My new wheels are coming in today, 18x8.5 and 18x9.5 both 20 offset. I was planning on stretching my stockers on them for a while since the tires appeared to still be in good shape, however I found that the very inside edge (about 1 inch) of both front tires are bald…like scary bald. I bought the car with 39k miles last month, so not sure if it just wasn’t aligned or if it’s the feathering issue.

Anyways, here are my options:

A) move my current rear tires to the fronts and put new: 275/40/18’s in the back
B) buy new 245/40/18’s for the front and stretch the current rears on the 9.5 inch wide wheel (assuming the RE040’s will stretch to that)

Here is what the diameters will look like:

Stock
Front – 25.97” with 225/45/18
Rear – 26.68” with 245/45/18

Option A
Front – 26.68” with 245/45/18
Rear – 26.66” with 275/40/18

Option B
Front – 25.71” with 245/40/18
Rear – 26.68” with 245/45/18

What would you use and why?

 

Those are the same size as the NISMO wheels. We just went through recommended tires the other day.

 

I am not looking for recommendations for all brand new tires, I know what sizes I want when I get all new tires. I'm looking for a recommendation between the two options posted above.

 

I'm all for having the back taller than the front. But that's only .02 difference on your other option with the fronts being a lil taller. Just whatever you like best I suppose.

 

I agree, I would like to keep tire diameter as close to stock as possible, but Option 2 would also leave me with the correct size tire for my wheel up front, and a stretched rear tire that is the same width as the front.

This is why I'm trying to get opinions, because I'm just not sure what would be better. Keep in mind this won't be for a long time, maybe 5k miles until I replace the other 2 tires with the correct size.

 

Keep in mind that “overall tire height” assumes that wheels and tires are properly matched. A 9.5 inch wheel - 245 mm tire is a stretch. Actual “overall tire height” and chart height will be significantly different.

 

I have read that the steel belting on the tires determine the overall diameter, so "stretching" a tire will cause very little, if any change to the overall diameter.

 

This one (your question) is too “close to call.” I’m being facetious since actually either scenario you present might work.
____________________
Option A
Front – 26.68” with 245/45/18
Rear – 26.66” with 275/40/18

…is risky since the fronts are taller (albeit, very slightly) than the rears. Going “too tall past spec” in the front, and adding “front higher than rear” is asking for trouble.
____________________
Option B
Front – 25.71” with 245/40/18
Rear – 26.68” with 245/45/18

…is within specifications and will definitely work. In fact you are not stretching excessively with this tire width on your wheels.

========================
I vote for Option B. When you wear out the rears, buy 275/40-18 tires as the replacement.

--Spike

 

Davidv is correct when he mentions stretching tires on wider rims that go past the tire’s specifications will result in less overall diameter. But, I don’t believe you will experience this with 245’s on 18” wheels up to a 9.5” width (which is just a little past specification for a 245 wide tire).

“Steel-Belting” sidewall construction is no guarantee that stretching will maintain overall diameter on your tire (which is David’s point that I reaffirm). If you stretch any tire past its specification, you will experience a reduction in overall diameter. Certainly it will be a very small difference and usually insignificant, but it could be significant when you’re “near the limit.”

I would suggest keeping David's advice in mind when mounting a stretched setup; especially in your case where you are considering fractions of millimeters for sizing.

--Spike

 

Thanks spike. Not quite sure where I read that, was just mentioning that I did read it somewhere online. We know how reputable random websites are though, lol.

Still not sure about the stretch though, I measured the width of the 245/45 on the stock wheel and at it's widest point it's maybe a hair over 9.5" wide. I measured the wheel from outside of lip to outside of lip and it measures 10.5" wide. inside to inside is about 10" wide.

Now, something may be said for keeping the used tires on the rear, since those are going to be the quickest to wear out and replace with correct sizing. I believe I have about 5k miles left til I can replace them without feeling guilty about replacing a perfectly good tire.

Thanks again for the suggestions guys.

 

No 245s on a 9.5. I'd go with option "A", if you have no other choices besides what you've listed. OR, you can scrap those options, and get a set of 255/35/19 fronts with 275 or 285 rears, IMO. Used tires sell, if that's your concern.

 

Option B and call it a day. It really won't be very streched considering its a 45 profile. People run 245's on here all day on 9.5 wheels.

 

^^ Well said (clearly and succinctly). As you point out, 245’s on a 9.5” wide wheel is a minor stretch (going only slightly past the tire manufacturer’s recommendation), and in fact, some prefer the appearance of this setup.

The only downside I see is a greater potential for scraping the wheel (curb-rash) which you avoid by being careful.

--Spike

 

Ya, I can't remember the last time I scraped a curb, so I'm not too worried about that. I am going with option B and am getting the tires mounted up tomorrow.

Thanks all for your help, hopefully I'll get some good pictures of the car on sunday that I can post.

 

^^ The car’s owner is the least likely driver to scrape a curb and ruin a wheel… it’s you gf, wife, or buddy who does this.

…Looking forward to seeing the pics this Sunday. Stretched tires are actually quite attractive (they look much better than bulged mounts).

--Spike

 

I guess I should be thankful my wife doesn't know how to drive a stick, and I never let my buddies drive my cars =)

My wife is a photographer, so if it's not 30 degrees out tomorrow then I'll do a quick wash and take some pictures. They are mounted and the car looks 10x better now than I did with stock wheels. I'm not a fan of the stretched look on the rear tire, so this summer it will definitely be getting the 275/40's in the back.

Thanks again for the help

 

couldn't sucker my wife into taking pictures, but I got 1 to post.

Wheels
Front 18x8.5 +20 Ruff Racing
Rear 18x9.5 +20 Ruff Racing

Current Tires
Front 245/40/18 General Exclaim UHP
Rear 245/45/18 Potenza RE040 (stock, for a few thousand miles til I get my 275's in back)

Thanks to Ken at Enjuku Racing for getting me a great deal on the wheels. No, they are not Volk's, but my car money generally goes into my 450 hp '66 Mustang GT

 

^^ Looks good… the rears are definitely stretched, but I like it!

Please take and post pics when you mount the 275’s.

Question: How do you rate handling with your current tire/wheel setup?

I’m guessing it’s good and mostly neutral, but I would like to hear your opinion since I like 245-width all around.

--Spike

 

Sorry for the delay, I'm an accountant and have been finishing up year end so I've been working long hours. I had to drop the damn wheels and tires off at discount on a saturday when they opened, and pick them up on the way home from work when they closed just to get that done.

anyways, the handling, like you said, is pretty neutral. I feel a little more grip in the front end right now (I know, i shouldn't with the general's up front, but they are pretty grippy for their treadwear rating), and I did fish-tail on dry asphalt a couple times when pushing it through a turn. But, I was pushing it, and the car is rear-wheel drive so thats expected.

I'll keep you posted when I get the 275's and post an update with my findings along with some more pictures.

 

^^ The fish-tailing you mention isn’t unusual when you begin driving a neutral setup. That fault goes away after just a little practice with hard turns. Since the front grips better and turns-in faster, you just wait a split second longer before applying power as you come out of the turn.

Under-steer makes a hard turn not difficult to execute since you can easily recover, but you lose time while the frontend plows. A neutral setup requires more skill since timing is essential.


--Spike