Fork bottoming too easily. . . Ideas?

[robwbright]

Tried 3 different searches and didn't find an answer. . .

When my scaphoid (wrist) got broken, I over jumped a 25 foot double by about 10 feet and flat landed a bit nose down on a slightly downhill landing.

The forks totally bottomed and broke the bone.

It was a pretty hard landing, but from the last year and a half of riding and racing the bike, I would not have guessed that the forks would have bottomed at all in that situation, and certainly would not have bottomed that hard.

When I reinjured the wrist before I knew it was broken, I intentionally landed nose high on an uphill landing and the forks still bottomed.

Any ideas? Could it be the fork oil breaking down? Or something internal?

 

[Masterphil]

Are your spring rates correct for your weight? Go to the MX Tech website and use their spring calculator.

If your springs are correct, what is your oil height? What is your compression setting? You might try increasing the oil height and/or increasing the compression.

You also landed in the worst possible way for overjumping. If you know you are going to overjump, make sure the rear touches down first, and make sure you are on the gas when it does. This will make flat landings much easier to absorb. I'd also guess that since you broke your wrist landing, your upper body was too far forward causing your arms to take the impact instead of your legs.

 

[robwbright]

Phil:

I assume the springs are stock as the seller never said otherwise, and he gave me lots of details which turned out to be correct. I'm 145 lbs, so I doubt I'm too heavy for them. MXTech's site is "Page cannot be displayed" at the moment, but I'm sure I've looked at that before and the stock one's were ok for my weight.

BTW, I didn't exactly expect to overjump the double - I had hit it 4 times already and landed perfectly on the downslope. I must have hit a higher spot or a kicker or something. Of course I would never intentionally overjump a double nose down. ;)

My point in the first post is that the forks now seem DIFFERENT from months ago. Prior to the incident in question, I could count the number of times those forks bottomed harshly on one hand and probably have fingers left over.

They feel ok thru the 1st 1/2 of the stroke, but seem to be running through the bottom part of the stroke much easier than before.

We added 4 (2 one time and 2 right after testing) clicks of compression. My brother then jumped back on both times and noted that the bike seemed to "stick" a little better, but didn't seem any stiffer thru the bottom part of the stroke. The wrist won't let me do any testing for another 5 weeks.

And no, I don't know the actual compression setting at the moment because the forks felt pretty good when I got the bike. Prior to the injury, I had played with moving it 2 clicks from where it was when I bought it, but I never actually went back and counted to see where the clicker is set.

 

[robwbright]

I guess I should have titled the thread:

"Fork action has recently changed for unexplained reason and is now bottoming too easily"

LOL.

 

[dirt bike dave]

Oil height plays a big part in bottoming resistance. Perhaps you have blown a seal and lost some oil, allowing easier bottoming.

If the main difference in fork behavior from what it was earlier is easier bottoming, I would check the level of the oil, and add some if necessary. Raising oil level 1/2" can make a big difference in bottoming resistance.

 

[robwbright]

Oil height plays a big part in bottoming resistance. Perhaps you have blown a seal and lost some oil, allowing easier bottoming.

If the main difference in fork behavior from what it was earlier is easier bottoming, I would check the level of the oil, and add some if necessary. Raising oil level 1/2" can make a big difference in bottoming resistance.

Thanks Dave - I haven't found any issues with the seals, though.

It's wierd because the forks feel pretty much the same through the 1st 1/2 of the stroke, but the end of the stroke doesn't seem like it was before.

It's embarrassing, but I haven't changed the fork oil since I got the bike in May 2005. No telling how long it had been in there before that. Thus, I wondered if it might be degraded.

I'm going to have my buddy take them apart, check them out and replace the oil, I guess. The cast makes it a bit difficult to do it myself . . .

Plus, I broke my wrist on his track, so I think he'll give me a good deal. ;)

 

[Vic]

Your valve shims could be getting fatigued.