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Thread: Forks bottoming

  1. #1
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    Forks bottoming

    Is this considered a normal amount of fork travel for a Factory?



    I tried adjusting the preload from 8 clicks off rigid to 3 clicks off rigid (out of 16 total clicks), to no avail. I also maxed out the bump damping while the preload was set at 5 clicks off rigid, also to no avail. Don't get me wrong: I can feel changes in the bike's handling...it just continues to bottom out. I can't feel it bottom unless I grab a sudden handfull of brake (then it smacks the bumpstops pretty hard), but the zip tie doesn't lie. The bike has about 750 miles on it. FWIW, I couldn't bottom the forks on my 749 if my life depended on it:


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    Are the springs the correct rate for your weight?

    I'm confused by 2 pictures. Are you saying that the second picture also feels like it is hitting the bumpstops? If so, that would mean you are hydraulically locking the damping circuit and you should be able to adjust it out.
    Last edited by mohawk; 04-16-2006 at 08:45 AM.

  3. #3
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    All the Aprilia Ohlins forks come with too little oil, set the oil level to 110mm spring out for street riding or 95-105 spring out for heavy track riding/racing. compression and preload adjustment wont effect bottoming

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    Quote Originally Posted by clarkie49
    All the Aprilia Ohlins forks come with too little oil, set the oil level to 110mm spring out for street riding or 95-105 spring out for heavy track riding/racing. compression and preload adjustment wont effect bottoming

    Why do say that preload doesn't effect bottoming? I've adjusted preload to achieve the desired degree of fork travel.

    Are you talking about hydraulic lock and not bottoming the forks?

  5. #5
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    preload effects rideheight, handling and where the forks will sit in the stroke, sure if you crank the preload all the way you may reduce the amount of travel you are using but you are opening yourself up to a lot of other handling issues

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    Quote Originally Posted by mohawk
    Are the springs the correct rate for your weight?

    I'm confused by 2 pictures. Are you saying that the second picture also feels like it is hitting the bumpstops? If so, that would mean you are hydraulically locking the damping circuit and you should be able to adjust it out.

    pic #1 - Aprilia
    pic #2 - Ducati


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    Quote Originally Posted by clarkie49
    preload effects rideheight, handling and where the forks will sit in the stroke, sure if you crank the preload all the way you may reduce the amount of travel you are using but you are opening yourself up to a lot of other handling issues
    Okay, now I'm with you.

    I agree cranking down on the preload is no substitute for the correct spring rate.

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    Thank you all. Mohawk, as Clarkie49 pointed out, the second pic is of my Ducati. Regarding the bump and preload not affecting bottoming, I can confirm that. I knew that in theory, preload wouldn't be the answer because it doesn't change the spring rate. I also knew that in theory bump damping wouldn't affect bottoming because it only affects the rate at which the springs compress, not how far they compress.

    But I wanted to see for myself. I also thought that under the snenario which I grab a fistful of front brake for maybe half a second, more bump damping would slow the compresion enough to not allow it to bottom within that half second. But it didn't slow things down at all. Even with the little screw turned to full bump. It was almost as if I was adjusting only the low-speed bump and not the high-speed bump. Hmmmm, what is the blue nut in front of the fork? It doesn't seem to turn and it's not really mentioned in the manual, but it sure looks like it does something:



    That isn't, by chance, the hi-speed bump adjuster is it?

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    if you undo the blue nut you will see the compression piston and valving, with no load on the forks (ie. front stand under the tripple) you can remove the compression assembly without losing any fluid, this way you can revalve on the fly.

    the adjuster and any set of forks (except the new R6) only effects low speed bump, to change the high speed you will need to revalve the shim stack with a couple of smaller shims. if you want to reduce fork dive under braking play with the mid valve or just add another wave washer to the rebound circuit.

    The only OEM fork that comes with high speed compression is th enew R6 and that adjuster just preloads the shim stack so it isnt really a ture high speed adjuster

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    Quote Originally Posted by clarkie49
    if you undo the blue nut you will see the compression piston and valving, with no load on the forks (ie. front stand under the tripple) you can remove the compression assembly without losing any fluid, this way you can revalve on the fly.

    the adjuster and any set of forks (except the new R6) only effects low speed bump, to change the high speed you will need to revalve the shim stack with a couple of smaller shims. if you want to reduce fork dive under braking play with the mid valve or just add another wave washer to the rebound circuit.

    The only OEM fork that comes with high speed compression is th enew R6 and that adjuster just preloads the shim stack so it isnt really a ture high speed adjuster
    Damn...guess I should go buy an R6 (kidding)! My failed attempts at masking the issue with damper and preload settings would have just been band-aids anyway. Looks like I need either a) more/thicker oil or b) heavier springs.

    Seems odd that the springs in the fork would be inadequite for a 180lb (w/o gear) rider...I'm not that abnormally heavy. Maybe the oil level is just too low, as you said. I wonder if that would be considered "warranty work" or "suspension tuning"

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    the fork springs are 1.0's which are fine for a 180lbs rider (actually a little heavy), but the issue is that the forks oil is usually around 130-145mm spring out and that is why you are bottoming. add some oil, or better yet get James Sidal @ Scuderia to revalve the forks with the good stuff

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    Quote Originally Posted by clarkie49
    the fork springs are 1.0's which are fine for a 180lbs rider (actually a little heavy), but the issue is that the forks oil is usually around 130-145mm spring out and that is why you are bottoming. add some oil, or better yet get James Sidal @ Scuderia to revalve the forks with the good stuff

    I would have expected the Ohlin's to be good stuff.

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    Oh it is good stuff, but if you wanted to go to the next level James could install the same components as the Factory Graves/Yamaha Susperstock bikes have in them, James just happens to be the suspension guy for them and Scuderia is a fully certified Ohlins centre

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    Quote Originally Posted by clarkie49
    Oh it is good stuff, but if you wanted to go to the next level James could install the same components as the Factory Graves/Yamaha Susperstock bikes have in them, James just happens to be the suspension guy for them and Scuderia is a fully certified Ohlins centre
    Hmmm...that's where I bought the bike and the salesman told me something about his suspension guru when I picked up the bike. Guess I'll be talking to those guys again soon! Thanks, Clarkie.

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    Quote Originally Posted by clarkie49 View Post
    the fork springs are 1.0's which are fine for a 180lbs rider (actually a little heavy), but the issue is that the forks oil is usually around 130-145mm spring out and that is why you are bottoming. add some oil, or better yet get James Sidal @ Scuderia to revalve the forks with the good stuff
    Hi Aaron , sorry to bring up this old thread , are you measuring from the top of the outer or inner tube ?
    SPEED IS RELATIVE OFFICER

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