The Tuesday Tune Ep 7: Less Obvious Aspects of Sag - Video

Dec 13, 2016
by Vorsprung Suspension  
Views: 7,503    Faves: 42    Comments: 3



This week on the Tuesday Tune we're going back to basics to look at some of the less obvious and less commonly discussed aspects of sag setup.

We aren't here to tell you what the "right" amount of sag is - no single number is correct, and what works best will vary according to the frame/fork/shock/rider/ability/terrain variables. For this reason, discussing specifics needs to be done in context; 15-percent sag on your Pike is fine, but that's extremely stiff on the back end of your downhill bike, for example. This video is aimed at those who already have a basic grasp of sag, so we aren't going to show you how to measure it, but if you want to learn more about that, DVO have a short and helpful guide to sort you out.

What we are looking at, however, is what the relevance of sag is, why it's useful as a transferable and comparative value even between different riders on different bikes, and how to make sure your measurements are consistent. We'll also go over what the practical limitations of sag are, both in terms of measurement and relevance to performance. Although it's far from being the be-all and end-all of proper spring rate setup, sag is very useful as a starting point and a baseline indicator of spring rate relative to body weight.



MENTIONS: @VorsprungSuspension




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58 Comments

  • 46 0
 oh boy its my favorite time of the week to be on Pinkbike. Love all of this guys, thanks for making it happen!
  • 25 0
 alarm went off, got up took a pee, threw on a hoody, stepped into video room, hit record (prepped the night before), started speaking...
  • 22 0
 Beanie hair does that! hahah
  • 14 3
 Finals are making my mood sag but this video makes me spring back to my happy self.
  • 2 0
 Awesome!
  • 6 0
 @VorsprungSuspension request: Any chance you could do a video or post on why Rock Shox(or other vendors) tune the compression circuit so differently between RC & higher end models? I'm currently finding out about it on a Pike, but my previous gen Lyrik was similar: The RC damping it started with had a much firmer tune than the RC2DH I eventually retrofitted it with.

I'm curious if you can deconstruct their motivation behind this: Why do they feel a RC rider needs a firmer tune than a RCT3 rider?
  • 2 0
 Could be difference between an oem fork and something from a supplier? Oem suspension will generally be valved for the bike its on but aftermarket stuff I've often seen with just medium tuned dampers.
  • 6 0
 We had that discussion in a local forum as well. The best explaination is: RS wants all forks to have something close to a lockout (which is a stupid requirement on the Pike, if you ask me). In the RCT3 they have an additional adjuster for that (the "tube" around the shaft, which houses the LS comp needle).
In the RC they don't have that adjuster (cost) and then felt the need to increase the comp Shimstack to ultrastiff (via thicker shims (0,15 ->0,2) and huge amounts of preload in the stack (RCT3 stack is preloaded as well)), to achieve enough LS compression with the needle fully in / lockout function (as Steve said a week ago, your max amount of LS compression is limited by the amount of HS compression.
This results in a too stiff HS damping and is a common problem. The massive preload in the stack does not make it better.
But ultimately the RC is the better damper with more potential, because it does not employ an adjuster, that might compromise oil flow. One suggestion would be to get rid of the preload in the stack (ring shim plus 16mm centering shim) and adjust the amount and thickness of the remaining shims to your likings in HS compression. Good starting point would be to put the 16mm centering shim at the end of the stack after removing it from its original position after the face shim. But depending on rider weight and aggresiveness you have to find your own setup in the end. Hope that helps, good luck.
  • 1 0
 @ArturoBandini: Good info there guy. I will say that they don't feel that way about EVERY fork: if you've ever ridden a RC2DH, they don't have enough compression adjustment to deal with standing pedal bob(which was my only complaint, as some of my rides require uphill road pedals.)

But that's minutiae. Overall, I think you're on to the right track. When you talk about removing the ring shim & the 16mm centering shim, are you saying because of the preload, you can just leave them out of the stack & things will still tighten down, or are you saying to move them to the end of the stack?

