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I had typed out a big post to this thread... and somehow hit refresh and lost it. So I'm going give the abbreviated version...
I have been testing a 170mm push 9.1 (v1 with the air hbo) for the last week and have 4 rides on it. I have been testing it on my SC bullit so that I could get a lot of descending in on it.
Here's the short summary:
Spring Rate: I'm 175lbs running a green spring (50lb) with 40psi in the air bottom out. I'm technically on the stiff side as the green spring spans 185-210. Despite that, I had several HUGE bottom out events with very loud metal on metal noises. I've run into this before with acs3 kits where I have to run 1-2 springs higher then I would run on a smashpot and will still have hard bottom outs. For example, I have two forks with smashpots, with 45lb and 50lb rates and am able to use the hbo to control bottom out events and rarely experience harsh or audible bottom outs. I believe that pushes air plunger bottom out system is simply not up to the task, so it's good that they are switching to a hydraulic setup. I also feel like push is using a bit too much spring pre-load in general as the bike/fork does not settle into it's travel under it's own weight. My experience with coil forks and proper pre-load is that when setup right, the fork will sit 2-3mm into it's travel... I tried multiple springs with this 9.1 and it did not do that with the blue/green or black springs.
Damping: There is enough damping force available from the damper where I don't feel that anyone will be wanting for additional damping... That being said, similarly to the hc97 in the past, I do find that there is a theme of more harshness then there needs to be for the requested level of support. I find that if I try to unwind LSC or HSC independently, that the harshness will go away, but not until there is no where near enough support from the damper. Overall, I think the damper is good, better then a grip 2 vvc, better then an hc97 charger 2.1... but I'm not sure it's better for me then say a grip x2 or a mrp lift damper.
Chassis: This is the biggest point of concern for me... I have never, in my life, struggled to hold a line or end up on the trail where I planned to end up like I do with this fork on my bike. I can feel some of the advantages that are lauded with USD forks like less bind when the fork is loaded up on the brakes and the right mix of being active, but maintaining geometry in those circumstances. However, there is a noticeable lack of accuracy out of the front end of the bike. It was honestly so bad that I actually tried two separate front wheels (reserve HD/AL with dt350 front hub and a Reserve 30 Carbon with 1/1 front hub). It was slightly better with the 1/1 hub and the carbon front wheel, but still completely un-acceptable from my pov. To further that point, I can visually see the front wheel turn towards the left when I hit the front brake. In addition, if I lean the bike over turning to the left and stab the brakes, I can not only feel the side knobs change how they are digging into the ground/pavement/dirt but I can hear the sound the tire is making change. This is something that is hard to quantify, as it's hard to separate what you think you're feeling vs what you are... but the bike is noticeably harder for me to slice through janky off camper rock moves, large features with big compressions and any chunky feature that has direction changes in it.
I did notice that the fork seems to perform better when you have tons of weight in your hands all the time. I'm for the most part, a weight the front of the bike with my feet rider, with select inputs of heavy hands on the bars to get the bike through sections. The only way I could get this thing to feel better, was to constantly have what felt like a ton of weight in my hands all the time. It did not solve the above mentioned in-accuracy of the front wheel in technical sections... but it starts to get the fork to feel closer to how I'm assuming it was intended to feel.
When going in a straight line and not braking, the fork does have some amount of magic sauce going on. The problem for me is that once I'm braking heavily with the front brake, steering/leaning the bike, or guiding it through technical sections... that magic sauce immediately dissapears and I'm left with a question machine of where the front end of the bike is going to end up.
Other notable things:
-This particular fork weeps oil from under the crown on the daper side of the fork. This is oil that is coming out of the bleeder assembly.
-There is always air build up in damper side fork leg for whatever reason. For what it's worth, I am continually either starting or descending into sea level (50-100') and climbing to 1,000-1,500. I'm not sure if that's playing into this or not... but it's strange.
