Set my rear sag

[beatle]

A couple months ago I installed a Penske 8983. I didn't have a friend around to help me set the sag, so I fiddled with the compression and rebound adjusters and found what I thought was about right, though the bike still threw me off the seat on heavy bumps. I didn't want to keep dialing in more rebound since it already felt pretty stiff. I guess this is just "sporty," right?

I even took the bike to the track. I was riding harder than I did when I went to CSS back in May with stock suspension, but I didn't really feel much faster.

Today I had a buddy of mine come by and help me measure the rear sag. I had to check that I was doing it correctly several times because the static sag was practically nothing! When I sat on it, I found my total sag was only about 8mm! Wrenching the preload adjuster for what felt like forever finally dialed in about 8mm of static sag, and 32mm of total sag. The bike felt so spongy it was ridiculous, and it didn't match the front (R6S forks) at all when I pushed down on it. I turned the little adjusters until it felt about right and then I went for a ride.

I was actively searching out bumps to see if I could upset the bike. I couldn't do it. It still felt pretty planted, but I wondered it if was still too soft. After all, I had been riding with what felt like almost no suspension in the rear for a while! I gave the rear a few more pulls on the adjuster to increase the preload, thinking it would put me in the 30mm range (no way to measure now). I'll tune it more on my rides into work this week, but it really is amazing how much better the bike feels.

I say I shouldn't be surprised at what good suspension can do. I rode around with "ok" suspension on my Miata for years. It was stiff and I thought the car was pretty fast. I finally sprung (no pun intended) for some top shelf stuff with springs 2x as stiff as I was already running, but the car felt so much better over bumps and grip was off the charts. I figured my lack of riding experience was to blame for me not getting the most out of the suspension. That's still true to an extent, but not the extent I thought originally!

 

[FinalImpact]

No doubt about it that more people is better for checking. Its quick and easy. That said, it can be done alone but you have to get creative.

I happened to have 4ft section of carbon fiber rod 1/8" in diameter. I placed one end of the rod on the rear axle bolt and taped it in place. On the seat/tail light area I secured some strong cardboard sticking the long end of the rod through a hole in the cardboard which sticks out over the rear axle. When you sit on the bike the rod moves through the cardboard. Make sure rod holder is secure and won't move and that the rod angle forms a 90° angle to the earth (Rod pointing straight up; not leaning forward or backwards). I used tap to secure the cardboard and it held fine.

Place a Zip tie on the Rod just under the cardboard.It should move but not fall down from its own weight.
While the bike is on the center stand place Sharpie a mark on the rod where it meets the cardboard. Push the Ziptie up to and touch it on the cardboard.

1) Carefully lower the bike to accept its own weight and measure the distance the zip moved from the mark on the rod. Here is your Bike static sag!
2) Sit on the bike in riding position near a post or wall so you have one hand to hold yourself up. This will push the ziptie down some more. Measure the difference from the mark. This is your basic rider sag. These two numbers are direct so you get what you measure.

Repeat these two steps 3X and verify you get the same results.

I know it doesn't take into account stiction of shock seals and all that but its a good ball park number to reference. Save the values as springs do change over time.

A ziptie on the stanchion tube up front and you get the same type of measurement system.