When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The taller rear really improves the car aesthetically. I have my rear suspension cranked up a bit and front down to exaggerate the look, it makes the car look more balanced.
I have my Arctic Silver 996 Turbo running 18" Apex SM10 wheels (9"/12", 245/40, 315/30) and my Polar Silver on 19" Wheel Dynamics 808 wheels (8.5"/11", 235/35, 305/30).
While I like both, I prefer the looks and driving characteristics of the 18" setup. Preferences vary for sure...
The taller rear really improves the car aesthetically. I have my rear suspension cranked up a bit and front down to exaggerate the look, it makes the car look more balanced.
I have my Arctic Silver 996 Turbo running 18" Apex SM10 wheels (9"/12", 245/40, 315/30) and my Polar Silver on 19" Wheel Dynamics 808 wheels (8.5"/11", 235/35, 305/30).
While I like both, I prefer the looks and driving characteristics of the 18" setup. Preferences vary for sure...
Arctic/Apex/18"
Polar/WD808/19"
My primary reason for doing this 19" upgrade is to hopefully improve traction, at least a little bit, with a tyre that has a higher load rating.
My problem with the 19" setup is that there really isn't a readily available tire combo that properly biases the AWD viscous coupler in widths that make sense....
Ideally, the rear tires should be a slightly SHORTER diameter than the front, so it spins just slightly faster, and begins to pre-load the viscous coupler for torque transfer. When the rear starts to spin, it further engages the viscous coupler quickly and transfers torque to the front. When biased this way, the car feels very much like a RWD car unless and until the rear breaks traction.
When the rear is TALLER than the front, the viscous coupler is biased the wrong way... The front is spinning faster, and it's preloading the coupler the wrong way. This causes some drag on the front axle, and requires the rears to slip/spin even more to first overcome the incorrect bias, then actually start to transfer torque.
If you have a RWD conversion, this makes no difference. If you have a 997 Turbo, this also is not an issue, as they replaced the viscous coupler with a electronically controlled clutch pack. But on a 996 running AWD, I think it makes a notable difference in how the car feels.
Example of my preferred 18" tire/wheel setup:
Front: 245/40-18 (25.7" diameter)
Rear: 315/30-18 (25.4" diameter) Rear is slightly SHORTER, therefore turns slightly faster, and biases the viscous coupler CORRECTLY.
Example of typical 19" tire/wheel setup:
Front: 235/35-19 (25.5" diameter)
Rear: 305/30-19 (26.2" diameter) Rear is slightly TALLER, therefore turns slightly slower, and biases the viscous coupler INCORRECTLY.
There are theoretically other fornt/rear tire combos in 19" that would provide correct bias, but not readily available these days. For example, 235/35-19 (25.5 inches tall) + 315/25-19 (25.28 inches tall). This would be freaking perfect, BUT tire rack lists not a single tire available in 315/25-19 let alone a matched set with the fronts...
You could also run 225/40-19 (26.1") and 295/30- 19 (26"), but that gives up so much needed tire width (20mm front and rear vs. my preferred 18" setup), and it's kind of tall in the front causing potential fitment issues. But at least it biases the viscous coupler correctly.
I running 19" wheels with 315's on the rear with no issues on KW's
What 315? 315/25-19"? Have you checked into availability for replacing your rears when they wear out? The only availability I've seen in that size lately are on ebay, Continental Sportcontacts being shipped from Europe, often with older date codes and typically at quite high prices. Nitto's in that size were available for a while, but seemingly no longer.
01-11-2024, 02:38 PM
