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post #1 of 21 Old 09-15-2010, 03:32 AM Thread Starter
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Need your help with this measurement

Could anyone with stock forks measure this dimension for me please (from the bottom of the lower triple to the axle center)? It has to be taken when forks are completely extended (front end is free in the air).
I can't find my old notes and stock forks are long gone.

thanks in advance

p.s. The more precise the measurement is, the better



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post #2 of 21 Old 09-15-2010, 05:50 AM
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If it gets PM'd to you, post it here and I'll add it to the helpful topics. I'll measure mine shortly and post, but will wait for other measurements to verify.

Also take into account that some have raised their forks 10mm so that will affect the measurement.

EDIT: I just measured and with stock fork height on my 2003 919, it was approximately 18-13/16 inches from the bottom of the clamp to the center of the axle bolt.

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post #3 of 21 Old 09-15-2010, 01:02 PM Thread Starter
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Quote:
Originally Posted by cmurphy84 View Post
If it gets PM'd to you, post it here and I'll add it to the helpful topics. I'll measure mine shortly and post, but will wait for other measurements to verify.

Also take into account that some have raised their forks 10mm so that will affect the measurement.

EDIT: I just measured and with stock fork height on my 2003 919, it was approximately 18-13/16 inches from the bottom of the clamp to the center of the axle bolt.
thank you. So far you are the only one who replied. Just to verify, this was taken with front in the air, right? I'm glad you have '03 with no adjustable forks, no preload setting to alter the measurements Although 919 or f4i forks have such a stiff/short top-out spring and soft fork spring, preload wouldn't affect fork growth to make a significant difference in measurements.

I wonder what is the free sag than, when bike is sitting under its own weight on '03 non-adjustable forks? Basically if you measure the same distance when bike is on the ground (straight, not on the side stand) and subtract it from 18-13/16", it should give you free sag number

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post #4 of 21 Old 09-15-2010, 01:43 PM
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That was not with the front off the ground. My previous measurement was on the side stand.

Sorry about that.

I just went out there and leaned the bike onto the side stand with the front off the ground. 19-7/8

That would put my static sag at 1-1/16th on the side stand. Pick it up and it may be more.

EDIT: With the bike standing straight up, I held the front brake and 'bounced' it a bit. Holding it up straight, I measured 18-9/16. So 1-5/16 static sag???

Clarification:
18-9/16 - Bike up-right
18-13/16 - Bike on side stand
19-7/8 - Front off the ground

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post #5 of 21 Old 09-15-2010, 01:54 PM Thread Starter
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Quote:
Originally Posted by cmurphy84 View Post
That was not with the front off the ground. My previous measurement was on the side stand.

Sorry about that.

I just went out there and leaned the bike onto the side stand with the front off the ground. 19-7/8

That would put my static sag at 1-1/16th on the side stand. Pick it up and it may be more.
unfortunately one can't measure the sag with the bike on the side stand. It has to be sitting upright.

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post #6 of 21 Old 09-15-2010, 02:06 PM Thread Starter
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very good. So '03 non-adjustable forks give you about 33.4mm of free sag.
Almost close: ideal is 20-30mm.

The reason I asked the first question as I'm going to be removing my rc51 forks for the rebuilt and I can't find my records of the original setup.

It's good to have this info as not to change the original geometry too much.
thanks man

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post #7 of 21 Old 09-15-2010, 02:33 PM
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The problem with what you are asking is that lots of us move the forks up/down in the triple clamps to tune our ride height and handling characteristics. Mine are moved up 5 to 7mm for example. Your requested measurement (from the bottom of the lower triple to the axle center), is subjective at best. I have a set of unloaded forks hanging on the wall if you want overall measurements? then you could simply subtract the difference from your particular placement. They are 2003 non-adjustable forks BTW. Let me know.

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post #8 of 21 Old 09-15-2010, 03:27 PM Thread Starter
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Quote:
Originally Posted by MotoCycho View Post
The problem with what you are asking is that lots of us move the forks up/down in the triple clamps to tune our ride height and handling characteristics. Mine are moved up 5 to 7mm for example. Your requested measurement (from the bottom of the lower triple to the axle center), is subjective at best. I have a set of unloaded forks hanging on the wall if you want overall measurements? then you could simply subtract the difference from your particular placement. They are 2003 non-adjustable forks BTW. Let me know.
I see what you are saying. But I don't see how moving forks up can throw of the measurement. If you tell me you are at let's say 457mm with forks raised 10mm, 457+10=467 is the number I'm looking for.

