What's the deal with the Rockshox C1 airshaft?

Has anyone installed the C1 airshaft or sealhead/footnut in their RS Lyrik? I think Cam reviewed back when they first came out in April for a couple rides. Any longer term reviews? I know the initial support is better, but how does affect the rest of the stroke?

I’ve been running one since June. The fork sits higher and runs best about about 5-10 psi less than the previous version to feel sensitive off the top and not overly tall.

Because the old Debonair was so soft of the top, I found I had to run it at a higher pressure to avoid excessive sag, but it would then feel a bit harsh on medium hits (think smashing down a rough trail with consecutive square bumps) due to that higher air pressure. At the lower pressure, the new air spring feels smoother on those medium hits without feeling overly divey when braking or in corners.

Overall, I like the new air spring.

One thing that is amazing is the marketing opportunity at Rockshox has turned this incremental change into. It’s quite something for a small part.

I picked up the C1 sealhead and footnut when they were released in May and rode it for about a little less than a month and then went back to the B1 version. I found it noticeably worse than the B1 version. 

The C1 spring has a positive top out (preloaded), which means it will always be less sensitive off the top, also ensures it sits at the listed travel when unloaded (doesn't let the bike's weight sag the fork).

It did help me realize that I had my fork set far too soft, so in that regard, it was money well spent. I've come to the conclusion that the Rockshox pressure charts are way off for me. I'm running 20psi more than recommended, but I find that it works really well. I think there's work to be done on the fork setup process, sag isn't very helpful.

While I agree they attempted to turn it into a marketing opportunity, I'd guess a huge motivation was to reduce the number of warranty complaints from people whose forks had less travel than they paid for.

Posted by: wingelabs

I picked up the C1 sealhead and footnut when they were released in May and rode it for about a little less than a month and then went back to the B1 version. I found it noticeably worse than the B1 version. 

The C1 spring has a positive top out (preloaded), which means it will always be less sensitive off the top, also ensures it sits at the listed travel when unloaded (doesn't let the bike's weight sag the fork).

It did help me realize that I had my fork set far too soft, so in that regard, it was money well spent. I've come to the conclusion that the Rockshox pressure charts are way off for me. I'm running 20psi more than recommended, but I find that it works really well. I think there's work to be done on the fork setup process, sag isn't very helpful.

While I agree they attempted to turn it into a marketing opportunity, I'd guess a huge motivation was to reduce the number of warranty complaints from people whose forks had less travel than they paid for.

One thing I've been thinking of trying is going back to the B1 but with 1 less token to try to tune out some of that harshness I was feeling deeper in the stroke. What did you end up doing for tokens?

Posted by: D_C_

One thing I've been thinking of trying is going back to the B1 but with 1 less token to try to tune out some of that harshness I was feeling deeper in the stroke. What did you end up doing for tokens?

I haven't made up my mind 100% (running a lyrik at 170mm, ~85kg). I started with 2 tokens at 90psi, and I was mostly happy, but I felt that I was getting deep into the travel pretty frequently. I'm currently running 1 token and ~98psi, which leads me to believe I was still running a little low with 2 tokens. I pretty happy with where it is currently fairly supportive thru most of the stroke, could maybe use a bit more ramp up at the bottom, but I think I'm going to try 2 tokens and ~95psi to see if that gives me what I want. (Last season I was running ~80psi and 1 token)

Posted by: D_C_

Because the old Debonair was so soft of the top, I found I had to run it at a higher pressure to avoid excessive sag, but it would then feel a bit harsh on medium hits (think smashing down a rough trail with consecutive square bumps) due to that higher air pressure. At the lower pressure, the new air spring feels smoother on those medium hits without feeling overly divey when braking or in corners.

Overall, I like the new air spring.

Not sure what your setup process was, but I would consider trying to set your pressure to maintain your geometry/bike shape most of the time rather than trying to achieve a specific sag amount or trying to ensure you bottom the fork out regularly. Bar height adjustments should likely also be part of this process.

Sounds like you might benefit from even higher pressure than you were running with the B1 and possibly one less token.

Posted by: wingelabs

Sounds like you might benefit from even higher pressure than you were running with the B1 and possibly one less token.

Yeah, that's along the lines of what I'm thinking.

By "avoid excessive sag," I should have said avoiding too low a dynamic ride height. I have no idea what my sag measurement is on my fork.

I'm about 75 - 77 kg depending on the season. I was running 85 psi and 1 token at 170 with the B1, and I've settled at 75 psi and 1 token with the C1. I've experimented with more air and 0.5 and 0 tokens with the C1 and I found it too ride too high.

So..... it's not better?

Posted by: Ouch

So..... it's not better?

It's definitely different. I am liking the new one better, but I constantly tinker and understand academically why the old one has some possible advantages. The old one required a higher pressure, which to some resulted in a mid-stroke that was more supportive, but to me felt a bit harsh.

I think the new one is easier to set up to feel good for most riders. It's also not an expensive part, so low-risk to try it out.

