Considering lower profile tires with a smaller diameter than stock--any issues?

[Dragster]

Hey everyone! I've got a 2015 GT PP, and I'm looking to finally get some new wheels. I like the SVE R350s, and I'm planning on going with a 19" staggered setup. Ideally, I would run a 285/35 and 305/35 combo to keep the diameters as close to stock as possible, but there aren't really any choices out there that fit this. The Pilot Super Sports come closest with a 275/35 and 305/35 combo, which I'm sure is a great choice. My car is not a daily driver, so I'm not concerned with wet performance--only in dry, warm temperatures. My car gets driven pretty aggressively on winding roads and the occasional track day.

The reason I ask about the smaller diameter tires is because my car has Comp Stage 1 cams and a GT350 manifold, so it makes power all the way to 8,000 RPM. As such, I was thinking that going with a 30 profile tire might be fun because it would change my effective gears and help me get up in the power band quicker. The problem is that the 305/30 tires I was looking at (Michelin 4S and Continental ExtremeContact Sport, among others) are 1.5"-1.6" smaller in diameter than stock. Getting the speedo calibrated is no big deal, but I've heard about people running in to ABS and TCS issues when changing diameters. The diameter difference front to rear would stay basically the same, but the overall diameter is less. Does anyone know if this would create any issues? Thanks in advance for the help!

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[Cardude99]

I'm only aware of speedo issues. Curious to what others say

 

[Genxer]

Depending on how much of a difference there is in the overall diameter of the new set, you may or may not notice it. If it's say, 1/4" you won't feel it. That's the difference in a new tire vs old tire from wear.

 

[Kep4]

I'm running almost that exact setup on my GT and have experienced no ill effects, no error codes, etc.

Michelin PS4S 295/30ZR 19's up front and 305/30ZR 19's in back. Handles corners and braking quite well!

 

[Dragster]

I'm running almost that exact setup on my GT and have experienced no ill effects, no error codes, etc.

Michelin PS4S 295/30ZR 19's up front and 305/30ZR 19's in back. Handles corners and braking quite well!

Awesome, that's good to know! Do you have any issues with rubbing in the front? I'm lowered on Sportlines, but I'll probably go with Ridetech adjustable coilovers in the future. Not sure if I can get a 295 up front or not...

 

[Kep4]

The front wheels are 19x10.5" with a 50mm offset, running Ford Performance M-5300W coil springs all around The tires clear the Magneride shocks by no more than the width of 2 credit cards laying flat... it's very close. No rubbing anywhere on the car front or back and I've run it very hard and fast thru corners. That has been on the street, canyons, and freeways though, I've yet to hit the track.

A 285/30ZR 19 on a 10" wheel would definitely give much more clearance, especially if you went with a bit less offset. My alignment guy had to work some magic to make mine work, though I didn't get the specs he used. All he said was it's set up for 'spirited' driving, between full on track alignment and street.

 

[Dragster]

The front wheels are 19x10.5" with a 50mm offset, running Ford Performance M-5300W coil springs all around The tires clear the Magneride shocks by no more than the width of 2 credit cards laying flat... it's very close. No rubbing anywhere on the car front or back and I've run it very hard and fast thru corners. That has been on the street, canyons, and freeways though, I've yet to hit the track.

A 285/30ZR 19 on a 10" wheel would definitely give much more clearance, especially if you went with a bit less offset. My alignment guy had to work some magic to make mine work, though I didn't get the specs he used. All he said was it's set up for 'spirited' driving, between full on track alignment and street.

Cool, thanks for the info! Your car looks great, by the way!

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