If you have forks off the bike, that would actually help too.
I would just need the measurement for the triple: top of the top to the bottom of the lower. I don't have my stock lower triple anymore


I appreciate all your help guys.

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post #9 of 21 Old 09-15-2010, 04:36 PM
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Quote:
Originally Posted by zaq123 View Post
I see what you are saying. But I don't see how moving forks up can throw of the measurement. If you tell me you are at let's say 457mm with forks raised 10mm, 457+10=467 is the number I'm looking for.

If you have forks off the bike, that would actually help too.
I would just need the measurement for the triple: top of the top to the bottom of the lower. I don't have my stock lower triple anymore


I appreciate all your help guys.
Dude.. I have read and reread your question several times and I got no idea what you are asking for. Just sayin!

The measurement from the bottom of the lower triple clamp to the the center of the axle hole on an unloaded front end would change if the the forks are moved to preference in the triple clamps.

I have a set of forks which are not on a bike. I can't measure where they sit in triple clamps because they are not in triple clamps. The distance from any point of an upper triple to the lower triple would be constant on a stock setup with no play or wear.

Please clarify what you need.


Thanks,

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post #10 of 21 Old 09-15-2010, 07:40 PM
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top of top tree to bottom of lower tree is 250mm

'04 Honda 919, Candy apple red met., 17/44t sprockets,f-16 windscreen,delkevic ss exhaust,Tharbars,givi engine bars, billet alum. led turns w/ running lights,red adj.levers from china, bar end mirrors,grip heaters,adj. foot peg brackets,adj. bar risers,dunlop Q2(that are better than your pp 2ct,lol)bike wired for gps and phone charger
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post #11 of 21 Old 09-15-2010, 08:19 PM Thread Starter
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Quote:
Originally Posted by drewvir View Post
top of top tree to bottom of lower tree is 250mm
excellent. Now if MotoCycho gives us the dimension of the fork he got off the bike (from the cap to axle hole), we can subtract 250mm from that measurement.

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post #12 of 21 Old 09-15-2010, 11:21 PM
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Quote:
Originally Posted by zaq123 View Post
excellent. Now if MotoCycho gives us the dimension of the fork he got off the bike (from the cap to axle hole), we can subtract 250mm from that measurement.
That I can do.

2003 OEM 919 forks, unloaded, topped out (fully extended), cap screwed in all the way, on work bench measure 29 13/16" from top of the cap to center of axle hole. Measured both forks and got same number, of course.

29 13/16 = 29.8125
29.8125 inches = 757.2375 millimeters

Note: I used a tape measure and eye balled the middle of the axle hole.. not what I would consider the most accurate measuring device and method, but I think close enough for this.
Account for error in my method or equipment I'd say 756mm to 758mm. If you need absolute accuracy I will have to get more creative.. but I can oblige. Just let me know.

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post #13 of 21 Old 09-16-2010, 03:49 AM Thread Starter
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that will do it. Thank you sir.


Quote:
Originally Posted by MotoCycho View Post
That I can do.

2003 OEM 919 forks, unloaded, topped out (fully extended), cap screwed in all the way, on work bench measure 29 13/16" from top of the cap to center of axle hole. Measured both forks and got same number, of course.

29 13/16 = 29.8125
29.8125 inches = 757.2375 millimeters

Note: I used a tape measure and eye balled the middle of the axle hole.. not what I would consider the most accurate measuring device and method, but I think close enough for this.
Account for error in my method or equipment I'd say 756mm to 758mm. If you need absolute accuracy I will have to get more creative.. but I can oblige. Just let me know.

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post #14 of 21 Old 09-16-2010, 10:00 AM
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2006

505mm

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post #15 of 21 Old 09-16-2010, 10:38 AM
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Quote:
Originally Posted by BB919 View Post
2006

505mm
That is the same as mine 19.875 in = 504.825 mm

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post #16 of 21 Old 09-16-2010, 11:41 AM
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Quote:
Originally Posted by zaq123 View Post
Could anyone with stock forks measure this dimension for me please (from the bottom of the lower triple to the axle center)? It has to be taken when forks are completely extended (front end is free in the air).
I can't find my old notes and stock forks are long gone.

thanks in advance

p.s. The more precise the measurement is, the better



Attachment 15090
zaq123,

Up on my lower triple supported front stand, the precise measurement is 19 - 29/32nds inch.
This with only the leading taper at the top of the fork tubes protruding past the top surface of the upper triple clamp.
The distance from the top of the blue aluminum fork cap outer flange area to the top surface of the triple clamp is 5.25 mm.
Is that accurate enough ?
My long vernier is too short so I had to resort to a steel tape measure.
If you need any other measurements, I'd be pleased to do them for you.