Ive had the same experience as you D_C_

Likes to ride high in the travel, lots of mid stroke support and requires less air pressure than the older version

At 188 riding weight, was running 89-90 psi and it felt a bit harsh- down to 80 psi now with 2 tokens and feel like this is perfect for summer dusty conditions

Once the rain starts to come, ill likely remove a token and take the air pressure down a few more PSI

Of a side note, none of the factory Norco boys run more than 1 token

https://www.pinkbike.com/news/bike-check-comparing-norco-factory-racings-sight-enduro-setups.html

Posted by: ehfour

Of a side note, none of the factory Norco boys run more than 1 token

https://www.pinkbike.com/news/bike-check-comparing-norco-factory-racings-sight-enduro-setups.html

Yeah, that article had me playing with tokens. After reading that, I tried a bit more air pressure and both 0 and 0.5 tokens. I ended up going back to the 1 token I had been running before. The lower end of stroke ramp made the fork feel more glued to the ground and less poppy, which is good in some situations but worse in others. I also felt like my ride height was too high with more pressure. 1 token feels like a good middle ground for me.

I did end up with 1 fewer token in the rear shock, though, which got rid of a bit of harshness I was feeling.

There was a comment in the comments section that I thought was pretty smart, basically saying that light aggressive riders will need to run more tokens than heavy riders.

"Speed has a MUCH greater impact on the total energy going into our bikes than weight. The velocity input is exponential, while mass input is constant. In other words, a fast, light rider needs to have virtually equivalent support at the end of the travel as a heavy rider going the same speed. Tuning the spring force in the initial phases of travel becomes the hard part. That is why it makes sense for lighter riders to run lower air pressures initially and have a good amount of ramp up (via volume spacers) at the end of travel to absorb the high-speed hits. A larger rider can utilize a more linear spring curve to achieve similar results while still having good small bump sensitivity in the initial phases of travel due to his/her greater mass."

Posted by: ehfour

Of a side note, none of the factory Norco boys run more than 1 token

https://www.pinkbike.com/news/bike-check-comparing-norco-factory-racings-sight-enduro-setups.html

I see that's with the 170mm fork, is that what you have? I have the 160mm travel.

Posted by: Ouch

So..... it's not better?

I basically agree with D_C_ its definitely different. It does deliver some of what RockShox says it does though.

Advantages:

It will ensure that your fork will extend fully when you're not sitting on your bike.*

It eliminates the need to equalize the negative and positive air chambers when setting your spring pressure.

Disadvantages:

The C1 spring will be harsher off the top than the B1 spring because of the preload at top out.

Neutral:

It reduces the ramp up in the lower leg (helpful for lighter riders who have a difficult time using full travel)

The C1 is less progressive than the B1 spring (again probably helpful for lighter riders)

The negative air spring volume is reduced, increasing the spring force in the first half of the travel. This may make it easier to use full travel**

*This is honestly not an advantage but its probably a big issue for RockShox and is apparently a sufficiently large sticking point that even Steve from Vorsprung mentioned on a different forum that the Secus preloads the top out ever so slightly (less than the C1) because people were unhappy with the Luftkappe robbing them of travel

**Heavier/aggressive riders using higher pressures to provide midstroke and bottom out support will lose beginning stroke sensitivity and will likely add tokens to provide bottom out support, lighter/less aggressive riders have more support higher in the travel while still being able to use full travel. I haven't personally done the calculations but from what I've seen, If you've setup your C1 with slightly less pressure (attempting to equalize sag), the spring force in the first ~half of the travel is higher, and the spring force in the second half is lower and will ramp up less than the B1 spring. (If you set it up at the exact same pressure as your B1, the spring force will be higher throughout the curve, and I don't think the change in lower leg volume is sufficient to make make the bottom out force match the B1 curve.)

Its not clear cut. Increasing the lower leg volume makes the progression of the fork more tune-able (for lighter and heavier riders), because you should be able to compensate by using more tokens. Preloading top out kind of sucks, but the warranty and setup advantages probably make more sense for an OEM product.

Posted by: D_C_

Posted by: ehfour

Of a side note, none of the factory Norco boys run more than 1 token

https://www.pinkbike.com/news/bike-check-comparing-norco-factory-racings-sight-enduro-setups.html

There was a comment in the comments section that I thought was pretty smart, basically saying that light aggressive riders will need to run more tokens than heavy riders.

"Speed has a MUCH greater impact on the total energy going into our bikes than weight. The velocity input is exponential, while mass input is constant. In other words, a fast, light rider needs to have virtually equivalent support at the end of the travel as a heavy rider going the same speed. Tuning the spring force in the initial phases of travel becomes the hard part. That is why it makes sense for lighter riders to run lower air pressures initially and have a good amount of ramp up (via volume spacers) at the end of travel to absorb the high-speed hits. A larger rider can utilize a more linear spring curve to achieve similar results while still having good small bump sensitivity in the initial phases of travel due to his/her greater mass."

I really wonder if the factory teams are running the C1 Debonair Springs. I know I keep mentioning Steve from Vorsprung, but he's mentioned in the past that there was a season where basically all the RockShox supported EWS athletes were running Luftkappes they paid for out of their own pocket. I wouldn't be surprised if the factory teams were running B1 springs.

As for that Pinkbike comment, its kind of all over the place, the energy equation part is just wrong...

Kinetic Energy: E_k = 0.5mv^2

The velocity component does play a bigger role in that equation. But when comparing two equally very fast (10m/s) riders one heavy (90kg), one light (70kg), the mass input isn't constant... the speed input would be kept constant, making the mass the only relevant part of the equation.

E_k_heavy = 0.5*90*(10)^2 = 4500 J

E_k_light = 0.5*70*(10)^2 = 3500 J

The heavier rider's fork needs to absorb ~23% more energy over its travel