Also, anybody got a line on where to buy shims? I'm not finding a lot of good sources online. Currently, I'm leaning towards just replicating the stack in the RCT3, & I'll need to buy some stuff to do that.
  • 2 0
 @groghunter: Yeah, you could move the 16mm centering shim to the end of the stack and throw away the ring shim as far as you can. The comp piston has a very digressive port design so there is no need for a lot of preload in the stack, which makes things even more digressive (don't get me wrong, a bit digressive is a good thing).
But you can try the RCT3 stack and then compare it to a firmer stack but without preload and see which one works better for you. On a stack without preload you might need to run the LS adjuster a lot closer to fully closed, which is not a bad thing imo. In the end it is absolutely worth it to try and find a good compromise between a nice and supportive LS damping and a supple enough HS damping. But from what I hear the tuning pistons (Fast, mst, novy,...) make things even better compared to what you can achieve with stock parts. Especially in the compression curcuit. So, let's fiddle around with dampers, it's fun. A good, educated guess up front helps of course.
  • 1 0
 @ArturoBandini: Yea, I was seriously considering the Ohlins piston from MST, but I hate throwing parts at a problem without knowing what the actual cause is, & I haven't felt unhappy with the rebound performance, which is the piston they sell(unless I've missed something where they have a similar kit for the compression side.)

Now that I know what the problem actually is, I know where to focus my efforts.
  • 1 0
 whoops, double post.
  • 5 0
 @ArturoBandini sounds like you should be working for us! Bang on description.
  • 1 0
 Between this post & some other research I've done, I'm going to reduce the face shim to .1, & increase the centering shim by .05. If I don't just send it back to RS first. I seem to have a lot of sticktion as well, far more than I've ever had on another fork.
  • 7 0
 Wow!!! All this time I've been setting my sag incorrectly!!! Watch out Gwinn I'm coming for ya!
  • 4 0
 I expressed my appreciation for these tutorials early on, as I realize they take time and effort to get right. It's a real skill unto itself simplifying complex subject matter. But I also suspect, things don't always go perfectly. Given the dry nature of the information, I'm betting the blooper reel would be absolutely hilarious.
  • 4 0
 If you had any idea the amount of stuff that gets cut out, and why... hahah
  • 3 0
 Anybody with bike data acquisition experience know what typical g levels are (I guess you'd want that measured on the unsprung parts of the bike like at the axles?) for different scenarios? Speaking in very simplified terms, he mentioned 25% sag roughly means that it takes 4 g's to take the spring to full compression. How many g's are generated by the impacts when a pro goes down a world cup course?
  • 2 0
 actually it would be more than 4 g's to bottom out, almost every frame has a progressive leverage ratio. Air shocks can be tuned to be more progressive too.

youtu.be/FF3R0KG-yzA?t=114
  • 2 0
 Peak acceleration seen at the wheels is actually orders of magnitude higher than that, but only very very briefly. A sustained acceleration (by sustained I mean more than 0.2 seconds or so, which sounds very short but isn't) of about 6-7g is required to bottom most bikes. Riders can't actually hold on to that for very long, the body is already buckling/compressing/absorbing by the time the bike bottoms out.

