safetyfastgt

I'm getting new tires in the next week. They will be on my 2010 GT500 wheels which are 18 x 9.5. I'm planning to get Michelin Pilot Sport A/S 3. I'm currently on 255 on all four. I want to keep same size on all four. I'm debating on whether to go to 275-40-18. I'm lowered on Steeda Sport Springs and Koni orange. Looks like I would lose about a 1/2" of diameter on 275. I figure with the way the tires will fit, I'll only gain about 10mm in width on the ground. The 275 are $200 more. Over the course of the next few years, I guess that's not too much. Just wondering if I will notice any noticeable improvement in grip for normal around town and mountain driving.

Thanks in advance. I know this question, in different forms, must be asked a lot.

CMcNam

Same sizes I'm running and I haven't found the limits of grip yet. I lose my nerve before I lose my grip!

Norm Peterson

Half an inch on the diameter is only 1/4" loss of ride height and only 1/4" increase in tire to fender gap. Not worth worrying about, at least in my book.

What you'll gain at the ground is separate from the 10mm gain in actual as-installed section width. For some reason that isn't at all clear, tread widths seem to get wider fairly rapidly when you first go wider than 255 and lower than 45 profile.

Michelin claims 8.7" tread width for the 255/45-18 (and I haven't stumbled across a 255/45-18 any wider than the 9.3" that Goodyear claims for their Asymmetric 2 summer tire). The 275/40-18 A/S 3 shows a 10.1" tread width, roughly a whole inch wider than almost any 255/45 for a nominal size that's barely 3/4" wider, and almost an inch and a half wider than some 255/45's.

Heh . . . the 265/40-18 PSS actually claims 10.2" tread width . . . same as their 285/35-18.


Norm

audioAl

Norm, your sig states: still not lowered. I want to install Koni sports struts & shocks w/ J&M cc plates and BMR LCA's and want to know your opinion about not lowering my 3.7 Cyclone. I have 275/40/18 tires and the gap is big because the tire is about 26" tall. This helps my 2.73:1 gear, will I see a big advantage lowering the pony or will it perform well at present height?

Norm Peterson

Koni yellows, Sam Strano's 35/22 bars, poly/spherical rear LCAs, and a fairly aggressive alignment (out near -2° camber). 18x11 Forgestars with 285/35-18 Michelin PSS tires. I'm still giving up two or three seconds a lap to the hundred HP stronger SS Camaros, but I can hang with a surprising number of non R-compound tired cars through the turns.

The biggest gain from lowering springs is from the increased rate, and that's what's responsible for people noting less nose dive, squat, and roll. Not the lower CG.

Here's a random video (the still shows the other Mustang driver pointing me by to his right side, which happens later in the video), and my GoPro is dash-mounted so any nose dive or roll you see is purely what the car was doing. I've gone about 3 seconds/lap faster since. I've also got a pretty good wet track video.




Norm

audioAl

Well, the video speaks for itself, and you only squeal the tires a few times, your driving skill is decent, ha. I am going to install the Koni's & cc plates w/ BMR poly LCA's and test the Cyclone's new struts, thanks for the camber number. I may try -1.5 first with 1 turn on the Koni's. Thanks for your input Norm, your the man!

Norm Peterson

Thanks for the kind words, Al. I know there are things that I need to work on, and not just working up the nerve to brake later. The tires are talking a bit more than is readily apparent in the video, but at least they aren't howling.

The car is pretty composed as it is - easy to drive with no surprises, but I'd like to eventually rein in the nose dive under braking a bit and dial out a little more of the understeer. But not so much more that it'd be too loose for me to drive in the wet. Just because ↓↓↓ . . . it was still easy to drive.




Norm

jRaskell

I bought those 265/40-18 Michelin PSS for the street, they're on a set of 18x10 Forgestar wheels.

All four tires stacked next to my AutoX tires, 285/35-18 RS-3s on 18x10.5 Enkei wheels are less than an inch narrower overall, that's with 2 inches less wheel width overall.