i know this has been covered probly countless times before, i couldnt find it in the searches tho :/

whats the stock tiresize for an 86GT, im not anywhere near my car atm, so i cant look in the doorjam...

also, is there a perfered optional wider tire?

88GT's have 215/60R15 - rear and 205/60R15 - front.
I would say the 205/60R15 would be stock for an 86.

quote Originally posted by Carver1: 88GT's have 215/60R15 - rear and 205/60R15 - front. I would say the 205/60R15 would be stock for an 86.

so a 225/55r15 and 205/55r15 front will probly fit nicely?

The rear tire is going to be taller.
Here is how I figure tire sizes.
225/55R15
225 is the tread width in mm (8.9 inches)
55 is the height of the tire from the ground to the rim. (55% of the first number) (4.9 inches)
R is radial
15 is rim diameter in inches. (15 inches)

Now add up the rim size to the profile to get the tire height! Don't forget to double the second number. (you have tire on both sides of the rim)
4.9 + 4.9 + 15 = 24.8 inches is the height of the rear tire.
4.4 + 4.4 + 15 = 23.8 inches for the front.

So 1 inch difference.

quote Originally posted by Carver1: The rear tire is going to be taller. Here is how I figure tire sizes. 225/55R15 225 is the tread width in mm (8.9 inches) 55 is the height of the tire from the ground to the rim. (55% of the first number) (4.9 inches) R is radial 15 is rim diameter in inches. (15 inches) Now add up the rim size to the profile to get the tire height! Don't forget to double the second number. (you have tire on both sides of the rim) 4.9 + 4.9 + 15 = 24.8 inches is the height of the rear tire. 4.4 + 4.4 + 15 = 23.8 inches for the front. So 1 inch difference.

That's pretty close, but the 225 in this case, is the section width, wich is the widest part of the tire, usually the side wall, when mounted on the correct width wheel. This can vay quite a bit from the tread width in manufacturers.

The specs for tires on the Tire Rack site, will give you a good idea of most all the info you would want.

Kevin

So my calculations are correct for finding the tire height, though right?

quote Originally posted by Carver1: The rear tire is going to be taller. Here is how I figure tire sizes. 225/55R15 225 is the tread width in mm (8.9 inches) 55 is the height of the tire from the ground to the rim. (55% of the first number) (4.9 inches) R is radial 15 is rim diameter in inches. (15 inches) Now add up the rim size to the profile to get the tire height! Don't forget to double the second number. (you have tire on both sides of the rim) 4.9 + 4.9 + 15 = 24.8 inches is the height of the rear tire. 4.4 + 4.4 + 15 = 23.8 inches for the front. So 1 inch difference.

hrm, maybe just keep stock fronts, make the rears 225/60?
fronts already gona be a littlebit lower after springs
give it a nice aggressive "angle"

quote Originally posted by Carver1: So my calculations are correct for finding the tire height, though right?

You are going the right route. There is just so much variance between manufactures, it is hard to come up with good numbers.

For example, I just checked Tire rack,

Bridgestone Potenza RE92 shows tread width of 6.2 inches, Section width of 7.7, and a diameter of 24.7 for the 205/55/15

Micheln Pilot does not give a tread width, a section width of 8.5 inches,and a diameter of 23.9 inches. That's about 3/4 inch difference in heigth for the same "size" tire. Go figure.

Kevin

you know, not to hijack this one... though it is a common occurrence, I had a similar question about tire sizes and the search failed me, shouldn't we have a sticky of common knowledge things? Tire sizes, available options, stuff that is constantly repeated over and over... or did I just repeat another "something" that has already been asked before? :P

Personally I think that's a TERRIFIC idea .... like maybe a forum section or something ...

quote Originally posted by hookdonspeed: whats the stock tiresize for an 86GT

Their stock tire sizes differ front versus rear, as noted in the GM tire inflation sticker and literature for my "original owner" `86 GT:

• Front: 205/60R15
  
• Rear: 215/60R15

quote Originally posted by project34: Their stock tire sizes differ front versus rear, as noted in the GM tire inflation sticker and literature for my "original owner" `86 GT: Front: 205/60R15 Rear: 215/60R15

This is the right answer. My 86GT says the same thing.. LOL Wal-Mart won't allow their employees to mount the different size tires on a car even though the sticker requires it!

quote Originally posted by PaulJK: i could be wrong about this, but here goes: all the GT cars prior to 1988 came with (4) 6 inch wide wheels....If you try to go wider on the 86GT stock rims, be aware that the width is only 6 inches. Most tire manufacturers will specify a recommended rim width for their tire sizes. Personally, I probably would not go wider than a 215 R 60 on a 6 inch wheel.

