Need help with calculating the following offset for a 1988 Fiero GT (widebody). CAN ANYONE PLEASE HELP?
Bolt 5 x 100

Front: 19 x 9 Offset = ?
Rear: 19 x 11 Offset = ?

The wheels I will be using are the ROH Modena custom made. I need to be sure before I place the order so I'm double checking. {EDIT} I also plan on adding bigger breaks... maybe the Vette C5r. Just want to make sure of the clearance. Almost forgot... I have coilovers, so height is fully adjustable on all four corners.

Thanks

[This message has been edited by dmancheno (edited 10-04-2006).]

Search for wheel offset diagram. It's got a visual aid regarding offests and widths of wheels. It is fairly accurate I might add.

How many inches per side did you add in width by means of the widebody kit?

Guess it would largely depend on whose widebody kit you have.--ie--how much you need to move the wheel out.
Mine is original DGP widebody and I have these on it---
245/50R16 at the rear (16"x9.5")
205/55R15 in the front (15"x7")

[This message has been edited by jeffndebrus (edited 10-05-2006).]

quote Originally posted by MclarenF1: Search for wheel offset diagram. It's got a visual aid regarding offests and widths of wheels. It is fairly accurate I might add.

I actually did use the diagram (Joe Torma).
https://www.fiero.nl/forum/Forum1/HTML/058236.html

quote Originally posted by Steven Snyder: How many inches per side did you add in width by means of the widebody kit?

This info is not relative. The wheel specifications is what matters. I can't start the widebody conversion until I have the rims.
But to answer half of your question the rear is 4" wider. I doing the same widebody as MadCurl's #15. And yes I did ask him about the offset he is using. He does NOT have the technical spec since HRE does NOT give that information out.

I currently have numbers for the offset and they are both NEGATIVE values. I double checking my numbers and needing some help to verify if I'm on the money. This is why I did not post my data.

Hey David,

I could be wrong, but when Archie was mocking things up for troyboy, i believe he did some
measurements that gave him a fairly accurate idea of the offset needed.

Might be a good idea to get his input to see if he can help you out ?

quote Originally posted by dmancheno: Need help with calculating the following offset for a 1988 Fiero GT (widebody). CAN ANYONE PLEASE HELP? Bolt 5 x 100 Front: 19 x 9 Offset = ? Rear: 19 x 11 Offset = ? The wheels I will be using are the ROH Modena custom made. I need to be sure before I place the order so I'm double checking. {EDIT} I also plan on adding bigger breaks... maybe the Vette C5r. Just want to make sure of the clearance. Almost forgot... I have coilovers, so height is fully adjustable on all four corners. Thanks

Two major point I've noticed.

1. The rims are made to order.
2. You own a 88 w/coil-overs

In this case, a 19x11 using a 35mm off-set is perfect for using a 305/25/20 (although 325/25/20 is a better tire) in the rear. You'll need home brew fender flares. For the fronts, you can use a 35mm or 40mm using a 255/30/19 or 245/30/19 but, you'll need a baby fender flare. On #015 (88) choptop I used 255/30/19 and now 245/35/19 and they don't rub but the suspension is "STOCK FRONT AND BACK" they do rub on the rears on deep dips in the road which is why I ordered coil-overs.


EDIT: Woops, I got ahead of myself, hehe. I thought you where getting a 19/20 combo, hehe. You'll need to check for a 285, 295, 305 or 325 in the rears. I think the max for a 275's width is 9-11"?

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

"Anyone can make a copy of something, it may look good but it ever is the real car. Make something from your imagination, something unique, something nobody has, anything is possible and, ideas can be a reality."

[This message has been edited by madcurl (edited 10-05-2006).]

quote Originally posted by dmancheno: This info is not relative. The wheel specifications is what matters. I can't start the widebody conversion until I have the rims.

I assumed you were using an existing widebody kit. Nobody can tell you what offset to use if they don't know how far you want them to stick out!!!

quote But to answer half of your question the rear is 4" wider.

In that case, for the face of the rim to be in the same position relative to the new widebody fender as the stock rim was in relation to the stock fender you will need the following offsets for your choice of wheels:
(assuming adding 2" to each side, which is 51mm):
11" wide rear wheel: 30mm offset

If the front fenders are not going to be flared then a 9" rim must have a 75mm offset to not stick out of the wheel well. Nobody is going to make these for you and they'll just hit the suspension subframe before you can turn the wheel all the way. I'm currently running a 7" wide wheel in front with a 55mm offset.
Assuming that you would add 2" to each side of the front fenders to match the increase in rear width, you will need a 24mm offset for a 9" wide rim.
These are positive offsets meaning the the face of the wheel is pushed further away from the centerline of the wheel toward the outside.


I doing the same widebody as MadCurl's #15. And yes I did ask him about the offset he is using. He does NOT have the technical spec since HRE does NOT give that information out.

quote I currently have numbers for the offset and they are both NEGATIVE values.

Check yoru calculations again. If the total width of the rear is now going to be 4" more than stock then negative offsets will stick the wheels waayy out of the fenders.

