Suspension Setup Series #1 – Set Your Sag Properly

bikerumor guide how to set up mountain bike suspension sag

At virtually every mountain bike and suspension launch we attend, we’re told to simply sit on the bike while someone slides the “fun-o-meter” ring to the base of the fork or shock, then we hop off and see where it lies. If it’s in the ballpark, we gear up and head out, fiddling with the settings as we ride.

Recently, I had some time with Rockshox brand ambassador and SRAM MTB marketing manager Duncan Riffle, who also happens to be a 2x U.S. National Downhill Champ and former World Cup DH competitor, so we discussed the finer points of suspension set up. The result is this 6-part series, with additional input from Manitou’s Eric Porter, who’s raced professionally in XC/DH/DS/DJ over the past 11 years, and Mark Fitzsimmons, Fox Racing Shox’s race program manager and pro athlete suspension tuner. As you’ll see throughout the multi-part story, there’s quite an art to getting it all dialed, but when you do, it’s pure magic on the trail.

So, ready to rethink everything about how your suspension is set up? Good. We’ll start with sag, which is the amount of travel your suspension moves through just by adding your own weight (body, clothes, pack, etc.) to the bike. This puts the suspension into an active state, letting it react in both directions, keeping your tire glued to the dirt. To get it right, there are two things to consider: Rider position and amount of sag. We’ll start with properly positioning yourself on the bike so that sag is set based on your actual riding.

But first, make sure your fork and shock both have their compression damping set to their fully Open/Descend positions, then hop on the bike…

bikerumor-suspension-setup-sag-position-seated02

“Understand that when you set your sag, it has nothing to do with your body weight (sitting) directly over the BB or shock,” says Riffle. “It has everything to do with how your weight is pressing on the bike in a neutral ride position. So, obviously, you’re going to want to set your sag accordingly.”

These images illustrate the difference rider position makes. With the same air pressure in the shock, it’s showing almost 40% sag when seated…

bikerumor-suspension-setup-sag-position-standing03

…and just 28% in an aggressive standing position.

To figure out how you should set it up, Fitzsimmons breaks it out like so:

  • Downhill bike: Set sag in a standing attack position.
  • Trail/Enduro bike: Set Sag in a seated position for every day riding and standing if you are bike park riding
  • Cross Country bike: Set sag in the seated position

It’s very beneficial to have a friend help you balance the bike and move the O-rings for you. With your usual riding gear on, including filled bottles on the bike or hydration pack on your back, climb aboard the bike. Once in position, bounce up and down a few times without holding the brakes, then settle into the desired position. Once there, hold steady while your friend slides the O-rings against the canister/lowers, then slowly lean over and climb off the bike. Don’t hop off – that movement can compress the suspension further and move the rings. If you want to be absolutely sure, have a third friend record the measurements while you’re still on the bike.

HOW MUCH SAG SHOULD I RUN?

Generally speaking, somewhere between 15% and 40%. Riffle’s preferred starting point is between 25% and 30% for his 160mm to 200mm travel bikes. When he was racing downhill, it was more like 30% to 35%, depending on the bike and the course. Cross Country bikes generally have a much shorter stroke to work with and get away with a little less, unless it’s a really rough course.

“Most bikes feel good between 20-30% sag, I like 25-30% most of the time,” says Porter. “If you are doing a ton of climbing you may like it closer to 20%.”

Ultimately, it depends on four things:

1) The bike you’re riding – how much travel does it have? How aggressive is its leverage ratio? If it’s a shorter travel bike, then you’ve got less to work with and should start off on the lower end of the spectrum, around 25%. If your bike has a high leverage ratio, then it can muscle through the travel too easily if you’re running too much sag, too, so start on the low end. Reverse that for longer travel bikes or those with weak leverage ratios.

2) The terrain you’re riding – more aggressive terrain means your shock is going to see a wider variety of impact forces, so you’ll need to experiment more to make sure you’re not bottoming out too frequently but that you’re still…

3) Getting full use of the bike’s travel – This one’s is the most tangible of the four and is easily measured with the little rubber ring around the stanchion or shock shaft. If you’re leaving travel on the table, then you haven’t made the most of your available suspension, and thus your bike’s potential performance.

4) Your preference – Ultimately, the bike should feel right to you while still getting all of its travel on most rides. Setting the sag at the proper point and while in the proper riding position is a good start to achieving this.