The reason I mentioned that concept was simply to illustrate why it is that we can't just run super low sag and expect it to be usable, as well as how it is that softer setups result in lower forces required to bottom out and what the relevance is to bodily strength.
  • 7 0
 I tried to measure my girlfriends sag and got a slap. Man I miss 1%
  • 10 0
 Dynamic ride height is probably a more useful concept in that situation.
  • 6 0
 Very informative video as usual, keep it up!
  • 2 0
 Says he won't teach how to set sag: teaches how to set sag...all shit aside this is a great series, keep em coming! I have two questions: how do I set sag and bottom resistance (i.e. Tokens) to maximize suppleness, especially in the mid stroke? I find that too much sag with tokens to compensate blows too easily through travel, but increasing spring rate, even while taking a token out, results in too stiff of a spring, which is hard to bottom and painful on the hands. Question two is thus: can you recommend a mid-travel fork that retains suppleness in that mid stroke without plowing through early stroke too easily to get there? Or is this more a matter of damping settings, of which I will need: {R, LSC, HSC...}? Please disclose professional bias if necessary.
  • 3 0
 Interesting question - I've had a chance assess a fox 36 for racing and have settled on 28% sag 2-large orange and 1- small blue 178lbs and here are the answers (my own opinion) to how the initial setup can be done effectively. 1) Set sag to 25-30% of total travel w/ stock tokens; hit the 'normal' style trail with drops, jumps, g-outs and make notes...where did you bottom out, did the fork dive in the g-outs etc. if this happened add a large token, check the HSC and LSC (write down all compression and rebound settings) and reset sag. Take the same run and ask the same questions and add tokens if you continue to bottom out fork. I would say that you should feel supported and be close to bottom out if not light hit only on the largest hits that you expect to take. If you over ramp the progression in the fork, your mid-travel hits will be rougher because the rapid increase in airspring force. Also note, that reducing low speed compression (maybe speed up HSR by one click also) in the fork really helps with small bump sensitivity but may reduce the fork ability to feel firm the final stroke of a big hit. You will know what is right for your body weight and terrain. I like to think of the air spring ,rebound and tokens as the pogo stick setup and the compression settings as fine tuning function. Lastly, if you are at a high elevation or have large changes in temps you may want to "burp" the lowers through the dust wipers with a zip tie. The symptom is usually a harsh fork.
  • 1 0
 This sounds similar to the problems I've been having. Are you on a Pike RC? Because if so, the wonky tuning on the HSC stack may be your problem. Look at my other comment for more info.
  • 1 0
 @DrStairs you need to find the balance with spring rate there. Sounds like you're experimenting with it quite a bit, so my first suggestion would be to make smaller changes (get yourself a digital shock pump if you don't already have one) and maybe even cut a token in half to make smaller changes there. You need to ensure you have it firm/linear enough that it isn't running into a wall of progression at the end of the stroke without enough positive travel available between sag point/ride height and where the ramp up becomes severe. You simultaneously need to balance that against having something that is soft ENOUGH initially. Mid-stroke sensitivity with air forks is almost never the issue in itself, it is the compromise between harshness in the initial travel (which is what typically causes that hand pain at higher speeds) vs having sufficient support in the middle of the travel that is difficult to achieve. More HSC may help you too but it's very difficult to diagnose without knowing the specifics of your setup - too much HSC could actually be the problem to begin with. If you're running a Pike or a Lyrik, we make the Luftkappe to assist with the exact issue you currently have (obviously we are biased towards it, we developed it!). Otherwise if a whole new fork is in the budget, the 36 and the DVO Diamond are both solid performers there.
  • 3 1
 A cycling buddy once said to me: you know you have the right spring rate when you bottom out once per riding session. That way you know you're utilizing the full travel of the bike. Thoughts on this sentiment?
  • 11 1
 If you averaged that out statistically over the course of a year that would be reasonable for sure. But for a lot of people, sometimes you ride mellow trails without a lot of big hits, other days you ride fast trails with lots of big compressions, so if you're using the same setup for both then you're going to find that either you bottom all the time on the latter, or you never quite use full travel on the former. And sometimes you just make a mistake and hit something really hard.
  • 7 0
 I think it's true if you are riding the right kind of bike for the terrain you are on. If you are riding a longer travel (6") kind of bike on mellow trails and you soften it up enough to use all the travel on that trail, the bike will feel slow and unresponsive in my opinion. You'd be better off on a bike with less travel. Or ride a 6" travel bike but don't expect to use full travel unless you are on hard terrain and just know that you have some untapped reserve when you ride easier trails.
  • 4 1
 @VorsprungSuspension: Yeah no kidding. Using the "bottom once per ride" method on the rear means you're going to break a lot of frames or bolts or rear wheels if you ride hard and ride a variety of trails. Even worse if you're a little bigger than average and a bit of a hack. Been there, done that. Now I only like to bottom in "oh shit" moments or on the biggest moves for my ability. Even then, I don't want to feel a harsh bottom.

Thank god for bottom-out tokens these days. Even 5 years ago it was hard to find off the shelf trail bikes that ramped up enough for aggressive riders without bottoming harshly resulting in lots of broken gear.
  • 2 0
 @VorsprungSuspension: Right, the context was more for DH riding back 8 or so years ago, and you'd only want to barely feel a soft bottom out when you messed up and hit something bigger than you meant. These days I don't think I ever feel an actual bottom-out, but even gauging by the dust on your stanchions that you're using all your travel without bottoming is a reasonable metric.
  • 1 0
 I think part of that idea is why pay for something you aren't going to use. If you spend a lot of time shopping and searching for 8" of travel and only use 4 or 6 inches then you either chose the wrong bike or have the wrong set up. Obviously if you have 1 bike for all of your trails than bottoming out on all trails, like what's been written earlier, is not the right idea.
  • 1 0
 You could be way off of your correct spring rate range and still bottom out once in a ride, if your damping is completely off the mark. For example a too stiff spring and not enough hsc damping.
  • 1 0
 @VorsprungSuspension I have a question. Do you have suggestions for a base tune of the Marzocchi 380 C2R2 Ti? I weight around 150lbs and I can't seem to find a good starting point online. You stated to not preload the spring. I believe in the instructions it has that as the first step to set sag. So just ignore that and work with the compression and rebound? Thanks for the videos!
  • 2 0
 which year model r u running ? the 2014 model came with a 5.5 NM spring and the 2015 one with a 6.5 NM

i'm at a similar weight with the 2014/5.5NM spring and took me forever to set up properly , still if i change from a smooth trail with jumps to a more steep natural track i feel a few adjustment are necessary.

