In trying to visualize and figure out what offest wheels to buy, I decided to draw a diagram to help me.
(new)This does take into account the actual lip thickness or the face of the wheel. The white "wings" are approxamately the thickness of most aluminum wheel flanges.(Note they probably vary from wheel to wheel so go by the inner lip)

I think I read some of the stock wheels are 7"/30mm.

I hope it helps


If you'd like a width/offset added here, let me know.

Here are what tire sizes may look like on wheels:

Sidewall height is next to the series...multiply by 2 and add the wheel diameter for overall height.

[This message has been edited by Joe Torma (edited 01-31-2015).]

Cool idea, Joe. Have a plus....I'm bookmarking this one for future reference.

Bob
Edit: I have a later copy of the version Joe posted....I'll post it here unless he wants it down...

[This message has been edited by RCR (edited 06-22-2013).]

Added some more...Geez, I wonder what happens to the bearings when you make some drastic changes in width/offset.

Awesome! Can you add 7" wide 55mm offset?

Also, how much thicker are the Corvette rotors compared to the 88 Fiero ones?

[This message has been edited by Steven Snyder (edited 03-22-2006).]

Sure can...corvette rotors are maybe +8mm to the stock 84-87hub, I don't know waht it adds to 88s.
I'll measure and post a little later.

[This message has been edited by Joe Torma (edited 03-22-2006).]

this will come in handy! how about 7/35 ? That seems like a common one I see around.

also, added a + for your effort

[This message has been edited by Formula (edited 03-22-2006).]

Updated

Awesome! You are the man.

How about a 7/40 (very common with Konig wheels) and a 7/48 and a 7/50 (common Subaru offsets, which also happens to fit our bolt circle. )

quote Originally posted by Joe Torma: Ask and you shall receive

Thank you sir!

I edited this post to say thanks instead of adding another post. I have asked Cliff to make this a "sticky".
It's one of the most useful topics I've seen in a while.

[This message has been edited by Raydar (edited 03-22-2006).]

Ask and you shall receive

i have a question (maybe stupid), what does blue lines represent?
the lip of the front and rear fenders.

thanks...

How about 8.5 / 48, I'm lovin the diagram

I'd like 18x8.5 /48mm, but it looks like it'll need quite a bit of clearance inside the wheel, any chance it'd need too much with a 255/35/18 tire?

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[This message has been edited by JamesCurtis (edited 03-22-2006).]

I was told that 6-35mm was stock for the 85-87, is this correct. What years was 7-30 stock (the one you have in yellow).

Added!
Blue lines represent faces of stock wheels.

What I'd like to do is make printable profiles for wheels & tires combos that you could put right up to the hub...but not too many people have 50" printers like I do.

http://home.xnet.com/~paulv/techtips.htm#Wheels

try this link it has the offsets for the factory wheels..

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2004 Pontiac Cosmos Purple GTO 1 of 334
1988 Fiero GT
1988 Fiero Formula
2004 Chevy Blazer

It does, and it doesn't. Nothing about the 7" Diamond spoke

I need a little clarification here. How come a 35mm offset on a 8" wheel is different than a 35mm offset on a 8.5" wheel. I would think they would be the same and the half inch would be to the outside.

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85 GT 3.4
Auto 3.08
14.9 @ 90 1.9 60"

Offset is center of tire to face of hub nounting surface. When the width increases, it adds 1/2 to each side.

I had 14x6 aluminum with 47mm offset on my 87 coupe that came off an '84 that I had. They probably were not Fiero wheels since they rubbed the struts. The handling was also horrible. After replacing the struts, I replaced the wheels since it could not be aligned with the aluminum 14x6-47mm wheels. I am runninf 17x7-40mm offset with 215/45-17 tires. The handling is great and the 17 diameter is clearing the struts and not hitting the control arms at full turn. Ther 17 diameter gets above the strut mounting that you would hit by just widening the wheels.

Brian

One of these days I'm going to throw together a 3D model of the suspension system and brake system so I can check exact wheel clearances in a really cool way

Is there anyway to add a line in where the strut would be so we know if they will rub or not?

I was wondering about other clearances (brakes, body, struts, etc) and the front rims. Any details on those?

So if i am reading that right i would want a 7" with a 47/48 or 50 mm off set wheel for the front of a 88 ? also what would that off set look like on the back of the 88 ?

quote Originally posted by Scurvy: Is there anyway to add a line in where the strut would be so we know if they will rub or not?

Thats why I run a 12MM offset on my 9" rims. That gives me 12.5mm clearence from the tire to the spring.

I to would be curious to see a extra line added for the Strut/spring where it would hit the tire.

On my 87 GT with 11.25" brakes I have 137 MM from the hub to spring on the strut assy.

BTW, Thanks Joe, great idea.

[This message has been edited by Earl-R (edited 04-02-2006).]

quote Originally posted by Earl-R: Thats why I run a 12MM offset on my 9" rims.

Wouldn't that stick out? The stock GT wheels are 7" wide with a 30mm offset. They're about even with the body. Your wheels add at least 1.5" outboard, compared to stock.

