with gear i'm about 220lbs, and on stock suspension, setting the sag to 30mm front and rear. i measured with the suspension unloaded to me on the bike. as per this video: twist of the wrist how to set sag. the bikes service manual says the usable spring length range is 177.7-187.7mm on the rear, if i wanted to get to 30mm of sag, my spring length with me on the bike is below 177mm. does this mean i'm too heavy for my spring?
Your logic or numbers are a little confusing. For the shock or rear of bike. You measure from a two fixed vertical points. From the axle to a mark or piece of tape on the tail works best. Measure with the bike sitting up and down in a chock or being held up from those two points. Then get on the bike in a tucked racing position and have a friend measure again. Subtract the second number from the first. If the number is greater then 30, then add some preload to the spring. Repeat the measurement. You should be getting closer to 30 or your target number. If you get near 177 with you off the bike, then you'll likely want a heavier spring. Springs are typically preloaded with about a half inch of preload (12 mm). You take out all the preload, then add preload to compress it the 12mm to start with a new spring or when starting over. You need to have some preload on a spring to start. The best thing to do is get with a suspension tuner in your area and start building a relationship. If you're at this for any amount of time, then you'll be visiting them annually at minimum. You'll also need to reset the compression and rebound adjustments when you're done with sag to balance the chassis.
Sorry, yeah my numbers were confusing. The way you set sag is your measuring from a fixed point on the swing arm to a vertical spot on the tail, and have someone measure with you on the bike, yes. I'm doing it pretty much exactly like in the video. But, I'm adding preload and getting closer and closer to 30mm, and I noticed that my spring seemed awfully compressed, so I wondered, "how much can this spring be compressed?" So I looked in the service manual, and the service manual says that the usable range of the spring is 177.7mm to 187.7mm spring length. As in the length from the top to the bottom of the spring. If I keep adding preload to get my sag(starting point was with the suspension completely unloaded, swing arm hanging down), the length of the spring Falla below 177.7mm, which is out of the usable range. With the spring length at 178mm, I'm at about 34mm, which for my purposes would suffice, but is not ideal, so I was wondering if this means I am too heavy for the stock spring? Or like, keep going? The manual doesn't really say if the usable range includes dynamic suspension movements like while riding, or if it just means static like when you're sitting on the bike and setting sag.
If you're at the end of the springs useable specification range, then yes, you should look a heavier spring. If you're serious about riding on the track or performance riding on the street. Or just like to keep your equipment in good condition, you may also want to look for an aftermarket shock or at minimum have a service performed on the existing shock to freshen it up and get a new spring.