-The brake adapter setup is fiddley and I would have much preferred a standard 180mm post mount. Instead, they use these individual spacers and their proprietary post mount setup. These are a bit of a pain to deal with, and if you were to lose one, you're completely screwed.
-The fender... is not so great and needs more development.
-There is no way to deal with this thing without needing a torque wrench most of the times you were to touch it. The axle mount definitely needs one, changing springs needs one to deal with the lugs... Not a huge deal... but it's notably annoying.
-The custom pin socket for taking out the air (soon to be hydro) bump stop is fiddly, easy to have walk out on you and annoying.
-The damper is noisy but not annoyingly so and it's not a sound that I find displeasing. It's got that smooth, non cavitation sounding squelch to it that reminds you it's doing work. It's not a silent fork however... I didn't grease the spring enough during one spring swap, and I was left with some clanking and clicking.
Overall, It's a decent product. I do not think I like it as much as a zeb/38 with a smashpot and grip x2 or mrp lift damper. I do not find the chassis to magical or significantly better then a zeb/38 with the bushings checked and clearanced with a .07 or .1 die. I am thankful that I got the chance to try this fork out without putting my hard earned money down... I would be immensely bummed had I purchased this fork. I have no doubt that the support from push and more time on it would help it get to a place where I would be happier with it... but the gap between where it is now, and what I'm looking for is wide enough that I don't think it would ever match my expectations for a 2k+ fork. I prefer the 38 stanchion forks that I currently have in my fleet over this product.
Next I'll be putting my 170mm smashpot, zeb, mrp lift damper fork back on this bike so that I can fall back and validate my impressions of the 9.1. I'll be demo'ing a fox podium within the next 2 weeks so that I can give my impressions on that and compare it to the 9.1
A couple of notes to consider.
Spring Rate. Yes, you're in the camp of riders that we developed the Sub Chamber system for. The V2 Sub Chamber is 100% backwards compatible with that fork.
Chassis. This is a tricky one as the the front hub plays a significant role in how the chassis performs. This is why there's such a broad range of rider feedback in regards to stiffness with inverted forks. My guess is that FOX didn't want to roll the dice with this variance, which is why they committed solely to the 20mmx 110 boost configuration. Our recommended hubs include Chris King, I9 Hydra, and Hope Pro. These hubs provide large and robust bearing interfaces, as well as providing options for Torque Cap hub end caps for more aggressive riders. In the case where you're on a full-power E-MTB I would recommend Torque Caps with a more robust hub to get you the desired stiffness. Unfortunately, the I9 1/1 hubs don't utilize a compatible Torque Cap.
So, why not just og 20mm? We can, but then riders have to get a new wheel, or at least a front hub and relace. We opted to build something around stock wheel compatibility. With that in mind, a lighter rider on a traditional MTB with that same fork and wheel setup that you're running may have a completely different experience. I have ridden both the DT hubs, as well as the I9 1/1 hubs with our fork, and they would rank at the lower end of the spectrum as far a support and stiffness go with our NINE ONE. The DT hubs IMO require Torque Caps to meet the minimum performance requirement, and the I9 1/1 would most likely be better if they offered a compatible Torque Cap end cap. I actually am prototyping some 1/1 end caps this week to have a look.
Darren
Interesting timing as I have been going through some hub/axle stuff as well.
Fully Floating System
What is found on inverted dirt bike forks; the fork axle can pass competently through the non-disk fork lug, and the hub end cap does not make contact with the ND fork lug. When the axle is tightened, the hub is pulled against the disk side fork lug, just like the Cannondale Lefty. Hub width has no effect on chassis alignment.
Non-Floating System
A system where the fork axle bottoms out on the outside of the fork lug and squeezes the hub between the fork legs. Maximum pressure and contact with the hub end caps, larger end caps such as Torque caps can make a difference in system stiffness (**see note below). Hub width (wider or narrower) can have an affect on chassis alignment as the fork legs can be splayed in or out.
"Partially" Floating System
The fork axle can pass through the non-disk lug, but the hub end cap has contact with the ND lug as well. If the hub is too wide, it can splay the legs outward and cause chassis alignment issues.
For fully floating and partially floating systems, the disk side hub end cap can have a notable effect on stiffness. The non-disk side has little to no contact with the fork lug and therefore the diameter of the end cap will not really effect system stiffness. On the 9.1 there is a small lip on the fork lug that the end cap rests against, but the majority of the stiffness improvement seen with Torque caps come from the larger contact area between hub/fork lug when tightened by the axle.(**see note below) There is no force pushing the ND end cap against the fork lug like there is is a non-floating system.
The I9 1-1 Torque end cap does not work with the PUSH 9.1 as the fork axle simple goes inside of it and cannot tighten the hub to the disk side lug. There is nothing for the axle to push on.
However, as I believe the ND side end cap does not has much (if any) effect on system stiffness for the PUSH 9.1, the end cap diameter is not as significant and there is no advantage to using a large Torque size end cap on that side. You can simply use the standard I9 1-1 end cap on the ND side, and use the Torque cap on the disk side where the larger diameter can improve system stiffness.
If PUSH has data that contradicts my thinking, or has tested the I9 1-1 "hybrid" end cap setup I run with this fork, I would love to see it along with pics of the testing setup, etc.
I am a huge fan of testing and data collection, but just saying that A is better than B without actual numbers and information to back it up is not very useful. Saying that, see my note below as I don't want to be a hypocrite. If I still had access to that information, I would provide it.
** Although I don't have numbers or pics of the testing setup, I was involved with testing Torque caps when RS came out with them 15+ years ago. It was around the start of the switch from QR to 15mm front axles, and we tested Torque caps on a open dropout fork (using a 9mm DT RWS thru axle) and compared data to the same fork that used the new 15mm thru axle (with standard size end caps). The forks were mounted to a steel test table and weight was applied to create a twisting force and deflection measured.
The Torque cap/9mm QR setup was stiffer torsionally than the 15mm axle fork. This was attributed to the larger contact area the torque caps had with the dropouts on the QR fork. This was all done in the Specialized test lab and setup by test engineers.
That's a pretty damn informative post, thanks. I only know just enough to be dangerous here... so please bear with me.
Question, I have to assume that there is an impact to stiffness based on how the front hub axle/end cap interface works? I've long thought that the end cap design of the dt350 is a standout weak point of the overall hub design. It seems like the 350 end cap/axle design is based on some baseline amount clamping pressure like a QR style axle would provide.
I've looked at a few other front hub designs, and there does seem to be some variation in how much the front axle protrudes past the face of the hub bearing, and into the end cap. In contrast, the i9 1/1 hubs, the end caps have shoulders that protrude into the axle, opposite what the oneup hubs, dt 350s & i9 Hydra hubs are doing. I have to assume that this aspect of the hub/end cap interface has an impact on stiffness when used in an USD fork. So, which standard would technically be optimum for this type of usage where the front hub axle/end cap configuration becomes a significant factor in front end performance?
Lastly, in my case what was most noticeable was a torsional stiffness issue. I had never really considered that torque caps would be beneficial in that way. Is it the total surface area of the face of the end cap to the face of the fork dropout that is contributing to this or is the lip of the dropout that makes contact with part of the circumference of the end cap?
I do understand how the torque caps can be a contributing factor in fork stiffness... but I have to admit that I have ridden a torque cap fork with standard, non-torque cap end caps for a ride or two and it was not immediately obvious and wasn't so impactful that I would discern it quickly. In contrast, what I was feeling in front in my trial of the 9.1 was immediately significant.
I think these USD forks are going to highlight a need for a re-design and re-think of the front hub/axle/end cap interface. It seems that we've been going along fat, dumb and happy without much innovation or re-evaluation on this part of the bike... and this whole stiffness discussion is going to change that.
I agree that DT Swiss hubs, due to how the end caps simply rest on the bearing face, are the worst in terms of helping torsional stiffness. Any hub where either the axle or the end cap goes all the way through the bearings will be better.
I don't know if the I9 1-1 system (where the end cap goes through the bearing and into the axle) or the CK/OneUp/Hadley system (where the axle goes all the way through the bearings and the end caps then go over the axle), is better. I would assume the latter would be stiffer, but have no data on this.
"Is it the total surface area of the face of the end cap to the face of the fork dropout that is contributing to this or is the lip of the dropout that makes contact with part of the circumference of the end cap?"
The testing at Specialized showed that it was the increased surface area and larger diameter of the contact between fork/hub that increased the torsional stiffness. This was also with a RockShox fork, so the axle system maximized the benefit of the larger contact area. Below is a pic of the PUSH 9.1 with a Chris King torque cap hub installed, and there is no contact between the fork lug and hub end cap on the non-disk side. The larger diameter torque cap does nothing in this case.
As for the lip, it really can't be in solid contact with the end cap or the system would be over constrained from a design stand point. If the axle is located by the bore in the fork lug, then the lip cannot also have a solid contact with the hub end cap OD due to production tolerances. Everything would need to be perfect every time with the fork and hub. If the fork lip/hub interface was a few thousandths of an inch off, it would either not make contact at all, or have an interference fit making it difficult to install the axle and perhaps be a source of creaking. The lip mostly serves to help locate the hub when installing the wheel, I don't think it makes meaningful contact with the hub end cap once tightened.
I see on the product pages of the Intend forks it says: No TorqueCap compatibilty from April 2025 on.
If it's supposed to be better, then why this change?
ever thought of asking them directly? i heard that could help with answering questions. i don't think anyone in here was involved in the design process, so why are you expecting someone being able to answer that?
Interesting! I’ve installed torque caps to my CK hubs on an intend Flash (Jan 2025). Whether it’s placebo or not (as I have no data), I feel a difference.
If I can find the answer by asking them, that means all the 8 billion other people on this planet could too. There are also other ways to aquire information...
If you're gonna get wise with me, you can just hit the road. This is a forum for the intended purposes of sharing information, period.
it's all good, rhetorical questions asked into the ether are not off limits. Either the hive mind answers them with knowledge, they get ignored or someone has a bright idea or question that stems off it.
intend is known for their a+ customer service and answering questions FAST. you could have your answer by now already by just writing cornelius and his team.
its probably the same answer than what they said when they explain certain features that were cut/not needed in their view (i.e. 20mm axles and stanchion guards): not needed, they found a better way to design and to save weight to reduce unsprung mass.
be carefull to mess with the intend-fanboys
yet, isn't the damper on all the new Intends still attached to the lower leg rather than at the crown?
the compression assembly is, but it's attached to the crown..
If you think you decide who are allowed to ask questions and who isn't in this forum you got entitlement issues. You are the problem and i couldn't care less what you think about it.
Those who want respect, give respect.
the answer is nobody knows but intend
Re-the torsional flex experience, there's IMHO a bit of brain adjustment required if you are used to the feeling of rigid forks like the 38. In my 1st week with the Essential, I was very aware of the difference between stiffer and flexier front hubs in the fork, and thanks to the USD lore, my mind was locked on the flex, looking for it / finding it / dreading it. I was pre-conditioned to dislike it. A few weeks later, I just didn't care anymore. My brain got used to it. I can still tell the difference between hubs but it doesn't impact my riding anymore. I am actually enjoying the little bit of flex in some situations, and I believe it's easier on my poor wrists, too.
PUSH 9.1 V2 Changes
PUSH Industries ended up replacing the entire 9.1 fork due to oil seeping from the crown and a persistent creaking. They also upgraded the spring unit to the V2 version which has some interesting features.
