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Discussion Starter · #1 · (Edited)
You can finally get a downcountry frame that ships factory-direct and looks badass.

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Light Carbon LCFS937
Price: $550 ($80 USA shipping)
Travel: 120-140mm front, 115-130mm rear
Head angle: 67[SUP]o[/SUP]
Reach: 500mm (20.5")
Frame construction: Full Toray 700 carbon fiber
Sizes: 17.5", 19", 20.5"
More info: Light Carbon website

Disclaimer: I will sell this complete build (with a new cockpit) in July for $4000 to make way for the next steed. $4k obo.

The FS937 might just be the most visually assaulting and forward-thinking carbon frame that's shipped consumer-direct by the factory. Even Pinkbike's Brian Park cautiously praised it in his article on "5 surprisingly nice catalog frames" last year. One Pinkbike commenter asked, "What's a designer like that doing on open-mold frames?"

Bicycle frame Bicycle part Line Bicycle Bicycle accessory

Pinkbike highlighted the "clean looking" LCFS937 frame (Photo: Pinkbike)

Indeed, this frame is an original and creative work of bicycle art.

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I built up my FS937 with 115mm rear travel and 120mm front travel, weighing in just over 22 lbs. However, you can match your course and style by choosing your suspension travel strategically. For example, you can limit rear travel by using a different shock stroke (40mm is ~115mm travel, 42.5mm is ~123mm travel, and 45mm is ~130mm travel). You can also choose your front travel, as axle-to-crown lengths corresponding to about 120mm-140mm of travel in a 29er configuration will play well with the geometry.

CONSTRUCTION AND FEATURES
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The FS937 is a looker. The massive seat-tube/top-tube triangle looks like an Evil bike on steroids, but the most original characteristic of this frame is the linkage sandwiched between a split seat tube. In theory, this linkage sandwich should be stiffer than a linkage forked around the seat tube. Indeed, it is.

Bicycle tire Mode of transport Bicycle wheel rim Yellow Bicycle part

The suspension linkage is sandwiched inside a split seat tube

Sandwiching the linkage between downtube stanchions is something that hasn't been done before in XC/trail bikes, as far as I am aware. This is well thought out. The layup above the split in the seat tube is very beefy and quite wide. The large triangle feature at the seat tube/top tube junction helps space the seat tube wide enough without looking strange. The linkage is quite wide, probably wider than needed, but this can only translate to more stiffness.

Grey Beige Synthetic rubber Tread Transparent material

The seat tube/top tube junction is overbuilt for stiffness

Nearly the entire frame is generously overbuilt. This adds a little weight, but it is confidence-inspiring when riding aggressively and provides outstanding stiffness. The seatstays are noticeably compliant, with integrated flex to accommodate the single pivot rear triangle design. The frame isn't a delicate XC specialist-my 20.5" painted frame weighed 2580g-it's built for burlier endeavors.

White Black Grey Communication Device Gadget

Front cable ports are tightly fit and look clean

Bicycle tire Bicycle wheel rim Bicycle part Bicycle accessory Spoke

Chainstay routing ports are clean and feature molded-in guides

Internal cable routing is nicely executed. The chainstay brake and shifter cables are easy to route thanks to molded-in guides, while the front ports are tightly fit and easy to handle.

Internally-routed dropper posts up to 170mm in size 17.5" and 200mm in size 19" can fit inside the seat tube. That, or you can stay rowdy and rigid like me.

Toray 700 carbon fiber construction provides stiffness and reliability on par with industry standards. Frames are tested to 130% of SGS industry standards. 2-year manufacturer warranty comes with the frame.

Light Carbon not only honors their 2-year warranty, they fix the problems. I have been in touch with a Cat 1 racer who somehow broke his trunnion shock mounting hardware resulting in a cracked linkage and front triangle. Light Carbon has since been shipping their frame with stronger (and heavier) trunnion mounting bolts and beefed up the layup in the linkage.

Wheel Bicycle tire Tire Bicycle wheel rim Mode of transport

The frame is 1x-specific and fits a 32T chainring. Light Carbon advertises that a 34T will fit, this would be almost uncomfortably tight. A threaded BB shell and integrated ISCG-05 chain guide mount are appreciated details, though I don't have a need for the chain guide mount. Rear spacing is 12x148mm boost, and the rear triangle clears 29x2.4" tires.

