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Custom Frame Build

Posted by Jim MacPhail on

A slightly different post this time; rather than introducing some new tool that we’ve added to our range, I thought I’d share a few pictures of a project that has robbed me of much of the time that should have been spent riding this summer!

This is the second front triangle that I have built, and the first time that I have attempted fillet brazing.  The tubes are 4130 straight gauge steel.

The goals of this build were: 

  • Reach of 515mm
  • Head angle of 65deg
  • Uber-steep seat angle (85deg!)
  • Chainstay of 445mm

The rear triangle and linkage are from a Specialized Enduro 29.  Though the pivots have been moved backwards to lengthen the chainstay, the relationship between each pivot and the shock has remained the same,  preserving the Enduro's original suspension kinematics.  

I’m happy with the results.  I’ve been riding the frame for a couple of months now and love the slacker headangle and especially the longer chainstay.  It rallies around corners in a way that my previous bike didn’t.

Lengthening the chainstay by changing the position of the BB relative to the rear axle path will inevitably have affected the pedalling behaviour, at a guess reducing anti-squat deeper in the travel, something I was a little concerned about, but in reality I haven’t noticed any adverse effect.

The seat angle experiment has had mixed results..  At first the seated position felt entirely wrong. After a little riding I’ve grown to really like the position on the climbs.  Seated on the flat though, it feels a little like I’m falling off the front of the bike. The next build might have an 80deg seat angle!


  • Hi Thijs, sorry for the late reply! I think that to make a steel hardtail frame you wouldn’t need specialist metal cutting tools. There are great online tools for ‘tube notching’ that enable you to print a paper template that can be wrapped around a tube to show where to cut to get tubes of any size to join at any angle. The thin walled steel tubes used for frame building can be cut very easily with a simple fine-tooth hacksaw and the edges shaped accurately and quickly with a good file. Fittings like dropouts can be bought pre-made. You’ll need to have the bottom bracket and headtube reamed in the end, but this can be done by a local bike shop. The tricky part might be bending the stays, but I think that this can be done with a little effort and ingenuity, perhaps they can be bought pre-made

    Jim on

  • Soubds like a really cool project, and the outcome looks amazing!!
    Last year I made an carbon fiber hardtail frame. I would love to make my next frame from steel, but have never worked with metals before. Do you think its possible to make a steel frame, without any special metal cutting equipment?

    Thijs Van Noordt on

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