AM Carbonda FM1001 - Black Betty

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Why a coil fork and air shock? Are there plans to match up air to air or coil to coil?
The air shock was predominantly chosen because of it having the ability to run a remote lockout lever on the bars. I’ve been really enjoying this setup on my other Carbonda, and the shock has performed much better than I thought a non-reservoir shock could. There’s also not a lot of progression in this linkage (it’s actually very slightly regressive in the last 25mm of travel), so in theory an air spring should match the linkage best. It also saves a little weight overall, which is something I’ll rarely grumble about.

Coil fork is ‘because traction’. This is my more descent focused bike, so the extra comfort and traction is hard to pass up.
 

pink poodle

気が狂っている男
The air shock was predominantly chosen because of it having the ability to run a remote lockout lever on the bars. I’ve been really enjoying this setup on my other Carbonda, and the shock has performed much better than I thought a non-reservoir shock could. There’s also not a lot of progression in this linkage (it’s actually very slightly regressive in the last 25mm of travel), so in theory an air spring should match the linkage best. It also saves a little weight overall, which is something I’ll rarely grumble about.

Coil fork is ‘because traction’. This is my more descent focused bike, so the extra comfort and traction is hard to pass up.
I used to be a bit snobbish about air shocks without a piggy back. I'm not sure when I would have last had one now. I think it was a ccdba...maybe.

Do you really find a coil fork holds the trail better for you? It's not something I've previously considered, but the only coil fork I are used for maybe 10 years is the 66 I'm running on my nomad.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Do you really find a coil fork holds the trail better for you?
Yep, but it's possibly slightly undersprung which might enhance the effect. Slight difference being if it was an air fork it'd be blowing through the travel like mad, but the coil midstroke props it up pretty well.

The main difference though is off the top. It's night and day different to the point I can hold the front brake while standing next to the bike, lightly push the bike back and forth (say off the saddle) and it'll move freely in and out of the initial travel. On my air 36 it wouldn't even break the seal stiction doing the same thing - I'd have to actually "bump" it into the travel lightly (or climb aboard the bike). I feel that soft initial touch lends a really "glued to the trail" sensation when going through chattery rocks. The front of the bike feels heavier when lifting it in/out of the car, but doesn't really feel any different on the trail.
 

pink poodle

気が狂っている男
I hear what you're saying about the initial stroke and have found similar with air forks. But I also run a lot of psi in my front end, is just put it down to the way i set up. I tend not to price on trail, but am not riding a lot of small bumps.

I'll be paying more attention.next time I get the nomad out.
 

moorey

call me Mia
Keen to try a coil fork again one day. It’s been a while, and technology has come a long way.
I was originally dubious about how much air forks have improved in recent years until banging a Lyrik ultimate rc2.1 on a bike. It’s by no means the top of the froth pile with forks, but it’s small bump sensitivity and ground hugging feel without blowing through travel is night and day compared to a freshly serviced RCT3 Lyrik on other bikes.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Evolutionary/experimental update…

Was still getting weird noises from the CK rear hub in the original build, decided to pull it and replace it with a spare Hope Pro-4 to gain uniformity across the fleet. So since I had to pull the 29” rear wheel out anyway, I slung a spare 27.5" rear wheel in the frame (with a Project 321 hub - there goes the uniformity, lol...). Took it for a spin around the backyard and it actually feels alright, so I'll take it for a spin later in the week and see just how low the BB feels on the trails. Needed to swap out the 30t chainring that had felt (borderline) too small on the full-29er spec anyway, and only had a 34t spare - so interested to see just how that feels going uphill. Also swapped out the decal on the shock for a 'stealth' matte black on gloss black version. Now I'm currently trying to hunt down a black O-ring to replace the red travel-indicator one because it annoys me. Oh, and I flipped the rear tyre around so it's now pointing the correct direction. Felt better reversed in the backyard, but I only have enough room to ride in circles there, so I'll try this on the trails first and if the BB isn't too low I'll try flipping back into reverse just for shits and giggles.
388539
 

link1896

Mr Greenfield
O-Ring should have 1-2% stretch to fit damper body just right

Measure damper body diameter, multiple by 0.98.

Look up O-Ring table, find closest fit.