GEOMETRY AND SIZING
SIZES (17.5")M (19")L (20.5)"
FORK AXLE TO CROWN530 / 540 / 550530 / 540 / 550530 / 540 / 550
STACK562 / 566 / 569623 / 579 / 582589 / 593 / 596
REACH445 / 440 / 436481 / 470 / 466505 / 500 / 496
WHEEL BASE1174 / 1178 / 11821210 / 1214 / 12181246 / 1250 / 1254
TOP TUBE HORIZONTAL589 / 590 / 591622 / 623 / 624657 / 658 / 659
HEAD TUBE ANGLE67.5[SUP]o[/SUP] / 67[SUP]o[/SUP] / 66.5[SUP]o[/SUP]
EFFECTIVE SEAT TUBE ANGLE75[SUP]o[/SUP] / 74.5[SUP]o[/SUP] / 74[SUP]o[/SUP]
BB DROP-40 / -36 / -33
CHAIN STAY LENGTH444.5
HEAD TUBE LENGTH95110125
SEAT TUBE LENGTH440480520
FORK OFFSET515151
REAR TRAVEL115mm (165x40) / 123mm (165x42.5) / 130mm (165x45)
MAX TIRE29x2.35" or 27.5x2.8"

The FS937 is the longest and slackest factory-direct frame in the Trail and XC category, with a 67-degree head angle, and a reach of 500mm in a size large.

The wheelbase is very long, at 1250mm in size large. This is great progression to see in a factory design, where geo typically lags 2-3 years behind industry leaders.

Unlike most Chiner frames, the design and geometry of this frame is entirely original, as far as I am aware. It's refreshing to see a factory producing a frame that can compete with leaders in the industry.


SUSPENSION DESIGN

The FS937 keeps things simple with a single pivot design with integrated flex stays. Suspension is supple through the entire stroke, even during heavy braking on demanding descents. The seatstay caliper mount does not affect suspension performance as far as I can tell.

Orange Machine Gas Steel Cylinder

The shock is mounted with a 21.8mm (or 22.2mm) spacer kit and two machined spacers provided with the frame

Black Carbon Synthetic rubber

The linkage is routed between a split seat tube

Mode of transport Yellow Orange Transport Bicycle part

A hole in the downtube doubles as an access point to the shock air valve and a drain for the cavity burrying the lower mount

The FS937 fits trunnion-mount 165mm eye-to-eye shocks. Fox offers 40, 42.5, and 45mm stroke DPS shocks (equating to 115mm, 123mm, and 130mm rear travel on this frame), and all you'll need is a single 21.8mm 8mm mounting kit. (54*φ10mm - 22.2*φ8mm). Light Carbon also provided some machined steel spacers to fit on either side of the shock kit. I ordered a 22.2mm kit and this was just too tight, it took a few taps from a rubber mallet to work the spacers into place. There was absolutely no play in the shock setup, snug and able to move quite freely with properly tightened bushings, but unfortunately bushings instead of bearings means there is considerable stiction at the joints.



BUILD KIT
Appx. Value: $4000
Trailside Weight: 22.26 lbs
Travel: 120mm front, 115mm rear

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Rear Shock Fox Float DPS Factory 165x40mm, Trunnion mount
Fork Fox Float 34 SC Factory, 29", 120mm Travel, 51mm offset
Headset ZTTO Tapered
Cassette SRAM X01 10-42T
Crankarms Race Face Next SL Carbon 175mm, OneUp 32T Switch
Bottom Bracket BSA 73mm, 30mm diameter
Derailleur/Shifter Shimano XTR 11-Speed
Chain PYC SP1101
Handlebar Integrated 680mm width 80mm stem -17-degree rise
Grips eBay Chunkies
Brakes Shimano XTR Race
Wheelset Speedsafe 280g 29" 28h 22mm internal width, Pilar XTRA 1420 spokes, DT 350 boost hubs XD straight pull
Tires Schwalbe Rocket Ron Liteskin Evo 29x2.25"
Seat Unbranded carbon shell/rails, foam padding
Seatpost Unbranded ultralight Hylix-style 31.6mm, 350mm
Pedals XTR SPD
Bottle Cage Can't decide

Many of my components are reviewed (briefly) in this thread: https://forums.mtbr.com/weight-weenies/best-weight-weenie-components-under-$50-1094616.html
White Line Composite material Gear Steel

Ashima Ai2 rotors all the way, light and strong!