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quote Originally posted by Earl-R: Thats why I run a 12MM offset on my 9" rims. That gives me 12.5mm clearence from the tire to the spring. I to would be curious to see a extra line added for the Strut/spring where it would hit the tire. On my 87 GT with 11.25" brakes I have 137 MM from the hub to spring on the strut assy. BTW, Thanks Joe, great idea.

My pleasure.
You really have 12mm offsets?

Keep in mind there is maybe 1/2" beyond the width for the lip. This probably varies by wheel manufacturer. The "strut line" may be difficult to place since it may really depend on the tire.

Updated, and organized.

They stick out maybe 1/2 - 3/4" past the edge of the fender. They've never hit the fender yet.

On my wheels the face where the wheels hit the hub is 1/2" off center or 0 offset.

My 9" wheels are approximately 230 MM wide including lip. The tire is even with the outer edge of the wheel, if the tire sticks out pass the wheel it's less than a 1/8" and not a factor because of the design of the spring, smaller top bottom larger on top. Take overall width 230 / 2 = 115 Add back in the offset of 12MM and I have 127mm from the hub to the spring. My spring is 137 from the hub face which gives me 10 mm clearance. This is the widest wheel I felt I could run and not stick out to far because of the fender and still have clearance on my springs and strut package.

The lip on both sides adds maybe 6 MM in overall width, 3 MM on each side.

Offset is measured from the center of the wheel. If the hub is closer to the outside of the wheel from center that is positive offset. If the hub is closer to the inner flange from center that is negative offset (typically Deep Dish Wheels)

That is why there is a difference between the 8" and 8.5" wheels with the same offset. The 8" wheels will stick out further than a the 8.5" wheel with the same offset. I was looking at the 8.5" wheel with a 48MM offset, that wheel should be hitting the stock spring. You would need coilovers to keep that from happening using that wheel.

[This message has been edited by Earl-R (edited 04-03-2006).]

Hmmm....would this be a help? I suppose it makes some assumptions, and the wall would be pulled in for those tires wider than the wheel, but does give an idea on the look.

[edit] moved to 1st post

[This message has been edited by Joe Torma (edited 09-20-2006).]

That good Joe, I'm sure it will help some people.

I knew that my wheel inside the lip was 225MM so I went with a 225 50R16 rear tire. So the tread is the same width as the wheel and does not exceed the width of the wheel.

Should I keep going? I've yet to see this all visually.
[edit] see below!

[This message has been edited by Joe Torma (edited 04-22-2006).]

Joe, good visual aids.

Heres a old pic of my car to give you a idea.

[This message has been edited by Earl-R (edited 04-03-2006).]

Why not add 265 x 50 x 15 to the list. That is what I am running on my stock Chromadora wheels (88 Mera) and they look pretty good.

quote Originally posted by Joe Torma: Should I keep going? I've yet to see this all visually. EDIT: Added 215-235 Should I add more?

If a tire sticks out that far beyon the rim (like the 235) wouldn't that effect performance negatively? It may not but it looks like it should. The sidewall isn't well supported anymore and might cause more deflection?

Mind you I have no idea on this topic, it just looks like that to me.

Wow this is a really cool write up. Nice work. So it looks like 235's would be the widest that one could go on the stock 7" inch rims right, or can i go wider. How about the 6" rims off the front of an 88, what would be the widest that i could go on those without effecting the handling??

quote Originally posted by Scurvy: If a tire sticks out that far beyon the rim (like the 235) wouldn't that effect performance negatively? It may not but it looks like it should. The sidewall isn't well supported anymore and might cause more deflection? Mind you I have no idea on this topic, it just looks like that to me.

I think you are correct. I think it's easy to see what's too wide for a particular width, and agree it probably will affect handling...at what point that happens I don't know. Tire manufacturers do list a range usually.

quote Originally posted by Joe Torma: Should I keep going? I've yet to see this all visually. EDIT: Added 215-235 Should I add more?

Can you do this with different size rims like 8inchers so we can see how wide we can go

quote Originally posted by hnthomps: Why not add 265 x 50 x 15 to the list. That is what I am running on my stock Chromadora wheels (88 Mera) and they look pretty good.

How wide of a wheel?

Joe,

I really have no idea how wide the Chromadoras are. They just came with the car and have only been off a few times for new shoes. I have a set of mesh rims for an 88 Mera (without tires) and will measure them later when I am home.

quote Originally posted by Joe Torma: How wide of a wheel?

Dude this is the best thread I've ever seen on here. Now people can finally see what will and will not fit as opposed to spending hours searching old threads or starting a bunch of new threads. This should be a sticky

I checked the mesh wheels last night and did a rough measurement (OD not ID). The smaller rims were about 7" and the larger ones 8". However, I still do not know what the measurements on the Chromadora rims are.

quote Originally posted by hnthomps: Joe, I really have no idea how wide the Chromadoras are. They just came with the car and have only been off a few times for new shoes. I have a set of mesh rims for an 88 Mera (without tires) and will measure them later when I am home.