Shortened fork tubes

[JALAIMO146577]

In the process of replacing pitted fork tubes I ordered them 1" shorter than stock to lower the seat height along with a 1" shorter Hagon Shock.

My queston is how much to shorten the fork springs. Forking by Frank that made my tubes suggested 1/2" to be cut off the springs. I guess that will stiffen up the front end a bit over stock K75 Springs.

Any suggestions on much the springs should be shortened will be appreciated.

[deilenberger]

You may want to check if your forks have a spacer above the springs.. most K75 forks do.. and it's lots easier to make a shorter spacer (some PVC tubing) then to try to shorten the springs (the ends of the factory springs are finished so they fit into a plastic bit that squares them off..)

If so you could make several different spacers to see what effect each has. If you have the sport forks (S) on your K75 - it's a dual-spring setup with different spring rates for the two springs, so the change might not be exactly linear.

[cayuse60]

I just finished replacing the sport springs with one piece progressive units. If you are reuseing your old springs cutting the PVC preload spacer one inch will retain stock operation.

[JALAIMO146577]

Great info, I haven't opend up the tubes yet the spacer is a much better alternative

Thanks,

[98lee]

A "better" alternative is to leave the forks stock (other than upgrading the springs. For the S, I prefer Progressives).

If you shorten fork tubes or shorten the spacer you will reduce front fork travel capability.

If you install barbacks (which also gives you a more comfortable riding position) you can just slide the fork tubes up in the triple clamps.

My wife's bike (an extreme example) is slid up 1 3/4". Her suspension is a full 2" lower. Plus I did some MAJOR modifications to the seating to gain another 2". She is 5'4" and can flat foot with both feet with 1/2" heels. Her seat height is around 28".


:dance :dance :dance

[Carguz]

Lee,
Did you modify the rear when you slid up the front forks?

[cayuse60]

A "better" alternative is to leave the forks stock (other than upgrading the springs. For the S, I prefer Progressives).

If you shorten fork tubes or shorten the spacer you will reduce front fork travel capability.

If you install barbacks (which also gives you a more comfortable riding position) you can just slide the fork tubes up in the triple clamps.

My wife's bike (an extreme example) is slid up 1 3/4". Her suspension is a full 2" lower. Plus I did some MAJOR modifications to the seating to gain another 2". She is 5'4" and can flat foot with both feet with 1/2" heels. Her seat height is around 28".


:dance :dance :dance

If you shorten the tubes by one inch and shorten the spacer by one inch how has the total travel changed? If you did not shorten the spacer I would agree travel has changed and it would be a bear to get the preload set.

If you slide the tubes up more then an inch you will need bar backs to keep the tubes from hitting the handle bars.

[98lee]

Lee,
Did you modify the rear when you slid up the front forks?

On my wife's bike, I went to the extreme. Progressives "short version" 412 shock is 13 1/2" long fully extended. The stock one is 14". I went through their spec. pages and found a shock that had the same valving, slightly softer spring (my wife only weighs 110), the same compressed height (bottoms out at the same place as stock in relation to the frame), but had, if I remember correctly a 12 1/4" extended height. I then had to do a few mods to get it to fit.

The down side is that the bike can not be loaded heavily, you can only ride two up in emergencies and the bike can't generate the extreme lean angles before the pegs drag.
But it's perfect for my wife at a very brisk clip through the twisties carrying her gear for a several day trip. I have to ride the bike more conservatively.

Here she is before we got Corbin to make a special seat (to go along with the lowered and narrowed frame rails under the seat):
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You want to keep the bike level when lowering to maintain the same rake and trail. You will not be going to this extreme.


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[98lee]

Here's the new seat:
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:dance :dance :dance

[98lee]

If you shorten the tubes by one inch and shorten the spacer by one inch how has the total travel changed? If you did not shorten the spacer I would agree travel has changed and it would be a bear to get the preload set.

If you slide the tubes up more then an inch you will need bar backs to keep the tubes from hitting the handle bars.

If you just shorten the spacer only, the bottom of the fork tube ends up closer to the bottoming spring in the bottom of the slider.

If you shorten the tubes AND the spacer the same amount the travel WILL remain the same, but you have the expense of shortening the tubes and cannot raise the bike back up (for resale, giving it to your son, readjusting your preference if you guessed wrong on how much to cut off, or if you grow) the bike is now not changeable with out new forks.

On an S, many people like the farther back and higher position that barbacks or C bars provide. By going with barbacks you cut the expense of modifying the forks AND buying C bars to just buying barbacks. And you have the flexibility to can fine tune the height of the front forks to get the desired rake and trail to match your rear shock length.

There are many ways to arrive at a given destination. I prefer this one for it's cost, flexibility, and being easily reversible.

The seat modifications on my wife's bike are not easily reversible but, the 2" suspension drop is (just needs a standard rear shock bolted on and reposition the fork tubes).

Your route to the same end may vary.


:dance :dance :dance

[JALAIMO146577]

Great advice all. I have purchased the 1" shortened fork tubes originals were pitted cutting the fork seals. I balanced the lowereing with a 13" Hagon shock 1" shorter than stock.

My concern is the best way to accomdate the fork spings in the shorter tubes. I live in south Florida "Twisties" not spoken here. No touring planned just a weekend Sunday morning ride bike. I don't care about resale or bringing it back
to its stock configuration.

When I finish the restoration you'l see why.

Thanks for the input.

[98lee]

Then use standard length springs and shorten the spacer the same amount that you shortened the tubes and all will be well.

What is it with you Florida guys?:dunno No twisties, no canyons, no mountain passes? Heck, you might as well own a Harley!:stick


:dance :dance :dance

[JALAIMO146577]

Then use standard length springs and shorten the spacer the same amount that you shortened the tubes and all will be well.

What is it with you Florida guys?:dunno No twisties, no canyons, no mountain passes? Heck, you might as well own a Harley!:stick


:dance :dance :dance

Sad but true, I've been coerced in that direction, but I'm sticking to my good sense.

[98lee]

Sad but true, I've been coerced in that direction, but I'm sticking to my good sense.

I hear you guys can drive right along the ocean. You call it Daytona Beach.












So can we. We call it the Pacific Coast Highway (PCH).
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[98lee]

Sad but true, I've been coerced in that direction, but I'm sticking to my good sense.

I hear you guys have thousands of beautiful scantily clad women in thongs on your beaches.:blah











Well we,............ ah.......... umm we................................................ ........ we got the PCH.
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Both pictures taken just south of Big Sur.



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[Zagando]

Maybe no twisties in FL but K-bikes do feel at home on a fast slab...:dance