"Race sag" - 06' DR-Z400S - how to adjust?


15 replies to this topic
  • Sasqui

Posted 07 September 2010 - 03:35 PM

#1

Just got DR2 Kouba links in the mail (from Norm himself - fantastic customer service).... reading the instructions which talk about "Race Sag". I understand what it is, but how do you adjust it? If it's spring pre-load, it requires a special tool, according to the OEM manual.

I'm sure there are threads on the topic here, point me in the right direction if so! Thx.

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  • ptgarcia

Posted 07 September 2010 - 03:52 PM

#2

Remove the right side frame cover and you can get access to the shock lock collar and adjuster ring with a long screwdriver or brass drift. Loosen the lock collar with the drift, then loosen or tighten the adjusting ring as needed. You can do this with the drift or screwdriver, also, or try reaching in and turning the spring with your hand. Typically that's how I do mine. Be sure to remove the pressure off the rear suspension beforehand.

  • paolo h

Posted 07 September 2010 - 03:56 PM

#3

The first thing to do when setting up your dirt bike suspension is to put the rebound and compression clickers for both the forks and rear shock in their standard position (your owners manual should tell you how many clicks out is standard), if you don't have the manual just set them halfway between hard and soft.

If possible find out what the standard rear spring was for your bike and make sure that's what is in it now. If you've bought your bike secondhand and the rider who owned it before you was heavier or lighter than you or was particularly fast then they may have put a different spring in it which can make dirt bike suspension tuning difficult, this can be the case for the forks as well.

To set the static sag on the rear shock you first need to set the preload.
Back off the locking ring and then you either tighten or loosen the main ring to increase or decrease the preload on the shock.
Put the bike on a stand with the rear wheel off the ground and measure from the axle nut to a point roughly above it on the bike (say, a mounting bolt for the muffler or a part on the rear subframe), now take the bike off the stand and let it stand upright.


With the bike off the stand now measure the distance between the axle bolt and the point on the bike itself.
Subtract that measurement from the distance measured when the bike was on the stand, there should be about 25mm of sag, if there's more than that wind up the preload or if there's less then back it off. This measurement is called static sag.

Now to set the laden sag (race sag). Take note of the measurement with the bike standing upright. Now with all your riding gear on sit on the bike in the attack position (head roughly over the crossbrace, elbows up and out and feet up on the pegs), have someone hang onto the bike for you and take a measurement again. The amount of sag should be between 90mm and 110mm, again if it's more or less then adjust the preload etc.

You should be able to get it set up approximately to those figures, if it's way out on either then that can indicate that it either has different springs than standard (if you bought the bike secondhand) or that you're heavier or lighter than the model used by the bike manufacturers. They base their settings on a theoretical rider who is about 5'10" tall and about 85kg.

These are just rough figures, read your owners manual for the bike, the japanese manufacturers have a decent section in their manuals on dirt bike suspension.

Taking some time to learn about and set up your dirt bike suspension costs nothing and can really improve your lap times.

  • paolo h

Posted 07 September 2010 - 04:02 PM

#4

i cut and pasted that by the way. the credit goes to another TT member by the name of dlkraniak.

  • Sasqui

Posted 07 September 2010 - 05:05 PM

#5

The first thing to do when setting up your dirt bike suspension is to put the rebound and compression clickers for both the forks and rear shock in their standard position (your owners manual should tell you how many clicks out is standard), if you don't have the manual just set them halfway between hard and soft.

If possible find out what the standard rear spring was for your bike and make sure that's what is in it now. If you've bought your bike secondhand and the rider who owned it before you was heavier or lighter than you or was particularly fast then they may have put a different spring in it which can make dirt bike suspension tuning difficult, this can be the case for the forks as well.

To set the static sag on the rear shock you first need to set the preload.
Back off the locking ring and then you either tighten or loosen the main ring to increase or decrease the preload on the shock.
Put the bike on a stand with the rear wheel off the ground and measure from the axle nut to a point roughly above it on the bike (say, a mounting bolt for the muffler or a part on the rear subframe), now take the bike off the stand and let it stand upright.


With the bike off the stand now measure the distance between the axle bolt and the point on the bike itself.
Subtract that measurement from the distance measured when the bike was on the stand, there should be about 25mm of sag, if there's more than that wind up the preload or if there's less then back it off. This measurement is called static sag.