Bicycle saddle Bicycle part Black Grey Metal

This 135g $29 saddle has nearly 2000 miles on it. You'd hardly know.

Bicycle accessory Bicycle part Bicycle Bicycle drivetrain part Carbon

Integrated $50 235g carbon bar and fancy top cap :)

Bicycle part Rim Spoke Bicycle Bicycle accessory

The stock axle that Light Carbon shipped with the frame is just 50g!

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This seatpost is <150g and <$30. Reminiscent of the Tune Skyline.

Winter Bicycle accessory Freezing Snow Geological phenomenon

The Fox Float 34 SC Factory fork is fairly light and handles bigger hits more capably than a Float 32

Bicycle accessory Red Bicycle part Orange Line

Good grips for $0.99. Chunky like ESI Chunkies, cheap enough to replace.



RIDE IMPRESSIONS

I was pretty stoked rolling into the trail for the first time on this build. My first impression was how incredibly stiff the entire bike was even through hard corners. This translated to impressive control, allowing me to push very hard through sections I normally would coast or dial back the power. I'm not sure if this is just attributable to the overbuilt construction, but the unique suspension design of this frame could also be part of this amazing stiffness. Certainly, if this suspension layout was an experiment, it's a success.

Descending. The most impressive (and fun) aspect of this bike is its incredible control and stability on descents. Huck as hard as I could, I could not get the rear to squeak, flex, or give under pressure. The long wheelbase was confidence-inspiring, providing great stability.

Flats. On the flats, the bike carried momentum very well. However, accelerating out of corners took consciously more effort than my 21lb Pro-Mance M7007 or 18lb FM-299B. There was also a bit of pedal bob under power, more than I'd like to feel. I tried playing with shock rebound and pressure but couldn't achieve a balance I liked. This may be an inherent limitation of the low pivot point required for this unique suspension design.

Climbing. For a 120mm bike, the LCFS937 climbs well, but certainly not as well as my M7007. I felt slightly slow on climbs and had a hard time navigating obstacles and carrying momentum. Perhaps it was the 22.3 lbs of weight, which is heavier than 21lb on the M7007 or 18lbs on my most recent build, the TanTan FM-299B. More likely it's the long wheelbase and slacker HTA. Of course, I'm judging by XC standards and can't expect this to perform like a 100mm travel bike. For what it is, though, it's very good. On an average ride, I'm super happy with it, but it may challenge my KOM-crushing ambitions.

Bicycle accessory Bicycle part Bracelet Synthetic rubber

The mud-collecting pool around the shock mount is drained by a hole molded into the side of the downtube, which doubles as an access point for the shock air valve. I don't expect dirt collection here to be an issue because it is quite well protected by the wide downtube and beefy seat tube. But, if gunk around your shock makes you feel psycho, simply squirt it down with a hose nozzle on jet after the ride.



BUILD TIPS


  • The frame requires a 180mm rotor in the rear.
  • Get a single 22.19 or 21.8mm M8 shock mounting hardware kit. For a Fox DPS Float Trunnion shock, get this: https://www.worldwidecyclery.com/pr...rdware-8mm-x-22-19mm-0-874-5-piece-aluminum-1
  • Only Trunnion shocks are compatible with this frame.
  • Shock eye-to-eye length must be 165mm, but you can choose between 40mm, 42.5mm, and 45mm stroke lengths to limit possible rear wheel travel (115mm, 123mm, or 130mm travel, respectively).
  • Plan on a 2-week lead time, and 1-2 weeks for delivery (to the USA).
  • Order directly from Light Carbon, or I'm happy to order your frame for you and help you plan your build at the cost of what Light Carbon would charge you. PM me with questions. I also can put together complete build kits for you.

Is this frame for you?
The FS937 falls confidently into the downcountry category. It can shred the downhills and carry speed on the flats but does not climb as efficiently as an ultralight 100mm-travel XC steed. That said, it offers control and stiffness like no XC whip can.

