Fork "sag", how much?

Roughly, how much does a standard fork compress from fully extended to the stop, to standing unloaded and no driver on it? Within half an inch....or so.... Measured from for example the underside of the lower yoke to the top of the dust cover?

With straight rate springs, laden sag should be about 20% of the travel -with short travel suspension like a Norton.
Unladen the sag should be very little. Maybe 1/4" ?

Apologies if you already know this, but the easiest DIY method for this is to measure the sag with cable ties.

Put the bike on the centre stand so the forks are full extended. Put a cable tie around the stanchion touching the dust seal.

Ease the bike off the stand, let it stand, ease it back on the stand. The amount the cable tie is sitting above the seal is your unloaded sag.

Do the same again, and this time sit on the bike before easing it back onto the centre stand, now you have the laden sag.

Same can be done on the rear shocks using the rubber buffers, or cable ties if you don’t have the buffers.

Fast Eddie said:

Apologies if you already know this, but the easiest DIY method for this is to measure the sag with cable ties.

Put the bike on the centre stand so the forks are full extended. Put a cable tie around the stanchion touching the dust seal.

Ease the bike off the stand, let it stand, ease it back on the stand. The amount the cable tie is sitting above the seal is your unloaded sag.

Do the same again, and this time sit on the bike before easing it back onto the centre stand, now you have the laden sag.

Same can be done on the rear shocks using the rubber buffers, or cable ties if you don’t have the buffers.

Click to expand...

and pull the forks out to full extension, in case there is a some stiction.

And take the measurements with the engine running. The vibration helps get a good measurement even with stiction.

Thanks everybody, but the reason why I´d like a number is that I don´t have the bike together, only have the frame in a jig. It´s not a standard bike, I´m about to order stanchions and need some hard numbers to calculate their length. I have the size of the wheel, have the lower fork tubes but would like to know how much, in inches, the fork sags from fully extended, at least roughly as I wrote. Can´t do what Jim proposes either, since the cases are empty and just sits in the frame for measuring purposes.....The 1/4" that Jim says seems very little, but with the bike unloaded maybe that´s how it is, it will of course compress a bit more when you sit on it....

Sag is best measured with the rider on the bike.
Weight on the front forks depends on rider weight, but also how you sit on the bike.
An upright sit will require more static sag than a more forward sit, like with clip ons.
Unloaded, around 25 -30 mm = more than 1 inch.
With rider: 35- 45 mm.
IMO, 1/4" ( 6 mm) without rider seems too low.
With an upright position and a little headwind, the forks might be fully extended at anything over 50 mph.
Rear shocks unloaded: zero static sag (or maybe 2 mm max ..)