Lest you worry about sagging too far into your travel affecting the performance, the suspension’s compression settings are based on speed, not position. So more or less sag won’t affect damping performance. It does play a role in spring curves, though, which is a story for another time.

WHAT ABOUT FORKS?

manitou mattoc

For forks like Manitou and Fox without sag indicators printed on the stanchions, the Saggle can help.

Setting the sag on your fork can be a little different. You don’t necessarily need the same percentage of sag on the front of the bike, it’s more about finding the right balance from front to back.

Fox’s Fitzsimmons says “If you race or ride at a faster pace, sag should be set up 15-20% on the fork and 20-25% on the shock. If you are a weekend hobby rider, 20% in the fork and 25% in the shock.”

Porter adds: “When checking the fork sag, you are looking for closer to 10-15% if you are sitting on the bike.  This is more accurate than ever due to how good the new class of trail forks are (Manitou Mattoc, Rockshox Pike, Fox 36, etc.).  When setting up the fork air pressure, I usually start out where the manufacturer recommends, then I set up the rear, then I cruise around in the parking lot bouncing up and down to make sure that the air pressure feels balanced between the front and the back.  Having a balanced bike is very important to making a bike feel good on the trail.”

For hardtails, it’s about finding the point where the fork is supple off the top and able to move through it’s full range of travel when it hits the biggest obstacle or drop on the trail.

From my own experience, after talking to Riffle on the trail, I ended up running more sag on the rear -changing from roughly 22% up to 30%- which let my 100mm Niner JET 9 RDO really soak up the little stuff. Mind you, I was happy with the bike’s performance before, but setting the shock up a little softer made a noticeable improvement in its small bump absorption with no discernible downside. Even if you think you’re happy with your current set up, I’d recommend experimenting throughout your next few rides.

COMING UP: In the next installments we’ll discuss the differences between the spring rate and damping tunes, how to tune your compression and rebound damping, and even how to tell if you’re using the right suspension parts and what to do if you’ve tried everything from 15% to 40% sag and things still don’t feel right. Stay tuned!

Comments

Equine Master - 07/24/14 - 6:18pm

Hello, where’s Autosag for forks?

kt - 07/24/14 - 7:04pm

Yes! Thank you!

Topmounter - 07/24/14 - 7:41pm

I’m surprised their hasn’t been more development on Active Suspension for mountain bikes, e.g. Magura’s eLect technology.

chris - 07/24/14 - 8:55pm

Good article. I’ve been playing with the sag in my fork lately. Very timely.

Le Piou - 07/24/14 - 9:08pm

I never realized how the position would affect the sag.
Great tip!

Thanks a lot!

ron - 07/25/14 - 12:09am

Thank goodness for this article! Before people talk about better forks, better stanchion coatings, more travel, newer suspension, custom tuned suspension, f1 suspension technology, dual chambered this and that, “Bottomless travel” technology that also climbs like a hardtail, they should simply make sure they have the correct damn sag!

J - 07/25/14 - 12:45am

This is good.

k - 07/25/14 - 12:45am

it blows my mind that people buy these bikes and don’t understand this.

read RACE TECHS MOTORCYCLE SUSPENSION BIBLE, for peets sake!

ginsu - 07/25/14 - 1:47am

Setting sag is very important, and during the process I always try to make one end of the bike noticeably stiffer than another, usually the front. This means the sag must differ from front to rear as well. I do this because if the spring rates are too close to each other you can get into a ‘pitching’ mode very easily if both ends ride near the same frequency where you buck forward and backward. This is especially noticeable when riding over tree roots or evenly spaced bumps. The feeling makes me sick and generally makes the bike ride bad.

I found out about this primarily in auto-racing, where it is recommended as well. I’m pretty sure it has something to do with resonance between the front and rear suspension. Obviously, it’s not a problem you encounter on hardtails.

huh - 07/25/14 - 6:07am

I strongly disagree with the comments that you should get different sag depending on whether you are standing or not. In the correct attack position you have 100% of your weight on your feet (no matter if its downhill or up). Its the same when your at the saddle pedaling, you are pushing the pedals. Of course this is easier said than done.

