I mounted a coil in this frame. As it's a Hightower v2 clone that was always going to be a challenge, but I thought I'd try.

My shock tunnel pass thru was around 50.5mm wide. Most 'modern' 1 3/8" springs run 52mm+ in outside diameter. So the first thing is that you won't be putting a Fox SLS, Cane creek VALT, or any other modern spring thru it. Just accept that. I looked high and low for springs that would fit, and even ordered a cane creek DB IL Coil (with 500 lb linear Valt spring). The spring is 53mm wide . . .

Luckily I'm old. Usually that's a disadvantage, but i happened to own a Specialized full suspension bike in 1997. And I swapped the spring to a lighter tension. That bike was stolen in 2002, but I somehow still had the old spring in a bag. Back in the day, springs were built on 1 1/4" inner diameter. This 400x2.0 spring measures around 48mm OD. I would've had a dance party but it'd hurt my back. It isn't the 'target' spring constant (calculators put my weight and the HT2 leverage curve for that weight at 30% sag between 500 and 525 lb/in, depending on the assumptions).

So I was excited to try it out, but not to hopeful I'd get sag on this spring. 400 to 500 is a big difference!

I tossed that spring on the shock (adapters will need to be made eventually for the shock collars, but it works ok to test), and after pull the upper link lower bolt, finagled it in there.

I"m still not sure on sag this frame is devil hard to measure coil sag on as one person, but I think it's around 15mm (33%). Which isn't ideal (I'd like 25%), but it's workable. And this is no preload, so I could dial it back a bit. I'm not sure why calculated spring vs actual spring is so different, but this isn't really a Hightower 2, so maybe the leverage ratios are different.

Some issues:
It's pretty hard to source these old springs. There are some on ebay, they aren't particularly cheap because they come with an old shock, and they're all too stiff at the moment. There's a 550lb for $130. Which is a bit steep.
the 2.0 shock is probably a bit short. at 2.25 would be ideal, a 2.5 would be better than a 2.0. The shock may bind before reaching full travel. It hasn't yet, but I haven't been out really riding yet. I go tomorrow.
It's red. I'd much much prefer an old Fox shock, they're black.

I have a medium. It's hanging on the wall, so not the best measurement, I got 45.5 or so. which is 1156mm. 120 fork. It's within and inch or two, which isn't very helpful probably. I'll try to grab a better one tomorrow when I have it down for a ride.

No worries so far, but it's used by a conservative XC rider. I'm not worried though. Send it!

BXT MTB 117
30.5lb with dropper and midweight trail tires on 35id Aluminum rims. No inserts.

@spcycle
Friend there are two seller on Aliexpress selling as Sp-cycle. Do you sell on Aliexpress? Your warranty is valid buying from there?

https://pt.aliexpress.com/store/116622?spm=a2g0o.productlist.main.2.3682653fDhX0lm
https://www.aliexpress.com/store/816505?spm=a2g0o.order_list.order_list_main.50.64f0caa4h8wJDq

I personally paid slightly more for a different SP Cycle frame, and bought direct from the sp-cycle internet store. It was worth 3% or so different to deal 100% directly with the manufacturer.

On frame flex, this version appears to have none. It is rock solld. And silky smooth. I have been afraid to torque to the 20Nm. I chickened out before my wrench clicked. I may try again after my next ride, at least to 15nm.

There are only a couple of minor quibbles.
The upper link is solid aluminum. Drillium could fix this.
The bearing races ride against washers. This is normal, but it's a little bit of a pain to sandwich the washers in between the link and frame and then put the bolt thru. Grease is your friend for this.

Thanks for all the info and build documentation! I'm in the market for something in the 130-150mm travel range and might go with this frame.
Grinchy, your BXT experience wasn't bad? I think that's my biggest concern right now.

I bought from the official BXT store on Aliexpress. Make sure you have the correct model, they are still advertising the v2 that doesn't have thru pivots.

My experience was completely fine. BXT verified the color, logo/no logo, and size. I asked some Q on the weight and verified it was thru bolt version, which they answered. They suggested I tack on $45 for Fedex shipping. This I did, but it was optional. The Q/A phase took a couple days, they were responsive, but there is a time zone difference and I have a job, so often I could only respond once a day, then they'd respond. Nothing unusual about that.

The order was sent to paint, and about 10 days later shipped out. Then about five days get to my location. In total it was about four weeks from order to receipt.

I have one question open with them regarding the upper link upper washer orientation, they haven't ghosted me, but it seems to be going in circles re: getting the info back, but I've already decided which way the washers should go, so it is only for verification at this point.

I've had the bike out once so far, with another, bigger ride this weekend. It's dead silent and absolutely a pleasure to ride. You should get one.