Below are pics of my current OEM ride height with the 19" Champion NG5s. I'm running 295/30/19 and on the front 235/35/19. I've just recently learned about the challenges of running 19" wheels and trying to upgrade suspension components. These wheels where on the car at the time of purchase, and I love them cosmetically. They ride just fine as well---no issues. But I guess where the challenge is coming in is what aftermarket spring to use with a new set of Bilstein Sport Shocks. It seems like H&R and Eibach are the top mainstream pics, but it is hard to tell if they will drop my car too low---damn I wish I could find an X73:-)

 

RG5 btw. About the lightest forged rims out there.

Skip the springs and shocks and get coil overs. Same idea about the same cost, but adjustable. The adaptability is great - last year I got a new house, and had the raise my car about 1/4' inch to clear the driveway slope.

Tom

 

My X73 is 25 5/8" front and 25 3/4" rear on brand new OEM Michelins (OEM pressures).

 

The tire diameters of what you are running is 26" rear and 25.5" front. Stock sizes are 25" and 25.1" respectively. That one inch won't make much of a difference as far as lowering goes. There is plenty of room.

The bigger concern is the .5" differential between your front and rear sizes. There are differing opinion on how much is too much on a 996, but .5" is borderline in my mind. You might get some strange PSM behavior in hard driving, and too much difference between the revolutions of the front and rear tires might create long term issues with the front differential.

305-30-19 with 235-35-19 is a better combination in my mind. Just my .02.

 

Lol...yeah I meant RG5...not the spark plug:-) Typo!

 

Good point...I'll watch for that, and go with 305s next rear set.

 

do a search on that first...I think that 315's is what's recommended for 19's. 225/35/19 and 315/25/19.

 

That combination will work also, although I like to go wider in the front as well. It just depends on the look you are going for.

 

Here's the rev's per mile for a few sizes:

225/35 R19: 825.3
235/35 R19: 816.6
235/30 R19: 847.20
305/30 R19: 793.8
315/25 R19: 825.3

So, the right match is pretty obvious above, BUT, I believe if you're within 2% you're ok. I drove my car with 997TT 19" (235/35 & 305/30) sizes on it and it was downright scary!

 

You're right. My old eyes read the wrong line on the chart. 245-40-19 would work better with the 305's, but maybe a little too wide for the front.

I think that is one of the reasons I backed away from the 19's. I couldn't get the balance I wanted in the look.

Now that I have the GT3 turbo offset wheels, I'm going to go with GT2 sizing on my next set.

 

After about 1500 miles, I haven't noticed anything strange. I've pushed it hard into a few turns and it was very good---maybe a little vague feeling because I am not used to it---but very good. I do wish that it was a little bit stiffer. However, there's no telling what it would do if I was driving hard frequently or the long-term effects. When I do come to a tire change point, I'll swap them out with maybe 315s or so; however, I don't want to go super wide as that might flare them out too much. I really need to see where my car sits after the suspension tweaks...but I am going to try to keep all of this as simple as possible---if I decide to do it at all. All of this suspension talk is making my head spin---literally. I might just go with a set of sway bars and call it a day. The whole ride height thing is getting insane. Everyone has been very helpful and answered all of my questions. However, what I am seeing is that this whole puzzle can get very complex and begin to build and build and build to the point where it gets overwhelming.

I wouldn't mind dropping the car down 1/2 to 3/4 of an inch and adding some stiffer springs...but not sure if it is going to be worth all the time and money to change something that I might only notice if I was driving at 9/10ths.

 

The 996tt AWD system is a bone simple mechanical system that relies on a speed difference between the front and rear wheels in order to transfer power to the front since both the front and rear diff is a 3.44. In other words, you need the rears to rotate just a touch faster than the fronts if you want a constant 5% or so of power transfer to the front wheels. The faster you go, the more torque is transferred to the front as the speed difference between front and rear becomes greater. Once the rears break loose and spin even faster than the front then more torque is automatically transferred to the front. This is why the correct size for 19s is 235/35/19 (25.5") and 315/25/19 (25.2").

 

Makes perfect sense...the light bulb in my head just went off...finally.

 

I need new glasses.

 

I am going to have a set of 315/25/19s put on the rear, and go easy on the suspension stuff. I'm getting in way too deep with this stuff and need to pace myself for 2013...I can't rebuild the car from scratch in one sitting!