Dylan renn - 07/25/14 - 10:09am

I find that also setting up the suspension in the gear you ride can make a big difference. Wether u wear Xc gear or go #enduro style or even if you carry a water bag on your back. All of those change the amount if weight on the bike.
I find as a trail rider that goes for the DH Predominantly that lifting the rear end off the ground( raising-it with a block, or curb) I can see what the sag is like or would be like descending. The parking lot is not the trail set the bike up for the trail.

FastWayne - 07/25/14 - 10:20am

I was setting my sag on Fox Float 150 at 30%, now that they were just rebuilt I will start around 25%, it feels pretty good there. Every time I ride it feels a little different, I should buy that sag meter thingy; )

King of Bollocks - 07/25/14 - 10:49am

When I set fork sag, I place the rear wheel on a cinder block, to simulate an attack position and to bias more weight forward. Standing straight on the bike, statically, usually does not cause the fork to compress, what with the stiction and all.

Tyler Benedict - 07/25/14 - 11:08am

FastWayne – Yeah, the Saggle is pretty cool in that it takes the guesswork out of sag % and makes it easy to repeat the settings once you find what you like. If only they’d make one that measures shocks, too, based on stroke length or something. As is, it’s based on MM of travel, so it only works on forks.

Chaz - 07/25/14 - 12:21pm

@huh. Sorry but I and physics have to disagree with “100% of your weight on your feet”. The last time I was in the “correct attack” position I was pretty sure I couldn’t remove my hands and not move. Your weight is spread across all points of contact with the bike, always. The ratio changes but the fact remains. It has to do with the center of mass of your body and how it interacts with the bike. As you lean forward the CG goes forward taking weight off the pedals and transferring them to your hands.

A super simple example would be the loss of traction that can happen when you are climbing while seated compared to getting out of the saddle and putting your chest over the stem…

Chader - 07/25/14 - 1:00pm

@huh,
When you are sitting on the saddle, the weight distribution on the tires is more rearward biased (something like 60% rear vs 40% front). That is true even if you are pushing fairly hard on the pedals.

When you stand, that shifts the loading directly to the pedals/bb. This has a tendency to alter the weight split to be more equal (something closer to 50/50 but likely still rear biased). This will change depending on exactly where you are standing, primarily the hip/torso location that contains the greatest mass. As you slide forward or back, this will affect the weight distribution.

The numbers above are all swags, but the general properties are true. You can see this if you mount a bathroom scale under your wheels. Make sure to use a even height block on the other wheel if you only have one scale. It’s cool to see real time though.

All this is to say, if you spend most of your time in one position (standing vs sitting) it can make a difference on the suspension loading and is appropriate to set sag in that position.

Seraph - 07/25/14 - 1:10pm

But how do I set sag for my slopestyle bike? Should I set it while I’m double tailwhipping off of a 50 foot step down?

satisFACTORYrider - 07/25/14 - 2:01pm

@seraph- always set it for the occasional yet inevitable ball ride. safety first.

MWD - 07/25/14 - 2:51pm

Great article! Keep this stuff coming, fellas.

Kark - 07/25/14 - 4:22pm

Guys, give ‘Huh’ a break. He’s obviously riding with 100% of his weight on his feet so he’s always ready to ride no-hands and wave to his adoring fans. (especially important to not ignore your adoring fans while you shred thru the techy descents)

..if you had adoring fans you would too. You’re just jealous.

huh - 07/25/14 - 4:56pm

Well, I don’t know what your idea of “correct attack position” is. Mine (or my goal) is something I have picked from MX’ing and its supported by MTB authorities too (f. ex. Mastering Mountain Bike Skills by McCormack and Lopez).

Its not easy or always possible, but I’ve found it makes riding much easier compared to the pulling or pushing of the bar I used to do and see so many peolple do. Now I can actually use my bars for stearing, not as a place to rest my upper body. If I have weight on my hands, it only means that my hips are too far forward.

Fantomphish - 07/26/14 - 5:51am

Might also mention that if setting up a new bike is to after a good few hours on the bike is to recheck the sag after the forks and rear shock have been broken in..

jason - 07/28/14 - 2:02am

Linkage design has a notable impact on rear end sag as well. It would have opened a can of worms but it’s worth talking about.

Chris Nelson - 08/13/14 - 2:54pm

anyone know what the yellow fun-o-meter is actually called. need one apparently.

J.J. - 08/23/14 - 7:47pm

Tyler, Great information and may I ask were you got your yellow sage marker/fun-o-meter?
Thanks for being there…… J.J. in Houston

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