Tire sizing help

[Voltwings]

So i realize this is a topic that must get beat to death, but i find myself here in an unusual situation.

My GF and i have recently gotten much more active in road course driving, and have gotten to the point where a spare set of rims / tires is almost a must to keep from burning out the street tires since we are both on 19 x 9.5's ($$$), and since we both race our budget is slightly tight...

However, up until now she has been driving an auto V6 and has decided it just wasn't cutting it and we traded it in on a new V6 with a stick. So, consider the ~3500 lbs the car likely weighs, and the ~280 or so whp it likely makes, and i don't think it will need a whole lot of tire, especially since she has been driving stick about 2 months and will probably not be driving 10/10ths.

For that reason, i think i may be able to use my Stock GT rims ( 18 x 8 ) and just get her a nice, sticky 245 or so and that should be enough to hold her over. Heres my concern though, i don't want to try to save money and end up wasting it on a tire that is too small, but i also don't think we're at the point where she needs a larger 18 x 10 with a 295 or something just yet... Basically, do you guys think i can get enough tire on an 8" rim for her to be able to go out, push the car, and have fun? we're still novices by all means, and are still very new to most of the tracks in our area, but i also don't want her to HAVE to take it easy because she doesn't have enough tire.

Any input would be greatly appreciated. Thanks guys.

 

[JScheier]

<edit> so I missed part of the post about 18x8... I'll make that up <edit>

a 225 would probably work better on the 18x8... a 245 will work (ran them on 8s on my M3)... I wouldn't go any larger than that.


If going to a larger wheel, cost wise, the 18x10 Drift (late model restoration) or 18x9.5 GT500 wheels are probably the best bang for the buck. The drifts are the lighter of the two.

On either of those wheels, a 245 would be pretty small. I ran 285x35 Hankooks and they looked small on the 18x9.5, but they worked REALLY well.

A square setup will allow you to rotate the tires all around the car and help them live longer.

 

[cosm3os]

Yes. I wouldn't go wider than 225s on an 8 inch, though. Sure you could go bigger, but pinching a 245 on an 8 inch is going to be detrimental to performance and wear which are your priority.

 

[Voltwings]

<edit> so I missed part of the post about 18x8... I'll make that up <edit>

a 225 would probably work better on the 18x8... a 245 will work (ran them on 8s on my M3)... I wouldn't go any larger than that.


If going to a larger wheel, cost wise, the 18x10 Drift (late model restoration) or 18x9.5 GT500 wheels are probably the best bang for the buck. The drifts are the lighter of the two.

On either of those wheels, a 245 would be pretty small. I ran 285x35 Hankooks and they looked small on the 18x9.5, but they worked REALLY well.

A square setup will allow you to rotate the tires all around the car and help them live longer.

I personally prefer a square set up for that reason, plus i just like the neutral feel, and funny you should mention the 18 x 10 drifts because those are exactly what we're looking at... Just hard to buy 8 rims and tires all at once haha.

I'm assuming both of y'all are suggesting a 225 because of the way the sidewall will sit? i had a short stint where i was just drag racing the car, so i'm doing my best to change focus since this is an entirely different driving style (and honestly a hell of a lot more fun) but theres just no way in hell a mustang can make its way around a track with a 225... i don't care how sticky it is. Hell, to maintain the required tire height it would be a 225 50 18, that just seems like way too much sidewall regardless of how stiff the tire is?

 

[Grant 302]

All good advice above...drifts and 275s...done!

How do you like the V6?

 

[cosm3os]

As I understand the post, the question is what size tires to put on stock sized rims that are 18x8. Well, start with the size Ford put on them. If it's 225 or above, than my recommendation is use the size Ford recommends for that rim. From a "allow her to push" perspective, anything 225+ in a reasonably sticky tire will be plenty of tire.

 

[JScheier]

Honestly, I wouldn't put a 225 on the car for track use. I'd go 245 at minimum if for no other reason that the overall weight of the car (even the V6 is porky).

