Pre Load Spacer help

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gtoron
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Pre Load Spacer help

Post by gtoron »

Since I seem to be slightly retarded in how to figure this out can someone tell me what size spacer to use to get a preload of 5mm?
I am using a XR spring which are 540mm long. 5mm seems to be what most people are going with so I will follow along also.

I will assume I should include the bushings that went under the stock metal spacer? I also will use the clips from the stock springs.
Thanks in advance for the help....for some reason I am just not grasping this measuring for a spacer
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Post by bezoar »

If you were to reassemble your fork with the new spring and without the stock spacer, there would be a gap from the top of the spring to the bottom of the fork cap. Lets assume that space is 20mm. If you were to cut a piece of schedule 40 1 inch pvc to fit that gap, you would then have a spacer with NO preload. If you made a pvc spacer that was 25mm, you would then have 5mm of preload. Your preload is the number of mm that your spacer is larger than the gap between the top of the spring ( and washer thingy) and the bottom of the fork cap,

Everything goes back in the same way, including the clip at the bottom of the stock spring which will go on your new xr spring. The only difference will be your new smaller spacer will replace your old spacer.
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Post by gtoron »

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bezoar wrote:If you were to reassemble your fork with the new spring and without the stock spacer, there would be a gap from the top of the spring to the bottom of the fork cap. Lets assume that space is 20mm. If you were to cut a piece of schedule 40 1 inch pvc to fit that gap, you would then have a spacer with NO preload. If you made a pvc spacer that was 25mm, you would then have 5mm of preload. Your preload is the number of mm that your spacer is larger than the gap between the top of the spring ( and washer thingy) and the bottom of the fork cap,

Everything goes back in the same way, including the clip at the bottom of the stock spring which will go on your new xr spring. The only difference will be your new smaller spacer will replace your old spacer.
OK got that part, so am I to assume that I need to measure from the top of the spring to the bottom of the threads in the upper fork leg to determine what size to use? Since once the cap is screwed on there is no way to measure.
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Post by Indawoods »

Correct... then add 5 mm.
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Post by bezoar »

You screw the fork cap onto the fork rod. You will not need the spring holder this time because there is not spring tension without the spacer. Your are not at the point yet where you screw the fork cap into the fork tube.

So you will assemble everything - spring, spring clips, the metal washer/clips that were on either side of the spacer. Without any spacer you will screw the fork cap into the thin rod finger tight. There will be a gap between the top of the spring (and metal spacer/clip things ) and the bottom of the fork cap. The rod/cap can be pulled up above the fork tube several inches to allow you to measure this. Measure this gap, add 5mm and this will be the size that your spacer needs to be to give you 5mm of preload.

One other thing. When you attach the fork cap to the fork tube - turn the fork tube, not the cap. this will prevent the spring from turning and binding.
Last edited by bezoar on 10:18 am Jun 04 2009, edited 3 times in total.
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Post by gtoron »

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Indawoods wrote:Correct... then add 5 mm.

Thanks....Now I understand, at least I am not as stupid as I thought :grin:
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Post by bezoar »

Maybe I got this all wrong, but I do not believe that you measure from the spring to the threads in the fork tube. See my above post.
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Post by gtoron »

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bezoar wrote:Maybe I got this all wrong, but I do not believe that you measure from the spring to the threads in the fork tube. See my above post.

OK we need clarification on this.
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Post by bezoar »

Do you have the forks apart yet? It was much more easy for me to understand once I had them apart. I just did this several weeks ago and I had a hard time visualizing it before I had them apart. Once I saw everything it was very easy.
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Post by gtoron »

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bezoar wrote:Do you have the forks apart yet? It was much more easy for me to understand once I had them apart. I just did this several weeks ago and I had a hard time visualizing it before I had them apart. Once I saw everything it was very easy.
They are all apart ready to be reassembled, just getting two different answers
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Post by canyncarvr »

You are not getting two different answers.

Re: 'I need to measure from the top of the spring to the bottom of the threads in the upper fork leg to determine what size to use?

What we've got here is FAILURE to communicate........

'The upper fork leg' would generally be assumed to be the upper round tube part of the fork...what the cap threads INTO.

