough the spring is too heavy. if you are in spec the spring is just right. with the conventional forks on your bike, if you want more preload, you have to cut and install pvc spacers on top of the springs.
you can only tell by feel, to my knowledge there is no spec for front sag or preload.

 

[needsprayer]

"this is static sag. if you have too much the spring is too soft for your weight"

Yota,

Please read Jaybirds response: 'Since you are showing a sag of 2" and spec is 1", then your spring is too stiff for you. '

I am getting confused by what appears to be contradictory replies.

I added the info about lowerng the clamps to inquire if this affected static sag in any way. I haven't read anything in the replies to cause me to believe that it does. Lowering the clamps improves turning control but introduces headshake at high speeds. I'll take this trade-off.

Thanks

 

[Shaw520]

Jaybirds reply is correct, Yoda, go back and carefully read Jays description. Although it is a confusing, he's got it right. If you have too much static sag with the correct race sag then the spring is too stiff. Not enough static sag with the correct race sag means your spring is too soft. You gotta think about it for a while, and It'll make sense.

 

[Jaybird]

Although it is a confusing

LOL...no wonder I wasn't a teacher. :)

needs, you'll be fine after you've done this sag set a few times. I would recommend you get the 30mm of fork thing out of your head though. You can greatly regret doing that one day, and prolly while going mucho fast. Take yota's advise on the fork height.

 

[needsprayer]

OK, I respect the voice of experience.

I'll raise the fork clamps to 8 mm below top of forks and play with the preload to see what sag I can achieve within the recommended limits of spring adjustment.

Thanks to all

 

[pro-design]

I also agree with raising your front end back to 8mm. However this will not I repeat will not effect you sag. Read your Honda manual that came with the bike it tells you step by step how to set sag. If you don't have it I'll give it a shot for you. STEP 1 put the bike on a race stand take a measurement from your seat bolt to the center of the rear axle. Write down that number. STEP 2 take the bike off the stand and sit on it with your gear on. Have a buddy or a wife or kid measure the distance from the same points you did in step 1. Write down that number , then subtract the figure in step 2 form step 1's figure. The answer will be your race sag. The figure you get should be 95 to 100 mm's depending on what kind of riding you do. NEXT issue free sag , free sag is relative to race sag you do not adjust for it. Free sag is measured by taking your bike off the stand and letting it stand on its own (without you on it). Measure the again from the same place as before . Once again write down your findings. Now take your free sag # and subtract from your Static sag number from step 1. This is your static sag . Your Honda manual recommends between 20 to 25 mm's of static sag. If your figure is way high or way low from what Honda wants and your race sag is around 100 mm. you need to buy a new spring.

 

[Jaybird]

pro-d,
I think that the gemoetry of the front can in fact effect the rear sag, but minimally at best. Probably no more than another 1/4 tank of fuel or a little fender mud will do.

needsprayer, once you've got the rear sag thing down, we can move on to front sag! :eek: