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The compression ratio as measured on an installed shock inherently factors in the negative chamber.
Like you said, it roughly gives an idea of average spring curve in so far as a start and finish. You can take additional measurements at given shaft extensions to plot more points, but it all seems like a faff anyways.
My own opinion, but I feel the best air spring is a nice linear coil spring.
I didn't say it roughly gives. I said it WOULD roughly give, IF... But said if is not true in modern air shocks.
Hey,
How did it go for you? What did you do in the end? Let us know
Cheers
Haven't gotten a chance yet - my buddy just ordered the parts yesterday. Hoping to get it done in the next week or two. I'll post back after we get it installed and the kid gets some ride time on it.
Friend here. This was for my son. We've spent more time bracketing. Swapped the rear shock to Vivid etc.
I got a 3.1 upgrade kit. I'd appreciate it if you could give us your suggestions based on the updated setup.
Rider: 9 years old: 142cm / 4'8"
Riding Style: https://www.instagram.com/reel/DOFnQTdjpPm/?igsh=NTc4MTIwNjQ2YQ%3D%3D
Rider Weight: 36kg / 80lbs with full riding gear
Bike: 2024 Santa Cruz Bronson V4.1 XS (14.35kg / 31.6 lbs)
Shock: Vivid RS-VIIVD-ULT-C1
- Rebound Tune: R25
- Compression Tune: C34
- Volume Reducer: 1 Token
- PSI: 72psi
- Rebound: fully Open
- HSC: 0
- LSC: 0
- HBO: -1
He uses almost all travel without a harsh bottom out. Rebound could be faster, but it's not excessively slow like he was on stock Super Deluxe. He struggled to use full travel, about 80% ish, with Super Deluxe with 0 tokens. He was asking to run higher PSI to get more pop but it makes it even harder to use more travel. Everything was fixed after we swapped it to Vivid.
So his fork is the next thing to be dialed.
Current Fork Setup
Fork: Lyrik Select+ FS-LYRK-SELP-D1
Damper: Charger 3 RC2
Token: Installed MRP Noken
PSI: 30psi
Rebound: Fully open
HSC: -2
LSC:- 7 (Fully open)
He started using a similar fork travel as I do after installing MRP Noken, however, the rebound (especially after the deep compression) seems slow.
We got the 3.1 upgrade kit. I'd appreciate if you could share some recommended shim setup for him.
I just want to make sure we don't make it too light for what he does now and what he'll do in the future.
He rides at the park and likes to jump and hit drops, etc.
The picture is after we hit the local trails at the speed. The trail doesn't have huge drops but has some jumps, step down, and high compression berms.
The memory of my 8 year old self is painfully jealous of your 8 year old son.
Ok a few thoughts -
Friction your biggest enememy, especially at this weight range and will add a significant amount of force slowing down rebound and preventing it from getting fulll travel. Things like having the bushings sized go a long way here, also make sure the air spring is lubricated and no one wiped all the grease out.
In saying that, dont look at getting full travel as a target - once things are running properly you might also start using more stroke but its not an issue to normally use 80-90% . All set ups need some kind of compromise and personally this is the first thing i would let go of.
The spring might be a little soft at 30psi, potentially 35 would be more inline with pressures at higher weights.
The slow rebound is probably a combination of low pressure and friction - you can also try very light oil with the tune from above, the stock is 7wt but I would at least use the rs/maxima 3wt or even something like the fox 1.5wt dropper fluid.
That tune should be ok up to around 45-50kg, maybe a little more but kids grow fast and will often need a new tune very soon anyway
Thank you for your insights. Yes, he shouldn't use full fork travel at the local trail without huge drops. So in terms of travel usage, it looks OK for now.
I got a SKF seal, and my friend plans to burnish the fork to reduce friction.
I'm slightly concerned about running a super light compression tune, as I heard Jordi at Fox say that compression is more terrain- and rider skill/style-dependent than weight-dependent, unlike rebound. I just want to make sure he'll have enough compression and rebound to dial in for bike park riding, like big drops.
