will the rim or tire define fitment?

[definitiveno]

Wret, I understand you are running a 8.5 inch wheel with a 245 series tire. Apparently adr is one of few wheel makers that offers this dimension so my options have been very limited. If I was to stick with the 245 inch tire could i get away with a 9 inch wide rim? Would clearance issues remain the same.. ie. The main concearn is tire rubbing the knuckle, and second concearn being tire rubbing the body?

What do yall think?

 

[igs]

Tire size varies with rim size, that's why tire specs always have a "measuring rim size" to keep things consistent, DOT mandated.

 

[ACM]

Most 245/45s can run on a 9" rim. Clearance issues will be entirely dependent on the offset you choose, just as with virtually any rim width. If the extra 1/2" is added all on the inboard side there will _probably_ be a clearance issue, but it may be fine; if the 1/2" is added on the outboad side the tyre may catch on the front arch lip at full compression - it's already guarranteed that it will hit the rear lip if sufficiently compressed.

At these wheel and tyre widths production tolerances play as big a part as anything in what touches where first. My 95 has a few more millimetres front fender clearance when compared to a certain Red 34ESP - enough for me to run a 3mm wheel spacer and clear the arch lip where he kisses the lip without a spacer. Same wheels, same tyres - quite literally.

Charles

 

[wret]

If you are asking “If a certain tire on an 8.5 inch wheel fits, would it also fit on a 9 inch wheel with the same offset?” then the answer is yes. But that depends on how you define “fit.” All other things being equal, the extra ½ inch of wheel would stick out ¼ inch more and stick in ¼ inch. There is plenty of room for the ¼ inch on the inside.

As Charles stated, when using 245/40/18 or 245/45/17 sized tires, clearances are very small; in the single digits of millimeters. I haven’t quite finished my tread width chart, but so far my research shows over 15 mm difference between tread width specs of different brands of 225/45/17’s. And that’s throwing out the narrowest and widest.

 

[definitiveno]

I plan on using a pirelli Pzero nero wich is ultra high performance all season. I am not sure what the treadwidth is, what the measuring rim size is, or where to find this information.

The offset on the wheel I'm looking at is 38mm, will that rub the fender? I am reading alot from the faqs but I still don't feel confident enough to make this decision without some help from you guys.


Thanks for your replies so far.

 

[wret]

Tirerack is usually my first choice for tire dimensional data, but you picked one that has the tread width listed as "NA." I assume that means "not available" rather than "not applicable," because it definitely is. The Pirelli website doesn’t have it either. Try contacting your tire vendor.

 

[definitiveno]

okay, after calling about 10 shops discount tire was able to hook me up with the specs on this tire. The tread width suprisingly is only 8.2 inches wide, the section width is 9.6 inches, and designated rim width is between 8 - 9.5 inches wide. Even though the treadwidth is so narrow the tire is rate as the best wet and dry ultra high performance tire they sell, longest lasting within the top 10 as well.


Again this would be going on 18 X 9 inch wheel with 38 offset. in your professional opinions "should" it fit? I only plan on lowering the rear of the car 1.5 inches to level it out if that helps.

 

[wret]

Hmm, 8.2? That's pretty narrow for a 245. In fact that's narrower than the average in my list of 235's. Clearance should not be an issue if that spec is correct. Just be aware that nine inches of wheel will stick out slightly beyond the fenders.

 

[definitiveno]

Hmm, 8.2? That's pretty narrow for a 245. In fact that's narrower than the average in my list of 235's. Clearance should not be an issue if that spec is correct. Just be aware that nine inches of wheel will stick out slightly beyond the fenders.

Wret, I double and triple checked those measurements with the guy. Just to be sure I am going down there to measure the width myself.

According to your measurments, giving a little room for error, what would be the largest tread width that should fit, maybe while I'm down there I will measure a few other tires so that i may have some options.

 

[wret]

About 8.8 inches.

 

[definitiveno]

Alright, after a little more searching I was able to find a knock off of the wheel I wanted in 18 X 8.5 but it only available in 35 offset. Would i be better off fitting the 8.5 inch wheel with a 245 (35 offset), or the 9 inch wide with 38 offset?

 

[wret]

Now you're splitting hairs. The difference comes down to a couple of milimeters. The performance choice would be the 9's. The practical choice would be the 8.5's (slightly less risk of curb rash). Choose.

 

[definitiveno]

Now you're splitting hairs. The difference comes down to a couple of milimeters. The performance choice would be the 9's. The practical choice would be the 8.5's (slightly less risk of curb rash). Choose.

See, this is where i get confused, with a section width of 9.6 inches on the tire i thought there would be .3 inches on either side of the rim of rubber to contact before the rim. If by chance i was using an 8 inch rim, wouldn't the section width remain the same as if using a 9 inch rim?



Without changing tire or offset, the way i imagine it, you could put any size rim under the tire you wanted as long as it was not as wide or narrower than the widest point of the tire. Sorry if this is getting repetitive. I think the 9 ich would have less clearance issues due to the more favorable offset, but I am no expert.

 

[definitiveno]

I take it back, the 8.5 inch wide would have a 3.35 mm advantage over the 9.


What would you do? Street car btw. I found the wheel in 8 inch too

 

[wret]

Somewhere there are probably people who care about section width. And yes, it changes significantly with wheel width. What concerns me most is tread width because the corners of the tread are what make contact with bits of the suspension and body (see Scylla & Charybdis).

Either of the wheel selections you mentioned provides adequate clearance for the knuckle. You didn’t give any specifics about your suspension, but if it is low, clearing the rear fenders will be a concern. Ideally, I would put 245’s on an 8.5 inch wheel with a 38-40mm offset. This keeps the tire as far to the inside as possible. When you lower the suspension obviously the tire gets closer to the fender arch, but when you correct your negative camber, this can be a problem. No big deal if you have an adjustable suspension.

 

[definitiveno]

Somewhere there are probably people who care about section width. And yes, it changes significantly with wheel width. What concerns me most is tread width because the corners of the tread are what make contact with bits of the suspension and body (see Scylla & Charybdis).

Either of the wheel selections you mentioned provides adequate clearance for the knuckle. You didn’t give any specifics about your suspension, but if it is low, clearing the rear fenders will be a concern. Ideally, I would put 245’s on an 8.5 inch wheel with a 38-40mm offset. This keeps the tire as far to the inside as possible. When you lower the suspension obviously the tire gets closer to the fender arch, but when you correct your negative camber, this can be a problem. No big deal if you have an adjustable suspension.

due to time money and uncertainty I am goin with the 8 inch and 235's. I wish I was more expendable to this project but nows not a good time. Thanks for your help though wret.