Effect of rear sag on front fork angle

[jaguar]

I've replaced the front fork springs for stronger ones (but not the rear) and was notating the free and race sag front and rear. Race sag (sag with rider weight) for the front is 43mm and rear is 85mm. (25.6mm=1"). Quite unbalanced but then I thought it may be to my advantage on the MX course since of course lowering the rear adds more fork angle. I think most MX bikes are around 30 degrees but my KDX is listed at 27 degrees (probably for tight turning in the woods). So with some rough calculations I figured that for every extra 1 inch rear sag there is 1.66 degrees more fork angle. Since my rear race sag is 1.6 inches more than the front then that means there's 2.65 degrees more making the total 29.65 which is closer to what most MX bikes have. If I'm wrong about 30 degrees for MX bikes then please let me know. I went looking thru my magazines for specs but couldn't find the fork angle on any tested bike.
UPDATE: I found a web site with some specs for 2003 bikes. Here's their fork angles: KX125 27.5 KX250 27 CR125 29.5 CR250 26.7 KTM (all) 27.
So only the Honda 125 has near 30 degrees. years back when the mags used to show all the specs I remember most of them being close to 30.
I'll probably try it as is on the MX track and then reduce the rear race sag and try it again. The theory is that more angle gives more straight line stability (going fast) and less tight turning capability.

 

[skipro3]

Is that race sag measurement from fully extended suspension? In other words, on a stand, no load on the suspension is the zero point. Standing on the pegs, no stand, wheels on the ground, in race position with the front brake on (without the front brake, the bike just rolls the front wheel while the rear suspension compresses) is the race sag? And just what are you measureing from? Is it the length of the rear shock from mount to mount? Or some other point on the motorcycle to the ground? At what angle?
Sorry if I don't make myself clear. I've been confused about how exactly to measure and what points I am to measure. Thanks!

 

[jaguar]

measuring race sag:
pull up on the fender and measure from axle to a point on the fender above the axle. this is measurement X
Sit on the bike with little weight on your feet where they touch the ground and have someone measure from the rear axle to the same fender point. this is meaasurement Y
race sag = X - Y

generally speaking, most bikes should be close to 1" free sag (no rider) and 4" race sag

 

[skipro3]

Thanks jaguar for the clairification on sag. How about the front end? Is there a free sag and race sag for that as well and how is it measured?

 

[jaguar]

Front and rear have the same specs and are measured the same way.
There is an exception for the rear. If there is any slop in the linkages then you'll need to measure the distance of free wheel travel up/down and subtract that from your free and race sag. I had probably 10-15mm lose movement before I fixed up the linkages with bearings and sleeves.