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Yeah thats pretty much what I was going to say!
When they say to start with "sag" I think they are just meaning to set the spring rate full stop, in whatever method so its at least in the ballpark. ie not just bolting it on with whatever spring or pressure it had in the box.
And I always like to work through spring rate first - find the point which is definitely too stiff and too soft and then work back in from there. Its amazing how often the "sag" can seem about right and not obviously too stiff or soft, but is actually a good chunk softer than what they end up settlign on.
Without spring rate set, the rest of the adjustments are fairly meaningless - compression might always feel too soft or rebound too slow no matter where you set it. Then I normally get rebound close-ish, then fine tune compression and then back to rebound. Thats a rough order of things, everyones a little different but I don't even think about the dials until I'm happy the spring rate is in the ballpark
After tyre pressure of course!
Do you piss on the general 25 to 30 percent sag in the rear (for pedalling performance) or do you fine tune the spring rate (in case of air shocks) with tokens after setting the general sag to the above window?
I've tried to avoid getting sucked into this conversation but I'll add my 2c worth:
Having a good initial spring rate (sag) is essential for the rest of the setup steps to proceed correctly for the average user. The sag IMO is not a be all and end all, but you need to be within +/- 5% of the correct spring rate for your weight as a starting point, as long as you are withing that area, the dials can compensate somewhat for the slight margin of error. From there on you need to adjust to your preferences, but at least if you have the sag in the ball park, the dials can't really mess it up too badly from there
The RS SDU is one of the most simple shocks to setup and get in a good place IMO, but more difficult to fine tune to really squeeze out those marginal gains.
You have to remember that the setup instructions in the manual are mostly catered to the beginner rider who really has no idea how suspension woks or how it SHOULD feel, so it is more about getting them to a decent starting place. They will likely never "tune" beyond the recommended settings and be just fine with that.
My recommendation would be to pull all of the volume spacers out and increase the spring rate (air pressure). That will give you more support and keep likely reduce harshness by keeping you out of the ramp up. Keeping the fork higher in travel also improves off the top feel since you are more often in the top of travel rather than bouncing off the progression.
You'll likely need to revisit damping settings too with the new air pressure.
So many factors influence correct spring rate for any given rider/terrain/bike combo, like steep or flat terrain, progressive or linear leverage rate, flat pedals or clips, long legs/short torso (rearward COG) or short legs/long torso (forward COG), preferred reach length relative to height (again, short reach/tall person will have a rearward COG, whereas long reach/short person will have a forward COG).
But I think 25-30% sag is a great starting point for all bikes. By always starting with 25 or 30% sag, over time you'll discover whether you're the sort of rider who consistently prefers more sag than recommended or less, which will also help when you get on a bike that's dramatically more or less progressive than what you're used to.
The order I'd recommend is: set sag, set LSR rebound by feel, set HSR rebound and compression clickers according to the manufacturers setup guide. If there isn't a setup guide for your fork or shock, I'd recommend setting compression knobs dead center to start, and set HSR proportionate to rider weight, aka if you're toward the lighter end of the spectrum, run less HSR and if you're towards the heavier end of the spectrum, run more HSR.
Once you've done that as your base setup, I would only mess with spring rate front and rear for A WHILE before messing too much with the knobs. If you make a big change to spring rate, you'll want to adjust rebound knobs to match, but otherwise I wouldn't turn to the compression knobs until you've done a lot of spring rate testing. I can't tell you how many times I've had "a fork tuning problem" that was actually a rear shock spring rate problem, or vice versa. Your front to rear weight balance is incredibly important for bike handling, and nothing affects that more than spring rate, even more than bike fit or cockpit setup, I think.
Depends on the type of bike, but without any other guidance I would start 30% sag and then tune from there based on feel. Like @notthatbryan mentioned I prefer to start with minimal tokens* and tune the air pressure like that, generally increasing pressure until you lose sensitivity or it isn't absorbing bumps. Then add tokens for the mid/end stroke ramp up if needed
Downhill bikes are usually 20-25% sag to start with, and some trail bikes can be up to 35%. I found an old post of mine recently where I made a large change in pressure on a trail bike but it only changed the sag about 1mm - it can be quite imprecise so I don't get too hung up on an exact value.
* - since air springs have the same volume regardless of fork travel, something like a 160mm Zeb normally needs at least 2 tokens to maintain a reasonable ramp up (ie otherwise the fork will behave like it has 30mm more travel when it gets to the end). A rule of thumb is each 10mm step you reduce a fork from its max, you add 1 spacer. Although the current 38mm forks are quite progressive so they often can do with 1 less than that again. This is just a starting point and people can go 1 or 2 tokens in either direction from there, but as a start I err on the side of less tokens
Yup this is a great method - the only thing extra I would add is maybe more of a technical/damper design quirk but if in doubt with HSR, go on the slower end of their range and just use the LSR to tune for you rebound feel. It normally has heaps of range and makes it much less confusing.
