Blackbird78

Dear all,


Happy to be here and appreciate all the info. Just bought a 2007 911 997.1 turbo tiptronic, with 53,000kms on the clock. The car is in great condition and I couldn't be happier. I took it on an official Porsche drive on Saturday and thought I was driving a train!!! 😋


The car came with Michelin sport cup 2 tyres all round but the rears are wider than spec. Namely they are 325/30R19 instead of 305/30R19. Unfortunately although they have a lot of life left in them the right rear has a noticeable bubble on the side wall and, although I've had varying opinions on the matter, I have decided to change them.


So my question is, do I revert back to OEM sizing?? My mechanic is going on about how the 4wd system is being unnecessarily over-stressed and that this was a badly thought modification done by the previous owner.


The car has a few modifications on it, done by the local Porsche workshop, the most important being the following:


Akrapovic titanium exhaust + cats (100)

Custom tuning + small increase in boost

GT2 rear wing


Previous owner claims about an 80hp increase which in his opinion warranted a wider rear tyre, GT2 spec!!


I'd love to read your thoughts on the matter.


Thanks in advance!

Hueneme997

Congrats on the car!! You scored with the exhaust as that’s not a cheap mod! I personally would stick with 305’s although I don’t think you are doing any damage to your drive train at all. There are plenty of people running 225’s out there.

Enjoy the car, I just upgraded to a TT also and it’s a choice I do not regret.

saabin

I'm certainly no tire/wheel expert, but I would be concerned about the front diff as your mechanic is. Others may chime in, but there is a calculator that will tell you if this is an issue or not.

Tires may be GT2 spec, but the GT2 is RWD, so no concern for the front diff..

Any idea on how many miles on this setup prior to you buying the car?

Flewis763

What size front tire are you currently running?
With 325 rears, you should be running 245 or 255 fronts vs the stock 235.
Persoanlly I'd keep the 325 rear size and make sure you have a 245/35/19 or 255/35/19 front. More grip and better handling.

TT Surgeon

Yes, as above
the 325s are fine as long as you run a 245 up front.
i wouldn’t mix 325 and 235 or conversely 246 and 305
i suspect the prev owner thought this out and ran 245 up front.
its all about the front to rear running diameter being within spec to protect the diff. If the 325 were too much they would’ve damaged the diff in short order I would think
c

Blackbird78

Firstly thank you all for your quick replies!

I do apologise for not giving the right info from the start. The car has 235/35R19 up front, hence my concern! I didn't think about upping the fronts to get closer to original ratio but then I'd be leaving completely from OEM spec but it's definitely an option! 👍

I don't know how many miles the car was used in this setup, personally I've done about 600 but I'm supposed to be changing tyres tomorrow morning. Also judging by the amount of tread left it shouldn't be much.

Thanks again

Flewis763

Nothing wrong from changing for oem. You should be fine, it dont think you fried the diff in that period but it needs to be changed. Either go to 245/325 or go back to 235/305 setup. Personally of run a 245/325 setup forsure over the own sizes

Nate Tempest

Do you run those with the stock wheel widths? I'll be in need for a new set of tires pretty soon, and might consider bumping the sizes up if they can be run on the stock wheels. Going 2cm wider in the rear on the same wheel seems like it'd be quite a stretch though.

Flewis763

Guy have done it and techincally you can but a 12 inch rear is better

Blackbird78

Dear all,

Thanks again for all your input and time.

I finally took the car to my tyre shop yesterday and had all at the tyres and wheels inspected. Firstly, the car has 5mm spacers installed on all wheels, and secondly, as I was advised, the bubble that had formed on the sidewall was not repairable, so I bit the bullet and bought and installed 4 brand new tyres.

I took the advice of a current tt owner and friend and opted for some fresh (2019) Pirelli pzeros, 235/35R19 – 305/30R19, as per OEM, rather than sticking with the Michelin Sport Cup 2s that were originally installed. I was advised away from the cup 2s since supposedly they suffer from aquaplaning and, since we do not have tracks in Cyprus and I would be using the car only on public roads, AND in the wet come winter, this would be the safest option.

I’ve only driven the car for about 30 miles and still haven’t put my foot down due to running in, but I’m really hating the experience. The ride has firmed up by 50% and there is a noticeable disconnect from road to steering wheel (mushiness)!! I’m hoping this will get better as I run in the tyres, but honestly the difference between the Pirellis pzeros and Michelin Sport cup 2s is devastating!!! It’s like I went from driving a train to a 4x4!!

Anyway, I know it’s too early to form an opinion but I will be giving some more feedback once I’ve driven the car properly. I’m hoping to get some mountain driving this weekend!!

Thanks,

Nic

Flewis763

Should have went ps4s. Pzero suck imo. Not a fan of pirelli tires.

Nate Tempest

+1. Went pzeros on our family hauler to try and save some money. Never again. Ride was harsh, and they wore much faster too. Michelin PS4S (Pilot Sport 4S) all the way. Or if you want to save money, Pilot Super Sport or even Bridgestone S04 would be fine for street tires. But I'd just get the PS4S.

cjcam930

I can't speak to the PZero but agree the PS4S is a phenomenal all-around tire. I did not want the noise and stiffness of the Cup2 on my TT.

nzskater

I've used PSC2 in the wet, they're fine, but I wouldn't run them in the snow. Just had a look at winter temps in Cyprus - you could easily run the Cup 2's all year round (I'm jealous of the weather there, sounds amazing!).

MexicoBlueTurboS

It takes some time for the tires to set up and stop squirming, so be patient. My Turbo S in on P-zeros and I don't mind them but I might consider a change to Michelin as many advise here. The trick is to get my front and rears to need replacement at the same time. I don't drive aggressively enough to be on the very best tires.

It was a smart move for you to go back to OEM sizes.