Ohlins rear shock set-up?

**Rupe** · 29th October 2007, 19:25

I've been told that I should set the rear shock to 100mm sag under the bikes own weight (not with rider on etc).

Does this sound right, is so mines way off

**Drew** · 29th October 2007, 19:35

Originally Posted by rupecopp

I've been told that I should set the rear shock to 100mm sag under the bikes own weight (not with rider on etc).

Does this sound right, is so mines way off

NO, perhaps ten. Get somebody to help and set it right with you on it.

My limited knowledge says 25 to 30mm static sag with rider on board, but a service tech is the right person to confirm or deny.

**dammad1** · 29th October 2007, 20:36

It varys a little between bikes but as a guide the free sag (i.e the difference between the bike being up on a stand and then sitting on the ground under its own weight should be 25-35mm.With the rider then sitting on it, it should sag a further 70mm for a combined total of around 100mm.

Small changes will make quite a big difference to the handling of the bike so you should try to find out exactly what your paticular bike should be.

Maybe find someone with a manual or perhaps Danger has had some experience with the gas gasers.

**Rupe** · 29th October 2007, 20:41

Originally Posted by dammad1

It varys a little between bikes but as a guide the free sag (i.e the difference between the bike being up on a stand and then sitting on the ground under its own weight should be 25-35mm.With the rider then sitting on it, it should sag a further 70mm for a combined total of around 100mm.

Small changes will make quite a big difference to the handling of the bike so you should try to find out exactly what your paticular bike should be.

Maybe find someone with a manual or perhaps Danger has had some experience with the gas gasers.

I know this sounds strange, but it was Linton from DAS (who really knows his stuff). Apparently as the system is so progressive on the gasgas that he doesn't set the bikes to riders weight, he just sets it to 100mm under the bikes own weight.

Just wondered what people thought of this?

**dammad1** · 29th October 2007, 20:44

That doesn't sound right.

**Rupe** · 29th October 2007, 20:48

Originally Posted by dammad1

That doesn't sound right.

Thats what I thought, but I'll wait to see if anyone has had any experience with the gasgas shocks

**Drew** · 29th October 2007, 21:16

Disregard my comments, (I'm sure you already did), I wasn't smart enough to realsie you were talking dirt bikes, just saw the post pop up in the spy thingy, and leapt in boots'n'all before pausing the required time it takes for my brain to switch on.

My bad

**Quicker_with_age** · 29th October 2007, 21:27

It will be 100mm of sag with you on the bike

**Rupe** · 29th October 2007, 21:37

Originally Posted by Quicker_with_age

It will be 100mm of sag with you on the bike

Thats how I set the bike when I got it. But when I mentioned this the other day while speaking to linton, he told me to set it 100mm under bikes weight.

I'll call him tomorrow as everyone seems to find this as strange as I did.

**scott411** · 29th October 2007, 21:40

100mm free sag (bikes on weight) is way to much, we normally use 25-35mm free sag and 100-110mm rider sag (rider and bike weight)

**Reckless** · 29th October 2007, 21:41

There are two types of sag Static sag (the bikes weight) 25-35mm and race sag (with rider & gear). 90-105mm. Its is a combination of both that determine if you have the correct rear spring.

You need a t least two people!!
Race sag.
Get your bike up of the ground suspension fully extended, like in the air over a jump, put a marker mark on the rear of the number plate or some fixed point (bolt) above the axle.
Measure the length from the axle to the marked/fixed point.
Now get all your gear on (this can make 5-8kilo difference), Stand on the bike in race position upright and balanced as if your riding.
Measure the length from the axle to the same fixed point.
Subtract one from the other. ie 520mm extended - 420mm with rider & gear = 100mm sag
This is rider sag.
Adjust to the compression of the spring to get the required amount required. I use 95mm approx for mx tracks with jumps ie Ardmore and Harrisville. And 105mm- 110mm for X-Country on the CR250. 100mm is generally accepted as standard. You will get to know your bike , Two full turns on the adjuster is about 10mm rider sag on the CR. I have mine marked with a felt pen mark. This adjustment makes heaps of difference to the handling for different disaplines.

