Soft Forks, Bike sags under its own weight

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Soft Forks, Bike sags under its own weight

Postby motofox2006 » 12:49 am Apr 17 2007

I just put some new .35 kg fork springs in my 91 kdx, originally I had the stock springs which were slightly longer. Just pushing on them they feel no different but I haven't ridden it yet.

Before on my stock springs I had the stock preload spacer(110mm) plus an extra 30mm spacer. It didn't sag under its own weight but it did felt harsh on bumps.

At the moment I have only about 10mm preload on the new springs and the bike sags 1 or 2 inches under its own weight, I don't see how it can possibly work with that much sag, are the forks meant to have static sag like the rear. What are your suggestings in getting them too work correctly, I don't want them to feel harsh.

All help appreciated thanks guys.
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Postby Indawoods » 05:56 am Apr 17 2007

Did you cut new spacers?
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Re: Soft Forks, Bike sags under its own weight

Postby Jeb » 06:42 am Apr 17 2007

>|<>QBB<
motofox2006 wrote:I just put some new .35 kg fork springs in my 91 kdx, originally I had the stock springs which were slightly longer. Just pushing on them they feel no different but I haven't ridden it yet.

Before on my stock springs I had the stock preload spacer(110mm) plus an extra 30mm spacer. It didn't sag under its own weight but it did felt harsh on bumps.

At the moment I have only about 10mm preload on the new springs and the bike sags 1 or 2 inches under its own weight, I don't see how it can possibly work with that much sag, are the forks meant to have static sag like the rear. What are your suggestings in getting them too work correctly, I don't want them to feel harsh.

All help appreciated thanks guys.


You don't hear much about sag with forks- most folks relate sag with the rear shock - but 1 to 2 inches of sag from the bike's weight actually sounds good!!

Check "race" sag as well - wrap a piece of duct tape around the front brake line so that the top edge of the tape is even with the bottom edge of the brake line guide. Get on the bike and - with one hand holding onto a wall - work the fork action deep several times. While on the bike and with hips located above foot pegs and shoulders, slightly standing, look down (or have someone look for you) and see where the tape is. The BOTTOM edge of the tape should be between the top and bottom edge of the brake line guide, i.e. about 2.5" or so "race" sag.
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Postby KarlP » 07:28 am Apr 17 2007

I second Jeb.
I've always understood that front AND rear race sag should be in the neighborhood of 1/3 total travel, with less in the front and possibly more in the rear.
My bike (or me) is very sensitive to the sag setting. 1/4" either way in the rear makes it steer terribly.
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Postby motofox2006 » 03:18 pm Apr 17 2007

I didn't make a new preload spacer but I did use the stock plus a couple of washers which works out to about 10mm preload.

Question on front sag, before on my old springs with more preload (probably 40 to 50mm preload) I found them harder to compress. Now with these stiffer springs along with less preload they are easier to compress and if I take my bike to top of the driveway and role it down and brake on the front brake the front end almost completely compresses, this is strange because I only weigh 148Lbs, why do they feel softer, I thought the idea of stiffer springs was also to stop the nose dive on downhills. I dont know about riding the forks like they are beacuse I think when hitting my deep sandy whoops with them like that I might just take a tumble. :wink:

Ill check the front race sag but to me it feels too soft.

How come new bikes out of the shop dont have front fork sag
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Postby 2001kdx » 03:59 pm Apr 17 2007

stiffer spring + less preload = softer on smaller hits, but stiffer on large bottom-outs.

It's a good thing, no doubt!
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Postby kawagumby » 05:06 pm Apr 17 2007

Preload affects ride height which drastically affects steering and handling. If the steering was correct before, the steering now will most likely be poor with too little preload (noticeably lower when you sit on it). This is due to too much weight transferred to the front while braking or when moving forward on the bike or running in loose or sandy soil. You should set the preload to be similar to what worked before (if the ride height was previously correct) and go from there if you want to reduce it in small increments, like 1/4 inch at a time. Generally speaking, if you increase the spring rate for the same rider you CAN decrease the preload as less deflection occurrs with the higher spring rate. I used to favor a higher spring rate on my 1990 KDX 200 with little or no preload - but the riding height was the same. The stock 89 springs were about 30's no? So you should be able to go with somewhat less preload.

Kawasaki's used to have adjustable preload forks, you could turn the fork top and increase or decrease the amount of preload for different kinds of riding surfaces. I had an 84 KX250 that had that feature.

BTW, 35's are still likely to be a little on the soft side for your weight, so correct preload is critical. PVC tubing makes great preload spacers.
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Postby motofox2006 » 06:27 pm Apr 18 2007

I have got somewhat less preload but ive just changed my preload and ive ended up with 1 inch race sag hopefully this will do for where I ride
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