Wzrd. dungeon report

Welcome to the dungeon

I will keep this up to date with my personal projects and some of my entertaining customer builds as well.


The unofficial winter training ground of some of the fast DH racers around is a mere 50 minute drive from my shop. Prior to starting wzrd I would be up there up to 10 times per winter. Last winter I only made it out twice (on my pink and purple hardtail) but this year I have already made it up four times (on my show bike, and hope to get back up once this winter storm passes. Prevost is only open when there is no fire hazard, so its a balance of that and snow.

While my hardtails hta’s in the 61 degree range, and 1300mm+ wheelbases can soak up a lot of steepness and speed, the lack of rear travel still gets in the way. I nuked two rear wheels last winter, and have already killed one this year - something needs to change!

This is where the DH bike comes into play. Its primary home will be Prevost in the winter, but will also see Whitler and some of the smaller lift access bike parks in the summer. The plan is to build something on the planted & fast side of things, rather than a more playful park/fr bike.

Front end geo will have a steeper hta and a shorter reach then my current hardtail, but the same length unsagged chainstay length. With a 44mm head tube and the fox 40’s straight steerer I will be able to adjust the hta and reach a fair bit with different headsets.

Reach - 500
Stack - 650
HTA - 62.5
BB height - 345mm (294 sagged)
CS length - 450mm (455 sagged)
Wheel size - 29/29

The current plan is a single pivot with a non-concentric idler attached to the chainstay. The pivot will be high and quite far forward sitting above & in front of the chain ring in the downtube. This layout will get me 209mm of travel from a 260x75mm shock.

Being a DH bike, I will be able to run a 84mm bb shell with external bearings for the cranks, gaining me a lot of room to play with for the pivot construction. I want this pivot to be as stout as possible as I fear the already high single pivot forces will only be exasperated by my chainstay length. So, the plan is to use a 68mm t47 shell with a 24mm internal bottom bracket. Being able to use my frame jig to make sure the main pivot gets brazed in centered and square is a bonus. Spinning up a 24mm pivot spindle with a clean m12 compression bolt shouldn’t be too hard either (for whoever I pay to do it as I do not have a lathe haha).

I want to add a downward curve to the chain stays to avoid any chain interference issues, but haven’t figured out curves on planes yet in Fusion. If someone has a good tutorial they can point me to on this topic I would be eternally grateful.

I am still stuck on coming up with cable routing that doesn’t suck. I have worked on dual suspensions that the cables saw into the frames (yetis) and others the saw into the cables (ibis aluminum). I normally run my cables in the top tube into the seat stays, but there will be way too much movement for that on this bike. I am considering through the down tube, through the main pivot and then into the chainstays. My only beef with that is then the brake line has to teleport from in the chainstay to on top of the seat stays. Cable routing keeps me up a night. I need professional help.

Anyways, here are the drawings and charts I have so far. Unfortunately I yeeted my PC last week, so I have had made a few small changes since these screen grabs.

Let me know what y’all think.

okay, talk soon.


For the main pivot you can also do the 44mm heattube and a pair of upper headset cups.

I have done this on several fs bikes now and no complaints.

This is from my first fs frame I built in 2014 and o think the first use of 44mm headtube as pivot. It was from @anon91558591 say in either his blog or on mtbr saying “if I was to do it again it would be…”. With this you need no special parts made via lathe, just use a steer tube off cut from a fork and two starnuts.


Yeah, I had done a bunch with BMX BB’s and 38mm BSA shells way back before 44mm head tubes were a thing, but I think you do get the prize for first doing a 44mm head tube as a pivot!

BMX BBs work fine but you have to chop up a 19/22mm spindle and those are crazy overbuilt and it ends up being a pain because of the built in splines that you don’t want/need.

I’d run AXS for the derailleur and then under/over the BB and up to the bottom of the swingarm for the brake. But that’s just me.


Hi Em,
Thanks for sharing! Looks like a big bike and an equally big undertaking.

Not sure exactly how your CAD is currently setup, but this might help you in the right direction:

Create a construction plane w/ your centerline:

construct > plane at an angle > click your virtual centerline

Sketch your centerline:

Create plane along centerline:

construct > plane along path > click your centerline

Draw your tube profile:

note: I usually do solid tube to save on computational power

Sweep your tube:

create > sweep > click your centerline and profile

Finally, a forum tip - GIFs are enabled and encouraged:


Bless this intel. Building the second plane off my initial center line was the missing link.

Sorry for boomerposting a link to a meme. I will do better.


@earle.b I was originally planning on doing a 44 ht, but have been leaning towards the bb shell as of late. I’m likely over thinking this, but I am worried about warp on the thinner ht as I’ll be brazing around 80% of it. The t47 shells have some reassuring heft to them.

@anon91558591 if this was getting a real drivetrain, I’d throw my axs kit on it for sure haha. This bikes getting a 7s DH drivetrain, cable shift only!

I think no matter how you lay it out a cable shift system is going to be pretty meh at best.

But a DH bike doesn’t need to shift perfectly, so whatevs.



This is gonna be sweet!

I’m curious why you would want to use a 260mm i2i and not a 250x75 shock? I’m not against custom length shock to fix problems but if you are designing from scratch?

Also, IF you wanted more progression (not saying you need it) then a trunion 225x75 would be easier to package at the expense of potential side loading.

I like the bb main pivot idea!

Good catch! I was typing off memory haha

I’ll be using the longest available fox x2 - 250x75.

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