[This message has been edited by Steven Snyder (edited 10-05-2006).]

a "BUMP" for Frank Dragon

quote Originally posted by dmancheno: This info is not relative. The wheel specifications is what matters.

This info is relative. If you plan to build the body around the wheels, you need to have a starting point. Why are you asking us for info on something you plan to try and build? You should be the one that has an idea of what you want to do.

For referance, my IMSA has 15x10 wheels on back with 0 offset. (These are for sale in anyone needs wheels for a rebody, IMSA, or needs drag racing wheels)

This is too over whelming (offset)... mentally this is upsetting me. I going have to mount the fenders on with tape do all the math calculations (measurements). I found this on ROH site "Wheel Arch Clearance" http://www.roh.com.au/docs/WHEEL%20ARCH%20CLEARANCE%20FOR%20WEB.doc

Thanks all.... I'll post my findings and formula.....

D


PS
The offset I got from the dealer for the rear "-19" (negative 19).

[This message has been edited by dmancheno (edited 10-10-2006).]

quote Originally posted by dmancheno: thx for the info but you forgot to mention how wide is your widebody. but no need. Might try posting your rims in THE MALL section of the forum.

It's an IMSA GTU, pretty standard kit. I"m not sure there are even any other widebodies available.

If you go with those rims you mentioned with negative offset your fenders are gonna have to be ridiculously wide..

You don't have to sweat this one, all you need is the dimentions from the builder of the widebody you are planing to use. Just buy the wide body on the car while using your stock wheels, and then meassuare how much the body sticks out from your stock wheels

Go to www.google.com and search for a wheel off set calculator and put in your stock wheels and off-sets, then play with the new stock sizes and off sets until you fill in the gap. Since the offset/calculator software is made to calculate how much your wheels will stick out of the car.

Here is a good start:

http://www.1010tires.com/WheelOffsetCalculator.asp

JG

First of all, you are asking us something we can never answer. You want to build something from scratch and you want to start with the wheels. You want us to tell you the offset of the wheels to fit something that's not even there yet. How can we tell you what offset you need on the wheels when we're dumber than you.

Oh, my widebody is between .25" and 12" wider than stock. That should get you going.

My wheels are still for sale. Contact me if anyone is interested so I can sell my wheels. I will sell them to someone for cash, or maybe some kind of Chinese hooker. I will sell these wheels or trade. Buy my wheels, someone! Billet Specialties wheels make great xmas gifts, so buy my wheels, someone.

[This message has been edited by SCCA FIERO (edited 10-10-2006).]

On my 308 Ferrari kit, I had 2" offset on the fronts and 4" on the rear and they looked about like above.

I got your PM...really need to know the width of the widebody, and where you want the wheel in there.

You mentioned 4" in the rear....you will have a negative offset about a 27mm, and you'll have about 1.5" of clearance between your strut and wheel.
I don't think the bearings will hold up too long like this.

A little confusion on both sides it seems. David is building a custom widebody so there is not kit to simply measure and give exact dimensions.

Now i don't know the first think about all this offset stuff, but David what you might do is what u suggested, go and head and tape the fender wells onto the car in the desired position you want and then take measurements from there as to how far they are going to stick out.

If those measurements can help the wheel gurus on the forum figure out what you need great. Remember you don't have to be exact as far as them sticking out, because you can always tailor the body to be flush with the rims, once you have them.

Even if they are a little off more or less than what you projected. Just my opinion. That is why it is better to have the wheels first, as long as you can get a rough widebody estimate.

[This message has been edited by exoticse (edited 10-11-2006).]

Going back to Joe Torma's thread, the 9" with 12mm offset sticks past the stock fender by about 25mm. The 11" with 14mm offset sticks past the fender by about 33mm. If you want to go further, subtract the extra distance from the current offset. For example, if you want 50 cm total on the front from the current fender you would need an offset of -13mm (12mm - (50mm-25mm)).

Bob

Thanks all you guys & gals (if any).
MclarenF1
Steven Snyder
jeffndebrus
exoticse
madcurl
SCCA FIERO
THE BEAST
rogergarrison
Joe Torma
RCR

I'm understanding this so much better. I've been going back and forth on trying to understand this offset thing for a while. I had a misunderstanding that the offset came determining the type of car (suspension) and dimention of the Rim. Now I understand what to do. I will duck tape the fenders on and measure. I will repost in a few days. Again thank you all so much for the feedback


aflac ........aflac ...... AFLAC!

quote Originally posted by dmancheno: Thanks all you guys & gals (if any). MclarenF1 Steven Snyder jeffndebrus exoticse madcurl SCCA FIERO THE BEAST rogergarrison Joe Torma RCR I'm understanding this so much better. I've been going back and forth on trying to understand this offset thing for a while. I had a misunderstanding that the offset came determining the type of car (suspension) and dimention of the Rim. Now I understand what to do. I will duck tape the fenders on and measure. I will repost in a few days. Again thank you all so much for the feedback aflac ........aflac ...... AFLAC!

Archie will have the spec on 11" & Troys 13" this week.