Should we run your suggested tune with 3wt oil, or should we run a stock-lighter tune with 3wt oil?
Thank you so much for your knowledge and insights.
Reference:
Max suggested height is 5'1" and the average weight is around 46 - 56 kg.
I'll try to keep it general to stay relevant to the thread, -
Even using that much travel on drops might be fine, or at least don't rule out running slightly higher pressure still.
Friction & spring are the 2 most important things (after tyres) so don't stress about the damper until those are fully optimised. If there is too much friction or the spring is too soft then there won't be much difference between those 2 tunes
I can't speak for Jordi but my thoughts would be a) the Charger 3.1 is very different to grip 2 or X2 in terms of damping levels, so while a grip2 damper is fine for very light riders, the 3.1 does have limits below a certain weight so is something worth tuning for light riders. b) the difference in optimum damping levels is quite small between something like a 60kg adult and 90kg adult so preference or speed is as big of a factor as weight. eg a top elite rider will have a stiffer spring and slightly more damping which will combine to feel very stiff to an average rider but each variable is only slightly higher on its own. But when you get down to light riders the proportion of friction is huge - ie there could be 10kg of total friction in a fork which is important but less noticeable to a 90kg rider than a 40kg rider. Friction is a form of damping so we often need to reduce compression damping more than what would theoretically be ideal to compensate for that.
Each production damper from brands like Fox and Rockshox have certain compromises - they will almost never be perfect for anyone so you will be trading something off no matter what you do with it. It's tough to predict the perfect setting for anyone so you often need a few attempts, therefore my suggestions, depending on time/patience/budget and what you have available locally would be -
Start by dialling in the chassis and air spring only - if it still doesn't feel right then try another damper tune
Do the chassis & air spring along with the soft tune (removing preload) - you might need to add some damping back but its basically a coin toss as to which you do first. I usually prefer to make a huge change first then dial it back so by going to a very soft tune the outcomes are either
a) it feels great
b) it still feels too stiff which means there is either still friction or you have reached the limit of the fork
c) it is too soft and you can step back to halfway between and it should be pretty good. If you only go to the slightly lighter tune to begin with and it feels better, but could still be improved you actually don't know if you should go softer or firmer from there.
last option - give a bunch of money to a good suspension shop to do it all properly and can take the time to work out the best options. If you are doing it yourself theres not really a quick way to the best setting so there will always be some trial and error. Normally the exact tune I would personally install also depends on me doing the rest of the fork too - everyone works different so if I knew the chassis was perfectly optimised (maybe using a coil spring too) then I would potentially use a bit more damping, but if in doubt I would oitherwise err on the side of slightly softer first.
Here's a dumb question: How difficult, expensive, or dangerous would it be to use a machine (I assume a lathe) to cut off material from a coil spring and tune spring rate?
I remember seeing this once from (I think a Kiwi) racer or tuning shop in a WC DH bike check, where a stock steel coil had a constant diameter of the coil shaved off to dial in an exact spring rate that was in between the manufacturer's 50-pound range.
This sort of thing could be helpful for a super light 80-pound rider who's looking to reduce friction (i.e. using a Smashpot in a Zeb where you might need to go lower than the lowest 25 pound spring), or for someone who buys a Marzocchi coil sprung Z1 that only offers four spring rates, creating big gaps between spring rates.
I imagine you'd need to insert something in the center of the spring to perfectly center it and stabilize it on the lathe, but once you're centered and stabilized... start shaving away, amiright?
Not an engineer, but my gut tells me that changing the shape of the coil rod from a circle to a clipped circle feels sketchy. I mean, you're probably not actually talking about taking much structural material off, but you're also creating a less snug fit from the catch plates.
I think a more practical way to achieve what you're looking for would be to have a suspension shop with a dyno test a bunch of springs and label them with their actual spring rate. There's enough variation in them that I'm sure you could find one with the right spring rate. I've heard that some of the WC teams (or RS/Fox racer support) do the same thing.