"Sub Chamber"
There is a knob on top of the spring side leg which acts to slightly increase the spring rate (if closed off). It has not been apart yet, but I believe it seals off a chamber within the spring side effectively reducing the lower leg air volume. If so, this increases the lower leg or "casting" ramp effect. The adjustment is effective and can be felt by simply pushing on the fork. A potentially useful feature that could take the place of swapping to a stiffer spring if going from trail riding to the bike park. I currently run a 45# spring for trail riding, but swap to a 50# spring for the bike park. Unique in that it is effectively an air spring and the rate change will be progressive in nature.
Hydraulic Bottom Out
The pneumatic bottom out system has been replaced with an oil damper system. It is differs from the Vorsprung Smashpot HBO system in that it is itself a tiny little damper with an air pressure backed IFP. No shims, just a little piston in a sealed damper unit. It it tunable through changes in IFP pressure, and oil weight. Orifice dampers in general are very progressive in terms of damping force produced at increasing shaft speeds, and are reactive to changes in oil viscosity. More tunable than the previous air sprung unit, and it should have no effect on fork rebound damping.
Those updates to the fork all seem really smart. Makes a lot of sense. Excited to hear your impressions once you're able to get out on the trail on it.
Your initial reply to me contradicts itself and now you continue to push the lie I debunked. What a pathetic piece of shit you are.
Other people in this thread have talked about something that I started to show interest in. In you come and start attacking me out of nowhere, which means it doesn't make any sense at all. The reason for this is that you have failed to stand up for yourself against someone in your personal life, and now you are trying to blame me as an innocent random person online for that because it's easier to do so while hiding behind a keyboard.
Absolutely nothing of what you direct at me has got anything to do with me, or you would have attacked the other people above who talked about the same subject, except you didn't.
It's quite sad that there are so many people like you online who will just keep walking till you knock your head into a wall, only to do it all over shortly after. I see this every single day...
Truth doesn't care what anyone think of it. You can kick it, you can spit at it or you can even try to blow it up. It will still be standing there staring you down, which is why the best we can do is simply to accept it.
So who ever it is in you personal life you hold a grudge against, you should rather start standing up for yourself so you won't make a fool of yourself attacking random innocent people for no reason.
You guys should take the arguing to PMs so you can effectively yell into the same echo chamber. In here, we should discuss upside down suspension stuff. You know, "Stranger things, season 4, forks and stuff"
unlike you, i speak german. unlike you, i watched propably all the interviews with cornelius that came out this and last year prior to my decision in investing in intend products (i do that thoroughly for every product i intend to buy). i also read all there is on their forks on mtbr and mtb-news.de. why they changed the lowers this year was never mentioned. so IF anyone outside their inner circle knows this, they would have just asked them about. because that is what people usually do when dealing with intend, they write them an email and get an answer a few hours later. which i told you to do, yet here we are, discussing. and you still without an answer. sad.
Because you're still trying to tell me another place to find information besides this forum you still believe you are entitled to decide who gets to ask questions in this forum, and who does not. When people continue the same behavior after being proven wrong, that is a mindset that has shut down.
So, is it your wife/girlfriend you are running from? One of your friends maybe, or could it be your boss?
When someone blindly attacks a random person out of nowhere, the argument is always with someone else. So, who are you running from?
die dumb then, i'll enjoy my flash in the meantime. without torque caps, although mine is still compatible. for whatever reason that is so very important to you.
Blaming others for our own mistakes is for cowards.
I think Pedal Bob and sethimus need to hug it out.
Please guys. Don't.
I think the spiking issue on moto forks is a result of going air on Moto forks about 10 years ago and why the Factory forks take the weight penalty and run coil.
I'm on the outside of moto world, but are most moto forks really running air now? I thought that was a blip and everyone went back to coils, on factory team bikes and on Joe Blow OEM bikes, too.
Not sure if you bought this Flash 35 just for testing purposes or for personal use, but if you decide to sell it, I'm a serious buyer.
After looking at the various USD options I intend to get the Flash 35 for a new Regulator build.
Have you worked anything out for guards for the lower stanchions?
Thx.
PS. Great thread btw!
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