How to run 19” Apex Wheels on your GT4RS/Spyder RS

Running 19” wheels on your GT4RS or Spyder RS is a very tempting idea, especially with the added width and tire options that the popular 265/35-19 and 305/30-19 open up. This is not without its nuances as multiple modifications are required with both brakes and suspension components. In this article I will explain in depth each mod required, how they impact the fitment, and anything else you may need to be aware of.

The big dollar item, brakes. The front brakes on the GT4RS are large to say the least. While the “normal GT4” has 380mm steel brakes that fit into 19” wheels safely, the 4RS gets larger 408mm steel brakes or optional 410mm PCCB (same size on the normal GT4). Our laser scan of both the PCCB and Steel option show the caliper is the same exterior dimensions and located in the same position between the two brake options. Meaning, there are no clearance differences between the two. This means we need to do something to gain some clearance on the front. Note that the OEM rear steel and PCCB brakes clear our 19” wheels. There are three main options, two of which we recommend. The popular OEM+ option is using 991 GT3 front calipers from a 380mm steel brake car, and the associated 380mm front rotors. This can be OEM rotors, Girodisc, AP, etc. If you are starting with a PCCB car, this would be a good time to convert the rear rotors to steel from an aftermarket rotor supplier. You will need new pads as well, Front pads at a minimum for a steel brake car, and front and rear pads for a PCCB car when you convert the rear rotor from carbon to steel. AP/Essex offer a 9661 caliper 394mm brake kit that offers easier pad swap and weight savings over the OEM steel brakes. The last brake option to mention are the sport 380mm kits from PFC. Those clear our 19x9.5”ET49 EC-7RS but not our 20x9”ET53 or the OEM wheels from what we have seen. For this reason the 991 GT3 and AP/Essex 9661 caliper kits are our go to recommendations.

Brake option comparison:

To round out the front modifications, let's talk about camber plates. These are required to pull the top of the wheel and tire inboard away from the fender's edge to allow that 9.5” wheel and most common 265/35-19 to fit under the fender. Adding camber from the lower control arm with shims does not provide the clearance necessary to make this work. LCA shims also have a knock on effect of changing the caster value and pulling the front wheel forward in the wheel arch. At some point this could cause rubbing near steering lock. This can be fixed with some caster adjustment. From what we have seen with common track alignments, when getting all the possible camber from the camber plate and then shimming the LCA, this generally does not happen.

On the rear axle there are two final modifications that are needed. The first is a new rear toe link. Because we are pulling an inch of diameter out of the car from 20” down to 19”, the inner lip of the wheel gets too close to the factory toe link. We designed our offset around the Tarett Engineering Motorsport Style Rear Toe Link which has a smaller footprint at the wheel upright giving us the required millimeters of clearance for the 19x11”ET48. Parts like the TPC offset and RSS toe link do not add any additional clearance for this application and are not suggested.

Last but not least are rear camber plates. These help pull the top of the wheel and tire inboard to gain additional clearance for the 305/30-19 tire. These not only provide clearance directly, but also reduce the number of LCA shims you need on the lower arms for your desired camber value to keep from pushing the assembly out anymore than absolutely necessary. Without camber plates on the rear, as you shim the lower arm to a track alignment, you will push the assembly far enough out to cause clearance issues between the tire and fender. Having camber plates helps make sure that doesn’t happen.

Parts List:

• Front Brakes
• • AP/Essex Front CP9661 394mm
• Front Camber plates
• • Tarett Front Monoball Camber plate
  • Suspension Secrets Front Camber Caster Plate
• Rear Toe Link
• • Tarett Motorsport Style Toe Link
• Rear Camber plate
• • Tarett Rear Offset GT4 Camber Plate
  • Suspension Secrets Rear Top Mount Camber Plate Stage 1

Brandon is a Porsche Fitment Expert at APEX Wheels. Prior to joining APEX in 2022, he worked as Office Manager for a Porsche & Ferrari service and race shop, guiding customers in all areas – suspension, power, aesthetics, you-name-it. His first foray into racing came In college when he was asked to assist at a PCA club race. Says Brandon, “I figured if I am already making the drive, I might as well enter the HPDE happening at the same time.” He hasn't stopped since. Among the various cars he has owned and/or tracked are a ‘74 Corvette Convertible, ’74 Firebird Formula 400, ‘17 GTI, ‘07 Cayman S, and his current ride, a ‘12 Cayman R (BGB X51 pack 3.8L) with staggered APEX EC-7RS 18x9”ET46 & 18x10” ET36 in Motorsport Gold. Fun Fact: Brandon is a big fan of SIM racing, which he uses to learn about a new track he’s going to or get a refresher on a familiar track, as well as improve his racecraft.Have questions about wheels for your Porsche? Use our contact form and ask for Brandon.