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Servicing my old Bird AM9 I went for a ride and was listening to an annoying creak for the whole time riding up. Trying to find it I finally undid the front shock bolt, the shock moved under it a bit, tightened it back up and all was quiet.
Since then I ALWAYS tighten shock bolts with the bike sat on the ground (just like I do with wheel axles, always tighten them witht he bike sitting on the ground).
I've been thinking about this as I just bought a Trek Session which runs a 72.5 stroke shock. I'm unsure if there is space as a full 29, I assume tyre to saddle is the clash, but I believe it you run mullet then you can run the shock at 75mm stroke.
I don't have the bike yet, but when I do I plan in getting a vorsprung Telum which I can change the stroke length in my own garage, I'll test it out but for sag I'll just use 72.5mm as the stroke number to work with.
75mm stroke with 27.5 rear works fine, no issues
Niche question: Are there any commercially available universal ISCG-mounted idlers that can be used to increase anti-squat?
Might be easier to just go for a smaller chainring (this will increase pedal kickback which the idler would not...). The limitation is the same as with an additional pulley, chainstay to chain clearance.
Rulezman from Italy was selling one for the banshee
That's the catch, that one DEcreases it, not INcrease it. To increase the AS you need to route the chain lower than stock vs. routing it higher to decrease AS (as Rulezman's solution does).
It's pretty sketchy, having a tall plate attached by short single shear bolts trying to support the tension of the chain, and ideally idlers need to be quite large in diameter to reduce wear and noise so I doubt its something you will see in large production. I would be extremely weary of using one
I have no idea how you'd have an idler with its resulting chain line being lower than the chainring. It isnt really something you can do without two chains and a lot of fucking around. It'd end up like the current two chains specialized proto.
I don't see how it's any different than the idlers that are currently used, but instead of the chain running over the top of the idler it would run underneath it. Obviously you would need a frame that allowed for something like this, and the performance might be not what most people are looking for, but theoretically I don't see how it's any different.
Thinking about it, does any kinematics (i.e. Linkage) Software even support this situation in the calculations? 🤔
Od course the Linkage can calculate this arrangement. I haven't follow the very last discussion but chain routed under the idler instead of over it (as is generally used) increases the required chain growth hence pedal kickback.
Well that certainly gives me pause...
Thanks all for your input.
Oh yeah. Duh.
Also took me a minute to realise the issue as the suspension cycled too- it would pull tighter on the chain, so really something like this needs to be mounted to the swingarm anyway, not iscg tabs
@CascadeComponents
Thanks for your response, it gave me plenty to think about. FWIW, I ended up ordering up one of your links mostly due to yolo and wanting to tinker. I do think that the additional chainstay length is going to be really nice as well, so I'm stoked to try it out.
To continue the conversation on my own issues/quest to mess with a perfectly good bike... As you may or may not have picked up, the bearings/hardware that my bike seems (maybe seemed) to be eating was the DU/Eyelet/Bearing hardware that is in the shock. The lower link bearings have always been fine, but my bike ate up 2 push spherical bearings alarmingly fast. They have since converted it to a standard DU bushing style hardware and it was fine after that. I have since been running a 24' float x2 and to answer the question posed by @TheSuspensionLabNZ that shock is running a rockshox 8x30 roller bearing with zero issues/complaints. Interestingly enough, to further what @TheSuspensionLabNZ suspected, Santacruz actually warrantied the first lower link my nomad6 shipped with as the tabs for the shock got bent inwards by 1mm in the process of trying to nail down this issue. We discovered this because the push spherical bearing would fit with their +/- end caps, but standard 8x30mm hardware would all of a sudden no longer fit. We mic'd the space between the tabs at `29mm iirc and inquired with SC and they elected to send a new link out. It's been fine since. I think I'll either run the 11.6 with a rockshox roller bearing or reach out to them and see if they can convert it for me at an agreeable sum of money.