Now to set the laden sag (race sag). Take note of the measurement with the bike standing upright. Now with all your riding gear on sit on the bike in the attack position (head roughly over the crossbrace, elbows up and out and feet up on the pegs), have someone hang onto the bike for you and take a measurement again. The amount of sag should be between 90mm and 110mm, again if it's more or less then adjust the preload etc.

You should be able to get it set up approximately to those figures, if it's way out on either then that can indicate that it either has different springs than standard (if you bought the bike secondhand) or that you're heavier or lighter than the model used by the bike manufacturers. They base their settings on a theoretical rider who is about 5'10" tall and about 85kg.

These are just rough figures, read your owners manual for the bike, the japanese manufacturers have a decent section in their manuals on dirt bike suspension.

Taking some time to learn about and set up your dirt bike suspension costs nothing and can really improve your lap times.


The Kouba instructions say to simply stand on the foot pegs to measure the height loaded (race sag). Obviously requires a second hand.

So from I've read here, the spring load is what determines race sag. Dampening adjustments have nothing to do with it, right?

Just want to figure out if I should try rotating the spring bottom stop myself, or bring to the dealer ($$$).

  • paolo h

Posted 07 September 2010 - 05:56 PM

#6

correct, the dampening adjustments have no effect on sag. if you take it to the dealer and watch them set it, you will kick yourself for having paid them to do something so easy.

  • Sasqui

Posted 08 September 2010 - 03:39 AM

#7

correct, the dampening adjustments have no effect on sag. if you take it to the dealer and watch them set it, you will kick yourself for having paid them to do something so easy.


That's what I was hoping to hear. What do you have for wheels?

  • npm

Posted 08 September 2010 - 07:48 AM

#8

Don't forget there is a limit on how much you can crank down the preload. Going past that will allow the spring to bind before the full travel is achieved.

  • paolo h

Posted 08 September 2010 - 07:55 AM

#9

That's what I was hoping to hear. What do you have for wheels?


00 drz400(kicker) & 02 yz250

  • Sasqui

Posted 08 September 2010 - 08:03 AM

#10

Don't forget there is a limit on how much you can crank down the preload. Going past that will allow the spring to bind before the full travel is achieved.


How do I know I've reached the limit other than performing a few aerial stunts? I guess the question is... is there's any way to measure how far to move the spring stop before you get yourself into trouble?

  • npm

Posted 08 September 2010 - 08:26 AM

#11

I knew you were going to ask that and I don't have my manual with me. I did a quick search using "minimum and preload" as the phrase and found this thread that says 9.74". It is probably correct but you should double check just to make sure. You can measure it with a tape measure with the shock unweighted (on stand, rear wheel off the ground)

http://www.thumperta...minimum preload

  • Sasqui

Posted 09 September 2010 - 08:06 AM

#12

I knew you were going to ask that and I don't have my manual with me. I did a quick search using "minimum and preload" as the phrase and found this thread that says 9.74". It is probably correct but you should double check just to make sure. You can measure it with a tape measure with the shock unweighted (on stand, rear wheel off the ground)

http://www.thumperta...minimum preload


THX dude!

I was looking at the bike last night (lovingly, lol)... and it appears the spring preload adjustment is on the top of the shock under the seat? I didn't see anything at the bottom that looked adjustable.

Edit: found a pic... indeed a threaded collar at the top of the shock:

Posted Image

Edited by Sasqui, 09 September 2010 - 08:11 AM.
Add pic


  • ptgarcia

Posted 09 September 2010 - 08:12 AM

#13

Correct, on the top side of the shock.

  • npm

Posted 09 September 2010 - 08:13 AM

#14

That's correct. The top collar is the locking collar, loosen it and then turn the lower collar to adjust the spring length, then tighten the locking collar.

  • FutZ

Posted 09 September 2010 - 08:51 AM

#15

Manual says Front fork spring pre-load adjuster standard is 3rd groove from the top and the Compression damping force adjuster is 7 clicks out.

For the rear the table shows Spring preset length

Standard
258.0 mm
(10.16in)

Soft
259.5mm
(10.22in)

Hard
247.5mm
(9.74 in)

Caution Do not set the spring less than 247.5mm (9.74in)

upper and lower mounting nut torque spec is 55 Nm (40 lb-ft)
lock ring torque spec is 90 Nm (65 lb-ft)

-FutZ

  • ptgarcia

Posted 09 September 2010 - 08:59 AM

#16

I don't think the cartridge forks have preload adjustment.





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