Setting KTM Sag!!!

[Kwi-Chang]

Not sure what the hell I'm doing but I can't get more than about 85mm of sag. I read an article about how much the rear sag can affect the front suspension causing defelection on small bumps etc -this is the problem I have been trying to get fixed for about a year now.

I have set the sag before but could only get a max of about 85mm (100mm is supposed to be normal...?) I am trying tonight and no matter what I do do I get from 70 to 85mm. The article I read said if you need more sag (which I do) loosen the locking collar. I've tried every combo and still the same. Free sag is about 35mm. I have an '02 520 with stock springs front & back (forks have RaceTech GV's). I am 200lbs.

Any ideas???

[Dobi]

Are you pulling down on the tire with the bike in the air on the stand? I read on KTMtalk that due to the linkageless design you have to stretch it out or your sag will always be short. With mine it usually is about 3cm worth of movement. That reminds me that I should probably check that again....

[dirtyboy]

The article I read said if you need more sag (which I do) loosen the locking collar.

I'm not trying to be smart here, but are you loosening the other collar also and then tightening the locking collar again? If you reduce the preload on the spring (by loosening both collars on the shock body) there is no reason why the sag would not get larger.

[Kwi-Chang]

As I was lying in bed last night it occured to me that I was measuring at a convenient place on the swing arm and not at the center of the axle. I did a quick check this morning and it made a huge difference! Gotta remember some of that basic geometry from school...

[Kwi-Chang]

Thanks for the ideas guys.

Dobi - on my bike the wheel settled at full extention.
D-Boy - on the older KTM's there is only one collar and it has a pinch bolt to hold the collar tight.

Doing the measurement from the *right* place did the trick. I have got the sag to 105mm & 25mm for the free sag (no rider). I'll give that a try.


kwi

[dirtyboy]

D-Boy - on the older KTM's there is only one collar and it has a pinch bolt to hold the collar tight.

Doing the measurement from the *right* place did the trick. I have got the sag to 105mm & 25mm for the free sag (no rider). I'll give that a try

Duh, it's the same on my new KTM with the allen bolt.

Based on your sag numbers it sounds like you need a stiffer spring. That's not enough free sag.

[Kwi-Chang]

D-Boy - on the older KTM's there is only one collar and it has a pinch bolt to hold the collar tight.

Doing the measurement from the *right* place did the trick. I have got the sag to 105mm & 25mm for the free sag (no rider). I'll give that a try

Duh, it's the same on my new KTM with the allen bolt.

Based on your sag numbers it sounds like you need a stiffer spring. That's not enough free sag.

D'Boy - what is the free sag supposed to be for KTM's? New springs front & back may make a big diff!

[knuckle]

Are you pulling down on the tire with the bike in the air on the stand? I read on KTMtalk that due to the linkageless design you have to stretch it out or your sag will always be short. With mine it usually is about 3cm worth of movement. That reminds me that I should probably check that again....

Yes the top out spring.

[dirtyboy]

what is the free sag supposed to be for KTM's?

I don't think that there is one answer for this but you need heavier springs.

The KTM manual (I think the information is outdated) says the race sag should be 100mm and free sag should be 35mm. Some guys on KTMTalk suggest what they call the golden rule. Set the sag at 45-50mm and the rider sag should be 115mm. They also say that the installed spring length should be more than 240mm if using a standard 250mm spring.

At any rate, if you set the race sag, then check the static sag and the static sag is less than the specified then the spring is too soft. If the static sag is more than the static number the spring is too stiff.

Not sure if this helps, but I'd guess you need at least a 9.2 rear spring to meet the KTMTalk GR set up.

[Kwi-Chang]

Ahhh - the KTM Golden Rule! If you buy a KTM be prepared to spend some Gold on getting it set up right...

The article I read was in TW MX and written by the factory Honda mechanic. According to him static sag should be between 20 & 35mm. I'm tending to go with what your saying as it is more brand specific. My spring is at 245mm right now.

Different sags for different lads!

[dirtyboy]

So you have 5mm of preload on the spring? That's good. Just thinking, is it a KTM spring that starts at 250mm? The newer stock springs are 250mm not sure about the '02's.

You can't go by what the Honda guys says since the KTM doesn't have linkage.

Your numbers don't make sense to me. Only 5mm of preload but static sag at 25mm and race sag at 105mm. I think you should double check your measurements. Do you have a helper when you are taking measurements? I know I have to bug someone to take the measurements while I'm on the bike. Don't forget to wear your gear when setting the sag. Especially if you ride with a tool bag or drink system.

[Kwi-Chang]

So you have 5mm of preload on the spring? That's good. Just thinking, is it a KTM spring that starts at 250mm? The newer stock springs are 250mm not sure about the '02's.

You can't go by what the Honda guys says since the KTM doesn't have linkage.

Your numbers don't make sense to me. Only 5mm of preload but static sag at 25mm and race sag at 105mm. I think you should double check your measurements. Do you have a helper when you are taking measurements? I know I have to bug someone to take the measurements while I'm on the bike. Don't forget to wear your gear when setting the sag. Especially if you ride with a tool bag or drink system.

Just double checked the measurements (with help) 105mm rider, 22mm static, 245mm spring length. No gear on.

[fryguy]

115 mm rider sag and 30-35mm static sag is typical PDS specs, however rider style, weight and height will vary your final setup. If you ride it with 100 you'll find it to be very stinkbuggy and twitchy. Bin there done that. more sag is better. You have to set it up so you get a good balance, it turns well, doesn't push the front, the back isn't always stepping out etc. Test your cornering set up on a faster flat corner. True test. My 05 berg was set up well till I used th esame setup in Slovakia, where the corners were flat and slick. It didn't take me long to realise that my balance, ie weight transfer was way off and the rear spring was to soft, allowing the rear to settle, stable, but it wasn't predictable on flat cambers.

Best thing to do is set up the basic and then tinker, and listen to how people set up their bikes, but don't always take their results as gospel. Their style, weight and height all affect handling.

Your deflection issue could be lack of sufficient sag or to much high speed comp dampening in the fork.

hope this helps

fry

[Kwi-Chang]

Your deflection issue could be lack of sufficient sag or to much high speed comp dampening in the fork.

hope this helps

fry

thanks

fryguy - do you know if the forks on an '02 520 have 2 sets of shims for high & low speed damping? Mine only has one set. I had my forks redone with RaceTech GV's etc by a shop in Calgary but have not been happy with the set up.

kwi

[fryguy]

Kwi

Sorry man, never had a set apart.

The GV setup can be perfect, but since it is a generic shim selection, the recommended stack has to be right. Its an easy mod to do, but agian if the Race Tech setup for your parameters sucks then so does your suspension.

I was going to isntall a set into my Wr 426 in 01, but Dan Watt talked me into the Delta valve. It replaces the comp adj at the bottom of the fork, giving you both high and low speed adj, with a screw driver and a 12mm. Highly recommended.