Making sure that your bike has the correct spring rate and amount of sag is the first step towards having your suspension set up properly. This Tech Tuesday takes a closer look at how to accomplish this, showing you the steps to go through and the formula that I like to use. Inside you'll find a video guiding you through the entire process!
Read on,If you caught
last week's Tech Tuesday you'll know what all of the terms mean, including sag, which is what we are taking a closer look at today. Getting your bike's sag set correctly is the first step to sorting out a suspension setup that works for you and how you ride. Only once the sag and spring rate are dialed in can you start to fine tune the compression and rebound damping settings. Below you'll find a video outlining the steps to take in order to figure out how much sag you are using, as well as some sag amount suggestions.
Watch the video to learn how to set sag:
There are a number of different calculations that you can use to figure out what percentage of sag you are using, but I like to use the one specified in the video. If you do some searching you will also be able to find some online sag calculators that will do the math for you, although you will still need to know the important numbers. Keep in mind that all numbers should be in millimeters.
To find fork sag:
Sag ÷ total fork stroke × 100 = Your sag in %
To find shock sag:
Un-sagged eye to eye length - sagged eye to eye length = Sag (mm), Sag ÷ total shock stroke × 100 = Your sag in %
Past Tech Tuesdays:
Technical Tuesday #1 - How to change a tube. Technical Tuesday #2 - How to set up your SRAM rear derailleur Technical Tuesday #3 - How to remove and install pedals Technical Tuesday #4 - How To Bleed Your Avid Elixir Brakes Technical Tuesday #5 - How To Check And Adjust Your Headset Technical Tuesday #6 - How To Fix A Broken Chain Technical Tuesday #7 - Tubeless Conversion Technical Tuesday #8 - Chain Wear Technical Tuesday #9 - SRAM Shift Cable Replacement Technical Tuesday #10 - Removing And Installing a HeadsetTechnical Tuesday #11 - Chain Lube ExplainedTechnical Tuesday #12 - RockShox Totem and Lyric Mission Control Damper ModTechnical Tuesday #13 - Shimano XT Crank and Bottom Bracket Installation Technical Tuesday #14 - Straightening Your Derailleur HangerTechnical Tuesday #15 - Setting Up Your Front DerailleurTechnical Tuesday #16 - Setting Up Your CockpitTechnical Tuesday #17 - Suspension BasicsHave you found this tutorial helpful? Share any of your hints or tips below!Visit
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48 Comments
there is no logic to your explanation about pressure, as air would surely escape from the place with the MOST pressure not the least. think about it more.
When setting sag at the rear, the shock sag does not always match up to frame sag, as the leverage ratio is hardly ever perfectly linear. (setting to 30% sag on the shock stroke may correspond to as much as much as 50-60% sag of the frames suspension on a frame with a progressive linkage). So you should talk to your frame manufacturer and ask for leverage ratio curves and sag settings.
For Banshee frame owners, refer here for sag graphs of all frames.
bansheebikes.blogspot.com/2010/06/set-your-sag.html
And he'd be right.
At start of travel:
1mm of shock compression = 3mm of wheel travel
at end:
1mm of shock compression = 2mm of wheel travel
The ratio changes, so the shock sag does not always equal the wheel sag especially on highly progressive bikes, or bikes with steep changes in leverage curve.
For example, on the Banshee Scythe (exapmle of progressive suspension frame without being extreme) 30%sag at shock = 70mm/100 x 30 = 21mm
But 30% sag at the wheel (60mm of wheel travel being used) happens at 18.5mm of shock compression.
So to get 30% sag at wheel you actually set the shock to roughly 25% sag. I'm not saying the difference is massive, but if you wan to do thing properly, it is something worth considering.
well at least we were on the same page +/- some values
Haha, don't worry man, I thought it was about the same as you said until I looked it up. Starts higher than I thought it was (presuming the data was accurate, which it claimed to be).
That means that 30% sag on the M6 is close to 30% of the travel. But if you want to set sag at 30% of the travel on a 951, you are going to need a nerdy chart similar to undercoverfreak's.
Back in the day, we just set dag so that we had a slight bottom out on the hardest hit on the course - if you ain't gonna use it, why have it. On my trail bike though, I do as Mike shows.