Interesting take, I’ll definitely check the video out…

I didnt  take into account sag too much since I thought that could be adjusted by saddle height, but didn’t consider new reach while  seated down at different saddle heights due to the Seat Angle…

Thx!

It's not just the seat tube angle that changes. Even standing, the "effective reach" changes as the suspension travels depending on the type of suspension. I was surprised that a reach difference of 40mm made the bikes feel similar.

There was more interest in inexpensive Chinese carbon frames during COVID when demand and prices for bikes were so high. Since the bike market crashed, and there are many more discounted new and used options, the cost / benefit ratio of these types of frames have dwindled or disappeared. If you realistically budget solid, proven parts, the savings over a currently discounted or used established brand are often modest at best.

Many people have unrealistic expectations about inexpensive Chinese carbon full suspension "all mountain" bike frames. For sure, they can be an adventure to assemble and fun to ride, but frustrating problems and surprises are probably more common than people expect. Fork crowns that hit the frame, suspension that gets stuck in the compressed position, or even rear triangles that can't be ridden as designed are examples. Consider what that says about the design and testing culture these frames come from. Unsurprisingly, kinematics and details like weather sealing are often inferior to name brands even when the frame is a "copy" of a well-known branded frame.

In my opinion, open mold, inexpensive Chinese frames are great for people who like a challenge and like solving problems. I don't think a 10kg 150/150mm all mountain bike is realistic.

I ordered a bunch of mountain bike parts on Aliexpress for a budget build including Shimano drivetrain parts. Most parts worked well, and almost all the shimano parts seemed genuine with a notable exception:

Losers

• A Mixed brand "dual color" CNC'd aluminum stem 45mm failed. Threads for the lower front plate bolts stripped while trying to tighten one day. Before that, the stem would slip easily on the steerer tube rotating out of place until I really torqued the bolts higher than spec. Though the stem looks cool, I suspect too much material is machined away for a reliable stem. Perhaps it wasn't heat treated correctly?
• Shimano Deore 12 speed chain was fake. Package was convincing. Fake chains seem rampant even on Amazon.
• Multi-tool that hides in the crank spindle attached with a magnet (All in multi tool copy). It's a cool idea but I lost it because the magnet wasn't powerful enough to keep it in place on rough terrain

Winners

• Genuine Shimano parts (except the fake chain) including Deore 4 piston brakes, SLX cranks and chainring, SLX cassette, Deore shifter + derailleur, bottom braket, clipless pedals
• Ztto dropper lever works as advertised
• Ztto "polished" shifter cables seemed smoother on the surface than other generic shifter cables.
• Foam tubing to quiet internal routed cables worked well. (Bicycle Frame Internal Line Housing Damper Bike Inner Line Sound Absorbing Tube 1.6M)
• CYCLAMI TPU Tubes are a lot lighter and and compact than traditional mtb tubes and don't cost much. Only used once in a friends flat, and it seemed to work.
• Mixed 5D carbon saddle has been reliable and comfortable so far
• A bunch of cycling tools ordered off alixepress worked fine for me.

An update to the problem of stuck suspension on bottom out:

On my size Medium frame, a 210x52.5mm shock does not get stuck at bottom out while a 210mmx 55mm shock jams in the bottom out position. At least one person reported that a size Large does not get stuck at bottom out while naeTech reports size Small gets stuck at bottom out at 52mm of shock stroke. The limited sample so far suggests that the problem gets worse as frames get smaller below size Large, but that's not confirmed.

I would still suggest that anyone with the frame test their bike by bottoming out the rear suspension with at a low air pressure in the shock to make sure the suspension does not jam at bottom out. Since the suspension is so progressive, you may need to reduce the air pressure in the shock to reach full bottom but you should have at least a small amount of air pressure to see the problem.

