OK, I'm about to pull the trigger on a square setup for track days. 18x10 with 285/35R18 Nitto NT05's. I've done my research and know they'll fit, but since they are much lower diameter than the OEM tires will that affect anything except the speedometer? I can fix the speedometer with the SCT but will the diameter change affect the ABS or other systems?

 

Technically it could but I dont think the difference is enought to make anything go haywire. I know plenty of people have run that diameter before without anything going wrong

 

I've got over 4000 street miles and 1200 track miles on my 285/35-18's (11" Forgestars, all four corners), and the only things I noticed were slightly improved response, having to add an upshift and a downshift on one of the courses at my home track, and having upshifts generally occurring at different locations on track.

There has been no unexpected ABS behavior up to about 1.0g or maybe a bit more - since I didn't have any datalogging for the first several events on the 285/35's I may have missed my tires' best braking grip (MPSS), but no funky ABS issues have ever surfaced.

I didn't bother with correcting the speedometer and probably never will (even though my DD size is now 265/40-18's on 18x9.5 GT500 wheels, where 255/45's used to live). It's just not worth it to me when the "error" at 60 mph is barely a couple of mph on my DD tires and an irrelevant 3 mph on the track set.


Norm

 

Thanks, I'll go with the 285/35's

 

Hi Norm, sorry for reviving the thread, but I just reread and I see you're running the 11" Forgestars. Are those the Vorshlag ones? Do they protrude at all? If they are not the Vorshlags can you give me the offsets you're using front and rear? I was set on 18x10, but If I can get away with 11" I might be able to squeeze 295/35's which are a bit closer to stock diameter. My car is already low enough without taking away an extra inch of tire. The 305/35 R18's are almost a match for the stock ride height but I know I'm not getting away with running those without either the Vorshlag or Cortex setup and I simply can't afford everything at once.

 

They're from Vorshlag.

Approximately stock height in the pictures, been lowered 0.6" or so since but I don't have any pictures at the new ride height with the 11's. Don't expect any problems, though.











Norm

 

I currently have 275/40/18 NT05's on my 07 GT on 07 gt500 wheels. Any opinions on going 285/35? will they fit safely on the wheels? i assume so as the stock gt500 had 285's on the back. Insight?

thanks

 

Your hunch is correct - both the 285/40 and 285/35 sizes are mfr-OK'ed for 9.5" wide wheels.

Engine revs will only go up about 3% at any given road speed and transmission gear from where they are with the 275/40's, probably not worth worrying about (I wouldn't).


Norm

 

I ended up going with 285/35R19's on 19x10 wheels. I know the 18's would have been lighter, but vanity got the best of me. I wanted to fill the fenders and the 285/35R18's left a big gap. Car behaved like a champ at last Sunday's track day though so I can't complain. Couldn't go with Michelin's sadly. The price hike from the 18's to the 19's made them unaffordable. Got Mickey Thompson's and was pleasantly surprised. They were much better than the Nitto 555's ever were.

 

Thanks brotha :-)