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31
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9/24/2017
Location
Midland, MI, USA
Hey all - my forks are harsh. Mostly over braking bumps and occasionally I’ll get headshake. My forks are sprung for me, sag is correct, I’ve messed with the clickers some… mostly compression. I’ve tried staying on throttle, pulling clutch in, putting weight further back to keep front end light and nothing seems to fix it. Pretty much have put it up to that’s just the way it is until I watched this video of myself. Looks like around :06 (right after I (red gear, Yamaha) come back into view) my fork bottoms out on a braking bump, then seems to kind of pack after that and finally recover once I get into the corner.
Have you tried slowing your rebound at all?
Also, you might want to look into a revalve. You'd probably benefit from a local tuner who can watch and help adjust/revalve.
I haven’t really, hadn’t really thought too hard until I saw this video… kind of looks like it’s packing a bit.
I had it revalved and set up but the guy hasn’t really been able to watch outside of when I first had it done and hasn’t been super helpful since.
Baby steps always best with clicker changes: Based on your video, +2 comp and -2 rebound may help. Looks a little low and slow. Try that for direction and don't be afraid to continue with incremental changes if they seem to help. Also - What are your current clicker baselines, fork height, and sag numbers? If you're at say 5mm FH, going to flush with just slightly opening the rebound may be a better option as the FH change will take weight off the front. (Which could also help with headshake but at the expense of some turn-in). Most headshake that you're describing is usually fork height related, fork rebound related, or sag related in my experience, assuming your fork comp is relatively close. Good luck and keep us updated!
Fork compression 12 out rebound 9 out
fork height I believe I already have flush… I’d have to check
sag is at 105, 12 out comp, 8 out for rebound, 1.5 out for lo speed comp
ride vet b/c level, mostly sand tracks with some hard pack sections
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Really hard to see anything profound in the video.
Typically for packing you would want to decrease rebound damping to allow the fork to return faster, but this doesn't look like packing as your wheel tracks the ground pretty well.
For bottoming resistance you would want to increase fork oil amount.
Looks like you were on the front brake which weighted the front wheel just as you hit the choppy braking bumps. If youre happy with your forks elsewhere, the best solution would be to ride off the main line. (Example, the guy that smoothly goes up your inside)
What's your static sag? And what bike, aluminum frame it seems?
I want to say static sag was around 35 mm. It was within range anyway. Bike is a 2021 yz450f… yes aluminum frame
With 35 static you will get harsh forks. Needs to be closer to 40. Try backing of some preload, it will get better. But one step up on spring will give less preload and would be best, more static = smoother ride.
You can also try and lower the rear, meaning go out of HSC 0.5-1 turn, and/or in on rebound 1-2 clicks. Will also take pressure of front.
Your only other option is stiffen compression on forks, it's needed because 35mm is putting a lot of pressure on them.
Pull your front wheel off and remount it. Make sure your forks arent binding and that the forks are sitting parallel on the axle.
I had slightly bent triple clamps and it was this. Put new xtrigs, as i was paying for clamps so i upgraded. So much better, that i had to valve stiffer as i chased plushness with bent binding clamps. Wasted a lot of races last year to find out it wasnt me or my suspension!
That’s interesting! How did you ultimately find out it was your clamps bent? I’ve had some pretty good crashes that I thought for sure would have bent the clamps
pull your entire front end apart, clamps and all out of the frame. put the the bottom clamp on a piece of glass or other flat surface. if they don’t sit flush and rock back and forth on the glass, they’re bent and need replaced.
Wouldn't you notice when putting the forklegs in the clamps? If it's twisted, they would not drop right down by themselves as soon as you losen up the triple clamps bolt?
i’ve never had a pair of forks that have just dropped straight out of the clamps when loosened due to friction of the clamps still somewhat holding them in. i’ve always had to twist a bit and pull down. i’m sure @Luxon MX can chime in a bit on this topic as well.
My KTMs, both power part, OEM and Xtrig triple clamps they drop pretty much right out when I open the bolts. Might have to twist just a few mm to get them going. For sure they should go straight up when mounting them or something is not right.
But that's how I check TC are lined up.
If I tip over or crash, sometimes I have to losen clamp up and it will realign.
Assuming nothing is bent, it all depends on the tolerances and quality things were manufactured to. Both the clamps and the fork tubes.
You might be surprised how much the fork tubes can vary in size, especially KYB and Showa. WP seems to do a better job on their tubes, but a rather terrible job on the clamps (though I'm not sure WP is actually making the clamps).
Diameter, roundness, surface finish, all play a part. It's not unusual to have to twist things some to disassemble or install, but you shouldn't have to try too hard. If they just fall right out, that can be bad too, just depends on how loose they are.
Maybe I have been lucky, but the last 6-7 new KTMs, since I learned to losen up TC when it gets difficult, all forks have gone smooth through almost falling out when completely lose.
If it's a little hard to rotate forkleg or push it up and align, I always just correct the TC and it's back to going smooth again.
I remember before I discovered this, I pull my hair out when trying to adjust fork height in TC. Like I could only turn the forkleg clockwise and it would move up/down. Tried to move it the other direction and it was like someone has welded the fork to the TC 😄
If they slide through super easy, either the fork tube is too small, the triple clamp bore is too big, or both. Not a big deal if it's over/undersized by just a small amount (likely), but it starts to get bad as things deviate from nominal too far. Not trying to worry you or anything, they're probably fine, just noting that sliding through super easy isn't necessarily a good thing!
In regards to turning the fork one direction and it moving, but the other direction makes it stick solid, have a look at the clamping slit location on the clamps. Turning it one way will naturally want to open up the clamp, turning it the other wants to close it. On stock Austrian stuff, the top and bottom clamp have this in the same direction, which is what you've discovered. We balance it out by having the top clamp opposite of the bottom (one of the reasons for doing that anyway). It helps to keep things aligned in a crash too as it doesn't want to rotate easily and move.
Pit Row
Thats how i found them out. Put them on a flat and lowers had rocking and light showing under when the other-side was flush. Kx450 it was on.
The improvement was huge. Had to revalve a fair bit stiffer after going softer to chase the plushness, that obviously i couldnt get. Man i was pissed as i raced many races and would struggle as the track broke down, getting beat and thinking am i losing it haha. A relief to know it wasn’t me.
I’ll throw this out there! Regarding revalved susp, there are a lot of guys out there that are capable of doing a revalve, but knowing what shims to change, that’s the tricky part! You can go in and change shims around, take some out, put some in, that doesn’t mean it’s Gona be good!
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