Project 996 Road Rallye: Part 4

Wheels, Tires and Brakes are proving to be the biggest challenge in this build.  Since our goal is to create a car that will work 90% on broken pavement and 10% groomed dirt roads, we are sticking with tire sizes that favor the road.  But we are looking to add compliance through larger side walls as well overall larger diameter to gain some ground clearance.  

Most of the Safari builds run the same size wheel and tire on all four corners and the fifth which they keep as the spare.  On dirt, this can work, as grip is usually minimal.  But our car is going to run on the road so tire size will defer to weight bias.  We wrote about tire selection on a previous Blog: HERE  Since these are rear biased cars, larger tires are needed at the rear.  We will follow what is typically used for the road cars with more sidewall.  Plus our tire should be quieter than one that favors dirt.

We started with tires and then are attempting to find rims that will fit.  I used a resource on the web that will compare wheel/tire sizes and visually shows the potential impact.  The rear option is shown below.  I linked the image to the website.

We have contacted several of our favorite wheel suppliers including: Braid, HRE, BBS and TireRack to see what options we can find.  Ultimately determing clearance with the new Elephant Racing suspension will be key.  We have a tool that should help us make that determination on rim width and offset.  We will post up pix of this tool in action when we get to this stage.

One of my friends, who is Ride & Handling engineer at Toyota, and races 911s, has suggested the Conti Extreme Contact Sport 2 tires.  These seem like a great solution that come in the sizes that I am after: 225/50R17 front and 285/40R17.  

The Girodisc brakes that we have ordered are slightly larger in diameter than stock.  This is due to the fact that  the 996 has a rear (in hat) drum brake for the handbrake.  Giro needed to make the rotor larger to clear the drum and up sized the front to match the rear  - to keep brake bias the same as stock.

We ordered their caliper rebuild kit as well since these have over 100k miles on them.  We will vapor blast the calipers and replace the seals and rubber boots.  New Stainless Steel brake lines are ordered as well as 25 yr old rubber lines don't instill confidence!

We are hosting a Tech Seminar on Nov 8th to show off the build.  We plan to have the tire/wheels selected and have the brakes installed by then.

IMS and engine upgrades related to reliability are also on deck once the car returns from dry-ice cleaning of the under-carriage and suspension area.