Do these control arms fit the Cayman GT4 or Boxster Spyder GT4?

No. The 981 GT4 and 982 GT4 use a different rear suspension geometry that requires a separate dedicated kit; the RLCAK 981 GT4 and the RLCAK 982 GT4 respectively. These standard RLCA arms fit the non-GT4 Boxster and Cayman variants only. Confirm your specific model before ordering.

How does rear roll center correction on these control arms reduce oversteer tendency in fast transitions?

When a Boxster or Cayman is lowered, the rear roll center drops further below the center of gravity than the center of gravity itself drops. This increases the lever arm the chassis uses to produce body roll; the car rolls more per unit of cornering force and the rear end can become loose in fast direction changes. The stainless spacers in the RLCA raise the rear roll center back up, shortening that lever arm and reducing the roll moment at the same spring rate. Less rear roll means less tendency to snap oversteer in fast transitions without requiring stiffer rear springs.

What additional geometry benefit comes from pairing the rear RLCA with the front SPL LCA kit?

With both the front SPL lower control arms and the rear RLCA installed, the height of both the front and rear roll centers can be individually adjusted. The imaginary line connecting the front and rear roll centers is the roll axis; the pitch of that axis has a significant influence on the car's balance through esses and multiple direction changes. A front-high roll axis tends toward understeer; a rear-high axis tends toward oversteer. Adjusting both ends gives the builder control over this variable, which is not available with any single-axle geometry upgrade.

What is the NVH tradeoff on a daily-driven Boxster or Cayman?

SPL characterizes the NVH as present and tolerable for most drivers; comparable to an OEM GT3 or GT4. Spherical bearings transmit more road noise and felt energy on rough surfaces than rubber bushings. On smooth roads, ride quality improves because the shock absorber can work without bushing bind. Reducing tire pressure moderately, running a more compliant tire sidewall construction, and using a quality shock absorber with optimized compression damping all reduce the felt energy for daily-driven builds.

Are replacement rod ends available for the RLCA?

Yes. Replacement rod ends are available from SPL Parts. Contact the Bulletproof sales team for the correct replacement for your specific application.

Description

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Description

SPL Parts Adjustable Rear Lower Control Arms for 98x / 718 Porsche Boxster / Cayman

The rear lower suspension on the Porsche 987, 981, and 718 Boxster and Cayman connects the rear wheel to the chassis through rear lower control arms that use rubber bushings — bushings that deflect under lateral and longitudinal loads, allowing the rear lower geometry to move away from its set values during the moments when consistent geometry matters most. The practical result is camber loss under cornering, bumpsteer over rough roads and track curbing, and a vagueness in the rear end’s behavior that makes the car harder to read and trust at the limit. The SPL RLCA 987 V2 rear lower control arms address all of that by eliminating rubber at every rear lower arm bushing position and replacing it with PTFE-lined, F1-spec FK spherical bearings manufactured in the USA. The bearings articulate freely without deflecting, holding the rear lower arms in their set positions under braking, acceleration, and cornering loads. Rear camber holds. Bumpsteer is reduced. The steering feel and rear feedback that rubber compliance was filtering from the rear lower suspension comes through clearly.

Features

Adjustable rear lower camber and rear roll center; corrects both geometry problems introduced by lowering the 987, 981, and 718
PTFE-lined, F1-spec, self-cleaning FK spherical bearings manufactured in the USA; eliminates OEM rubber bushing deflection at every rear lower arm bushing position
2.85lbs (1.29 kg) per side; 6061-T6 billet aluminum arms and clevis, anodized black
4140 Chromoly Double Adjuster, electroless nickel-plated; 360-degree rotating clamp locks without jam nuts; single allen key adjustment
Stainless steel roll center adjustment spacers; 4340 Chromoly heat-treated studs
Class 10.9 metric hardware; SAE Grade 8 imperial hardware; Ti-6Al-4V titanium socket head allen screws anodized blue
When paired with the front SPL LCA, allows roll axis pitch tuning for advanced over/understeer balance adjustment through combined front and rear lower geometry control