For all I know, that last statement above may very well be good advice for a Fiero with a 6-inch rim.

However, that particular caveat shouldn't be of any concern whatsoever to you, hookdonspeed: The `86 Fiero GT which you, as the originator of this thread asked about, had as stock equipment 7-inch-wide rims all around, not any 6-inch-wide rims.

Good luck with your tire replacement project!

Well gee Mr. wizard, you better call GM and tell them they got the 1986 Owner's Manual wrong.

[This message has been edited by PaulJK (edited 01-03-2009).]

quote Originally posted by PaulJK: i could be wrong about this, but here goes: all the GT cars prior to 1988 came with (4) 6 inch wide wheels - the stock tire size was 205R60 15. The 88GT had 6 inch wide in front (and 205 R60 tires) and 6.5 inch wide in the rear (with 215 R60) tires. If you try to go wider on the 86GT stock rims, be aware that the width is only 6 inches. Most tire manufacturers will specify a recommended rim width for their tire sizes. Personally, I probably would not go wider than a 215 R 60 on a 6 inch wheel.

Agreed on the 215 on a 6 inch rim. I tried a 225 and it felt like a balloon.

quote Originally posted by cujoe_da_man: you know, not to hijack this one... though it is a common occurrence, I had a similar question about tire sizes and the search failed me, shouldn't we have a sticky of common knowledge things? Tire sizes, available options, stuff that is constantly repeated over and over... or did I just repeat another "something" that has already been asked before? :P

A lot of info, not just stock... https://www.fiero.nl/forum/Forum1/HTML/058236.html

Bob

quote Originally posted by PaulJK: Well gee Mr. wizard, you better call GM and tell them they got the 1986 Owner's Manual wrong.

quote Originally posted by PaulJK:

I've no desire to start a flame war here. However, I also don't want to provide fellow PFF member, hookdonspeed, who originated this thread, erroneous information.

On page 3-2 of my "Pontiac Fiero 1986 Do-It-Yourself" manual, it reports the same information you cited above, namely, that the `86 GT has 6-inch-wide wheel rims.

However, fellow PFF and NIFE (Northern Illinois Fiero Enthusiasts) member, paulv, usually a very reliable source for Fiero information, reports on his website that 15-inch rims on 1986 Fieros were 7 inches wide (not 6): http://home.xnet.com/~paulv/techtips.htm#Wheels .

To help determine whether that information by paulv was indeed accurate, I just went outside and measured the widths of all 4 of my stock, original aluminum, "honeycomb-style" 1986 Fiero GT wheels, without their tires on them. Each is a total of 8 inches wide --- and with regard to the standard measurement of wheel width as I understand it, 7 inches wide, inner lip to inner lip.

Accordingly, unless I'm overlooking something, I conclude with this evidence that the wheel widths for the stock 1986 Fiero GT were either:

• 7 inches wide (like the ones I have), not 6, and GM did indeed "get it wrong" in their 1986 literature on this subject,
  
• or there was some sort of mid-year change in 1986 Fiero GT wheel widths, going from 6 inches wide to 7, which was not reflected in the "Pontiac Fiero 1986 Do-It-Yourself" manual that I received with my `86 GT.
  

Has anyone on this forum established via actual measurement that they have 6-inch-wide rims all around from GM --- instead of 7-inchers --- on an `86 GT? Although I seriously doubt it, I'm now curious to find out if my 7-inch-wide '86 GT rims are unusual.

i will have mine measured when i get tires this week... if it is 7" i will def be widening the rears

Don't even bother with measuring. Look behind the face of the rim and you'll find "15x7" cast into the rim. All wheels have there sizes cast into them. Some wheels even have the offset, too.

well, I hate to see ANYBODY provided with incorrect information. I normally trust the literature first or post what i know is true from working on my cars. Next, I'll trust only a handful of the people here; I've seen too much trash posted by people with long green bars under their names. (you wanna see a bunch of useless crap posted, read through the threads and try to decide if the radiator cap is vented or unvented - radiator cap = cap on radiator, not cap on engine covering thermostat). SO, maybe we can use this thread to straighten out the wheel stuff.

Let's start with the wheels that were offerred and see if people can provide VERIFIABLE references; maybe checking the sizes of these wheels if they actually have them on their car and can either measure them or verify the stamping in the rims.

This is an 85 and is supposed to have 14 x 6 wheels as shown. Anybody have these and wanna post their size - maybe a pic of the rim stamping ?




