I am looking at some wheels online and the sellergave me this for the tire size. WHat does it mean as I am used to seeing only three numbers?

Tire 215/70/50 r17 Michelin Pilot Exalto A/S

They are on a VW R32 and on AT Italia S5 rims. Basically I need the info to know if they will fit on my 86 basecoupe notchie.

Yah, way too many numbers there..

A 17" wheel on a fiero a good size is a 45 profile tire.

So, tire size would be: 215/45/17

215 is the width
45 is the profile (sidewall)\
17 is the wheel size

If it turns out they are 215/70/17 or 215/50/17 think they would work?

Tire size info breaks down like this:

215 = Width of the whole tire, sidewall to sidewall (not just the actual tread width) in millimeters, as measured on the tire's design rim width.

/70 = The aspect ratio of the tire, in plain English the height of the tire from the bead to the tread, as a percentage of the whole tire width. For instance, a 70 series tire is 70 percent as tall from bead to tread as it is wide.

R17 = diameter of the rim the tire fits on. Note, this is the bead diameter, the outside diameter is typically an inch larger.

So, let's crunch some numbers on the 215/70-R17 tire:

215mm wide equals 8.46" wide. The tire height is 70 percent of that, so 8.46" x 0.7 equals 5.93" from bead to tread. Multiply that by two to get the total height of the rubber, add the rim diameter of 17" and you get a total tire diameter of 28.85". I would think that's a bit too tall since the stock tire diameter is more around the low 25" range. You'd be adding almost 4" in diameter.

JazzMan

Thanks Jazzman I just found out it is 215/50/17. Maybe that'll work....
Looking online and the worse case offset on a VW would be 32.

[This message has been edited by 2.5 (edited 03-10-2008).]

http://www.miata.net/garage/tirecalc.html

This is pretty useful.

quote Originally posted by 2.5: If it turns out they are 215/70/17 or 215/50/17 think they would work?

No, these both will not work. 215 is the width , and 70 is the height. TRUCK tires are a 70 series.

215/50/17 is still too tall.

you need a tire that is 215mm wide, by 45 mm tall.

quote Originally posted by 88White3.4GT: you need a tire that is 215mm wide, by 45 mm tall.

The second number is a percentage of the tread width, not a mm size. Therefore, a 215/50/17 would come to 25.46" tall. A stock tire on the rear of GT was a 215/60/15....coming to 25.15". A 215/45/17 would come to 24.614"....which is real close to the stock front GT tire which was 205/60/15 (24.685" tall).

[This message has been edited by CowsPatoot (edited 03-10-2008).]

quote Originally posted by CowsPatoot: The second number is a percentage of the tread width, not a mm size.

Close, and in most cases accurate enough, but not quite. The aspect ratio ([section width(in mm) / aspect ratio(in %) - R diameter(in inches)] is the standard format for tire sizing) is actually a function of section width, not treadface width. So it's a percentage of tire width from sidewall to sidewall.

But like I said, it's really just a matter of semantics, and on low profile tires there is very little difference in section width versus tread width. It really only becomes an issue when you're dealing with OTR tires for semis and other large trucks.

Anyway, I have nothing of value to add here, so carry on and pay me no mind.

I've got 215/40/17's on my base-model '85 2M4 sport coupe.

The tires are only slightly larger (maybe a quarter inch?) than my 185/60/13's that came on the car when I got it.

I've got *plenty* of room in the wheel wells for a bigger tire. I plan to replace the 40-series tires with a slightly wider 45 or 50 series as I've manage to skuff the edge of the rim because the tire sidewall does not protrude past the bead.

The only issue you might run into is the tire may restrict your max turning radius. The tire may rub on your wheel well/suspension. Try turning your wheel to it's full stop and measure out the radius of the tire.

215mm * 40%(.4) = 86mm converts to 3.3 inches (according to google)

17 inch rim + (3.3 inch tire * 2) = 23.6 inches.

Radius = 23.6 / 2 = 11.2 inches

quote Originally posted by 88White3.4GT: TRUCK tires are a 70 series.

And some CAR tires...along with 80 series, and then there is the 145 SR 12's, with an approx aspect ratio of 82.

Kevin

quote Originally posted by Lambo nut: The "R" itself, stands for "Radial" tire Could also have a "P" in front for passenger car tire, "LT" for light truck. As in P235/75/15, or LT235/75/R15, the LT having a higher load rating The speed rating can also be in the nomenclature, as in "S", "T", "H", "V", "Z", etc. Examples being 225/70/SR15, or 345/35/ZR15 Kevin

Yeah, I know, but I didn't want to confuse him more than necessary.

I busted tires at Super Shops for a year and sold lots of BFGs, man I miss those days...

JazzMan

quote Originally posted by Icelander: I've got 215/40/17's on my base-model '85 2M4 sport coupe. The tires are only slightly larger (maybe a quarter inch?) than my 185/60/13's that came on the car when I got it. I've got *plenty* of room in the wheel wells for a bigger tire. I plan to replace the 40-series tires with a slightly wider 45 or 50 series as I've manage to skuff the edge of the rim because the tire sidewall does not protrude past the bead. The only issue you might run into is the tire may restrict your max turning radius. The tire may rub on your wheel well/suspension. Try turning your wheel to it's full stop and measure out the radius of the tire. 215mm * 40%(.4) = 86mm converts to 3.3 inches (according to google) 17 inch rim + (3.3 inch tire * 2) = 23.6 inches. Radius = 23.6 / 2 = 11.2 inches

Um, if you plug the numbers you quoted into a tire size calculator, you get a overall diameter of 21.7 inches for the 185/60/13's and 23.8 inches for the 215/50/17. That's 2.1 inches give or take. This is a substantial difference, and equates to over a 9% speedo error (when it says 60mph, you're actually going like 65.5mph)...

quote Originally posted by 2.5: If it turns out they are 215/70/17 or 215/50/17 think they would work?

