Home Forums Tech Talk How to: converting a 10mm-kingpin spindle to 8mm

This topic contains 2 replies, has 2 voices, and was last updated by  Samir Shah 3 years, 11 months ago.

  • Author
  • #47685

    Samir Shah

    Wanting to get more front grip for my son’s old Birel R31, I’ve decided to try out 25mm spindles and hubs. Hoping this gives the old girl more modern turn-in.

    I got hold of 2 used Intrepid PH1 25mm spindles ($70/pr on ebay). They are set up for 10mm kingpins. However, they use the same 22mm diameter bearing as the standard 8mm 608 bearing – they use 4 of them per spindle, 2 on top and 2 on the other side of the spindle. This means that the internal spindle crush spacer is shorter than ‘normal’.

    I took apart the 12D Birel 8mm spindle that we bent, and extracted the 8mm diameter crush spacer. It is exactly twice the length of the Intrepid PH1 internal spacer (which BTW is not perfectly shaped). Put it on a lathe, cut it in 2, and trimmed it to the required length. Now I have 2 crush spacers for the Intrepid PH1 spindle bearings that are for an 8mm kingpin!

    Waiting for new bearings and 25mm front hubs, but this should work! In fact, the Intrepid PH1 is shorter in height than the Birel spindle, so it will give me more chassis height adjustment as well. I’ll report on how if does after we try it out.



  • #47736

    Walt Gifford

    Why not endeavor to use a 10mm king pin if you’re beefing things up?


    FAA certified jet engine and aircraft technician,
    Nicholson Speedway class champion 2001,
    Yamaha KT100 Service Center,
    41 years karting experience

  • #47738

    Samir Shah

    I thought about also going to a 10mm kingpin, but that involves additional costs of a new kingpin, pills, spacers, and also I will have to drill out the holes in the chassis bracket that take the kingpin, so it will not be reversible. This way, I can use the 25mm for when my son needs more grip and switch back to 17mm when he does not. Or at least try both and decide which works better for my son.

You must be logged in to reply to this topic.