If that IS what you meant, that is NOT correct.

You MIGHT be referring to the threads on the cartridge ROD, in which case, you are pretty close.

Re: ' Since once the cap is screwed on there is no way to measure.'

And there's the crux of the communication failure.

That is incorrect. I assume you are referring to screwing the cap INto the upper fork tube. In that case, you could indeed not measure anything inside the tube.

But...that is not what's threaded. You install the spring, thread the cap ONto the ROD, not INto the fork tube. Be sure to thread the cap all the way down onto the rod..as far as it will go.

Be sure to NOT thread the cap ONLY 'to' the jam nut on the rod. The jam nut must be all the way DOWN on the rod threads to not interfere with the caps movement.

You could just take the jam nut off the rod. No reason to..just an option. Taking it all the way off will make the assembly harder to handle because the nut is generally used to HOLD the rod up (using something like a wrench, or your own 'special' notched tool).

THEN you measure the 'space' (distance) between the top of the spring (rod fully extended) and the cap. SUBTRACT the thickness the seats will take up, cut your spacer to THAT measurement +5mm.

You will likely have some trouble figuring the preload with the XR springs. They are considerably longer than the OEM springs. With an understanding of what you're after...filling up the 'space' measured plus your preload choice, you'll get it.

Good luck.

How about this: 'Preload' is the amount the spring is compressed when installed with NO weight on the fork. If you're working with a spring that has a 540mm free length, with a 5mm preload that spring will be 535mm long when installed. It will be 'squeezed' 5mm before it's ever compressed when riding.
Last edited by canyncarvr on 12:29 pm Jun 04 2009, edited 4 times in total.

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Post by gtoron »

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canyncarvr wrote:You are not getting two different answers.

Re: 'I need to measure from the top of the spring to the bottom of the threads in the upper fork leg to determine what size to use?

What we've got here is FAILURE to communicate........

'The upper fork leg' would generally be assumed to be the upper round tube part of the fork...what the cap threads INTO.

If that IS what you meant, that is NOT correct.

You MIGHT be referring to the threads on the cartridge ROD, in which case, you are pretty close.

Re: ' Since once the cap is screwed on there is no way to measure.'

And there's the crux to the communication failure.

That is incorrect. I assume you are referring to screwing the cap INto the upper fork tube. In that case, you could indeed not measure anything inside the tube.

But...that is not what's threaded. You install the spring, thread the cap ONto the ROD, not INto the fork tube. Be sure to thread the cap all the way down onto the rod..as far as it will go.

Be sure to NOT thread the cap ONLY 'to' the jam nut on the rod. The jam nut must be all the way DOWN on the rod threads to not interfere with the caps movement.

You could just take the jam nut off the rod. No reason to..just an option. Taking it all the way off will make the assembly harder to handle because the nut us generally used to HOLD the rod up (using something like a wrench, or your own 'special' notched tool).

THEN you measure the 'space' (distance) between the top of the spring (rod fully extended) and the cap. SUBTRACT the thickness the seats will take up, cut your spacer to THAT measurement +5mm.

You will likely have some trouble figuring the preload with the XR springs. They are considerably longer than the OEM springs. With an understanding of what you're after...filling up the 'space' measured plus your preload choice, you'll get it.

Good luck.
OK now I got it :grin:
The XR springs measure out at 540mm so they are a good amount longer.

Thanks
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Post by canyncarvr »

Check the last paragraph in my post. I edited it about the same time you posted. It might help you envision the 'preload' idea.

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Post by gtoron »

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canyncarvr wrote:Check the last paragraph in my post. I edited it about the same time you posted. It might help you envision the 'preload' idea.
Thanks....I just had it in my head I had to measure inside the upper fork tube some how, now I understand that you must just assemble the fork internals along with the fork cap to get this measurement.

Now I am clear on it....just could not grasp this before for some reason.
Its actually very simple, now that I understand it.
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Post by canyncarvr »

That's kind of the way things go. Pretty much everything is simple when you understand it.

Like string theory 'fer instance........... What I understand about string theory is: The longer the string, the more times you can wrap it around your finger.

:hmm:

I think there's a bit more to it than that. I'm still doing some research into the finer workings of it...................

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