Steering Spindles Ø25 mm

HST / SA2 / BSD Standard Spindle
This is the standard steering spindle for all large OTK karts with a Ø25 mm spindle and Ø10 mm kingpin bolt.
When to use it: The starting point for most conditions. A safe choice on low/medium grip tracks where more direct steering response is desired.

HST / SA2 / BSD 1B Spindle
The 1B version has a steeper kingpin inclination compared to the standard spindle.
When to use it: When you want to calm down the front end on high-grip tracks, as it reduces the tendency to “bind” into the asphalt and lift aggressively, while also making the steering lighter. A good alternative on tracks where grip has built up.

HST4 / SA2 / BSD 4F – Multi-hole Spindle
The new OTK spindle is the 4F model, featuring a longer steering arm and four holes for the tie rod – providing four Ackermann settings.
When to use it: If you want to adjust Ackermann via the spindle’s hole positions.

 Inner hole = More Ackermann and faster turn-in

 Outer hole = Less Ackermann and more stability in fast corners

Quick Rules of Thumb (trackside choice)

 Low/medium grip, need strong turn-in: Start with the Standard

 High grip, or if the kart “binds”/lifts too much at the front, or if lighter steering is desired: Try the 1B

 Need finer adjustments of steering response/front geometry to suit the track’s corner types: Choose the HST4and experiment with the arm holes (inner = more Ackermann/faster turn-in; outer = calmer)

Short Technical Background

 KPI (King Pin Inclination): The kingpin leans inward; more KPI increases self-centering and changes the load distribution (less lift on the outer front wheel, more drop on the inner), which can make the front end more aggressive on high-grip tracks.

 Ackermann via spindle arm holes: The inner hole provides more Ackermann (greater toe-out in cornering) = faster turn-in; the outer hole approaches parallel steering = more stability.