I had this exact idea years ago, to attempt to replace dual stage springs on side by sides.
The issue is you have to have the spring machined along its entire length. If you reduce the spring rate on just part of the spring, that part will compress until it bottoms before the rest of the spring will. Unless you had a progressively wound coil, the coils are too spaced out to bottom enough to push the load to thicker parts of the spring. And I assume you would have to re-heat treat the entire thing and repaint the entire thing too.
I wish I could find the example online again, but what you're describing is exactly what this athlete, team, or tuner did. It was a rear coil with an even amount of material trimmed off every coil for the length of the spring.
I'm not an engineer, but I share @AndehM's concern that this could do really bad things to the integrity of a spring... but I'm not an engineer, so maybe it doesn't?
Difficult: No. Dangerous: No. Expensive: Very. Machining it would require some custom jaws to clamp outward on the ID of the spring. You could then run passes along the outside of the spring to remove material. That would be expensive because of tooling and just paying someone to work it all out. The equation for the spring rate of a spring with a constant circular cross section is (G*d^4)/(8*n*D^3) where G is the modulus of rigidity, d is the wire diameter, n is the number of coils, and D is the mean diameter of the spring ((OD+ID)/2)). Of all the components of that equation, the number of coils is the easiest to modify. This is exactly what Sprindex does. Alternatively, since typical spring rate tolerance is +/- 10%, you could buy a bunch of springs and measure their rates until you find one that's right.
In theory it can work if done properly but I've come across fork springs where someone has attempted this and it always looked pretty horrific so put me off the idea....one of those things where the only guy I've heard try it isn't someone I look to for advice....and the effort it would take outweighs the benefit IMO. Spring steel is pretty hard so much be a nightmare to fixture and lathe down the OD. A 25lb smashpot should be ok down to 35kg/...pounds and below that it gets in to the point where a softer spring would only make a difference if you already had the tyres and friction perfectly optimised. Did I mention tyres already? Light casings and low pressure on lightweight rims with adequate width (I don't know the ideal width at that weight to be honest, just don't go toooo skinny for the sake of weight) always have a much bigger impact than anything suspension related. And then if I still wanted a softer spring I would either get a custom one made (lots of places can do it....costs a bit more than you would expect but its still easier and neater than the other option) or it probably wouldn't take much work to adapt a smashpot to use a second spring in the shorter travel configuration to reduce the overall rate. Kinda like the existing 2-stage spring they use for the DH cartridge but it might need custom spacers to work in a shorter setting
Lots of folks around here discussing shocks with the most capability and more features and more adjustments. All good. If I had the trails to justify it, I'd be pursuing that version of awesome as well!
But I live in the US Plains. Most of our trails are decades-old XC-style trails that I try to ride as hard and fast as I can for funsies rather than riding efficiently for Strava results. I'm always racing myself so I'm not trying to go slow - I enjoy the pursuit of improvement - but I'm trying to go as fast as I can while having fun and looking for ways to spend more time in the air or two-wheel drifting, etc.. One of those ways I have fun is by going on 2-to-3 hour rides (or more if I have time) where nutrition/hydration start to become a big concern that needs attention
Additionally, I sweat a lot and it's super salty turning that nutrition/hydration big concern needing attention into a huge potential problem that requires action.
My frame right now can only fit a 450ml bottle (that I fill with electrolyte/carb mix while also carrying a hydration pack of clean water). I'm considering going from a Super Deluxe Ultimate to a Deluxe Ultimate (or equivalent) on my 120mm-travel frame in order to make room for a larger bottle. Like I said, the most I can get it right now is a 450ml Fidlock. If my SDU didn't have its piggyback I could fit the 590ml Fidlock or something possibly larger. Increasing my potential in-bottle nutrition capacity by 33% would be awesome.