This all translates to more fun. If you aren't shaving grams to save milliseconds, this may be your ticket. It can nearly match the capability of a shorter travel rig on the climbs, but far outshines it on the descents. Along the way, it will absorb a few more bumps, add a little extra confidence, and just be an all-around fun trail bike.

Pros:

  • Progressive long-and-slack geometry
  • Original aesthetic design with unique suspension linkage setup
  • Remarkably stiff linkage with superb control
  • Affordable
  • Fits long-travel dropper posts

Cons:

  • Slightly sluggish on the climbs
  • Doesn't fit the newer crop of 29x2.6" tires
  • Pedal bob due to low suspension pivot point

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Stay tuned for a long-term update. Post up or PM me with any questions or comments!
 

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Discussion Starter · #5 ·
Wow, these forums are loaded with veteran trolls. Grow up.

For those who care about the bike rather than my semantics, I thought these pics might be of interest.

I've been in touch with a guy who built up an LCFS937 and raced it at Sea Otter recently and shared some pics with me. He qualified in dual slalom finals for pro with the Santa Cruz Syndicate, got a great placement in the UCI Elite XC at bear mountain two weeks prior, then got 3rd in the pro enduro the next day. Pretty impressive, goes to show how versatile the bike can be.

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Discussion Starter · #8 ·
Neato. Pics of someone else on a different bike. :arf:
This guy would have posted were it not for trolls like you that give these forums a bad rap. He told me exactly that. I thought others may still appreciate his experiences on the frame.

I suggest you check out the off camber subforums. I hope this thread is helpful for people looking for bikes like this, I didn't write the post for nothing.
 

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Thank you for taking the time to do this write up - be aware that it is appreciated.

I am interested in building a ~140/130mm F/R 29er trail bike, and the geo on this frame is very close to my ideal. I am hoping for chainstays no longer than 440mm though, but this isn't far off. Otherwise the geo is pretty much spot on.

I am not convinced that this design, with the internal approach to the way the stays/link are attached to the main frame, would be stiffer though. I was thinking that the usual approach, with the pivot bearings further apart, would be stiffer, and less susceptible to play if there were some slight gaps (or wear) around the bearing-to-pivot-pin interfaces. Interested in your thoughts. It is confidence inspiring that someone is using one for gravity related racing, but I suppose the issue I am worried about might not come up until the bike has been ridden a bit.

Seems pretty well priced, maybe low enough to give it a go.

Dunno if I'd call it latest geo though, as it seems that 2019 is the year of 77 degree seat tubes. Having said that, I am still finding ~75 degrees a bit steep, so I'm more interested in the slightly older 2017/18 geo anyway.

Do you have any links to similar (completed) build threads / ride reports on this frame? I have been following the one on chinertown, but, other than your contributions, it hasn't got very far yet.
 

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The dropper post cable routing looks like it might cause a few issues with that very tight radius from top tube up the seat post. Wonder if it's possible to route it via the bottom tube then directly up the seat tube?
 

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Discussion Starter · #14 ·
The dropper post cable routing looks like it might cause a few issues with that very tight radius from top tube up the seat post. Wonder if it's possible to route it via the bottom tube then directly up the seat tube?
Good point. It does indeed look like a very sharp angle there. There was a plastic routing guide in place when I got the frame, so actually routing the cable would be fairly easy, but that sharp kink could be challenging. I'm not running a dropper, so I don't know.

This is the pic LightCarbon uses to illustrate cable routing:

Yellow Bicycle frame Line Slope Font


I do not think it would be possible to route it via the bottom tube, the seat tube "stanchions" are thin enough and the layup seems like it should be thick enough to block any path through the tube.
 

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Discussion Starter · #16 ·
I am not convinced that this design, with the internal approach to the way the stays/link are attached to the main frame, would be stiffer though. I was thinking that the usual approach, with the pivot bearings further apart, would be stiffer, and less susceptible to play if there were some slight gaps (or wear) around the bearing-to-pivot-pin interfaces. Interested in your thoughts. It is confidence inspiring that someone is using one for gravity related racing, but I suppose the issue I am worried about might not come up until the bike has been ridden a bit.
Thanks, this was my main concern as well when buying this frame without any prior experience shared online as well. Personally, this bike is so much stiffer than my Pro-Mance M7007 which used a similar single-pivot design but with pivot bearings farther apart, so it's a fair comparison. There is absolutely *zero* play anywhere in the rear triangle or linkage. There is no sign that the linkage can be torqued side to side by pushing or pulling sideways on the rear wheel when holding the front triangle.

