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Description

SPL Parts Adjustable Front Caster Arms with Anti-Dive Geometry for 991 / 98x Porsche 911 / Boxster / Cayman

Front caster is one of the most impactful alignment settings on the 991 911, 981 Boxster and Cayman, and 718/982 generation — and the front caster arms are what control it. More caster improves steering self-centering feel, high-speed stability, and front grip through the steering arc’s camber gain. It also compensates for the left-to-right caster variation that builds up after any front geometry modification. The problem is that the factory front caster arms use a rubber bushing that deflects under load and provides limited adjustment range — adequate for factory ride height and factory tolerance, but not adequate for performance-aligned builds or for the geometry changes that come with lowering and upgraded front lower control arms. The SPL TR 991 adjustable front caster arms provide the full adjustment range needed to set caster precisely at any ride height, equalize it left-to-right after any geometry change, and tune anti-dive geometry independently. When the SPL LCA front lower control arm is also installed, these front caster arms can also be used to position the wheel forward or rearward in side view to prevent tire contact with the front bumper or fender — a practical geometry consideration on lowered builds running wider tires than factory.

Features

Wide-range front caster adjustment via adjustable front caster arms; extends significantly beyond the factory arm’s range; allows caster optimization for turn-in response, steering feel, and left-to-right equalization
Anti-dive geometry tuning via included 6061-T6 aluminum spacers; adjusts the effective front caster arm angle at the subframe to control front nose dive under braking independently of caster
When paired with the SPL LCA front lower control arm, the front caster arms can also position the wheel longitudinally to prevent tire contact with the front bumper or fender on lowered builds
Gun-drilled billet 2024 aluminum hex rods; precision CNC-machined; lightweight billet 6061-T6 aluminum clevis
Computer Aided Design validated by Finite Element Analysis; structural performance of the front caster arms confirmed across all load cases before production
SPL exclusive 360-degree rotating clamp; blue anodized titanium hardware; locks caster without jam nuts; single allen key adjustment
FK spherical bearings eliminate rubber bushing deflection; front caster arms hold their set position under sustained braking and cornering loads
Designed for use with OEM or OEM-style front lower control arms; not a standalone replacement for the FLCA

Specifications

Body Material: 2024 aluminum hex rod (gun-drilled)
Bushings: PTFE-lined FK USA spherical bearings
Caster Adjustment: Wide range — both axes corrected
Anti-Dive Adjustment: 6061-T6 spacer set included
Origin: Made in the USA

Applications

Porsche 911 Carrera: 991 | 2012-present
Porsche 911 Carrera 4: 991 | 2012-present
Porsche 911 Carrera 4S: 991 | 2012-present
Porsche 911 Carrera 4 GTS: 991 | 2015-present
Porsche 911 Carrera GTS: 991 | 2015-present
Porsche 911 Carrera S: 991 | 2012-present
Porsche 911 Carrera T: 991 | 2017-2019
Porsche 911 Targa 4: 991 | 2014-present
Porsche 911 Targa 4S: 991 | 2014-present
Porsche 911 Targa 4 GTS: 991 | 2017-present
Porsche 911 Turbo: 991 | 2014-present
Porsche 911 Turbo S: 991 | 2014-present
Porsche 911 GT2 RS: 991 | 2018-present
Porsche 911 GT3: 991 | 2014-present
Porsche 911 GT3 RS: 991 | 2016-present
Porsche 911 R: 991 | 2016-2017
Porsche Boxster: 981, 982 | 2012-present
Porsche Boxster GTS: 981, 982 | 2014-present
Porsche Boxster S: 981, 982 | 2012-present
Porsche Boxster Spyder: 981 | 2015-2016
Porsche Boxster T: 982 | 2019-present
Porsche Cayman: 981, 982 | 2012-present
Porsche Cayman GT4: 981, 982 | 2015-present
Porsche Cayman GT4 RS: 982 | 2021-present
Porsche Cayman GTS: 981, 982 | 2015-present
Porsche Cayman S: 981, 982 | 2012-present
Porsche Cayman T: 982 | 2019-present
Porsche Cayman R: 981 | 2012-2016

Notes

Installation Instructions
SPL components are made-to-order in the USA; build time will be confirmed at the time of order.

Frequently Asked Questions

Why does any change to front camber require adjustable front caster arms on the 991, 981, and 718? On the 991, 981, and 982/718 front suspension, caster and camber geometry are interdependent. When the front lower control arm is lengthened or shortened to change camber, it also changes the longitudinal position of the wheel hub relative to the front strut centerline — which changes caster. Conversely, changes in ride height that affect camber also affect caster. Without adjustable front caster arms, the caster cannot be corrected after any camber change, and the car cannot be properly aligned. The SPL TR 991 front caster arms are the required companion to any front camber adjustment on these platforms.
What is the practical benefit of anti-dive geometry adjustment on the SPL front caster arms? Anti-dive geometry describes how much the front suspension resists compressing under braking load. More anti-dive means the front end stays flatter under hard braking — better front tire contact, more stable corner entry, and more consistent braking behavior. The 6061-T6 aluminum spacers in the TR 991 front caster arms allow the anti-dive geometry angle to be changed at the subframe connection point, tuning this characteristic independently of the caster setting. For track-prepared builds with dedicated brake setups, this is a meaningful additional variable that most aftermarket front caster arms do not offer.
Can these front caster arms help prevent tire rub on a lowered build with wider tires? Yes, when paired with the SPL LCA front lower control arm. The SPL TR 991 front caster arms change the longitudinal wheel position in side view in addition to the caster angle itself. Moving the wheel slightly rearward via front caster arm adjustment can provide additional clearance between the front tire and the bumper or inner fender on builds running wider-than-factory tire widths after lowering. SPL specifically notes this application in the context of the combined LCA and TR 991 front caster arms kit.
Are these front caster arms designed to replace the front lower control arm, or are they a separate component? The TR 991 front caster arms are a separate arm from the front lower control arm — they are the caster/thrust/tension arm, which is a distinct linkage in the 991, 981, and 982/718 front suspension. The front caster arms are designed to be used alongside the OEM or OEM-style front lower control arm; they do not replace it. For a complete front geometry upgrade on these platforms, the TR 991 front caster arms pair with the SPL LCA front lower control arm, which provides camber, roll center, and track width adjustment.
Do these front caster arms work on both the 991 Carrera and the 911 R/GT cars? The TR 991 front caster arms cover the 2012+ Porsche 991 broadly. The 991 GT3 and GT3 RS use different front suspension configurations with different front caster arm geometry. Confirm your specific 991 variant is covered before ordering — non-GT 991 Carrera, Carrera S, Carrera 4, Targa, and Turbo variants are confirmed fitments for these front caster arms.