Only if you jack the car up to be truck height. a 215/70R17 will be nearly 29 inches wide.

215/50R17 will be 25.5 inches wide. 215/45R17 are 24.6 inches wide and will ffit the hole nicely. the 50's will possibly rub, although a 215 is a skinny tire so it might not. The 70's will rip your fender off and will require a big hammer to force into the 28" wide wheel well.

NOTE: dont be fooled into thinking you got a lot of room in the wheel well unless you are going to use skinny bike tires. bigger tires are typically wider and they rub. Rubbing in a tire = dead tire and damaged wheel liner or worse. never EVER install a tire that rubs.

[This message has been edited by timgray (edited 03-11-2008).]

quote Originally posted by timgray: Only if you jack the car up to be truck height. a 215/70R17 will be nearly 29 inches wide. 215/50R17 will be 25.5 inches wide. 215/45R17 are 24.6 inches wide and will ffit the hole nicely. the 50's will possibly rub, although a 215 is a skinny tire so it might not. The 70's will rip your fender off and will require a big hammer to force into the 28" wide wheel well. NOTE: dont be fooled into thinking you got a lot of room in the wheel well unless you are going to use skinny bike tires. bigger tires are typically wider and they rub. Rubbing in a tire = dead tire and damaged wheel liner or worse. never EVER install a tire that rubs.

Not quite. The 215 is set in stone, that's the section width. The 45 (or aspect ratio) is what is determined by the section width. The 45 is 45% of 215mm for the sidewall. A 215/45/17 is 8.46 inches wide with a sidewall of 3.8 inches high and is 24.61 inches in diameter.

A picture is worth...



More explanation here: http://www.heeters.com/tirechart.shtml

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3.4L S/C 87 GT www.fierosound.com
2002/2003/2004 World of Wheels Winner &
Multiple IASCA Stereo Award Winner

In my experience, albeit limited, not all 215's (or whatever first # you have) are created equal. A 215/40/R17 can very well, if not always, be wider than a 215/70/R17. This I get from my experience with a set of Sumitomos (sp?) that my brother bought. The reason for this is the first # measures the distance from where the tread starts on one side of the tire to where it ends on the other side. The 70 series tire would have more tread on the sidewall because it's a taller tire. Thus the same inner-2-outer tread measurement on tires of dissimilar series can result in different overall tire curb widths. Maybe Sumitomos are odd, but this was definitely true in our case.

Correct me if I'm wrong, but I believe that each tire company will bring its tread down the sidewall a different distance, thereby making tires of the same size ratings but differing brands have different widths.

-Michael

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"A guy know's he's in love when he loses interest in his car for a few days." -Tim Allen


Check out my restoration!

quote Originally posted by Fierology: The reason for this is the first # measures the distance from where the tread starts on one side of the tire to where it ends on the other side.

The correct measurement is across the widest point of the sidewall of the tire. The manufacturer will use a specific width wheel so the sidewalls aren't bulged out or pulled in excessively. Most low profile tires have virtually flat sidewalls, but standard tire sizes the sidewalls have a noticeable bulge due to the height of the sidewall (and of course the fact the tire will try to be rounded across the treadface due to the air pressure inside acting like a balloon).

There are no 'official' inch numbers for any tire size. A 215/60r/16 for example will vary quite a bit by measurements just by brand name. Always replace a tire with one of the same brand/ style as the opposite one... Another words the same size on sidewall can vary an inch or so between say a Goodyear and Dunlop tire. Some places like Tire Rack give you the actual diameter of the tire in sales info.

quote Originally posted by rogergarrison: There are no 'official' inch numbers for any tire size. A 215/60r/16 for example will vary quite a bit by measurements just by brand name. Always replace a tire with one of the same brand/ style as the opposite one... Another words the same size on sidewall can vary an inch or so between say a Goodyear and Dunlop tire. Some places like Tire Rack give you the actual diameter of the tire in sales info.

I used to build tires at a Pirelli tire factory, and I know this to be true.
Also note that the different tire manufacturers will list the same size tire that will have different max and minimum rim width. So Kumho will list a 255 45 17 that will fit a minimum width rim of 8" but Goodyear will say a 255 45 17 needs a 8.5" rim minimum width. Tires ARE NOT rubber balloons, they are complex equipment for your car. Different manufacturers will design and build a tire differently than others to meat specific performance goals. So not all tires of the same size are the same size or same capabilities/tolerances.

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Ok thanks I think this thread will help future users who search as well as me, so I got the tires which are on "AT Italia S5" rims late last night, they are only 6" wide rims so that help with the fitting a bit. I am mounting them tomorrow, and I'll let you know how it goes. I'm still one of those lam-o users who can't quite get a pic posted though. I know they will be a tad taller than stock but no biggee to me.
One more question,
...are 1990 Grand Am lug nuts the same as 1986 Fiero lugnuts in thread and diameter?

Well they fit nice, stick out maybe 3/4 to an inch farther than my previous ones and are about 3/4 inch larger in diameter. I had 195/60/15s on before, from an 03 Sunfire. These suckers look a lot better too!

[This message has been edited by 2.5 (edited 03-14-2008).]