If you go to a 9.5 or 10" wheel, you also have the option for take-offs (275x35 or other sizes) which will reduce overall tire cost.

 

[F.D. Sako]

Ya, I wouldn't waste money on 225s, just because I used to run 225's on a corolla, which is a lot lighter car than the V6, and I could've always used more grip :

If your going to have dedicated track wheels and tires, you might as well go 245+, because she can easily end up overheating the skinny tires and you won't get optimum performance/longevity out of them.

 

[cosm3os]

OP, I think you are on the right track using a set of stock rims you already have lying around. I'm reading into your post that your GF is still a novice. If I'm right, she doesn't need 10 inch wide rims and 275s. She needs tires that will let her feel the car at its limits (where the limits are still relatively safe).

Run the widest tire you can run on the 18x8 without deforming the contact patch (Tire Rack has some pretty good guidelines). No need to run hoosiers, or any "r compound". One of the Direzza-like tires will be perfect.

Now, if she's advanced, quit f'ing round and get some 18x10s and Hoosiers and hope she doesn't beat you!

 

[Voltwings]

All good advice above...drifts and 275s...done!

How do you like the V6?

Honestly, considering the marginal weight difference from her '14 v6 to my '13 5.0, the car is surprisingly nimble and just easy to drive. I personally haven't driven it on the track yet, but it is kinda fun. The stock 2.73's are just WAY too long though... we're debating if we shouldn't try to swap something shorter in for our next track day as well, 50 mph in 3rd gear is a tick under 3000 rpms -_-. I figured i can kind of cheat the system because her stock tire is 28" tall, and the size i was looking at for my stock rims (245 45 18) is about 26.5" so that would effectively make up some gear there.

As I understand the post, the question is what size tires to put on stock sized rims that are 18x8. Well, start with the size Ford put on them. If it's 225 or above, than my recommendation is use the size Ford recommends for that rim. From a "allow her to push" perspective, anything 225+ in a reasonably sticky tire will be plenty of tire.

Ford had a 235 on there from the factory, which is why i believed you may be able to get as much as a 245 "safely" on there. Granted, the contact patch may not be optimal as was suggested above. Still not sure how i feel about a 3500 lb car on a 225, but i'm hardly an expert.

OP, I think you are on the right track using a set of stock rims you already have lying around. I'm reading into your post that your GF is still a novice. If I'm right, she doesn't need 10 inch wide rims and 275s. She needs tires that will let her feel the car at its limits (where the limits are still relatively safe).

Run the widest tire you can run on the 18x8 without deforming the contact patch (Tire Rack has some pretty good guidelines). No need to run hoosiers, or any "r compound". One of the Direzza-like tires will be perfect.

Now, if she's advanced, quit f'ing round and get some 18x10s and Hoosiers and hope she doesn't beat you!

Was basically looking for a ~200 treadwear tire, something with a good bit of grip, but yeah no R compound or slick. Oh and don't worry, she's "already the better driver, i'm just lucky i have a GT" haha.

 

[Grant 302]

Honestly, considering the marginal weight difference from her '14 v6 to my '13 5.0, the car is surprisingly nimble and just easy to drive. I personally haven't driven it on the track yet, but it is kinda fun. The stock 2.73's are just WAY too long though... we're debating if we shouldn't try to swap something shorter in for our next track day as well, 50 mph in 3rd gear is a tick under 3000 rpms -_-. I figured i can kind of cheat the system because her stock tire is 28" tall, and the size i was looking at for my stock rims (245 45 18) is about 26.5" so that would effectively make up some gear there.

I agree about them being 'surprisingly nimble' but I think that's because they're about 200 lbs. lighter up front. I drove a V6 performance package, and even the 3.31s seemed a little tall. If you go to a 275/35-18, you could drop down to 25.6" tall at the tires. It's also like 'free' lowering of the CG which should also help.

I rarely see V6 mustangs at the track, but the more I think about it, the more I want to make one my dedicated track car.