About SPL Parts

SPL Parts is a USA-based manufacturer of high-performance suspension components engineered for both professional racing and demanding street applications. Built on the core principles of strength, lightweight construction, low friction, and precision, SPL Parts products deliver the adjustability and alignment performance required by top race teams and discerning enthusiasts alike. Every component is produced using USA-sourced, certified materials and machined by experienced local shops to exacting tolerances. Professional TIG welders ensure maximum weld integrity, while each part is hand-fitted and treated with anti-seize and 3M internal panel coating for lasting protection. SPL Parts conducts all research and development in-house, allowing the team to leverage firsthand product knowledge and deliver unmatched customer support. Their suspension components feature innovative adjuster designs for quicker, more precise alignments, and utilize spherical bearings with Teflon liners that are self-cleaning, self-lubricating, and built for long service life. From concept to assembly, SPL Parts is made with pride in the USA by skilled machinists and welders who are committed to quality, innovation, and performance.

Additional Information

The Bulletproof Automotive website contains many thousands of products purchased in multiple different currencies. All of the prices are entered manually and accurately at the time of entry. Due to the consistently fluctuating international exchange rates, at times prices may not be able to be honored at their original intended rate. We apologize for any inconvenience this may cause, unfortunately our website is unable to compensate dynamically for what can at times be volatile changes in the cost of items due to currency values fluctuating, changes in prices from suppliers, changes in shipping and import duties, and other factors. Rest assured that any order you place on line will be at zero risk to you in this area. If in the event your order cannot be fulfilled at the original intended website price we will offer you a 100% refund, no questions asked. We will continue to do our best to maintain updated prices and we will always continue to offer our price match guarantees as well to ensure our prices are always the best for you. In short, prices may change without notice. It is always advised to give us a call prior to placing your order online to confirm availability and to confirm current pricing.

Shipping Policy

Items that are in stock in the US, either at Bulletproof’s warehouse or at a supplier’s warehouse, are generally delivered within 7-10 days. Special order items from overseas take considerably longer. As a courtesy Bulletproof offers delivery estimates to our customers which take into consideration manufacturer availability and shipping schedule. These estimates represent our best guess based on previous orders from the manufacturer and do not in any way imply a guaranteed delivery window. Many manufacturers work in a “just in time” inventory system and often take 2-20+ weeks to produce an item once an order is submitted. All deliverable items are then sent to our Japanese warehouse. Bulletproof ships a minimum of one full ocean freight container every month from Japan, oftentimes more than one a month. Ocean freight takes an average of 4 weeks. Typically it breaks down to one week in Japan for paperwork and customs, two weeks by boat and one week in US customs/clearance. Due to the wide number of variables between manufacturer and shipping schedules, delivery estimates are simply just that – estimates. We attempt to estimate conservatively and we usually deliver faster than our estimates suggest. It is not Bulletproof’s policy to guarantee delivery time of any special order item, this is impossible for us to do. By ordering you acknowledge that there is no required delivery ETA and an order may not be canceled or altered due to manufacturing or shipping delays, all ETA’s are provided as a best guess only. Please review the full Terms & Conditions here.

BP Pricing Difference

We do pricing a little differently on our JDM brands and we believe in making things simple and clear. No hidden fees or surcharges. Every price you see includes the shipping cost to our office in Los Angeles, California and all the associated taxes/duties/fees for bringing the products into the US. The only shipping you ever pay is from our facility in the US to your location. Be wary of resellers that don’t include the cost of international shipping in their pricing on JDM parts. While we believe we’ll always have the lowest all-in price on JDM products, we offer a price match guarantee for all authentic parts purchased from authorized dealers as well. For many international customers, it’s much more affordable to ship from the USA than from Japan directly, as the air freight and ocean freight costs are typically much less. However, for customers looking to ship directly from Japan outside of North America, or domestically in Japan, we can provide pricing specifically for that scenario. Please do not hesitate to contact us with any pricing questions or concerns. Please email us at sales@bulletproofautomotive.com with any inquiries.

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SPL Parts Adjustable Front Caster Arms with Anti-Dive Geometry for 991 / 98x Porsche 911 / Boxster / Cayman [SPLTR991]

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SPL Parts Adjustable Front Caster Arms with Anti-Dive Geometry for 991 / 98x Porsche 911 / Boxster / Cayman

Features

Specifications

Applications

Notes

Frequently Asked Questions

About SPL Parts

Reviews