Regards,

McTavish McRomo

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post #17 of 21 Old 09-16-2010, 11:49 AM Thread Starter
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Thanks everyone.
I think I got enough info to get me in the ballpark.
I'm waiting for my rc51 fork parts to start tearing them up, hopefully before the trip next week.
I'll be changing those 150mm top out springs with 55mm ones and that will make my forks grow a little bit.
Still don't know or can find somebody to explain me why RC51 sp2 engineers design that bike to have negative 5 preload.

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post #18 of 21 Old 09-16-2010, 12:11 PM
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Quote:
Originally Posted by MotoCycho View Post
The problem with what you are asking is that lots of us move the forks up/down in the triple clamps to tune our ride height and handling characteristics. Mine are moved up 5 to 7mm for example. Your requested measurement (from the bottom of the lower triple to the axle center), is subjective at best. I have a set of unloaded forks hanging on the wall if you want overall measurements? then you could simply subtract the difference from your particular placement. They are 2003 non-adjustable forks BTW. Let me know.
Care and caution on the raising of fork tubes, in the sense of what one is after vs what someone may want to retain.
Guideline rule is for every 4 mm or rise, you lose a nominal 1 mm trail. True, that is based on typical supersport front end steering head angles, but my guess is that the trigonometry will vary that much from those angles to that of a 919's 25 degrees. The 919 has 98 mm trail. A 7 mm fork tube raise likely takes that down to around near 96 mm, and who knows what it is if one also has ride height adjusters that on a later model. One could easily be down to less than 95 degrees, which is said to be a bit of cut line for front end "feel". I'd rather have to muscle mine more than sacrifice front end feel, although that is only a valid statement for Track Day riding and not really relevant for the street.

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post #19 of 21 Old 09-16-2010, 02:42 PM
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Quote:
Originally Posted by mcromo44 View Post
Care and caution on the raising of fork tubes, in the sense of what one is after vs what someone may want to retain.
Guideline rule is for every 4 mm or rise, you lose a nominal 1 mm trail. True, that is based on typical supersport front end steering head angles, but my guess is that the trigonometry will vary that much from those angles to that of a 919's 25 degrees. The 919 has 98 mm trail. A 7 mm fork tube raise likely takes that down to around near 96 mm, and who knows what it is if one also has ride height adjusters that on a later model. One could easily be down to less than 95 degrees, which is said to be a bit of cut line for front end "feel". I'd rather have to muscle mine more than sacrifice front end feel, although that is only a valid statement for Track Day riding and not really relevant for the street.
The 919 has pretty forgiving rake. I think mine are only 3 or 4mm up in the clamps.. but have been like this for several years now and I get no wobbles or other adverse handling. That said, I know some here will raise them as far as 10mm in the clamps. My comment was merely to point out the subjectivity of the measuring points not advocate a particular adjustment.

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post #20 of 21 Old 09-16-2010, 02:55 PM Thread Starter
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Quote:
Originally Posted by MotoCycho View Post
The 919 has pretty forgiving rake. I think mine are only 3 or 4mm up in the clamps.. but have been like this for several years now and I get no wobbles or other adverse handling. That said, I know some here will raise them as far as 10mm in the clamps. My comment was merely to point out the subjectivity of the measuring points not advocate a particular adjustment.
I had mine f4i forks raised 8mm. I wouldn't go more than 10mm.

As far as subjectivity of the measurement goes, I still can see how it can be an issue if one can inform that his forks are raised X mm and give the requested Y dimension from the triple. It's not the rocket science to perform X+Y.
The reason I asked for the measurement from the lower triple is that my new lower triple has about the same distance from the steering neck as OEM setup. Top triple is way different size etc and can't be used to compare to OEM setup. When one gives me the requested dimension, I can easily transfer it to my bike without any additional calcs. I hope this make any sense

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post #21 of 21 Old 09-24-2010, 05:24 AM Thread Starter
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thanks everyone for your input. I had to mod my rc51 forks. Part of it was replacing 120mm top-out spring with something shorter in order to set proper sag. As a result, stock rc51 sp2 forks grew in their length. Thanks to your numbers, I was able to figure out proper length as not to change 919 geometry too much.

Just for the future references, here is a pic of SP1 (left) SP2 (center) and VFR (right, length the same as 919/f4i)

As you can see, due to the extremely long top-out spring, SP2 fork is shorter.




and here is why, left - new SP2 spring, center-SP2 original spring, right - SP1 spring


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