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Discussion Starter · #1 ·
Ok, I've heard about adding spacers to the fork springs, do you only do this with new progressive springs, or can you do this with the stock springs to stiffen them up a little, if you can, how big do you make them ?
 

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On the stock springs,I've seen them 1/2 " longer than the stock spacers.They used sch.40 cpvc.You replace the stock spacer with the cpvc.We did this with our dirt bike years ago and seemed to be ok.We also used a thicker oil and changed it frequently.
 

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Longer spacers will preload the springs, making them effectively stiffer. They will also reduce the overall travel, since the longer spacer takes up that room.

The spacers on the progressive springs are shorter (as I recall), and the uncompressed springs are longer than stock. The overall uncompressed length is about the same. Here are the stock spring/spacer and the progressive spring/spacer for comparison.

 

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If you really want to tune in the suspension for your needs. You can shorten your stock springs to increase the spring rate, then install longer spacers to provide the proper preload. This was posted on the old site, I don't have links but look for a coil spring calculator online. Deals with the # of coils, diameter of the coil, diameter of the wire used to form the coil. Our stock spring is somewhere around 28lbs per in. By reducing the number of coils the spring rate goes up. The calculator will help you determine where to cut. The longer spacer is required to keep the fork tube full.

The progressives are 28/40 meaning 28lbs in the initial travel, then become 40lbs when they compress. This is done by the coils compressing until they touch and effectively reduce the number of coils in the spring.

Very basic overview, hope it helps.

TW
 

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Discussion Starter · #5 ·
Ok, all really great info. Though I can't really see how cutting the stock spring would increase the rate, even adding a longer spacer, isn't the stock spring a constant rate ? I think for the effort, I'll get a set of progressive springs. How much of a difference do they really make, is it something you would notice immediately ?or something you only notice with hard riding ? I've changed stock fork springs on my old RM 250, so it's an easy swap, but that was 30 years ago, and with stock replacement springs only.
 

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Discussion Starter · #7 ·
I'll try the cpvc spacer, I've got a couple hundred feet of sched 80 in my shop.
 

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gunny said:
Ok, all really great info. Though I can't really see how cutting the stock spring would increase the rate, even adding a longer spacer, isn't the stock spring a constant rate ? I think for the effort, I'll get a set of progressive springs. How much of a difference do they really make, is it something you would notice immediately ?or something you only notice with hard riding ? I've changed stock fork springs on my old RM 250, so it's an easy swap, but that was 30 years ago, and with stock replacement springs only.
Ah, Physics...The longer a spring is, at a constant coil, the softer it is. Here's a little demonstration you can do....

Take a ball point pen spring, compress it and feel the tension, now cut it in half and feel the tension of the shorter spring.
It's about double right?

TW
 

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Discussion Starter · #9 ·
d'oh ! :D It's been a long week, I'm on pain killers until the doc can yank this tooth. I shoulda known that about the spring.
 

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Discussion Starter · #10 ·
well I did my fork springs today, changed the oil and added kynar spacers {instead of cpvc} I used 15w belray fork oil, I seem to recall the stock weight was 10 ? I know I mentioned it someplace else, but don't use cpvc if you can avoid it, cpvc doesn't like being saturated in oil, the stuff gets brittle, get some kynar, can't miss the stuff, it's red.
 

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Discussion Starter · #12 ·
well, I didn't have the chance to ride it, but it does feel a whole lot firmer than what it was, I'd say it felt like my buddies drz forks feel, kinda on the stiff side, but smooth. I'll take it for a ride Sunday if the weather holds up, yeah I'm pussin out, but my head still hurts from the surgery :sad:
 

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Discussion Starter · #14 ·
PVDF kynar, good stuff. Took the KLR out for a ride today and I must say I was impressed really, brake dive was about 50 to 70% reduced, rebound was much nicer, I did go to a 15 weight belray fork oil. I cut them 1 inch longer, rather than just a half inch. It wasn't hard to get the caps on either. I would have to say the front end feels a lot more firm and in control than before. The real test will be a ride out on the highway next weekend after I get the doo done. I just rode it out in the yard for a few laps, a couple small jumps, things like that.
 

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McMaster.com you can get various materials that are oil resistant and they will deliver same day in CA. (Cut to length stuff most of the time)
 

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Gunny:
My new progressive springs should be here by Monday. I read your threrad with great interest. One question....Where does one find "Kynar"? I don't think that I have ever heard of it before.
harley dog :lol:
 

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harley dog said:
Gunny:
My new progressive springs should be here by Monday. I read your threrad with great interest. One question....Where does one find "Kynar"? I don't think that I have ever heard of it before.
harley dog :lol:
You can read Biker Scout and my posts on this thread for some information. I had never heard of it before.
 

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larryboy said:
in sacramento i'd be willing to bet that capitol rubber carries it.
Some day after work I will stop by and see if they carry it. I checked for a webpage, no luck.
 
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