Modern Vespa

I replaced my worn out original front shock with a "performance" shock from Scooter Mercato. It works and it was cheap, but I suspect it's not much better than stock. The roads around here are terrible and I'd like to upgrade my suspension. I watched one of the SIP videos on suspension set-up and saw that they suggest 2cm of "sag", that is, 2cm difference between the bike unladen, and the bike with you on it.

When I sit on my bike, there is no sag at all. I'm 180lbs./82kg so I would expect something. No wonder I hate the roads around here; I'm riding without any negative spring deflection.

I'm curious, how much sag do you see on your scoot? How happy are you with your shock set up?

Good on you to absorb that SIP video. Many people have no idea how spring preload is supposed to work.

Anyway, the rear shock carries most of the weight on these things and most of the sag happens there. If you only replaced the front shock, you probably are dealing with a rear shock that is frozen or has the preload cranked up way too far.

The rear is stock and it sags just fine but the front doesn't move a mm with me on the bike.

I have the Carbone adjustables (which I think are the same thing as the Mercato performance shocks). I weigh 175 lbs and have the preload on the lowest setting. Just rechecked. Sag measured at the floor boards is about 1 inch but most of that is coming from the rear. I wouldn't say sag in the front is zero, but it is pretty small. I guess that's just the way they are.

I have the Malossi RS24 on my smallframe and was able to dial in the sag with ease.

Zip-tie around the shaft to mark the travel
One person holding the bike for balance
The other gently sits on the bike in the riding position and then gently get off
lift the front of the bike a bit to make sure the shock is not compressed
measure the distance from the zip-tie to the shock body = sag

Patrick pretty much nailed it spot on. There's also "race sag" and "static sag". They SHOULD work in harmony with each other. The problem is with all over the counter performance scooter shocks, it that their's only a couple different spring rates that are available. Ideally, you would buy the particular shock that you're after, then you would buy a spring that had a particular .xxkg spring rate (for lets say a 175lb to 185lb rider)...but then you would also have to factor in what sort of terrain and roads you will be on, how much your all gear protective gear weighs, how much camping/traveling gear is being carried, ect. Then you have to factor in possible poor shock valving that many of the aftermarket scooter shocks are speced out to. I've spent thousands of bucks on all my KTMs dirtbike's suspensions over the years. I've come to the conclusion that when it comes to scooter shocks, you get what you get, and you don't throw a fit. Just remember that increasing he sag does NOT increase the spring rate! It won't make the suspension any stiffer whatsoever! It will only change the ride height (which is what sag is).

Thanks everyone. Your comments make sense and reinforce my understanding. I think I'm going to spend a little on improving my suspension.