Does Sag Actually Matter In MTB Suspension Setup?
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- เผยแพร่เมื่อ 19 ต.ค. 2024
- Shop Talk EP.5! The first of many suspension videos to come to the channel. Today we break down sag: how I set sag, some good general practices with sag, and discuss whether or not it is relevant in suspension setup. Hope you enjoy!
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I have recieved a ton of questions about my suspension setup over the past few months, and I hope this video can help answer a few of those. That said, if there is anything you are still curious about, feel free to drop a comment and I will definitely get back to you 🤙🏼
Additionally at 11:29 when I mention 'total suspension', I am referencing your total stroke length. You find what percent the amount your dust wiper moved, is of the total stroke. Sorry for the confusion there ✌
I just ordered the motion instruments system, so I will be following along with you as I learn it. I'm recruiting some of the data eningeers at my job who previoisly did suspension at Motorcycle OEMs. If they help me figure out something special, I'll let you know haha.
That is rad to hear! Hope you enjoy it 💯
Appreciate the detailed discussion! Stoked for the deep dive on sus this summer!
Thansk for watching!
IMO sag is recommended differently by manufacturers that use extra volume air chambers because of the location of the transfer port of the positive and negative air chamber. Too little sag and you're basically riding in the negative chamber only (I'm exaggerating), and too much means you only get to access the negative chamber when you're airborne, which completely negates its design on the ground.
So when it comes to Fox forks, it would probably be wise to limit your working sag (after you've tested your starting sag on the trail and adjusted spring rate) to just under 25%. If it still feels harsh and you've never opened your fork, then get it serviced ASAP. Your fork is guaranteed to have blocked transfer ports from grease.
If you've done all that and your fork still feels harsh, take out a volume spacer. Reduced volume means that your fork's working range, more specifically, the "midstroke support", has moved towards the top of the travel slightly, so you want to move it back and get more sensitivity around your dynamic sag.
If it still feels harsh, you may need to get a fork with a larger negative air chamber, or dual adjustable chambers (Öhlins, Manitou, etc.), one of those Vorsprung kits, or just git gud.
Sometimes you're already running the best spring rate and damping possible. Your settings are probably so ideal you could KOM anything at your best. The fork's not actually harsh. You're just too slow to be even hitting the threshold of your body weight's spring rate. We're just not good enough to be maximizing what is essentially commercially available race suspension. Yep, that includes me lol.
That point about shock pumps almost sent me into a fugue state. I definitely lose pressure every time I disconnect the pump. This might be because I'm pretty heavy, and so my suspension is pumped up pretty high. Just last night, I was adding a few PSI since I'm heading up to Northstar for opening weekend this week (somehow going from 280 to 310 in the rear didn't seem to affect sag?), and every time I disconnected from the front I'd lose 2-4 PSI, and 10-15 in the rear. This has been a consistent problem across a number of pumps, including a basic analog Fox pump, a nice digital Topeak pump (which actually had a two-piece valve that mostly solved the problem, but only went up to 300 PSI), a very nice Specialized floor shock pump (which lost about 100 PSI every time I disconnected it from the rear, despite following the procedure designed to prevent this exactly), and my current pump, a digital Entity pump that goes up to 600 PSI.
This being the case, what in the heck am I doing wrong?
Yo, sorry to hear about your troubles! From my understanding, there is no way to actually see that you are losing PSI in this instance. This is because as your reattach the pump the shock needs to refill the pump's air hose to read the pressure, leading to a pressure drop (longer the hose, more pressure drop - hence why the floor pump gave you a wild reading). The only way to know what is in there to begin with is when you first pump it up and see what the pump says... hope this helps, happy to clarify more if needed. Hope you enjoy Northstar!
Another awesome and helpfull vid. Just stop waving your hands at me bro. 😂 just messin around. I do the same. You must have some Italian in you! 🤣🤣
Glad you found it helpful, thanks for watching!
Hi Peter, What do you say about servicing the fork, do you service it every year, or how do you decide when it is required?
