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Is this because the AR1 is on the narrower side? Porsche has been using 305 on 12" since 997. Curious on the AR1 as well for my 997 gt3
The N-rated 305 (OEM Michelin and Dunlop) is built specially for use on the rear of a GT3 with 12” rims. It is much wider than a normal 305 (built like a tire between 315 and 325). I have no idea why Porsche does this.
However, most 305’s (not N-rated) will be recommended for up to 11.5” rims (so having the upper limit as 11” for these tires is a little unusual).
Any more updates about people using these on 991 GT3 with stock wheels?
I decided to give the Nankang AR-1 a try after discussing them with their rep at SEMA last month. I missed the memo on them supposedly not fitting the rear 12", so if that is the official stance from the manufacturer then I would advise following the manufacturers recommendations. But I'll share my experiences so far after running them through ~13 sessions across two track days.
Rear Fitment
The rear 305/30-20 on the stock 12" wide wheel is definitely stretched. I was concerned about this at first, but the tire installer (who tracks a ton) said he was not concerned at all.
Road Noise
They are LOUD on the road. There is some sort of tread pattern resonance that really starts to ring in the car around 55-60 MPH in these tire sizes. They get quieter down around 45 mph and below, and 70 mph and up. As a result they really wouldn't be a great tire for a daily driver / weekend fun car, and are really more for the track.
Feel
They feel GREAT to me. The first thing I noticed was how "stiff" they felt in turning. With the MPSC2 (and more so with the Maxx2), I always felt like there was some squirm in the tire when I turned in that I was always managing. I didn't feel any of this with the AR-1 tires, and I believe this (for me) was a big contributor to my confidence when driving on this tire. I'm still not sure what the optical tire pressure is for these (really need to pick up a tire pyrometer...), so for nowI've been keeping them around 33/34 psi hot front/rear similar to the MPSC2. Towards the second half of the sessions after the tires get pretty hot, I do notice that the rear tire traction is dropping off faster than the front tires, resulting in the car transitioning to more oversteer. But I haven't found it to be unmanageable or significantly different than I've experienced with the other tire models, and I assume there is some more tuning I can do with pressures to help.
Performance
During my first event with these tires at Laguna Seca, I was significantly faster around the track than I had ever been before on MPSC2 or Maxx2, by about 1.5 seconds. In fact in one of the sessions, I beat my previous personal best by 1 second or better for 3 successive laps back to back, which speaks at least a bit to their consistency. It's of course hard to control for conditions etc., so take such results with a grain of salt.
I'm now just waiting to see how they perform for subsequent days to determine how their performance (and tread life) falls off. I'm at 13 sessions currently, and the conditions were worse on the 2nd day (track was damp from rain the evening before), yet they still performed surprisingly well in the dry sections (horrible in the wet of course). I'll have a better idea on a next dry track day #3. If I can get at least 3 solid performing days, then I'm sold as that would put them at about the same cost per day as MPSC2 spread across 4 days. Pics below.
The Time Trial crowd at NASA is gone crazy about these tires, and their feedback matches yours. They are faster than the TrofeoR for the first 4 heat cycles, which speaks volumes, because the Hoosier R7 is faster than the TrofeoR but not by a lot, so if this tire sits between Hoosier R7 and Trofeo R, for the narrow body GT3 (and pretty much any 991 car that wants to be on track except the RS ones), it is a winner.
If they build a 335 or 345, the Viper/C6/C7/RS crowd will be quite happy.
10-25-2019, 12:31 AM