Regarding topout, leverage rate and rebound. I think I somehow got incredibly unlucky with the topout thing. Push acknowledged that something had gone wrong with my 11.6 requiring some parts replacement and that was leading to the top out. It's a long story, but I had a super deluxe just freshly rebuilt with a new tractive tune when push released the 11.6 tune/configuration for the nomad 6. So I ended up with two freshly rebuilt and serviced coil shocks, within 2 weeks, for the same bike. Somehow, both ended up with topout at the recommended rebound settings. I chalked that up to very eery bad luck... but the initial slap of harshness on touchdown that I was experiencing with both, combined with the above mentioned shock hardware issue just kept getting in my head. I just so happen to do a lot of yanking up on crummy features with chundery landings with my local riding here in laguna, so I think my riding style and terrain was exacerbating it.
At any rate, Push and vorsprung both seemed to recommend a 475lb spring rate +/- for me (180lbs, 6'2" on an XL). Looking at the leverage ratio chart from the N6 cascade link landing page, it seems that stocking with that 475 rate as a starting point makes sense. I generally find that I need to run 25-50lbs more spring rate then most spring rate calculators out there. That was true of my v1 megatower, orbea rise (w/cc link and coil shock) and my transition relay. I'm not sure if that's because of my riding or what... Any comments on what you'd expect the starting/target spring rate to be for me on this setup?
In regards to spring rate, it depends on whether you run it in the short travel or long travel setting. Short travel would be 475 and long travel would be 525. Personally I'd split the difference and go with a 500.
When you said linkage side bearings I assumed you were talking about bearings in the link as opposed to the shock end so I did miss that. Spherical bearings are just another form of plain bearing, as they have no rolling elements. Usually they are PTFE lined to help with friction. Unfortunately bearings like that do not hold up will to fine particulate and/or water very well. They do isolate the shock from side loads, but bikes like the Nomad don't really side load shocks much so the benefit is kind of lost.
@ebruner sounds like you might need our(Push) warranty roller bearing kit for Santa Cruz & Forbidden bikes. The kit is a drop-in at home install and replaces the spherical with two roller bearings similar to Fox & RS. We ultimately determined the rotational frequency and aptitude in those two applications was not ideal for the spherical and they were better suited for a roller bearing. However, it sounds like we might have swapped eyelets to get you on the bushing as a stop-gap while we designed the roller bearing kit. You should chat with customer service as they will know the history and can recommend a warranty fix at no charge.
Putting this here because it's potentially kinematics related and you guys are smart:
I've got a 2024 Firebird with an EXT Storia v3 and it is the worst rear suspension I have felt in a long time. There's a lot to complain about (squeaks, rattles, harsh, slow) but I want to focus on how it doesn't have a very deep feel and how rough it is on repeated hits.
When using the full 65mm stroke orientation of the shock, with a non adjustable HBO, could the HBO be limiting my travel. As in, do they retune the HBO for a 65mm vs a 57.5 or does it kick in at the same depth of travel regardless?
Also, could that be compounded by the fairly progressive nature of the Firebird? I'm 150lbs and running a 300 pound spring at 33% sag. I've loved the feel of many Rockies which are usually more progressive.
To top it off, EXT seems to like their rebound really slow, potentially packing up my shock.
Could this all combine to have me just stuck in the middle of the travel, not recovering but not able to use more travel?
I don’t know how much the leverage has changed since 2022 but it sounds like you have a shock tune issue.
Have you opened the rebound all the way?
I had an issue with an EXT shock and it was very stiff shim stack/slow Reb. I sent it back twice for different tunes but still wasn’t happy so I sold it.
I’ve anecdotally also felt that the CNC shock body and large shock shaft added rigidity to the frame. I went back to DHX2 and found much more comfort in the shock construction and the tune.
Same as the 2022.
