Hi all,

Another question. I have been shopping wheels hard on two different sites (tirerack and discount tires; the latter because that is where I will likely buy my tires and have them installed). One place (discount tire) has a lot of wheels with 7.5 instead of 8 widths. Is an 8 just a rounded up 7.5 or do they require different tires?

I am thinking the below on my 2006 GT (stock except for CAI and Cat-Backs). I can adjust accordingly, but curious if those tires will fit on x9 and x8 without the .5's...oh, and if they should work well on a daily driver....thanks in advance for any insight...

Rear 18x9.5 w/285/40-18
Front 18x8.5 w/255/45-18

 

Any rounding of wheel widths is to the half inch (and would usually be just a manufacturing tolerance thing), so a wheel advertised as being 7.5" measures 7.5" between the insides of the bead flanges. Outside to outside is about an inch greater due to the thicknesses of the two flanges.

Your 255/45 fronts would be just barely approved for 18 x 8, but the 285/40's are half an inch out of spec on 9" wide wheels. Part of this is that those wheels do not offer design support to those tires' treads while cornering and might give more rapid second rib wear as a result. But the more important part is an increased heat generation in the sidewalls issue due to the greater sidewall "bulge" and amount of flexing. Stick with the 8.5" and 9.5".


Norm

 

No. The 8's are not, or rather, SHOULD not be rounded up 7.5's.

This is really an odd size for a wheel and measurement is taken between the lip where the tire makes a seal. They will also not "necessarily" require different tires, but most tires that will fit one, will fit the other. The wheel fitment is set by the manufacturer of the tire and they will vary to a degree.

285's are really too wide for a 9" wheel and pushing it a bit for a 9.5".
255's are probably too wide for an 8" wheel, but the tire manufacturer will give you acceptable fitments for ALL their tires. You may find a higher profile 285 will be OK for an 8" wheel, but none to my knowledge.

If you go 8"s & 9"s, I recommend 245's and 275's to be the widest in general for nearly all manufacturers.

Jazzer :-)

 

No. The 8's are not, or rather, SHOULD not be rounded up 7.5's.

This is really an odd size for a wheel and measurement is taken between the lip where the tire makes a seal. They will also not "necessarily" require different tires, but most tires that will fit one, will fit the other. The wheel fitment is set by the manufacturer of the tire and they will vary to a degree.

285's are really too wide for a 9" wheel and pushing it a bit for a 9.5".
255's are probably too wide for an 8" wheel, but the tire manufacturer will give you acceptable fitments for ALL their tires. You may find a higher profile 285 will be OK for an 8" wheel, but none to my knowledge.

If you go 8"s & 9"s, I recommend 245's and 275's to be the widest in general for nearly all manufacturers.

Jazzer :-)

 

So just so I am clear...

18x8 fronts w/245/45-18
18x9 rears w/275/40-18

will work and not cause the heat/wear issues? And it should be reasonable on a daily driver (I realize I won't be able to rotate them for longer life - any tire brand recommendations? I was thinking GY Eagles)?

And don't be shy...if I shouldn't mix sizes, tell me before I spend my $$$$$$...was just searching for the true muscle car look...bill

 

Those sizes sound fine, but need to confirm acceptable fitment with the actual tire you plan to use via manufactures fitment guide (I don't forsee a problem with that)

As for tires, you will not have an issue going staggered widths or series as you have listed. As for the actual tire itself, it really depends on two things: The first being your budget, as this will ultimately determine what you can afford. Next, is your driving needs/wants.

What kind of driving do you do? Cruizing? Launching? 1/4 miling? Cornering?

Let us know your budget and driving needs and will be happy to make some recommendations.

Jazzer

 

Based on the mfr acceptability, which I think exists in at least most cases for those combinations (it does in the half dozen or so cases I looked at), you're at least OK from a heat point of view. One has to figure that the tire mfrs are being pretty careful about this, given the uproar around Explorers and Firestone tires only a very few years ago.

Whether you get second rib wear is less certain, as it also depends on the tire internal construction. But chances are if nobody has reported unusual wear in the reviews for the tires you're looking at, you'll be OK here too. Pay most attention to the reviews that are designated "Spirited" for driving or mention auto-X and open-tracking. FWIW, I did read somewhere just this week where somebody has recently experienced this kind of wear, but I don't remember where I saw it.

I can't give you any recent information of my own concerning second rib wear although I have seen it. Then again I've tended to choose wheel widths toward the wide end of the range for any given tire, after selecting the tire size to suit the car and its use.


Norm

 

Here is what I am leaning towards (with both front and rear fitments and recommended tire sizes)...I have read a lot of folks recommending tirerack, so can I assume their recommendations are proper and safe? Oh, and will I have trouble with those lugs if I ever need to change a tire - they come with adapters...

http://www.tirerack.com/wheels/Wheel...All&sort=Brand

and for tires,

http://www.discounttire.com/dtcs/tir...ABINT&pc=30039

available in both sizes.

I have a red fire GT, and am going with a red/black motif when I get to striping (as soon as I find some that aren't on every GT in the country). I figure the gunmetal wheels would be a good fit, and the machined lips will offset my magnaflow stainless steel tips.

If you have other suggestions, I am trying to keep my total package (4 wheels/4 tires) between 2-3k installed. Driving is about 30 highway miles daily (7.5 mile chunks) with about 20 non-highway. No racing except the occassional WOT when accessing the highway =). Weekend trips to the grocery store, carwash, etc. I am more about the appearance of my car and "knowing" I have the power available.

Thanks again for everyone's help...so many choices...lol, what ever happened to Cragar's?

 

I'm not sure whose recommendations you mean. IOW, is it the folks who recommend TireRack or the TireRack sales personnel. Proper tire choice isn't all that difficult - the tire has to have sufficient load capacity for the car and be mounted on a wheel of acceptable width.

Without saying anything bad about forum members either here or elsewhere, there is not only no guarantee that you'll get a completely proper recommendation - you frequently see some strongly defended (but misguided) suggestions to use a wide tire on a too-narrow wheel.

Wheel & Tire suggestions from TR or Discount are much more likely to be correct, but I do think that a few marginally "unapproved" tire sizes for existing or separately sourced wheels have snuck out from time to time, either in the name of making a sale or because the wheel size was unknown/unspecified by the purchaser.

Load ratings and wheel width information can be found on the "Specs" pages for many tire makes/models at TireRack (and other sites as well for some of the tires that TR does not carry). As far as maintaining load capacity is concerned, the simplest approach is to make sure that the load index for the tire size that you're considering is at least as much as the load index for the minimum OE size tire for your specific car model. IOW, if you have a GT, use the base GT tire size here, not necessarily the smallest tire fitted to a sixxer.

I stay out of almost all discussions regarding subjective "appearance".


Norm

 

Thanks. Already changed my mind again lol, decided I didn't like the offset center that would look lopsided when those wheels turned. Gonna stick with the Goodyear F1 All Season tires due to excellent reviews, so now searching for wheels around their available tire sizes.

Is there a site somewhere that will tell me what size wheel is required for a given tire size? I tried the goodyear site, but I went to their "fitment" tool, they want to just tell me what they think will fit on my car, defaulting to the 17" stock tires (unless I am just being obtuse and not seeing an obvious tire to wheel fitment tool).

Also, if anyone has any experience with the ride a 19" wheel would give on a GT, I'd be interested to hear thoughts on smoothness of ride and road noise.

I know it's a lot of questions, but it's a lot of money and I value the opinions of those with experience....thanks, bill