~~~ Nikomi Bikes

[Nikomi]

After the v1 was completed, I started to design a fatbike for me. I had a Trek Farley 5 before, which I mostly liked, but the geometry was a bit too traditional for me. The seated position is fine for longer days on the saddle, but most of my riding is on the local MTB / enduro trails in the winter also, so the short reach was something that was too different from my enduro bikes. Also, I had some knee pain occasionally, and my hunch was that the long 175mm cranks combined with the wide q-factor was at least part of the issue (I’m 170cm = 5’7”).

Also, the Farley 5 had 27,5 x 3,8 in the rear and 27,5 x 4,5 in the front. I often felt that the rear tire did bite well and had just enough float for me (on groomed trails with fresh snow), but the front tire was eager to wash out.

So the fatbike had to have enduroish geometry and somewhat narrow q-factor, with at least 26 x 3,8 tires.

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The tubing is basically the same as in v1, straight gauge Docol R8.

Downtube: 35 x 1

Toptube: 30 x 1 ovalized to ~ 35 x 25 x 1

Seattube: 35 x 1 (with 3d printed PCTG insert to 31,6 id)

Headtube 45 x 1,5 (ends stretched with mandrel to 44 id)

Chainstays: 19,05 x 0,89 (front ends ovalized)

Seatstays: 15,88 x 0,89

BB: 38,1 x 2,11

Dropouts are cast steel UDH from Framebuilder Supply.

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We rented a shop with Olli during the time, and I also bought a manual lathe and milling machine. So a lot of time was spent on setting up the shop and machines, and also repairing them. And learning to use the machines, since my experience with actual machining is close to zero. And of course, the framebuilders favourite, designing and building tools

Few pictures from SolidWorks:

To be continued…

[Nikomi]

Happy New Year 2026! I hope you all make lots of good bikes this year

Here is a photodump of the Pulska. Please ask if any questions come to mind!!

As you can see, I like the tool building also. Most of the stuff here is purely for prototyping and testing the ideas of the tools. Well, the tube bender has seen a lot of use,and you know what they say, “Imitation is the sincerest form of flattery”. In that case there must be a certain Joe who is most certainly flattered

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Here is how the design actually ended up, with different gusseting for the headtube to allow space for the Mastodon fork.

Geometry with Mastodon 120mm @ 20% SAG

HTA: 67

STA: 77

Reach: 460

Stack: 625

Chainstay: 445

BB drop: 45

[sunshine.fab]

@Nikomi

LOVE this bender!! It looks similar to mine, but like you seriously improved just about every aspect of it. Really nice work throughout!

[Jukka4130]

Simply superb from start to finish!

[Nikomi]

Thanks for the comments!

Went for a quick ride today with Pulska. It’s been quite windy and cold here lately

I thought about the geo a lot while riding, and atleast on the undulating trails that we have here, it’s very close to perfect. I had two pedal strikes also so I don’t think the BB is too high It is very easy to switch between this and the enduro bike when the geo is almost the same. With Farley there was always a long adjustment period.

But of course on long flat sections there is some extra weight on the hands, compared to a traditional geo, and that is the only tradeoff I can think.

Otherwise, the frame came out maybe a bit too stiff on the front, could have probably done without the HT gusset tube. I also have a super stiff carbon bar (for keeping hands a bit warmer) on this which adds on top of that.

The Pulska has a 82mm BB, with SB+ cranks, which are only few mm wider than T-Type cranks. Which I really like since I’m not that tall / wide person

I made it work with a 0-offset Wolftooth chainring and 177mm rear hub with 4,2” tires. Although there are some minor marks from the chain on the tire. But I haven’t noticed anything while riding so I don’t mind.

[Nikomi]

Okay, on to the v2!

The main goals for v2 were:

• improve rear suspension lateral / torsional stiffness
• improve manufacturability, especially on rear triangle
• maintain mostly same geo
• maintain mostly same kinematics (can be more progressive)

With these in mind, the main pitfall in v1 was the main pivot construction. Having main pivot bearings in frame with gearbox and a 24T chainring is next to impossible (without high-pivot), so I was intrigued by the dual-link (yes some Dave something, who knows, patent expired) design. In this design, the lower link has the much needed torsional stiffness while having the bearings outboard of the gearbox, so it can be packaged while having reasonable kinematics.

Big plus also on this design is that all the bearings can be in the machined aluminium parts, so the bores are not subjected to welding distortion.

A lot of the time that I spent was changing the pivot points 1mm here and there, rotating the gearbox 1 degree and going through all the variations again. Short dual link suspension is easily quite progressive and really sensitive on the pivot locations!!! At least when you don’t have much space.

Initial design while going back-and-forth in Linkage X3:

The rear suspension really screamed for 3D-printed parts, so early on, I started to model the parts as printed. You can tell I really struggled with SolidWorks Loft-feature Total PITA. Should have learned Surface-modeling perhaps…

Clearance is clearance!

Say yes to PLA 3D-printing your designs before going too far! You get much better feeling of the structure.

Some FEA to find the hotspots and drive the design forward.

Going through lots of options as always.

You can probably also tell I’m not an industrial designer While doing a bike for myself with my own money, this is totally useless, but still! Kind of fun.

To be continued…