Maybe I'm not getting what this is for, but can't you just put two separate spacers on the outside of the bearings using the existing through bolt without redrilling the linkages?

daifanshi, naeTech is talking about a spacer between the outboard bearings that appears as a tube labeled "spacer" in the attached picture of the hightower v2 linkage. They bridge the inner races of the bearings accrding to naeTech's diagram. The hightower has them and the bxt doesn't. I experienced some binding and friction at low torques from these pivots. The spacers may help with this, but it looks like you have to modify the linkage and fabricate the spacers.

naeTech, did you add 2 spacers to the lower linkage as in the attached diagram?

While the BXT 117 may look like a hightower v2 copy, the kinematics, weird stuck suspension problem, and lack of linkage refinement like spacers suggest the copy isn't very good . The progression of the leverage curve is significantly greater on the BXT (some might say extreme)  if naeTech's model is accurate. I don't think you could call the kinematics the same.

All sizes of the hightower 2 accept a 55mm stroke shock, but the same stroke on the BXT 117 will cause suspension to jam at bottom out. As I understand, the 2020 hightower 2 had a 52.5mm stroke shock for "140mm" travel and the next year they shipped the same frame with 55mm of stroke for "145mm" travel in all sizes. I tested and jammed it with 55mm stroke and low air pressure on a size medium. naeTech says it happened at 52mm of stroke on size small.

If you revert to a 50mm stroke shock, the actual travel on this frame seems to be about 136mm, and the progressivity may make it difficult to use full travel. The takeaway is that the suspension travel falls short on this frame not because of marketing exaggeration but a defect that prevents you from using a 55mm stroke shock as designed. (Edit: This may happen only on some size frames. See reply #61 for more info)[/b]

If you have this frame, I suggest you try for yourself because it could be dangerous on the trail (although the high progressivity might make it difficult to reach the bottom out point). I believe you will need at least a bit of air pressure in the shock to get the suspension to jam. It's the extension pressure that cams the linkage into bottom out position.

naeTech has posted some great information about this frame. I built up a bike using this frame, but I haven't been able to ride it much due to snow season, but here are some quirks I've noticed so far.

• The suspension gets stuck when the shock is bottomed out with a 210x55mm shock. (Edit: This may happen only on some size frames. See reply #61 for more info) The lower linkage rotates to the point where it gets cammed in the bottom out position, and the suspension won't extend. naeTech says this happened to him at 52mm, so the practical option is to use a 210x50mm shock for 136mm of travel according to his model. This bike is not a 150mm rear travel bike.
• According to naeTech's model, the leverage rate of the suspension has a 39.2% progressivity through 136mm of travel. This seems a bit extreme, and I couldn't find another example of a trail bike with similar travel and that much progression.
• I experienced excessive friction on the upper linkage / lower bolt at low torque. I tried some different washers that helped somewhat. In an mtbr thread, naeTech has found that a spacer that bridges the inner races of the bearing here on the hightower is missing from this frame. A custom spacer might help here. The linkages are not very refined. Many of the bolts experienced friction at torques much lower than SC hightower specs.

Some of the quirks might be addressed with some tinkering, but understand that you are getting 136mm travel with almost 40% progressivity with this frame. It seems like these numbers would be hard to change unless you are able to take some extreme measures like fabricating a new linkage. (Edit: Maybe not accurate for all sizes. See reply #61 for more info)[/b]

If anyone can think of a way to get closer to full 150mm travel and a less extreme leverage progressivity, I'd love to hear it!

Edit: I tried a super deluxe select + on a medium frame, and it seems to fit fine. The BTX rep quoted me the wrong size shock, and tried to sell me a inferior shock. Treat their advice with some scepticism. The reps don't have much expertise and are selling lots of different models of bike frames.

This frame is on CyberMonday sale through today. Aliexpress seems to be offering $80 off $450 (code: BFUS80) plus $4 of every $20 up to $16. I guess that means you could get $96 off the current sale price, and I think that would apply to any frame you order from Aliexpress.