What would I be giving up by going from Super Deluxe Ultimate to Deluxe Ultimate?
What other shocks in that compact, in-line size should I be considering? Is one a stand-out winner in the 190x45 size?
Is it necessary to match your fork and shock? I've considered a Fox Float or an Öhlins TXC2Air but worried either would function in a way that would make a bad pairing with my current 140mm Pike Ultimate w/Charger 3.1.
I appreciate any info/thoughts/opinions/experiences you all can share!
I've done similar to get the right length coil spring for the DIY coil kit I made for a RS Revelation fork. But I was buying lighter springs and trimming them to length, closing the end then facing the closed end.
https://www.instagram.com/p/Ck0ChBIhA46AKRBQQ9IYz4gqNb_lM-hHal3LZc0/?igsh=czI1Y2FrdmJnMnAw
Carbs in the bladder? Just flush it out and chuck it in a freezer. If you keep up with the cleaning, it will last years without getting moldy. I've ran sugar in my bladder backpack for over 15 years now. Ideally the bladder will open up to enable turning it inside out and clean it properly once in a while (after a riding trip where a freezer is not available for example). Also, I had the exact same problem on the old bike and I just moved the bottle cage with a adaptor to make a 600ml bottle fit.
Sorry for the off topic...
As for taking off the outer diameter of the spring, what about grinding it off? Wouldn't a machine that grinds rods to a given dimension (centerless OD grinding machine) work for this?
What kind of frame is it? You would mostly lose some performance in the medium-to-big bumps where the damping isn't quite able to control those faster impacts, as well as maybe a little less grip. The deluxe ultimate isn't super common aftermarket so I haven't seen/heard much real feedback on it though
I've always been a fan of the cane creek inline - damping is probably better for aggressive riding than something like a super deluxe but in a smaller package, so were always great upgrade options. I haven't sold as many in recent years though, I think because they don't suit longer travel bikes or anything with a clevis mount (which is a lot), plus they went up quite a bit in price. No experience with the ohlins sorry
Is the riding like the Maah Daah Hey trail there? I remember that doing those 100 miles on a burly 170/160mm bike with a CCDBA wasn't optimal, and that water management was a major PITA indeed. I'd get as many strap-on water bottles as possible if I were to do it again.
Yeah, Maah Daah Hey is a really good average of the trails we have. There’s some interesting singletrack, some flat, but nothing too technical out on the MDH.
Much of the stuff locally is more technical and faster than the MDH but there’s also plenty that’s just like it.
The bike is a Yeti SB120 Lunch Ride, SusLabNZ.
(Edited to add “Lunch Ride” and a little clarity above)
You will be giving up nothing* by switching to a non-piggyback Deluxe Ultimate. It's a great shock and can take a beating. Honestly, super impressive for what it is. And back in the day we had to race multi-thousand foot enduro track on air shocks before they even had reservoirs. They were mostly fine. I think the bigger shocks only come into play when you're hitting repeated big nasty impacts and generating a lot of heat over and over and over again. The only time I really hated that non-piggyback shock was when I took it into the Whistler Bike Park. That sucked.
*provided you get a new shock with the correct tune for your bike, ideally the same one your current shock came with. If you don't get exactly the right tune, all bets are off.
I second this. I believe resident suspension engineer @Dave_Camp was the engineer on this one. I tested a pre-production unit at some point and liked it a lot as long as the descent was not crazy long. I often ran the rebound a touch slower than usual to account for fade, since the shock would speed up as it got hot (less oil...but it worked great).
One other note: it might have been the most durable shock I ever owned. I still have it, never rebuilt, and it has served as a backup on a number of frames.
I'm considering one of those myself (a deluxe ultimate) to have as a spare, or to become my main shock even, depending on the performance. Where I live is very often muddy, winch and plummet style riding, I just started to build an Airdrop Filter MX (140mm travel). I order the frame with a vivid ultimate, the intention being to test the xtremes, although I don't think I will go coil (it's a chunky boi alredy for what it is) I might if I find something cheap (the spare of the spare...)
