Tires sizing 18x11 inch wheel: 295/40r18 vs 315/30r18

[SlowstangGT]

Hi All,

I'm interested in running the Falken RT615K+ square on some 18x11 inch APEX SM-10 wheels. Rear ET52 offset, Front ET27 (effective with a 25mm spacer).
There are two sizes that interest me, the 295/40r18 and the 315/30r18.

Anyone here have fitment experience with either of these sizes? Any issues with fender or sway bar rubbing?
I'm a little worried about the height of the 295/40r18s (27.2 inches tall) and the width of the 315/30r18 (12.6 inches overall width)

Right now, I've max'd out my plates and am at 1.9F/1.4R camber. In the future, I plan on cutting open the struts and running something like 2.5F/1.8R. Additionally, I am running the Steeda Roll Center Correction kit, which reduces the track width by 0.4in (0.2 each side). I know I need to run a steering rack limiter to prevent scrubbing the inner part of the fender at full lock.

I'm also open to other tire recommendations, but keep in mind that I'm a novice and would ideally like to avoid R compound tires, favoring something that provides more feedback as I approach its limits while also being durable enough to be driven to and from the track (200TW non-cheater tires). I already have a pair of 19x10 PS4Ss that I'm using for daily driving duties

Thanks!

 

[Beermoney]

I'm running the Falken 615k+ tires in 315/30/18 on Forgestar 18x11 CF5s. No fitment issues, you do have to take out the liners in the rear fender wells but in sure that's any 315.

I'm using Vorshlag camber plates and run -2.5 camber, my strut towers aren't equal somehow. I could get more on the passenger side but that's max on drivers side as the spring (OEM style) rubs with anymore than -2.5.

In short though the 315s will fit easily with camber plates.

 

[SlowstangGT]

I'm running the Falken 615k+ tires in 315/30/18 on Forgestar 18x11 CF5s. No fitment issues, you do have to take out the liners in the rear fender wells but in sure that's any 315.

I'm using Vorshlag camber plates and run -2.5 camber, my strut towers aren't equal somehow. I could get more on the passenger side but that's max on drivers side as the spring (OEM style) rubs with anymore than -2.5.

In short though the 315s will fit easily with camber plates.

Glad to hear you don't have fitment issues I'm now pretty set on buying the 315/30/18s.
What offsets are you running on your CF5s?

Camber is the same story here with my MM camber plates, but opposite sides lol. Locked out at 1.9 because that's the max on the passenger side for some reason (drivers side could go up to 2.2, annoyingly enough). Steeda RCC kit greatly reduces the amount of camber I can run, sadly. Definitely am switching to Vorshlag once I cut my strut holes open.

As an aside, how do you like them on the track (wear characteristics, tolerance to heat, grip relative to other tires, etc.)?

 

[Beermoney]

The CF5s are the same offset, run a 25MM spacer up front.

Wear wise they are good, good grip for an entire session without overheating. I'm only in HPDE 2 so I would say someone more advanced may cook the tires sooner, but they work well for my situation.

Not the fastest tire but very good for seat time at a decent cost IMO. At least until you want to run scrub slicks.

 

[xr7]

I autocross and have Falken 615+, 295-40-18's on Apex 18 x 11 EC7. The newer Falken 660 is a quicker tire. I am also debating what size to go with when I replace my tires. I like the 315's for the additional rubber but the shorter sidewall is going to put me on the rev limiter forcing shifting into 3rd for a couple of seconds. So I may stick with the 295. As far as different camber settings from side to side there is some slop in the subframe mounting and that might account for that if you subframe is offset to one side. I running Vorshlag camber plates, -2 camber, going to cut my towers eventually to get a little more.

 

[Ludachris]

For what it's worth, Apex Race Parts has their S550 Mustang wheel/tire fitment guide that might be helpful:

S550 Mustang Wheel & Tire Fitment Guide

2015-present S550 Mustang Wheel and Tire Fitment Guide Vehicle Covered in this Guide2015-present Mustang Chassis IntroductionFor 2015, the Mustang underwent its first major overhaul in over ten ye...

support.apexraceparts.com

I'm guessing that since this is posted in the S550 forum that you have an S550? When you get a chance, please do post a Vehicle Profile for your car here on the site - which will auto generate a build thread and create a signature thumbnail for your car so we can all quickly see what you have. It will also help people give you better advice when they can see your car's specs.

 

[SlowstangGT]

For what it's worth, Apex Race Parts has their S550 Mustang wheel/tire fitment guide that might be helpful:

S550 Mustang Wheel & Tire Fitment Guide

2015-present S550 Mustang Wheel and Tire Fitment Guide Vehicle Covered in this Guide2015-present Mustang Chassis IntroductionFor 2015, the Mustang underwent its first major overhaul in over ten ye...

support.apexraceparts.com

I'm guessing that since this is posted in the S550 forum that you have an S550? When you get a chance, please do post a Vehicle Profile for your car here on the site - which will auto generate a build thread and create a signature thumbnail for your car so we can all quickly see what you have. It will also help people give you better advice when they can see your car's specs.

