[Andrew-4ce]

Hey all... looking for a little advice...

Riding a 2002 ktm 640 smc
Got Metz M1's on it, 28psi front, 28 psi back
I'm 6', 150lbs.

The suspension is great most the time, but in faster sweepers (fast enough that I wanna put a knee out instead of a foot or just sitting normal) that have some bumps in them the front suspension doesn't seem to absorb the bumps. It feels almost solid and you skip a bit off the bumps and drift across the road some. Little unnerving to say the least... this normal? I'd think not. Is there a point when leaning that the suspenion kinda stops working? THe forces are always going up the forks are they not?

I don't know much about tuning, but any guesses where to start adjusting?

 

[brian]

too much compression, not enough rebound.........Tire pressure 24/26 ??
4 clicks off the compression first and leave the rebound for now as a baseline
I'm no expert but thats what worked for me............ my 2 c's

 

[Andrew-4ce]

Thanks for the 2 cents

Tires still softer eh? How do you know when they are too soft?

 

[SMR]

I'm no expert, so take or leave these thoughts as you see fit...

First thought is that you've too much compression damping tuned into the forks and that if you back it off a click or two at a time (This is guessing that you have the adjustment on the KTM), you'll find that things improve.

Could also be that your sitting farther back on the seat and this is making the front end flighty. I'm just so used to feeling like I'm pushing myself up onto the front wheel that it's always the rear that seems to move around and not the front.

Your tire could also be shagged.

If your leaned over far enough to drag the pegs (doesn't sound like it though), your forks do have a harder time of dealing with the bumps your front end encounters.

 

[Andrew-4ce]

Tires are good. Never managed to get them looking shaggy yet.

Not leaning far enough to touch anything but getting over pretty good.

I could be back on the seat a little bit.

Thanks for the tips... I'll try playing with the compression a bit.

Anyone else, feel free to through your money in the pot.

 

[Dan 155]

I don't know about the suspension but I used to get the same feelings on my Aprilia before I got my motard. After taking a class at a superbike school, I learned that it was caused by my body stiffness. After I learned that I started to let my body and arms act like a raw steak to absorb big impacts. This along with keeping your eyes focused on where you want to go have help my riding a lot, even on my crf. Give it a shot and good luck.

 

[bdmmotard]

something to think about, the rear too stiff can also cause the front to push. i had that problem on my lc4. most guys keep a decent amount of sag, like 80-100mm on the rear.

what the other guys said about front compression sounds good too.

 

[brian]

Thanks for the 2 cents

Tires still softer eh? How do you know when they are too soft?

I'm not sure yet ??? But I can tell you that having 18/20 on a sweeper on a backroad doin 70+ mph I can feel the back tire start to squirm. almost feel like it wants to roll off the rim.... But I'm 230 with a 350 lb bike with Diablos....
Me, personally, seems to be 24/25......... :hmmm:and yes I left the rebound alone and backed off the compression 4 clicks which put it halfway.

 

[katoom_duke]

Tires are good. Never managed to get them looking shaggy yet.

Not leaning far enough to touch anything but getting over pretty good.

I could be back on the seat a little bit.

Thanks for the tips... I'll try playing with the compression a bit.

Anyone else, feel free to through your money in the pot.

Hi Andrew,

It is always difficult to know what is best as we do not know what changes you have made to the settings if you have used the bike on the road; you will have made some changes yes?

The general rule about suspension settings is to make a note of your start point. Change one thing at a time and keep notes as you go. Concentrate on one aspect of the track to solve problems.

From what you originally said, I would say BACK OFF the compression unless you have not changed compression settings since riding on the road. If I assume you have brought the bike racing from riding on the road it is normal practice to leave the compression alone and raise the rebound. Picture your bike wheels moving over the surface of the track or road. On the track you are moving faster than on the road so you would hit the same type of bump (not the size but the shape) and move over it much quicker. Imagine your front wheel moving up and down while going over the same shaped bump twice, once slow then once fast. If you increase the compression it will be harder for the wheel to move (compress) as quick as it needs to go over the bump faster when before it was fine. Similarly, it will have to rebound much faster to stay in contact with the track when it comes down the back of the bump while moving faster.

In this situation;

It feels almost solid and you skip a bit off the bumps and drift across the road some.

The wheel has not followed the back of the bump and has lost contact with the surface, so you understeer. Remember also, on a fast sweeper you are leant over so the force of the bump will come from an angle on the fork legs so there will be flex and this causes stiction. This may be the source of your feeling that the compression phase feels solid (unless you had already increased compression), stiction is BAD! Use good oil and grease your seals, check they are ok and that there are no burrs on the fork inners.

The best you know is the best you remember

Good luck :thumbup:

 

[SMR]

Just had another thought while reading back over these posts...you might also pay close attention to your reaction with the throttle when you encounter bumps mid-turn. You just might find that your cracking the throttle closed or in the middle of rolling off the throttle as you are going through the turn and over rough pavement, and thereby loading up the front tire, which would make the trouble your feeling worse. Just more food for thought.