I have a stock 1995 Schwinn Letour with 700 x 25 tires. This is the biggest tire I can mount with fenders. I'd like to go bigger on tires but need to switch out front forks to something with posts to mount different brakes. I am not sure how to measure my current forks to determine the length, offset etc. This is the first time I'm attempting to understand about forks, geometry and really what not to do. I've been told by biking friends this is a very important thing not to mess up because the bike will be unsafe? So, I thought I'd ask for the collective wisdom of everyone on how to measure my forks. Wardie

Unsafe? Not so long as it fits properly. It will handle differently if the geometry different.

Basically, your head tube is the straight line you need to measure off of. Using the center line of the head tube, draw a line straight down towards the ground. Then draw a line from the center if the dropout, up through the centerline of the fork blade, to the head tube. From this you can measure the fork angle & the rake(measured from dropout to the centerline of the head tube, parallel to ground.
Also good to know is the offset of the wheel. From the head tube centerline to the ground, you measure to the center of where the tire hits the ground. On a 74 deg head tube, 2 to 2-1/4" makes a really nice handling bike.
Drawing this up On a piece of paper can be really helpful. When I built my frame, it took measurements from the bikes I had & transferred them all into autocad & tweaked them to fit me a little better. Cad is a lot easier to work with, once you get through the learning curve. It really allows you to easily make changes & find results

Thanks Blue Belly. This seems like a little bit of work and it needs to be pretty close. Are there any recommendations you might make knowing what this bike is and it's intended use , short tours and overnighters maybe you could suggest a fork out there that might bolt up and keep geometry similar?

Really tough to know, without knowing what you first, have