Added the profile, great suggestion . The APEX link helps a lot, but I'm still a little worried about how the Steeda RCC lateral links and my reduced track width affect fitment in regards to rubbing.

 

[SlowstangGT]

Additionally, this thread might be moot now, after a thorough discussion earlier today with @flyhalf , I may be going with 305/35r18 NT01's. I was worried that I would be heat-cycling them dead before the tread wore away, but upon investigation, it seems they're more durable than some 200TW tires out there (the RE71R/A052/RT660 "cheater" tires specifically).

 

[SlowstangGT]

I autocross and have Falken 615+, 295-40-18's on Apex 18 x 11 EC7. The newer Falken 660 is a quicker tire. I am also debating what size to go with when I replace my tires. I like the 315's for the additional rubber but the shorter sidewall is going to put me on the rev limiter forcing shifting into 3rd for a couple of seconds. So I may stick with the 295. As far as different camber settings from side to side there is some slop in the subframe mounting and that might account for that if you subframe is offset to one side. I running Vorshlag camber plates, -2 camber, going to cut my towers eventually to get a little more.

Subframe slop... Mhm, Ford's [lack of] QC never ceases to amaze me
Oh well, we did get what we paid for, can't really beat a Mustang or Camaro in terms of value haha.
Are you running any roll center correction?

 

[xr7]

Subframe slop... Mhm, Ford's [lack of] QC never ceases to amaze me
Oh well, we did get what we paid for, can't really beat a Mustang or Camaro in terms of value haha.
Are you running any roll center correction?

I am planning on installing the Ford racing lower control arms with the extended ball joints, just need to decide if I'll do it during the season or wait until winter.

 

[SlowstangGT]

I am planning on installing the Ford racing lower control arms with the extended ball joints, just need to decide if I'll do it during the season or wait until winter.

I'm curious if the S197's get reduced track width with those. The Steeda RCC arms pulled the knuckle so far in, I had around 5 degrees of toe out post-install

 

[gwilliams38]

I'm curious if the S197's get reduced track width with those. The Steeda RCC arms pulled the knuckle so far in, I had arund 5 degrees of toe out post-install

With the RCC arms, -3.2 camber, and springs that give me about a 0.75" front drop, I had only one small spot of rubbing on the fender liner with 305/30r19 supercar 3rs on 19x11 with an effective offset of +22. The NT01s in 305 are a pretty safe bet IMO.

 

[SlowstangGT]

With the RCC arms, -3.2 camber, and springs that give me about a 0.75" front drop, I had only one small spot of rubbing on the fender liner with 305/30r19 supercar 3rs on 19x11 with an effective offset of +22. The NT01s in 305 are a pretty safe bet IMO.

I take it you cut the strut tower hole open? Or do you have some adjustable lateral links / k-member mounting points? -3.2 is awesome

 

[gwilliams38]

I take it you cut the strut tower hole open? Or do you have some adjustable lateral links / k-member mounting points? -3.2 is awesome

Yes, cut the strut tower hole. Wish I had some smarts beforehand so I would've contained the sharp metal shards that went all over my engine bay and floor but... ya live ya learn, via cuts.

 

[Fair]

I prefer the 315/30/18 or 305/30/19 on the S197 and S550 (both on 11" wide wheels) over the 295/40/18....



The 315/30/18 is a shorter tire (25.5" tall) so that will effect your final gearing - maybe for the better, maybe for the worse. You weren't asking about competition tires (Hoosier) so lets look at 200TW...


The 295/40/18 size looks good on paper - its the same height as most stock tires on S197 or S550s - but in reality it has a giant sidewall in this 18" size, and VERY few tire models to choose from (approaching 1).



I've run that size in Hoosiers on the same event as 315/30/18, and the TALL 295 tire was a big squishy mess. Granted, we ran it on the narrow end of the range of recommended wheel widths. Still, there is just no upside to using this tire size over a 305 or 315.



The easy button for 200TW tires is the 305/30/19 size, shown above on 19x11" wheels. Lots of wheel choices and THE MOST tire choices of any size discussed in this thread.


The Falken RT660 is a good FAST 200TW choice here, with some heat resistance (for longer stints) and great one lap pace (for Time Attack competition in 200TW classes).


An even better choice for HPDE in this size might just be the Hankook RS-4, shown above. It wears like STONE and has the BEST heat resistance in the 200TW range. Single lap pace is going to be a little slower than the RE-71R, A052 or RT660, but on pace with the RT615K+ and the average lap times will be higher.



I've done several track days on the RS-4 this year on a 2006 Corvette, which is a lighter car (3117 lbs) but on a narrower size (275/35/19) so roughly the same weight-per-mm of tire width. They take a few laps to come up to temp (unlike the RE-71R/A052/660, which are fastest on lap 1-2) but they just don't fall off. After hard 30 minutestints they are running the same times as on lap 2-3. Amazing longevity and consistency.



Hope that helps your choice... again, for S197/S550 on 200TW, 19x11" wheel and 305/30/19 tire. Pick the best compound for your end use.

Cheers!