 

[Voltwings]

I agree about them being 'surprisingly nimble' but I think that's because they're about 200 lbs. lighter up front. I drove a V6 performance package, and even the 3.31s seemed a little tall. If you go to a 275/35-18, you could drop down to 25.6" tall at the tires. It's also like 'free' lowering of the CG which should also help.

I rarely see V6 mustangs at the track, but the more I think about it, the more I want to make one my dedicated track car.

I've got a soft spot for turbo 4's (came from a mazdaspeed3) so I'm pretty much set on getting an ecoboost when they come out. 3500 lbs from the factory (shouldn't be hard to get 3400 - 3300) and about 300 - 340 whp should be a fun, zippy little car.

I suppose I could make her tire 25.6", I was just worried about making it TOO short, but I suppose with a 2.73 theres no such thing...

 

[HackBoss2901]

Stick with the 18x8s. Its plenty of wheel for a novice. I have ran 245/45/18 and 245/40/18 on a 8 inch wheel for years on both my 07 GT and a friends 2010 GT with no issues. Sure bigger is nice, but when the budget is an issue you can't beat 245 prices and grip is relative anyway for a novice. As novice your main goal is to learn car control, which best learned with lower grip levels and then increase grip as your skills improve.

Good luck with your decision

 

[Voltwings]

Stick with the 18x8s. Its plenty of wheel for a novice. I have ran 245/45/18 and 245/40/18 on a 8 inch wheel for years on both my 07 GT and a friends 2010 GT with no issues. Sure bigger is nice, but when the budget is an issue you can't beat 245 prices and grip is relative anyway for a novice. As novice your main goal is to learn car control, which best learned with lower grip levels and then increase grip as your skills improve.

Good luck with your decision

I agree with this to an extent, and can appreciate where you're coming from, I just don't want to waste the money and ruin her weekend because she cant drive the car hard enough you know. A very unlikely situation it may be, its still just something to consider, so I'm trying to consider all views and inputs in this thread...

 

[Grant 302]

I've got a soft spot for turbo 4's (came from a mazdaspeed3) so I'm pretty much set on getting an ecoboost when they come out. 3500 lbs from the factory (shouldn't be hard to get 3400 - 3300) and about 300 - 340 whp should be a fun, zippy little car.

I suppose I could make her tire 25.6", I was just worried about making it TOO short, but I suppose with a 2.73 theres no such thing...

Or stick with your 18's and the BFG Rivals in 245/40-18, currently $189 each.
http://www.tirerack.com/tires/tires.jsp?tireMake=BFGoodrich&tireModel=g-Force+Rival&partnum=44WR8GFR&vehicleSearch=false&fromCompare1=yes

I hear you about the ecoboost4, but I'm having a hard time thinking I'd make *another* brand new car see track duty. I'm trying to find a 2012 V6PP for under $14k or so.

 

[TMSBOSS]

I agree about them being 'surprisingly nimble' but I think that's because they're about 200 lbs. lighter up front. I drove a V6 performance package, and even the 3.31s seemed a little tall. If you go to a 275/35-18, you could drop down to 25.6" tall at the tires. It's also like 'free' lowering of the CG which should also help.

I rarely see V6 mustangs at the track, but the more I think about it, the more I want to make one my dedicated track car.

I have a V-6 performance package 2013. It is fun on the track. Daughters car and we both have had it on the track.

Yes, even with the 3.31 rear you are wanting move rear gear.

The car tops out at 115mph. More gear would not tax the motor and there is plenty of gear left in the trans for economical cruising.

 

[VTBoss302]

Another thing to consider (not right away, but soon if you keep tracking it) is doing something to add more negative camber in the front

It will allow the tires to last a lot longer under track conditions

Plates are the preferred method around here

 

[Mad Hatter]

Very true. Camber plates save you lots of money on tires. Dunlop Direzza Z2 tires are a a good 200 td tire. Really last a long time.