HSR adjusters are often extremely sensitive to tolerance so -4 on one damper could be the same as -6 on another, but that can normally be corrected with 1 click of LSR so its much easier to make sure its on the "slow" side to begin with at least. You can come back later and fine tune it when the rest is dialled in, but unless you have a dyno there isn't an easy way to know if your HSR is in the right spot or not
Thanks all! Sorry to suck you in @Sonofbovril2, I guess I have bogarted this thread a little bit. I like the style of more general discussions here vs MTBR's often hyper-specific threads, but I probably should have started a new one.
Since I'm kind of starting from scratch with the new shock tune, I'll probably pull the token from the fork for now (160mm Lyrik is at max travel), leave the 4 stock tokens in the shock, and start bracketing air pressures again with an eye towards f/r balance and bump absorption.
I've really enjoyed the in depth discussion about sag
Haha, not your conversation, just my own issues. Sorry if it came across like a grumpy old man 😂
No tokens always seems like the logical place to start for me. Don’t add them unless you find that you need them. I’m a big fan of the MRP ramp cartridge personally.
Okey people with knowledge!
A "funny" problem has occured on my Fox 38, perf. elite Grip2.
Over the weekend, the compression adjuster suddenly has no effect at all, the fork dives without damping, BUT! The rebound is now so slow that when is fully closed it uses 4-5 seconds to extend after compression, with 105PSI. Need to be almost fully open to have ok rebound speed.
Sooo, what has happened? I know it will need a service, but just curious what the problem can be.
Broken compression shim that's stuck in a position that is blocking some or all of the rebound ports in the piston?
Just a wild guess.
This was a good tuning suggestion. I upped the spring rate, LSC, ands HBO and that helped a lot. I still want more HSC but the HSC knob feels terrible so I’ve just been leaving it open.
34 vs 36 forks for your next trail bike? We thought this would be an interesting topic to explore, so we did: https://www.vitalmtb.com/videos/member/trail-bike-fork-selection-34-v-36.
Not sure if this has been discussed in any other thread, but figured this might be good place to get some discussion/insight to my question. In other coil shock applications (cars etc), coil binding is often dealt with by using a flat axial needle roller bearing. I was thinking about testing this on my bike, but figured maybe someone has experience or have good reasons why this would not work. Opinions?
I do understand that mud can easily get in and cleaning and care must be done often.
With MTB's using very high spring rates, using a bearing definitely offers a performance advantage:
i remember thrust bearings were popular for a hot minute maybe 10 years ago now? I actually still have one in my old 40 coil. seems like this solution serves the same purpose but with less complexity.
edit - googled to confirm, sprindex includes a similar delrin adapter to account for spring rotation too. they sell them standalone as well.
Is the push one delrin also or something more fancy (ertalyte, nyloil etc)?
Update question for my Sentinel Saga:
What suspension changes should be made for transition seasons (pun not intended) when it starts to get colder? I thought I was pretty close to having things dialed, but took a week off while it poured rain, and yesterday my suspension felt extremely firm. I tried speeding up the rebound to increase oil flow but that just made it feel like I was being bucked around.
Also, if the Sentinel Saga should make its way to another thread, let me know. It’s just my vehicle for learning about suspension right now.
The easy fix for wet conditions is to wind back compression damping, since your not going as fast you need less damping, and it'll reduce the risk of a slide out from loading the bike too much in a corner (you can only load the bike as hard as the compression+spring force push back at you).
A more complete setup you would also change spring rates front and rear, and therefore rebound too, a bit more sag in the wet can be helpful for some, but it means having a totally different setup.
Easy fix is just winding out LSC a a bit and maybe a tiny bit of HSC front and rear.
lower your tyre pressure 2psi or so
It is not Delrin, and is in fact something very fancy. The red material we use is fundamentally a bronze-filled PTFE product that is designed to act as a bearing, supporting very high loads while having an extremely low coefficient of friction. We machine the material in-house very carefully, as the material alone costs us $278 per foot! 😒
Really cool. I have to ask, is this materially better than two delrins stacked ontop of each other? We do this all the time in the snowmobile (CVT clutch) world with solid results.
Delrin also has a very low coefficient of friction. The red bearing material we use offers better long-term wear and durability, especially in harsher environments.
I like the simplicity in this solution (albeit being expensive material in the first place) and keen to buy a couple of "washers". I could not find it on your website. is it only for shock buyers?
I might add that I went deep into the rabbit hole of plastics yesterday and it is suprising to me that we don't see more use of "fancy" plastics in these kind of applications.
FWIW, if you get measurements you can very likely source what you want online (delrin, not Darren's more fancy version) for a few bucks. Cheap solution if you want to functionally add something similar.
Fwiw, it's likely cheaper to just buy a sprindex and use their bearing/spring adapters to accomplish the same thing. I have used the 11.6 bearings listed above and I can tell you that the sprindex products are not anywhere near as sophisticated... but they do work.
I'd wager you could probably source something along those lines from McMaster or Grainger too. Dims might not be optimized without some dremeling
Appreciate all tips. Still a bit surprised we don’t see more off the shelf options if coil bind up is happening on all coil shocks
What are folks’ opinion on Shockwiz? I’m thinking of renting one to try out since I’m just about at my wits end with the Sentinel.
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