Yo! Thanks for watching! It really changes for me with each bike. Certain bikes I ride more than others, and sometimes I have more bikes to spread the wear and tear across. For instance, last season I had 10 bikes so I only serviced two forks because I spread my riding across many bikes. This year, I only have the HD6 at the moment, so I plan to do regular service about every two months due to the amount I ride. Hope this helps! Tough to give a specific recommendation, so many factor can come into play...
Loving the shop talk! I wonder if there's a way to calculate what lb coil spring you'd need to run based on what psi air spring you run on the same frame. This is pretty tough considering the differences between air and coil like stiction and progression, but would this lead to a good starting point? Would it just be a waste of time? Thoughts on running Sprindex?
Glad you are enjoying the videos! That would be great, but difficult due to the difference in airsprings/volume of various air shocks. Maybe one day though! Additionally, you bring up a good point with stiction, as the coil will have less friction in general. Lots of things to consider there... As for Springdex, I haven't tried one yet but maybe will in the future!
I bought a springdex for my rockshox super delux ultimate coil and it was a great way to get my sag correct on my coil without purchasing 3 different springs!
@@terr256 Glad to hear you had a positive experience with the product 🤘
I can't get my rear shock to Fox's recommended sag at all on the 160mm Evol Float X. It came set up for a heavier rider with the 0.9 spacer in it. The shop asked me all about my weight, etc., but it's still in the 40% range as for the Fox 38 170mm. I've got four volume spacers in there right now. It's sitting at 33%ish. I might be able to work with that with a bit more PSI before adding the fifth volume spacer. It's an EMTB, brand new, and has never been out because of this crap! It really gets your back up, lol! I've heard a lot of people running five volume spacers in the forks that are two times lighter than I am. It must be harsh as heck! I'm just getting back on a bike after 15 years. I had a bad accident on a DH bike one time, then life took over, but I'm back now, taking it easy to get into it right now, but this sag is annoying.
Glad to hear you are getting back into riding! Suspension setup is a little different on the EMTB from my personal testing. I rode a YT Decoy with max volume spacers in the fork and shock last season and it felt great ✌ Hope this helps!
Sag is controlled via the air spring pressure for air shocks and for coil springs via the coil weight which should be in your weight range (based on the bike suspension geometry, as you might need different spring weights or different frame suspension geometries for your weight) + a coil spring preload adjuster, which pretenses the spring to get the correct sag. Volume spacers only affect the sag in the sense that you will need to put a slightly different pressure in your shock than what is recommended in the default table of your shock/fork vendor, to obtain the same sag, as it reduces the amount of air available in the shock to act as a spring. In essence the only thing that adding volume spacers do is create a more progressive spring (the more the fork compresses the more it will oppose compression via the air spring), as opposed to a more linear feeling when no volume spacers are added (the same rate of compression is kept across the stroke). Keep in mind both of these are highly impacted on how open the compression dampener is, as if you start closing compression dampener you will also notice more progressive or linear stroke, depending on how the shock is tuned (shim stack configuration). So, if you cannot reach proper sag because your shock is at the maximum allowed pressure, you are probably too heavy and will need to upgrade to either a coil shock, or to a air shock that allows for higher pressures for your weight. Adding or removing spacers will just affect the progressiveness of your shock and create a slight offset of the pressures you need to put in your shock for your weight.
It was literally 2 weeks ago I found out that the manufacturer dictates your rear sag instead of just going with your basic 30% in the rear.. Santa Cruz recommends 21-24% sag on the V10 because of the leverage ratio and how the kinematics are supposed to work for your bike. lol... I always just went on 15-20F and 30R. I'm such a dummy =p
What matters is that you are always learning 💯 Finding what bike setup works best does not happen overnight! Thanks for watching the video 👊
@@PeterJamison I think one thing that isn't quite understood by most people is spring rate vs harshness. Some people think that increasing sag will make the bike feel more supple but in most cases this causes an assortment of issues including packing. Most of the time we need a higher spring rate to make the suspension more supple than the latter. I'm sure you'll go over that in the upcoming videos. Thanks for the clips Peter!