Specifications

Body Material: 2024-T351 aluminum (gun-drilled, black anodized)
Bushings: PTFE-lined F1-fit FK USA spherical bearings
Adjustment: Track width, camber, and roll center
Hardware: Heat-treated chromoly with high-misalignment studs
Origin: Made in the USA

Applications

Porsche Boxster: 987, 981, 982 | 2005-present
Porsche Boxster GTS: 982 | 2017-present
Porsche Boxster S: 987, 981, 982 | 2005-present
Porsche Boxster Spyder: 987 | 2010-2012
Porsche Boxster Spyder RS: 987 | 2011-2012
Porsche Boxster T: 982 | 2019-present
Porsche Cayman: 987, 981, 982 | 2005-present
Porsche Cayman GTS: 982 | 2017-present
Porsche Cayman R: 987 | 2011-2012
Porsche Cayman S: 987, 981, 982 | 2005-present
Porsche Cayman T: 982 | 2019-present

Notes

Installation Instructions
Not compatible with 98x GT4
Replacement rod ends available from SPL Parts, please contact us
SPL components are made-to-order in the USA; build time will be confirmed at the time of order.

Frequently Asked Questions

Do these rear lower control arms fit the Cayman GT4 or Boxster Spyder GT4? No. The 981 GT4 and 982 GT4 use a different rear lower suspension geometry that requires a separate dedicated kit — the RLCAK 981 GT4 and the RLCAK 982 GT4 respectively. These standard rear lower control arms fit the non-GT4 Boxster and Cayman variants only. Confirm your specific model before ordering.
How does rear roll center correction on these rear lower control arms reduce oversteer tendency in fast transitions? When a Boxster or Cayman is lowered, the rear roll center drops further below the center of gravity than the center of gravity itself drops. This increases the lever arm the chassis uses to produce body roll — the car rolls more per unit of cornering force and the rear end can become loose in fast direction changes. The stainless spacers in the rear lower control arms raise the rear roll center back up, shortening that lever arm and reducing the roll moment at the same spring rate. Less rear roll means less tendency to snap oversteer in fast transitions without requiring stiffer rear springs.
What additional geometry benefit comes from pairing the rear lower RLCA with the front SPL LCA kit? With both the front SPL lower control arms and the rear lower RLCA installed, the height of both the front and rear roll centers can be individually adjusted. The imaginary line connecting the front and rear roll centers is the roll axis; the pitch of that axis — whether it tilts front-high or rear-high — has a significant influence on the car’s balance through esses and multiple direction changes. A front-high roll axis tends toward understeer; a rear-high axis tends toward oversteer. Adjusting both the front and rear lower geometry simultaneously gives the builder control over this variable, which is not available with any single-axle geometry upgrade.
What is the NVH tradeoff on a daily-driven Boxster or Cayman? SPL characterizes the NVH from the rear lower spherical bearings as present and tolerable for most drivers — comparable to an OEM GT3 or GT4. Spherical bearings transmit more road noise and felt energy on rough surfaces than rubber bushings. On smooth roads, ride quality improves because the shock absorber can work without bushing bind in the rear lower arms. Reducing tire pressure moderately, running a more compliant tire sidewall construction, and using a quality shock absorber with optimized compression damping all reduce the felt energy for daily-driven builds.
Are replacement rod ends available for the rear lower RLCA? Yes. Replacement rear lower rod ends are available from SPL Parts. Contact the Bulletproof sales team for the correct replacement for your specific application.

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 Rear Lower Control Arms for 98x / 718 Porsche Boxster / Cayman [SPLRLCA987V2]

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SPL Parts Adjustable Rear Lower Control Arms for 98x / 718 Porsche Boxster / Cayman

Features

Specifications

Applications

Notes

Frequently Asked Questions

About SPL Parts

Reviews