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springs swap and sag settings how to calculate.. numbers are not working!

measuring method
ok. so.. I used a zip tie (loosly tied) around the fork leg and measured from the tripple tree to the zip tie.
1. lift wheel off ground measure extended length.
2. remove top caps (come along from roof) lower front end till bottomed out. measure measure again.
The difference between 1 and 2 = total travel I got 101.51mm (manual says 109mm) but I didn't get that.. now if I use the 109mm math works if I use 101.50 math dosn't..

on to next part.
set preload, stand bike up and measure (same as above), sit on bike, measure.. bounce bike, measure. average sit and bounce the difference is the resultant sag.. My numbers are in the table below

So the problem is the only way these numbers make sense is if I use the 109mm travel the manual says. If I use my measurments I have a sag of around 16% preload full out..

Note.. when I looked on the sonic site it says I should be running 1.0 springs.. I have 1.0 but my current springs are .90, and seem to be too aggressive as is..

Other info.
Weight geared ~175lbs
riding style.. I like a stiff fork.. less dive.. I get to the track a couple times a year.. more of a weekend worrier.. not a day to day commuter..

suggestions please!

thanks

Note: as you can see the first couple of turns do nothing.. my spacers may be a little short.. but if the end number is right then it really dosn't matter as I don't want to ride set at 7

Wolverine

Check out this link. As per our fearless leader:

I recommend setting the sag to about 1/4 of the total travel of the fork. Stock VTR forks have 120mm of travel, so setting sag at 30mm is about right. Thus, you will have 90mm of fork travel in the direction of compression. For the rear, I like about 25mm sag.

To do this, first measure between the dust seal and the bottom of the lower triple clamp while the forks are fully extended. The best way to do this is to tilt the bike on it's sidestand until the front wheel comes off the ground. Have someone else measure for you. This is measurement A.

Next, get on the bike fully geared up and get into your normal or aggressive riding position, for street or track respectively. A second person needs to hold the bike balanced at the back end. A third person compresses the forks slightly, slowly release the compression, and takes a measurement. This is measurement B.

Do the same thing except slightly extend the forks, slowly let the bike settle, and take a measurement. This is measurement C.

The reason for extending and compressing the forks is to take into account the stiction in the seals and bushings.

Now calculate: Sag = A - [(B + C) / 2]

Adjust preload as necessary. More preload for less sag, and vice versa.


How long are your spacers? Mine were 68mm and I had no trouble getting sag set where Greg recommended.

JamieDaugherty

For your weight at 165lb without gear (assuming) you should have no more than 0.85kg/mm springs. 1.0's are WAY too high. 0.90's are high but could be ok depending on how you ride.

Your spacers should be 65mm long which will net you 15-16mm of preload. If you get the correct sag with that physical setup your spring rate is correct.