Genuine Mazda Front Castor Adjustment / Alignment Bolt Kit • G-NC0-5-005

Genuine Mazda Front Castor Adjustment / Alignment Bolt Kit

Three-piece Genuine Mazda castor-adjustment kit for all Mazda MX-5 Mk3, Mk3.5 and Mk3.75 NC models with 1.8- or 2.0-litre petrol engines.

This eccentric adjuster assembly is installed at the rear mounting point of the front lower wishbone. Rotating the eccentric bolt and cam plate changes the position of the wishbone mounting point, allowing the front castor alignment to be adjusted.

Correct castor alignment contributes to steering stability, self-centring and consistent steering response. A seized, corroded or damaged adjuster can prevent the suspension geometry from being set correctly.

Each kit contains one Genuine Mazda eccentric bolt, one Genuine Mazda cam plate and one Genuine Mazda flanged nut. One assembly is fitted on each side of the vehicle, so two kits are required when renewing both front castor adjusters.

Bundle identification: G-NC0-5-005 is a MazSpec kit SKU rather than an individual Mazda OE part number. The three Genuine Mazda references contained within the kit are listed below.

• Product type: Front castor adjustment / alignment bolt kit
• Common names: Castor cam-bolt kit / eccentric alignment bolt kit / lower-wishbone adjuster kit
• Installation area: Front suspension
• Installation position: Rear mounting point of the front lower wishbone
• Adjustment function: Front castor alignment
• Side application: Left or right
• Kits fitted per vehicle: 2
• Kits supplied: 1
• Components supplied per kit: 3
• Eccentric adjustment bolt: F151-34-66Z
• Cam plate / eccentric washer: F151-34-473
• Flanged mounting nut: 9YB04-1406A
• Brand: Genuine Mazda components
• MazSpec bundle SKU: G-NC0-5-005
• MX-5 fitment: Mk3, Mk3.5 and Mk3.75 NC

Kit contents:

• 1 x Genuine Mazda eccentric castor-adjustment bolt – F151-34-66Z
• 1 x Genuine Mazda cam plate / eccentric washer – F151-34-473
• 1 x Genuine Mazda flanged mounting nut – 9YB04-1406A

Typical reasons for replacement:

• Eccentric bolt seized inside the wishbone bush sleeve
• Adjustment components heavily corroded
• Cam plate distorted or damaged
• Bolt threads damaged or cross-threaded
• Nut seized, rounded or damaged during removal
• Adjustment markings no longer clear
• Castor cannot be adjusted correctly during wheel alignment
• Front lower wishbone or rear wishbone bush being replaced
• Original alignment hardware cut out during suspension repairs
• Incorrect non-eccentric hardware previously installed

Quantity advice: One complete kit is used on each side of the vehicle. This listing supplies one three-piece adjuster kit; order two kits to replace both left- and right-hand castor adjusters.

Fitment advice: This kit is for the rear mounting point of the front lower wishbone, where castor is adjusted. It should not be confused with the separate camber-adjustment hardware used at the front mounting point of the lower wishbone.

Replacement advice: Where the eccentric bolt has seized inside the wishbone bush sleeve, removal may require cutting the original bolt. Inspect the wishbone bush and inner sleeve carefully before installing the replacement hardware.

Bush inspection: Check the rear lower-wishbone bush for splitting, deterioration, excessive movement or separation from its sleeve. New alignment hardware will not correct a worn or damaged suspension bush.

Mounting-point inspection: Inspect the front subframe adjustment slots and cam-plate seating surfaces for corrosion, elongation or impact damage. The eccentric plate must seat correctly against the locating surfaces for accurate adjustment.

Alignment advice: Record the original cam position before dismantling to provide an approximate starting point. A professional four-wheel geometry alignment is required after installation.

Tightening advice: Do not fully tighten the wishbone mounting hardware until the suspension is positioned as required by the applicable Mazda workshop procedure. Tighten the nut using the specified procedure after the castor setting has been established.

Other items to inspect: Check the front lower wishbone bushes, ball joint, opposite-side adjuster, front upper wishbone bushes, track-rod ends and shock-absorber mountings while the suspension is dismantled.

Useful tools / consumables: Vehicle lift or axle stands, socket and spanner set, breaker bar, calibrated torque wrench, penetrating fluid, alignment reference marker, reciprocating saw where seized hardware must be cut and suitable corrosion protection.

Difficulty guide: DIY Difficulty: Moderate to Advanced. Straightforward replacement is possible where the original hardware is free, but bolts seized into the bush sleeves can substantially increase the work required.

Why Genuine Mazda? Genuine Mazda adjustment hardware matches the original bolt dimensions, eccentric offset, cam-plate profile, thread and mounting arrangement. Correct geometry of the eccentric components is essential for achieving the intended alignment adjustment range.

What’s in the box: One Genuine Mazda eccentric adjustment bolt, part number F151-34-66Z; one Genuine Mazda cam plate, part number F151-34-473; and one Genuine Mazda flanged nut, part number 9YB04-1406A.

Installation notes: Raise and support the vehicle safely, then mark the position of the original eccentric adjuster before removal. Remove the nut, cam plate and bolt, using appropriate methods if the bolt is seized within the bush sleeve. Clean and inspect the wishbone bush, front subframe slots and cam seating surfaces. Install the new bolt and cam plate in the correct orientation, start the nut by hand and set the eccentric close to its recorded position. Tighten according to the Mazda workshop procedure, then complete a full four-wheel geometry alignment before normal road use.