Static sag or free sag - no rider.
Get your bike up of the ground, put a marker mark on the rear of the number plate or some fixed point above the axle. Should be the same as per previous measurement above.
Take it off the stand and than measure the bike standing under its own free weight. You might want to push down, release, take a measurement then pull up, release, take a measurement and split the difference. This is difference called suspension Stiction.
If this measurement is not in the required range ie 20-35mm it means you have a spring in that is either to soft or to hard for your weight.

ie If free sag is only say 5mm it means you are compressing a to soft spring, to much, to get the rider sag of 100mm. And your bike will be harsh with to little travel on the spring and the shock.

I've only been riding MX a year so I hope I've got it correct!
The measurements could be heaps different for your KTM but the above are generally accepted for Hondas, yammys and suzis etc

Ruecopp do a google seach its to hard to explain properly here.

**Danger** · 29th October 2007, 22:37

Set sag (you on board) to 105 to 108mm. Your preferences may dictate a variation from this.
Spring preload (spring free length minus set length) should fall between 10 to 15mm. This is a good place to start from and fine tune from there. The rear sag can be used along with fork tube height and other variables (HS adjuster for example and spring rates) to fine tune the handling characteristics. With more rear sag, say 115mm the rear sits lower and rakes out the front end (slower steering, more stability).
With less rear sag, say 95mm the rear will ride higher and allow it to steer quicker but will give up stability.
All these measurements can effect trail and front tyre grip, but thats probably a bit advanced to go into for the purposes of this conversation.
Combine all of this and throw in the position of the rear axle in the swingarm and you have a lot of variables to fine tune or totally goof up you bike for your specific needs. I like to think that there is not any right or wrong numbers, only guidelines. Its up to you to take notes and try making changes to get the result thats right for you.
Or just bring your bike around and I will set the sag up for you. No charge of course.

**Reckless** · 30th October 2007, 00:59

Shit if Danger hasn't corrected me I must have got it right! lol

And just to add to what Danger said the firmer 95mm sag at sprint tracks also helps with the big jumps where you want a firmer spring setting for the landings so you don't bounce. The quicker steering helps too I think?
Most of it learned from Danger and what little experiance I have. I quite like the tech side of setup.
Take Danger up on his offer to set your sag you'll learn heaps he's a magician.

**Danger** · 30th October 2007, 07:24

Kind of but not entirely correct Reckless. Preload sets the ride height and the initial bump impact. It will have little effect on the big jumps but can make smaller bumps more compliant. Control any bounce (movement or velocity) with damping. Spring controls position, damping controls velocity. The reason your back end bounces on the big jumps could be because you have your compression backed off too far trying to get small (high speed) bump compliance and your shock is moving too far into the stroke too quickly and that stored energy in the spring needs to be released via rebound and your high speed rebound is too quick for you. The front end has these issues taken care off which can make the rear worse in some respects because it is out of balance with the front. Because you increase preload at Ardmore you maybe decreasing damping for the small bumps, then paying for it on the bigger jumps. Your robing Peter to pay Paul so a catch 22.
The jumps at ardmore are more of a low speed impact so increaseing preload will help to some extent because the demands are not great and if you slow the begining of the stroke you will get less stored energy and less bounce. But on bigger impacts the added preload is quickly overcome.
Think of low speed and high speed in terms of suspension speed, not bike speed.
I would think that a 100-105mm range would be adequate if you required any adjustment between disciplines. 95-110 seems a little extreme. I pretty much use 103mm rider sag on the RM for all disciplines. A change at the HS adjuster can have an effect on rear end ride height and turning.
Sorry Rupecopp if we have got a bit of topic and made this anymore confusing. 105-108 should be good for you and your bike and the riding you are doing. But don't be afraid to experiment from there.