I'm planning on picking up a 2002-2004 996tt in a month or so, and would like to upgrade it to the 19'' 997tt rims. I'd tried searching and finding definitive answers to these questions, but I want to double check some specifics:

The wheels I want to put on look like this: http://www.vistawallpaper.org/vista-...-997-turbo.jpg

1. The 996tt in 2002-2004 comes with 18'' wheels, and it appears this design for the 997 are 19'' wheels only. I want to make sure this will fit on the 996tt. I'm seeing contrasting reports of whether I need to use spacers, but it looks like I will, at least on the rear, else the tires will rub. I've called two different Porsche service departments and they have been completely unhelpful with this question, saying basically you cannot put the 19'' rims on a car originally with 18'' wheels, which is clearly BS considering how many people do it. I've found the following comment and wanted to verify it:

235/35/19 in front
315/25/19 in the rears
7mm spacers in front
15mm spacers in rear

2. I'd love to pay $900 for the Ebay replicas, but those are certain to be extremely heavy cast monsters vs the forged originals and I'm concerned about safety considering I will be taking this car 100MPH+ quite often. Comments here?

3. It looks like I just missed this great opportunity, as I'm in Ohio too, for the ones I'm looking for: https://www.6speedonline.com/forums/...eels-sale.html

Anyone currently selling or looking to sell these wheels (preferably with tires) within the next month or two? Please PM me. <!--QuoteEnd-->

 

997TT wheels will fit on the 996TT. But you have to change the tires like you said above.

 

I'm buying a set of used original wheels from a fellow esteemed 6speed member off his 2007 Porsche 911. They are the 19'' turbo style wheels like these here http://4.bp.blogspot.com/_nqVlojKKcr...26210245kq.jpg and have the following specs:

Front: 8.5 x 19, 56 offset.
Rear: 11 x 19, 51 offset.

I spoke with TireRack today and and they assured me that these wheels, despite 19'' vs 18'' and wider than the stock 996 turbo wheels, would fit fine without need for any spacers. Still, I want to verify this, as there is so much conflicting information floating around and I certainly do not want to rub against the diff.

So, can I simply plop on these wheels without spacers, which I'd prefer to abstain from unless they are necessary. Thanks in advance.

 

plop them... make sure you run a 315/25 not the 305/30 that comes with the 997TT.

 

Thanks, but could you explain why 315/25 instead of 305/30? If its for performance, I'm not planning on tracking the car currently.

The wheels I bought currently have PS2 tires on them already at 235/35/19 on the front and 305/30/19 on the rear I believe. Fronts are 55% and rears need replacing. My plan was to get the Hankook V12 305/30/19 at Tirerack for $215 each becuase I was told that it'd be a better mix when keeping the PS2's on the front as opposed to going to the Bridgestone RE11 on the rear. I'm also a huge fan of the $215 price each for the Hankooks and the reviews I've read have been great, especially for street only use. The RE11's are $329 each on the rear, so I would consider those, but I simply cannot justify paying PS2 prices for road only use, and it looks like PS2's are about all that is available in 315/25/19 size.

 

305/30 will ruin your center diff. 315/25 is the correct size for the 996TT.

 

Thanks for the info.

Anyone have an alternative experience? I'm not doubting vividracing, only that I'm SO resistant to spending $1k on new rear tires right now I want to double check. Would really love someone with confirmation that 305/30 will be fine, or if not, will adding a spacer fix the potential problem?

 

The problem comes from a change in rear wheel diameter and hence rotation speed in relation to the front wheels
This causes overheating and excessive wear on the center diff.
Adding spacers does not change anything to resolve that problem.

 

TireRack told me that the idea setup here would be 225/35/19 on the front and 315/25/19 on the back, as both would be exactly 25.2 in height.

They said that 235/35/19 would be ok with 315/25/19 as thats within 3/10 in height (25.5 front and 25.2 in back). Anything more than that is going to cause problems as you guys said, including the 305/30/19 which is 26.2 in height.

Thanks for explaining this. Any recommendations for the best value wheel for street use at 315/25/19?

 

Nitto Invo is a good inexpensive option.

 

Ok, so I think I figured out the diameter/revs situation and found the best value sizes. Please tell me why this combo would not work from TireRack, in terms of performance (street) and profile looks. Again, my car is a 2002 996tt, and the rims are off a 2007 19'' 997.

My new 997tt 19'' Rims off a 2007 sizes are:

Front: 8.5x19''
Rear: 11x19''

Best value tire sizes from TireRack:

Front: 225/40/19 Hankook V12 - $151 each - 26.1'' diameter ; 796 revs per mile - says fits 7.5-9'''

Rear: 295/30/19 Hankook V12 - $206 each - 26.0'' diameter ; 798 revs per mile - says fits 10-11''

That's a damn near spot on perfect match for about 30% of the price of what 315/25/19 will cost. Assuming I'm not missing something, why in the hell did the three Porsche dealerships and four calls to Tire Rack not suggest this when I asked if there were any potential combos like this available?<!-- google_ad_section_end --> <!-- / message --><!-- edit note -->

 

I did what you want to do 2 weeks ago. changed my 18 to 19s from 997. after talking w WHEEL ENHANCEMENT, i bought 5mm spacers and bolts. NO PROBLEMS AT ALL!

 

The problem is not with fit or rubbing here, in fact, you don't even need the spacers to prevent that apparantly. The problem is that the rotation of the front and rear wheels must be fairly close (aka revs per mile rating on the tire, which is directly proportional to the diameter, hence the importance of that figure), more so on the 996 than on the 997. The 997's differential is electromagnetic, and can handle these differences better than the viscious diff on the 996, without overheating. If they are mismatched by too much, it will cause overheating on the center diff. This is not a immediately noticeable problem, but gradual, and one day you'll end up with a big repair bill. At least this is what I'm told. That's what I've learned/read today at least, take it for what it is.

Said another way, think of rolling a penny and a quarter across the table, only having them attached to each other. The different rotation speeds puts stress on the differential to absorb (not sure if that is the right way of putting it), which causes overheating and stress, which causes failure over time.

 

i bought NITTO INVO tires w the same overall dimensions, front and back. there will never be any problems i'm sure.

spacers were used for rear mostly for the look btw.