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.

The chainstay length in the chart seems to be a lie. If you zoom in on the drawing, you can see the dimension of the chainstay is 450mm (plus or minus 3mm). The drawing probably has the true chainstay length since the chart doesn't add up. The wheelbase should equal the front-center plus chainstay length (rear-center).

This is a long chainstay length while the Scor 4060 has short chainstays.

A couple posts on this thread (and maybe Light Carbon's marketing) incorrectly call the suspension "VPP". VPP has counter-rotating links, and this bike seems to have co-rotating links.

Kinematic analysis and "corrections" to the geometry chart.
https://insanityofgravity.blogspot.com/2021/02/8-linkage-check-fly-bike-fm1156.html

Suggestion for shock
https://insanityofgravity.blogspot.com/2021/02/17-linkage-welch-art-von-luft-oder.html

Found these browsing the interweb so not my analysis. Not sure if this has been posted here already.
TLDR:

• Pretty flat leverage curve.
• Relatively low antisquat.
• The blogger suggests Megneg shock
• Geo chart isn't quite accurate.