Look outside metric lists for a better fit
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
O-Ring should have 1-2% stretch to fit damper body just right

Measure damper body diameter, multiple by 0.98.

Look up O-Ring table, find closest fit.


Look outside metric lists for a better fit
I looked in the O-ring drawer at work. ;)
388561


Looks wonky because I pushed it up the shaft by hand to feel how snug it was, but the fit is perfect! :)
 
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beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Ahh well nothing is quicker then O-Ring drawer trial fit method.

The ones that were a bad fit, all tossed into the largest O-Ring section right, for an apprentice to sort on a slow day?
Haha, heck no - I hated it when people put stuff back in the wrong spot, so make sure I don’t do it now I’m on the other side!

I measured the shock shaft this morning and eventually found one that was ~1mm smaller ID. Guessed that would be about right and it fit mint.
 

moorey

call me Mia
Evolutionary/experimental update…

Was still getting weird noises from the CK rear hub in the original build, decided to pull it and replace it with a spare Hope Pro-4 to gain uniformity across the fleet. So since I had to pull the 29” rear wheel out anyway, I slung a spare 27.5" rear wheel in the frame (with a Project 321 hub - there goes the uniformity, lol...). Took it for a spin around the backyard and it actually feels alright, so I'll take it for a spin later in the week and see just how low the BB feels on the trails. Needed to swap out the 30t chainring that had felt (borderline) too small on the full-29er spec anyway, and only had a 34t spare - so interested to see just how that feels going uphill. Also swapped out the decal on the shock for a 'stealth' matte black on gloss black version. Now I'm currently trying to hunt down a black O-ring to replace the red travel-indicator one because it annoys me. Oh, and I flipped the rear tyre around so it's now pointing the correct direction. Felt better reversed in the backyard, but I only have enough room to ride in circles there, so I'll try this on the trails first and if the BB isn't too low I'll try flipping back into reverse just for shits and giggles.
View attachment 388539
TLDR. Front valve looks at around 11.58, not 12 o’clock. Can’t unsee it now.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
TLDR. Front valve looks at around 11.58, not 12 o’clock. Can’t unsee it now.
Surprised to see you pop into this thread, so I’ll respond to the curiosity I suspect is buried in the subtext - No, the BB didn’t feel excessively low with the 27.5” rear wheel in. ;) Need to take it for a spin down Boulder to be sure as that awkward right-hander with the double-rockstep on the apex is normally the ultimate test (and then also try climbing some techy sections), but it felt fine going down all the typical flow trails. FWIW, it surprised me too.

[EDIT] Probably also worth mentioning that this bike’s BB drop is a pretty conservative 28mm (for 135mm travel) with a linkage kinematic that is fairly linear. I tend to run shock pressures fractionally firmer than average, so in this instance dynamic ride height around sag is flattering to the mullet swap, but the remaining travel is still easily accessible. A bike with a really progressive kinematic may not work as well for a 29 -> 27.5” mullet conversion as using a higher spring rate to subtly raise/support the bike at sag might make the bike ride harshly or prevent deep travel being accessible.
 
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moorey

call me Mia
Surprised to see you pop into this thread, so I’ll respond to the curiosity I suspect is buried in the subtext - No, the BB didn’t feel excessively low with the 27.5” rear wheel in. ;) Need to take it for a spin down Boulder to be sure as that awkward right-hander with the double-rockstep on the apex is normally the ultimate test (and then also try climbing some techy sections), but it felt fine going down all the typical flow trails. FWIW, it surprised me too.

[EDIT] Probably also worth mentioning that this bike’s BB drop is a pretty conservative 28mm (for 135mm travel) with a linkage kinematic that is fairly linear. I tend to run shock pressures fractionally firmer than average, so in this instance dynamic ride height around sag is flattering to the mullet swap, but the remaining travel is still easily accessible. A bike with a really progressive kinematic may not work as well for a 29 -> 27.5” mullet conversion as using a higher spring rate to subtly raise/support the bike at sag might make the bike ride harshly or prevent deep travel being accessible.
TLDR.
Please fox that tyre and repost.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
@moorey, it did just very lightly kiss the chainring on the Boulder steps, but I also came into it well sideways after the back broke free on the approach. 32t would’ve cleared fine. I know you don’t care, but there you have it. :p
 
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