How to Adjust a Mizuno ST Driver: Quick Switch Settings & Weight Tuning Guide

The Mizuno ST driver uses a Quick Switch hosel with 8 positions across a 4° range. Each click changes loft by 1° and shifts the face angle slightly (open or closed). The table below gives all settings for a 9.5° or 10.5° head.

Quick Settings Chart

Position	Loft Change	Face Angle	Effective Loft (9.5° head)	Effective Loft (10.5° head)
1	–2°	2° open	7.5°	8.5°
2	–1°	1° open	8.5°	9.5°
3	–0.5°	0.5° open	9.0°	10.0°
4 (N)	0°	Neutral	9.5°	10.5°
5	+0.5°	0.5° closed	10.0°	11.0°
6	+1°	1° closed	10.5°	11.5°
7	+1.5°	1.5° closed	11.0°	12.0°
8	+2°	2° closed	11.5°	12.5°

Start at the “N” mark (position 4) if you are unsure. Lie angle changes about 0.5° per click (flatter at lower lofts, upright at higher lofts). The adjustable range is legal under USGA and R&A limits; verify locally for strict amateur events.

Step-by-Step Adjustment

Remove the shaft from the head

Loosen the screw on the sole using the included torque wrench or a 3/8” drive bit. Pull the shaft straight out. Do not twist or rock it side-to-side.

Select the desired Quick Switch position

Rotate the hosel ring on the shaft tip to the number or “N” you want. The ring must click into a defined detent at each position. If it spins freely without a positive stop, the ring may be misaligned or damaged. Stop here and inspect for debris or a broken retaining clip. If the ring feels loose in every position, do not install the shaft — contact Mizuno support for a replacement hosel assembly.

Re-insert the shaft and tighten

Slide the shaft into the head, keeping the alignment marks matched. The mark on the head’s hosel bore must line up with your chosen position number. Tighten the screw to 36 in-lbs (4 N·m) using the Mizuno torque wrench. If using a third-party torque wrench, set it to 36 in-lbs — never exceed that value.

For ST-G models: adjust the dual weight tracks

The ST-G has two 7g weights (one in the front track, one in the rear track). Use the included weight tool to slide or swap them. Moving the weight forward (toward the face) lowers spin; moving it back increases launch and forgiveness. You can also place one weight heel-side and one toe-side to fine-tune face angle at impact. Heel bias promotes a draw; toe bias promotes a fade.

Success check: After tightening, the driver should sit square at address. If the face looks noticeably open or closed, double-check that the alignment marks are still matched — the ring can rotate during insertion if not held firmly. If you hear a rattle, the screw may not be fully seated; retighten to spec. If the rattle persists after re-torquing, stop using the driver and inspect the weight tracks for loose components.

Common Settings (Draw / Fade / High / Low)

Draw bias (right-to-left ball flight)
– Hosel: position 6, 7, or 8 (closed face). Start with +1° (position 6).
– Weight (ST-G only): place a 7g weight in the heel track. If using both tracks, put the heavier weight in the heel and the lighter in the toe.

Fade bias (left-to-right ball flight)
– Hosel: position 1, 2, or 3 (open face). Start with –1° (position 2).
– Weight (ST-G only): place a 7g weight in the toe track.

Higher launch and more spin
– Hosel: position 7 or 8 (+1.5° to +2° loft). This also closes the face slightly, so adjust your aim target left.
– Weight (ST-G only): move both weights to the rear track for maximum launch increase.

Lower launch and less spin
– Hosel: position 1 or 2 (–2° to –1° loft). The open face helps reduce spin on center strikes.
– Weight (ST-G only): move both weights to the front track. Front weight sacrifices forgiveness on off-center hits.

Important: The ST-Z has a fixed weight in the back cavity (no adjustability). The ST-X has a fixed heel weight for inherent draw bias. Weight tuning is only available on the ST-G.

Torque & Tools

Torque specification: 36 in-lbs (4 N·m) for all Mizuno adjustable drivers.

Tool: Use the Mizuno torque wrench that came with the driver. If lost, buy a compatible replacement (3/8” drive, 36 in-lbs max).

Common mistake: Overtightening can strip the screw threads or crack the hosel ferrule. Under-tightening can cause the shaft to loosen during the swing.

Check periodically: Before each round, give the screw a quick quarter-turn with the wrench to confirm it has not backed out.

Stop and escalate threshold: If you feel resistance before reaching 36 in-lbs, or if the screw will not turn at all, stop immediately. A seized or stripped screw requires professional removal. Do not apply extra force — take the driver to a certified club fitter or contact Mizuno warranty support.

FAQ

What torque should I use for the Mizuno ST driver?
Always tighten to 36 in-lbs (4 N·m). Using a standard socket wrench will likely over-tighten.

Can I adjust loft without changing lie angle?
No — the Quick Switch hosel changes loft and lie simultaneously (about 0.5° lie per click). For a pure loft change you would need a different shaft or head.

Does the ST-X have adjustable weights?
No. The ST-X uses a fixed heel weight to promote a draw. Only the ST-G has dual weight tracks.

How many settings does the Quick Switch hosel have?
Eight total positions, covering a 4° range (from –2° to +2° loft relative to the stamped loft).

Will adjusting the loft affect my driver’s legality?
The adjustable range is within USGA and R&A limits. As long as the loft setting is not physically altered beyond the ±2° range, it remains conforming. Verify locally if you play in strict amateur events.

What if I lose the torque wrench?
Use a 3/8” drive torque wrench set to 36 in-lbs. Do not guess — hand-tightening is unreliable.

Does the Harmonic Impact Technology change with setting adjustments?
No. The sound and feel are tuned into the head structure itself, not affected by hosel positioning or weight placement.