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fork full compression, need measurement...

Old 08-09-2011, 07:32 PM
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fork full compression, need measurement...

As stated, I would like for someone to put a ziptie around one of their forks, and go for a ride, rough roads or maybe full on the brakes. Then measure from the ziptie to the bottom of the lower triple. Working on clearance issues. When I compress my forks with a strap as far as I can, I get 1.9 " from top of the dust seal to the bottom triple, I would really like to hear what others are getting. I have .8 kg/mm RT springs and full preload.
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Old 08-09-2011, 08:28 PM
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you do realize everyone is going to have a different answer right?
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Old 08-10-2011, 01:09 AM
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Originally Posted by jay956 View Post
you do realize everyone is going to have a different answer right?
Not only different, but irrelevant...

Originally Posted by superhen View Post
As stated, I would like for someone to put a ziptie around one of their forks, and go for a ride, rough roads or maybe full on the brakes. Then measure from the ziptie to the bottom of the lower triple. Working on clearance issues. When I compress my forks with a strap as far as I can, I get 1.9 " from top of the dust seal to the bottom triple, I would really like to hear what others are getting. I have .8 kg/mm RT springs and full preload.
You are better of reading up on suspension setup... With a correct setup, you will get unladen sag, laden sag and full compression to within a certain span, where most people end up "if correct"... And that's a meaningful number, for you, on that bike... Others number are a bit more complex, and you need to know more than just the measurement and spring stiffness...

BTW what's your weight? .8 Kg/mm springs calculates out to a rider weight of around 85 Kg +- a few, and that is converted to say 180-190 pounds...
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Old 08-10-2011, 05:35 AM
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Originally Posted by jay956 View Post
you do realize everyone is going to have a different answer right?
Let me know when you've got a number...Yup, I realize the numbers will be different.
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Old 08-10-2011, 05:38 AM
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Highly relevant to me...I weigh 190 lbs, thanks for asking. Yup, I know all about sag. I am trying to get a rough idea of whether or not I'm going to put my front wheel through my fan and or radiator. Very tight tolerances. So, back to my question, got any measurements for me?

Originally Posted by Tweety View Post
Not only different, but irrelevant...



You are better of reading up on suspension setup... With a correct setup, you will get unladen sag, laden sag and full compression to within a certain span, where most people end up "if correct"... And that's a meaningful number, for you, on that bike... Others number are a bit more complex, and you need to know more than just the measurement and spring stiffness...

BTW what's your weight? .8 Kg/mm springs calculates out to a rider weight of around 85 Kg +- a few, and that is converted to say 180-190 pounds...
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Old 08-10-2011, 06:24 AM
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Originally Posted by superhen View Post
Highly relevant to me...I weigh 190 lbs, thanks for asking. Yup, I know all about sag. I am trying to get a rough idea of whether or not I'm going to put my front wheel through my fan and or radiator. Very tight tolerances. So, back to my question, got any measurements for me?
You do realize I'm running an USD fork of a CBR 1000RR do you? Which is about as different from the stock fork as can be... Like I said, irrelevant...
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Old 08-10-2011, 06:34 AM
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Yes, everything you've posted in regard to my original question is indeed, very irrelevant. Thanks for contributing, Tweety.
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Old 08-10-2011, 06:38 AM
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you could drop a fork, take out the spring, and find your mechanical bottom out point. thats what i did on my track bike.
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Old 08-10-2011, 07:05 AM
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Originally Posted by superhen View Post
Yes, everything you've posted in regard to my original question is indeed, very irrelevant. Thanks for contributing, Tweety.
I do indeed detect a note of sarcasm there... O lordy...

One, any and all numbers you get, from anyone will be rather irrelevant, since they tell you almost nothing about your particular sag... Mine more than others, since I have a different fork...

Two, the sag and the rideable compression isn't a very reliable point to use when you set your radiator up for clearance... Even if you are never, ever going to compress the fork more than that in normal riding, the day you hit a pothole and bounce the tire of the radiator it's going to either hurt or cost money, or both... Much better idea to follow jay's suggestion of finding the mechanical bottom point and using that as a reference... If the tire/fender barely scrape at that point, it's safe, and at worst you end up with a scratched fender...

Hence, why I said in my initial post, the numbers where irrelevant, and in my way of thinking, your entire question was irrelevant... But you make the deciscions on how you build...
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Old 08-10-2011, 07:51 AM
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Put a floor jack under the oil pan. Jack up the bike so the forks are fully extended. Unthread both the fork caps. Lower the bike until the forks bottom out. Take measurements. Jack the bike back up to the starting point. Rethread fork caps and tighten. This is the ONLY way you'll know your minimum clearance, and still, I'd add a cm or so for fork deflection under hard braking. They do bend under braking you know.
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Old 08-10-2011, 08:01 AM
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+1 to Jay956
If you're concerned about clearance between the top of the front fender and the bottom of the triple clamp or between the fork guards and the triple clamp, support the front of the bike, remove the fork springs and compress the forks with the fender mounted. It can be a bit messy and you will have to top up the suspension fluid before you reinstall the springs. You'll be able to measure clearance to your heart's content. Write the numbers down so you don't have to do it again. If you have the time and inclination, you could drain the forks and completely replace the suspension fluid.
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Old 08-10-2011, 09:49 AM
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I guess I should have my head examined, what was I thinking asking such an irrelevant question in the first place? Maybe the forum could have a filter where all posts would pass through Tweety first and if he deems them relevant then they could be posted? Usually if I don't have anything to add, I just move on.

OK, back to my original question, I thought there might be a chance that of the 703 forum members, there might be a handful of them that would have a very similiar setup to mine (spring rate, preload, weight of rider being the most important here), and I might get a quick idea of where I'm at. To me, that would be Relevant. Thanks to the other guys for the information. I was trying to not mess with the forks, i've removed and installed stuff so many times during this build! But my best bet would be to pull the springs out. Allright, back to the garage for me!
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Old 08-10-2011, 01:07 PM
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Originally Posted by Hawkrider View Post
Put a floor jack under the oil pan. Jack up the bike so the forks are fully extended. Unthread both the fork caps. Lower the bike until the forks bottom out. Take measurements. Jack the bike back up to the starting point. Rethread fork caps and tighten. This is the ONLY way you'll know your minimum clearance, and still, I'd add a cm or so for fork deflection under hard braking. They do bend under braking you know.
Right on, that's what I did. It was an interesting exercise too, I never thought that the forks would compress quite that much. Thanks to Comedo, Jay5xx and Hawkrider. My setup with front radiator is going to work (it's already in place). Hopefully tonight I can ride it!
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