dbbarron

(Although I drive a 997.2 GTS, I thought this topic more appropriate for this forum).

Currently run CUP2s on my 997.2 GTS and looking for new tires. My use of the car has moved mostly to DE/AX - very little street. However, they still need to be streetable. Thus, I am considering moving to NT-01s to both save cost and at least keep, hopefully improve, performance at DE/AX. Opinions? Other choices?

(I have found very little direct comparison of these two tires on the forums)

db

ELange0322

When I got my RS in Sept I had the center locks removed and 5 lugs put on. I wanted to move to 18" rims as have heard that's the way to go with tracking the car. Of course I couldn't get a set of 18" rims in time for my next event so got a set of 19" and had the MPSCs put on as that's what I had run on my '03 Carrera since I purchased and used for track.

Of corse I got 2 sets of the 18" rims over the winter and the MPSC isn't made in a rear width big enough for me (they top out at 295 and I needed 325). So, I got 2 sets of the NT-01s based on the advice of Mooty (as always, amazingly helpful).

They will be "greasy" the first day or so, but then the grip comes in. Heat cycling doesn't help. Watch your numbers as far as sizing... I'm not 245 front and 205 rear as they tend to run wide, but thinking of going 275 / 335 as was having a lot of rotation on the car and want some more rubber in the rear to stick a bit more.... TBD.

My car is also registered for the street, but mostly DE. Some will say that after you track the Nittos that they are really loud on the street. Whatever. My whole car is loud on the street and hasn't bothered me.

Overall, I'm really happy that I got them and plan to order a couple more sets to have on hand. If you like the MPSC, you really like the Nittos (IMO)

ddaudi

So what size NT01's are you running?
I run 245/40-19 and 305/35-18.

powdrhound

I ran NT01 245/40/18 and 305/35/18 for several years. I just did two track days on NT01 275/35/18 and 335/30/18. This combo is a significant improvement on all fronts. A solid 1.5 seconds quicker on a 2 min lap. You will need 9.5/12.5 wheels at a minimum with 10/13 optimum.

ELange0322

Crap - I'm sorry. I didn't follow this and see your question. Yes, I was running 245 front and 305 rear.

ELange0322

I asked someone outside of Rennlist about this. My last track day, I was getting a lot of grip in the front and a lot of rotation in the rear. Suggestion came from an instructor whether I could move to a 335 rear...which I suppose I could and reasonably certain they would fit. Question is whether the 275 width fronts would be to wide (was told might need to roll my fenders, whatever that means).

I've got a 2011 GT3RS - is the front track width on your car comparable ? I'd love to go with the extra size if it fit.

powdrhound

My car is based on a 996 wide body. The trick to getting the front to fit is to flip the upper mounts to the motorsport configuration and run the LCA with minimal or no shims along with a wheel what has an offset that will just clear the inside coil over. In the front I run rear 997 RSR LCAs which are 5mm shorter than the street LCAs. This helps tuck the wheel deeper into the wheel well. You want to roll the fender nice and tight. Zero clearance issues. You can run a 10" front and 13" rear wheel. 9.5/12.5 is the minimum with the 275/335. It takes some careful planning to make it all work but it's worth it as the performance gains are significant over the 245/305s. I spent the last 3 days at the track and crunched some Motec data looking at the before and after number and it's black on white.

[url=https://flic.kr/p/HVJLUF]

[url=https://flic.kr/p/H7mJhV]

[url=https://flic.kr/p/HBGtzw]

ELange0322

My car is based on a 996 wide body. The trick to getting the front to fit is to flip the upper mounts to the motorsport configuration and run the LCA with minimal or no shims along with a wheel what has an offset that will just clear the inside coil over. In the front I run rear 997 RSR LCAs which are 5mm shorter than the street LCAs. This helps tuck the wheel deeper into the wheel well. You want to roll the fender nice and tight. Zero clearance issues. You can run a 10" front and 13" rear wheel. 9.5/12.5 is the minimum with the 275/335. It takes some careful planning to make it all work but it's worth it as the performance gains are significant over the 245/305s. I spent the last 3 days at the track and crunched some Motec data looking at the before and after number and it's black on white.

Hey Powdrhound - thanks for this....even if I have zero understanding of what you wrote (thats on me). My car is just stock, so have no idea about what flipping mounts means. Sounds like I would need to bring to my shop (2+ hrs away) and have them do that. I also dont know what an LCA is, or what it means to roll a fender. Honestly, I dont think I wanna be doing all of that to my car anyway. I just got 2 sets of Forgeline rims in 18", with the fronts being 9" wide and the rears 12". So doesnt look like the 275's would fit anyway because if I have read correctly the 275s need a 9.5" width. Again, thanks for your detailed explanation, but doesnt sound like an option for me at this time. Best - Erik

Steve W

275s will fit on a 9" 18" rim fine. My street wheels are 275 and 305 RA-1s on 9" and 12" CCW 18" C10s and looking at the 275s mounted they look totally normal. I've been running like this for 8 years. On the track they are fantastic, maybe only 3-4 seconds off of full race slicks. If I were using NT01s, I'd use 275/35/18s with 335/30/18s.

dbbarron

Some great comments above on NT-01s and sizing. Any thoughts/comparison experience with NT-01s v Cup2s?

powdrhound

Your experience running RA1s unfortunately does not translate to NT01s. 275/335 RA1s run significantly narrower compared to the same size NT01s so suggesting NT01s will work on 9/12s is flawed.

Here is how the 275/335s compare to the previous set up of 245/40/18 and 305/35/18 NT01s. All listed measurements are actual side by side measurements, not Nitto listed measurements. Nitto, for example, lists the diameter of the 245 and 275 both at 25.5" when in reality the 275 is 4mm shorter. You can clearly see this when you place the 245/275 side by side. Measured tire width is overall width, not tread width.

Fronts: 245 vs. 275

245/40/18 25.55" tall, 10" wide, load 1433 lbs
275/35/18 25.4" tall, 11.5" wide, load 1521 lbs

The NT01 275 are actually more of a typical 285 tire width.

[url=https://flic.kr/p/Fx5Gkj]






Rears: 305 vs. 335

305/35/18 26.4" tall, 12.65" wide, load 1819 lbs
335/30/18 26.0" tall, 14.00" wide, load 1874 lbs

[url=https://flic.kr/p/F7Pkpj]

As you can see the width difference is substantial, 3" of extra rubber in the front and 2.7" more in the rear. The rear 335s are very wide at 14" overall width but most importantly they have a load rating of 1874 lbs. which is very important for our cars.

As such, if you try to fit the NT01 275/335s on a 9/12 wheel, you will find that the tires will have a very significant muffin top bulge on the wheel. I've done a test fit on 9/12s and it's clearly obvious that won't work without looking very funny. Looks aside, performance will obviously suffer when running wide tires on skinny wheels giving you a lot of sidewall rollover with high lateral loads. You want the tires to square up on the wheel, ideally with a small amount of sidewall stretch. 10/13s are the way to go with these sizes for best performance. 9.5/12.5s are a good option also giving you the flexibility to run both the 245/305s or the 275/335s.

powdrhound

Same size comparison, NT01s will have more grip compared to Cup2s.

powdrhound

No worries Eric. It's doable but as I said will require a good bit of work to make it work without issues. It's not exactly a direct bolt on.

Steve W

9.5 and 12.5 may be ideal, but if you look on Nitto's website, you'll see they list 9.0s as acceptable for 275s, and down to 11.5 for the 335s. I'm just providing real world feedback on what has worked for many years. I've run Nitto NT01 275/35/18s on the rear of my narrow body 3.2 track car and they are 275s and are are in no way like 285s. 285s won't fit on the back of a 911. Yeah you can say a 245 NT01 is more proper for a 9" rim, but as you noticed, with a 275, you were 2 seconds faster. Even if it's not as stretched as a 245, with so much more front grip, you eliminate understeer, and can soften the rear sway bar and stiffen the fronts, and with proper springs, when the rear breaks loose, it's smooth controllable progressive slide, instead of snap oversteer that comes from too stiff of a rear bar.

Also my track wheels are Pirelli Cup slicks which are on the wide side of average, where I run 275/645/18s and 315/680/18s on CCW 9s and 12 with no problems. With them I'm not exactly the slowest wheel in the paddock. Try it sometime. Don't be surprised if you outrun some 3.8 Cup cars.

If you want more examples, myself and friends have fitted some very wide tires on a narrow body GT3 that most people on the internet would think impossible. For example for autocross you can fit a Hoosier A6/A7 255/35/18 on 9s on the front, which is actually a cheater 285 the same thread width as a A6 285/30/18, and clear the springs and fender lip. And another friend has been running 335/30/18s on 12s in the rear with no issues. These are SCCA Pro-solo national champion drivers. Of course you will have to use every trick in the book to align the wheels into the wheel wells, but if you are determined, it will fit and work well.

powdrhound

Of course it's possible to muffin top the 275/335s onto 9/12s. It's just hardly optimal. Not many guys will recommend pinching wide tires onto narrow wheels is all...