i run roughly 3 turns of pre-load , LSC 10 clicks from fully closed , HSC 14 from fully closed , LSR to your liking -- I run about 15 from fully closed , HSR - basicially in the middle ( i think about 10 clicks from fully open)
*** by "closed" i mean - slowest rebound // firmest compression

for steeper natural terrain - i go to faster HSR and firmer LSC - to avoid dive while braking

compared to the boxxer i was running previously - the marz. are running quite deep in their travel . . .
  • 3 0
 @shilohtech basically I am not a fan of "setting" sag per se - more like measuring it and swapping springs out if it is inappropriate. Preload is a ride-height adjustment, which is critical for cars and motorbikes and far less important on mountain bikes. If your measured sag is in the right ballpark, that's an indication that you're on an appropriate spring rate. If you fudge that by preloading the spring to try to compensate for a spring that's too soft, it won't perform the way it could and should. Compression and rebound won't affect sag on that fork either. At your weight I'd recommend the 6.5N/mm spring if you aren't already running it. Check the high and low speed damping video from last week too if you're interested, and also take note of what @zemaniac posted as well, as he's got specific settings laid out for a rider of similar weight which would be a good starting point.

Be aware that all Marzocchi springs are on the soft side. Their firmest spring sits between the Medium and Firm spring that Fox offer. Running an overly soft spring pushes you towards either highly progressive setups or running a lot of compression damping, both of which are easy to overdo, so I recommend running a stiffer spring than Marzocchi themselves recommend.
  • 1 0
 @zemaniac: Thanks for the response! Sorry this was a couple days ago, I wasn't able to get back on. I have the 2015 version. I read a lot about the 2014 model being too soft, so they made the 2015 stiffer. But I feel it is maybe a little too soft still. Thanks for the settings, I will give them a try, I mostly ride a jump line trail, So I too will probably have to change settings when I go to a rough DH track.

According to @VorsprungSuspension it will be the appropriate spring for my weight. So it sounds like I will need to reduce the amount of pre-load and work with the compression more. So far I like the fork even though I don't have it completely set up right. Hopefully soon it will actually be set up right. haha. Thanks again guys for all your help!
  • 4 0
 @VorsprungSuspension : should sag be set with all dampers open or at ride settings ?
  • 1 0
 +1
  • 5 0
 Unless you have a platform effect from your compression damper (ie you have lockout switched on) it won't affect sag.
  • 1 0
 @VorsprungSuspension Good video as always. These really are one of the best things on pinkbike at the moment. It would be good to hear about the effects of too little or too much sag in various situations, under different riders etc.or the different ride characteristics that can be achieved by adjusting sag
  • 4 0
 Gives me a more precise thought about sag, thank you for the video!
  • 1 0
 What if you set your sag while your bike was on a slope, then the reaction forces would be more representative of what your body weight would exerting in a real scenario? Just a thought!
  • 1 0
 The problem with doing it on a slope is that you need to make sure the slope is exactly the same each time, as well as preventing the bike rolling away, which in itself skews the way the suspension is loaded for sag measurement.
  • 1 0
 @VorsprungSuspension: I agree, I was thinking more of a big step to avoid the rolling action and braking for more controlled weighting. I will try it though just to find out and learn. Can't wait for the next vid guys!! Loving it!!

Thanks!
  • 2 1
 Seems like you could be injured more by testing sag in this manner then a 10 foot drop! Kidding - great video. Learned a lot.
  • 3 0
 The fork on the demonstration bike looked extremely low angle.
  • 11 0
 It's not set up to go uphill Smile
  • 1 0
 he's also sitting on it which makes it slacker than it actually is
  • 1 0
 What @jaydawg69 said: you're used to looking at bikes unweighted, but they look way different when you actually are on the bike & not moving.
  • 3 0
 Great vid as always, thank you @VorsprungSuspension for doing that
  • 1 0
 It would be really great if you could do a video showing the entire set up process with one rider on one bike from start to finish.
  • 2 0
 Who knew!!!, thanks guys , great job
  • 2 0
 Awesome work, keep it up!
  • 2 0
 Professor Steve
  • 1 0
 Just when you think you know it all...
  • 1 0
 Another banger of a tech video. Demystifying suspension.

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