@@_Jake.From.Statefarm_ Definitely! It is all a balance, in particular, more sag with higher volume reduction can be very 'spikey' towards the end of the travel where increasing spring rate (with less volume reduction) with a lower sag number may actually work better for you and your bike. All takes time to play around with different setups to find what is best for you. 🤘
And was today I found out cheers lol I'm away to go check this for my new bike now! Can't get my sag set atoll it's annoying me abit now as can't get out on the damb thing! 7k sitting in the hall as a paper weight just now!
@AFV85 which bike did ya get?
No pump connection/disconnection is perfect, so you will always lose up to 3 PSI when connecting/disconnecting the fork/shock pump depending how good the quality of your fork connector is. Given that shocks require 100+ PSI the air loss dues to connection/disconnection is negligible (3% or less depending on the required pressure).
🤘🏼
Here is what I don't understand. Jordie always says start with sag and to run 15-20% on the fork for example. I generally find that if I run 15-20% that the fork is really harsh. I get this with all Fox forks, 36/38 etc. But you stated in your video that sag is important, but then recommend reducing pressure on the trail until you like how the fork feels. Yet if you do that, then check sag, you may be running 30% for example. I find that this always leads me to chasing my tail, because I've had some setups that made the trail feel like I was riding on a pillow, but then other times it beats me to death. Anyway, I just bought a super Z and with that fork I'm running about 88 PSI, and the recommended compression/rebound with two tokens and it feels incredible. For reference I'm also 175 lbs. Is the Super Z just better, or have I had some bunk forks from the factory? I wonder.
Interesting experience, thanks for sharing. Suspension feel will vary by the grade of the trail, which may be what you are experiencing here... steeper tracks weight the fork more and a more mellow track weights the shock more. Just some food for thought. Either way, glad you are having a good time on the super Z, it is an awesome fork!
Probably because the air transfer port is blocked with grease. Stops proper equalisation of the positive and negative chambers. Really common problem on fox forks. I had a fox 36 where this was a constant problem. Always felt harsh. RS Lyrik perform much better for me
Jordi works mainly with DH/Enduro riders. As the descent grade gets steeper, the fork sag gets less and the rear shock may be more. They also work with stack and bar height to reduce weight on the front. If you recall, setup between very steep tracks like Leogang is different than a track like Snowshoe. Mere mortals that spend more time on flat or much less gravity oriented would probably do better with 20-25% fork and 25-30% shock.
Rear sag is a measured % of the stroke length, not rear wheel travel. 30% of a 205x55mm shock (this is a really common size) is 16.5mm, vs 30% of 130mm rear wheel travel bike is 39mm, which would be almost 70% sag…
With rear shocks the larger # is the eye to eye, the smaller # is the stroke length. Eg, 205x55, 230x60, etc. Can also measure the stanchion minus a few mm’s.
Forks don’t have linkage, so yes just measure % of travel, eg 20% of a 150mm fork is 30mm. Personally I only really measure fork sag when setting up other peoples bikes or customer’s bikes. Usually 20-25% is a good starting point.
Yes, exactly, sorry for the confusion.
To be perfectly honest even for tire pressure I often do the "by the feel" adjustments not by manufacturer spec and then I start fiddling and all that good will goes out the window.
I need some discipline.
😂 Thanks for watching!
i run 10% sag front in my dh bike and it just feels right haha, more than that i ride slow and fell going otb
Glad you found what works best you 💯
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dude why is your camera do that I got sick watching it
Sorry to hear - what exactly is going on?
@@PeterJamisonI see it too, the background looks like it is moving back and forth like you’re on a boat. I think it’s a strange video stabilization artifact. For taking videos you might be better off setting the camera down rather than holding it. Otherwise good video and good info!
@@ShakaFPV Thanks for the feedback, yes, that is from the IBIS on the Canon R5. I have noticed that in the past, but you two are the first to mention anything here on the channel, thanks for letting me know and glad you enjoyed the video 💯
@@PeterJamisoni think your content is very good but you should work on getting some b-roll to spice up your videos! No insult but looking at you talking for 15 minutes is quite boring. Some clips of your bike or of riders shredding could make your videos easier to watch. +1 sub for the content
@@taylordarion3477 Thanks for the input, and glad to have you following along 🤙🏼
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