I'll try opening the rebound all the way again. The shock becomes unacceptably noisey with moderately quick rebound so I've not ridden much like that. The thing is, even in a parking lot test, the suspension just doesn't feel like it's very deep. I've had it retuned and put on a softer spring, it feels better but the issues I'm describing are from after the retune.
The thing is, in the parking lot test, it doesn't feel very deep either.
I have tracked down a dhx2 to try tomorrow.
300lb is extremely soft, i would suggest 350-375 on that frame - also are you calculating 33% sag over the 65mm or 57.5 stroke? You will want to keep the same mm of sag as you would with the 57.5 stroke.
Also the hbo travel is internally adjusted relative to the stroke of the shock so it will be engaging at the right point
I agree 33% at shock is too much. Stiffer spring and open your compression clickers to let the shock move.
Unfortunately you also might need to accept that you don’t like the tune/shock or that it doesn’t pair well with your bike. I think you know the feel you are looking for, just maybe the EXT doesn’t provide that for you.
I started with 350. That gave me 28% sag at the shock. Sag calculated on 65mm. 350 felt very harsh. The distributor/tuner and Bryn Atkinson recommended up to 35% sag on this bike. If I’m not bottoming out, what would too soft of a spring result in?
Good to know hbo is tuned specifically for the shock length.
@carlinojoevideo I’m fully willing to accept that I don’t like the tune because I think it feels like shit. I would sell this shock in a heart beat as I really dislike my experience with it but the X2 doesn’t make the bike feel amazing either. Perhaps it’s the bike. I have a bearing that is a little rough right out of the box which I’m trying to replace but I find it hard to believe that is the problem.
I was mainly curious about the specifics effects of my original question.
Sorry, super frustrating experience. I’m not looking to vent about it, just curious about specific aspects of suspension performance.
On the theme of learning, where else would you measure sag? At the wheel? How would this change things?
Another data point - I have a 2017/2018 (the 27.5 Firebird) with an EXT on it and at 185-190 pounds I'm using a 425 spring and I'm pretty happy with the setup.
I would expect that at 150 pounds you would be in the 375-400 ball park depending on how you ride and what you like in how the bike feels.
Why would you suggest setting it up with 24% sag if I’m looking for a more supple ride?
because your "midstroke" is likely a wall of progression too deep in the travel, going stiffer puts you in the more linear part of the curve, combined with open compression it could be your solution and a mistake many people make, a softer spring rate doesn't always equal a supple ride.
I’ve marked where 33-35% will be for sag in Red and 25% in blue. The farther down the leverage the stiffer the shock will be and the more force it will take to move at that point. It might not seem like a lot but at 33-35 it will take a lot force for the suspension to react.
You might have a shock tune that is just too stiff so you keep going down in spring rate. The answer might be softer tune and stiff spring. There’s not really an answer any of us can give you exactly because so much depends on rider style, speed, trail type and even dirt.
I think the leverage ratio looks decent so you should be able to get it to feel good. Sounds like some tuning is needed and help from someone who can get you in the right ballpark.
If the springs too soft it will feel sluggish, wallowy, lacking pop and and also lacking grip and sensitivity because you are too far in to the stroke where the spring rate at the wheel is stiffer. A spring that is too soft with a fast rebound tune can "feel" slower than a rate or 2 stiffer with a slower tune (to a point)
It is possible to have as shock set up too soft and still not bottom out - another reason why bottomouts are a misleading metric for tuning.
as for where to measure sag, you can only measure it with any reliability at the shock, but it is worth knowing that the wheel tracks differently depending on the bike. With 30% shock sag, shorter travel/less progressive bikes might use 25% of the wheel travel, but longer travel/progressive bikes (eg DH) could be at 35-40%, hence why some DH bikes are often set up with 15-20% sag at the shock since that probably translates to 30% at the wheel. The important thing is not to get too locked in to your sag percentage - its just a start point and if it feels too soft you need to go to a stiffer spring.
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