Dunno if I'd call it latest geo though, as it seems that 2019 is the year of 77 degree seat tubes. Having said that, I am still finding ~75 degrees a bit steep, so I'm more interested in the slightly older 2017/18 geo anyway.
I wouldn't want a much steeper seat tube. I really like the longer reach this kind of geo gives, and I wouldn't want to sit any further forward over the BB. I have a feeling steeper STAs are more relevant in much longer-travel bikes.

Do you have any links to similar (completed) build threads / ride reports on this frame? I have been following the one on chinertown, but, other than your contributions, it hasn't got very far yet.
Just the one on Chinertown: Lightcarbon LCFS937 Build
 

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Great review, i learned a lot about this frame

Personally, this bike is so much stiffer than my Pro-Mance M7007 which used a similar single-pivot design but with pivot bearings farther apart, so it's a fair comparison. There is absolutely *zero* play anywhere in the rear triangle or linkage. There is no sign that the linkage can be torqued side to side by pushing or pulling sideways on the rear wheel when holding the front triangle.
Do you think this "extreme" stiffness can explain the feeling you had of slow acceleration and slow climbing too as the bike is probably not lively enough under power
It's known that some manufacturers do not go for maximum rigidity to keep grip and more easy bike for the commun biker.

I really like the longer reach this kind of geo gives,
You kept the same cockpit as your previous bike, is that a choice not to adjust stem to longer reach and maybe different stack?
Do you plan to test with shorter stem, wider bar to stick more with the DNA of that frame?
 

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Discussion Starter · #18 ·
Great review, i learned a lot about this frame. Do you think this "extreme" stiffness can explain the feeling you had of slow acceleration and slow climbing too as the bike is probably not lively enough under power. It's known that some manufacturers do not go for maximum rigidity to keep grip and more easy bike for the common biker.
Thanks, good questions! No, I do not think the slower acceleration is due to the stiffness. If anything, a stiffer frame means more efficient power transfer. To be clear, the frame still accelerates quickly :) It's dependent mostly on the rider and build weight, but increased pedal bob due to lower pivot point is also a factor in how efficiently power is transferred. To address this I am running higher pressures in the shock than I'd consider ideal (200 psi vs 165 psi for my weight of 165 lbs).

You kept the same cockpit as your previous bike, is that a choice not to adjust stem to longer reach and maybe different stack? Do you plan to test with shorter stem, wider bar to stick more with the DNA of that frame?
I understand most people have different preferences than me, but I like shorter bars because I clip trees often. I'd rather have shorter bars than more crashes. I went with this stem length because I wanted to run this particular integrated handlebar. The longer reach is perfect for me, and neither is the stack too low--I like a low position! True, if this were going to be used as a trail bike I can see most people going for wider bars, more spacers in the steerer tube, a short stem, maybe even shorter fork offset. This would all translate to faster steering and a more upright position, but wouldn't change my review.
 

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It's very clean actually. You can see the hole that takes in the lockout cable here, then it's just routed right up the downtube. I'm not using remote lockout.

View attachment 1247154
Ok that's pretty good. These lower antisquat bikes are great for tech climbing but they need a remote to climb mode or lockout for the smooth stuff.

I'm also looking at the seat stay design. It looks too thick to facilitate a flex stay type action. The M06 type stay looks a lot better.
 

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Discussion Starter · #20 ·
Ok that's pretty good. These lower antisquat bikes are great for tech climbing but they need a remote to climb mode or lockout for the smooth stuff.

I'm also looking at the seat stay design. It looks too thick to facilitate a flex stay type action. The M06 type stay looks a lot better.
True, a remote would be very helpful on this bike.

The Dengfu M06 has a very thin seat stay, easily able to flex, but Light Carbon reps also insist there's a flex stay built into this frame. It's a thick stay, I agree, but whatever it is it works well.
 
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