One virtue I find of the deluxe is that it looks fairly simple for a DIYer with a little bit of experience with forks, to dip his toes into servicing rear shock dampers
For DIY servicing it's hard to imagine it gets any simpler than a Super Deluxe Ultimate. Especially so for the B generation of the SDLX. The non Super platform of the Deluxe is a smidge more involved and requires a few more tools to get the job done (IFP positioning and bleeding the damper and the like).
Warranty % wise Deluxe R and super deluxe R are the most durable shocks in the RS lineup.
Less parts, less seals and the designs haven’t changed much in probably 6-8 years at this point.
The inline air shocks are great to have as a backup especially because they usually cost less than $100 used.
Update: We decided to do the following
1. SKF Seals
2. Burnishing
3. 7WT to 3WT oil
4. Light Rebound Setting
5. Upgraded to Charger 3.1 from Charger 3
His immediate reaction was "Much better. Easier to jump".
We are still in the process of fine-tuning, but we are currently at
Model: Lyrik Select 150mm
Spring: 35psi with Noken (Unchanged)
Rebound: 1 click from Open
HSC: 0
LSC: -3
We started as HSC0 and LSC0. He couldn't tell the difference between HSC 0 vs HSC -2 when LSC is 0; however, he clearly didn't like it when we tried HSC -2 and LSC -3. He said the fork is too divey and harder to jump.
We tried HSC 0 and LSC -3 and he said he likes it better than HSC 0 and LSC 0.
We only did six laps. It's not really "dialed" yet, but I'm getting a sense that he's in the adjustable range.
SKF and Burnishing did a lot. Woody feel disappeared, and it became objectively smooth off the top.
He finally said he likes the new bike better than his old bike with Manitou JUNIT.
Thank you for your guidance.
I did the super slow-mo on this video. You can see the suspension movement. Unfortunately, I didn't do super slow before the custom tune.
https://youtube.com/shorts/ULRlQ75GE5I
*This is not our bracketing trail. He likes to jump after the bracketing session.
In product news today, Öhlins just dropped a coil kit for their new RXF36 m.3 fork (the kit is not backwards compatible with m.2 and older):
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Earlier this year we introduced the RXF36 m.3 fork, and now the time has come to launch the new coil version and coil kit. With a lighter chassis, a new stanchion surface treatment, and enhanced sensitivity and comfort, riders can enjoy the predictable and plush feel of a coil spring along with the excellent traction and control it delivers. Installation is very easy and only requires the 18867-01 coil kit tool. As with our other coil kits, it is possible to switch freely between coil and air springs.
The RXF36 m.3 Coil brings the unmatched sensitivity and comfort of a coil spring to the most capable trail fork in the Öhlins lineup. Delivering a supremely supple ride with predictable support, it is built for riders who want maximum control and confidence on the roughest trails.
The coil spring system delivers consistent performance throughout the entire stroke, giving the rider a planted and predictable feel in demanding terrain. Thanks to its cartridge based spring design, riders can easily switch between coil and air to fine tune the fork’s character for different trails and riding preferences.
The new coil system is not backwards compatible with the RXF36 m.2 or earlier versions because the chassis was reworked between the m.2 and m.3 generations to reduce weight and increase bushing overlap.
Weight of the coil kit is 120 g, and the springs range from 158 to 313 g. For comparison, a 160 mm air spring weighs 186 g. The total weight of the RXF36 m.3 Coil with the lightest spring is 2142 g.
All parts can now be ordered and are in stock.
The RXF36 m.2 coil I had is one of the best forks I've had, on par with my Intend. Really glad to see it make a return.
I've heard the Ohlins coil setup seals off the lower legs to effectively create an air chamber using the lowers. This would allow the lowers to function as an additional air spring to provide some bottom out support. Does anyone have any knowledge or experience with this? I've thought about getting the coil spring for use on my DH38.
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