These gray honeycombs came on 86 and 87. Safe to assume they are all the same ? Either 15 x 6 or 15 x 7 ? Pics ?

[This message has been edited by PaulJK (edited 01-05-2009).]

These black honeycomb came on 88 and are two different sizes; wide on back and narrow on front. Anybody wanna verify these if they have them ?



I'm curious to see of people have different widths of wheels that look the same (for example, one guy has 15 x 6 grey honeycombs and another guy has 15 x 7s).

this COULD get interesting (or maybe the 86 manual is just wrong). The 87 and 88 manuals do not have the wheel widths listed. How wide are the two size black honeycombs ?

[This message has been edited by PaulJK (edited 01-05-2009).]

My '84 with 14" aluminum wheels is 7" out side of lip to out side of lip. Measured them twice to make sure (not on car).

They look like these:


Bob

I have the 86-87 type silver wheels on my 86 which look like this:



And this is what I found behind it:

From the inside of the front 15x6 lace wheel on '88 GTs and Formulas only:



All of the lace wheels on '86-87 GTs are the same size and offset:



The rear lace wheels on '88 GTs and Formulas are 15x7 and are identical to the previous year lace wheels.

Much discussed here:

https://www.fiero.nl/forum/A...031229-2-040757.html

I've got a bunch of 14" tech wheels off Fieros (the front wheel drive versions are different offsets) that I'll measure when it stops raining.

JazzMan

quote Originally posted by hye_4_life: Don't even bother with measuring. Look behind the face of the rim and you'll find "15x7" cast into the rim. All wheels have there sizes cast into them. Some wheels even have the offset, too.

Thanks for your comments, hye_4_life. I initially didn't see the wheel size stamping you'd mentioned because I was focusing nearer the center of the backside of the wheel. However, your second picture in this thread got me to look elsewhere. There, on one of the diagonal ribs on the backside of the honeycomb pattern of each of my `86 GT wheels, I find raised lettering which says on each of the front and the rear wheels:

15"x7"x30.0
The second number I mentioned just above confirms my earlier measurements of my `86 GT wheels' widths. The third number I see, the 30.0, assuming it's referring to millimeters, would appear to be the identifier of the wheels' offset you'd mentioned earlier:

quote Originally posted by hye_4_life: Some wheels even have the offset, too.

Thanks again, hye_4_life!

You're absolutely correct Project34. It has an offset of 30.0 mm.
Happy to help.

My '85 with 225/50-15 back and 205/50-15 front on 15x7s all 'round.




(and, Yes, I am working on lowering the ride height... )

------------------

'85 SE 2M6 automatic
'84 SE 2M4 manual
'98 Ford Mondeo Si
'73 Peugeot 304 S Cabriolet

here's one that no one posted yet. I found it on eBay advertised as 13" x 5-1/2", 5 lug, 100mm alloy factory wheel for the 1984 - 1985 Fiero. No way to verify.

quote Originally posted by hookdonspeed: i will have mine measured when i get tires this week... if it is 7" i will def be widening the rears

One could measure the rims' widths first, as I did. Alternately, as I subsequently learned from the second, very helpful, picture posted above earlier by fellow PFF member, hye_4_life (and later, from similar pictures from Jazzman as well), one could just look in the "right'" places for the stampings identifying the rims' widths, rather than bother to actually measure them.

My Fiero, like yours, is an `86 GT.

As I'd mentioned in an earlier post to this thread, I saw raised metal lettering on one of the diagonal backside "ribs" of each of my stock, `86 GT "honeycomb" wheels. Those letterings confirmed my actual measurements of those wheels' 7-inch widths all around. Those stampings' location is somewhat different from the location hye_4_life helpfully pictured, but his picture at least got me to look eventually in the right place for the wheel rim width stampings on my `86 GT.

Your `86 GT presumably should have the same, stock 7-inch-wide rim widths as does mine. The raised metal lettering identifying the rims' widths on your `86 GT presumably will be in the same place as the raised metal lettering on my `86 GT's stock, 7-inch-wide, "honeycomb" wheels.

Given that you started this thread, hookdonspeed, please keep us posted on what you ended up finding out about your `86 GT's wheel rim widths, and what you'd ended up doing in selecting tire sizes for them.

OE tire sizes for 86-88 GTs, yes 88s too, is 205/60/15 up front and 215/60/15 in the rear. Because Fieros are rear wheel drive, replacing the rear tire with one of a drastically different size will offset the accuracy of the speedometer. If you decide to get different size tires, you can use this tool to get an approximate difference in speedometer readings.

http://www.discounttire.com/dtcs/infoTireMath.dos