Remember, rotor thickness gets added to 88s fronts, and 84-up rears.
Whoa! That I did *NOT* know! If that was posted in the thread before, I totally missed that! That's really important. So when picking out wheels, use the graph to "shift" the offset line outwards by the thickness of the rotors (where applicable). Thank you very much Joe!!
Just wanted to say thank you! I could not have fit my wheels without this!
I got Drag dr-34 black with red lip...
Car has all poly in the frt and rear suspension. I converted to coilovers in the rear... 10 inch 300lb Summit springs with the 7 inch Coleman Racing sleeve and perch. In the front, I cut 1.5 coils off the stock WS6 springs (stiffest WS6 springs avail on 84)
18x8 front 47 offset with a 8-9mm spacer... effectively (39-40 offset). I knew a brake conversion was in my future and I found out the brake convesion added about 8-9mm, so this offset will dial me in perfect once that is completed! Front tire for now 225/45 (cheap used pair to get on the road) In the future I will be going with the same width or possibly wider but either way will be with a lower profile.
18x8.5 rear with 45 offset... only just a tiny bit of rubber out of the wheel well... just how I wanted it... Tire is a 265/35... Did not feel confident enough to try the 285s yet... maybe with an alignment I will have the space back there. I have about a finger b/w the spring perch and tire.
Everything fits perfect with no rubbing issues!
------------------ 1984 Indy Fiero SE Pace Car Replica #770 "SE": Stormtrooper Edition Rescued, resuscitated and reversibly modified! (I'm so not done yet!)
Pardon my ignorance...but what is the point of having this chart if we still need to add 10mm to include rotor thickness? and where are we supposed to add 10 mm too? the offset? so if we go with a 7" wide rim with a 35mm offset, we are acutally supposed to reference a 7x45mm on this chart? Im sorry, it just doesnt make much sense to me.
Pardon my ignorance...but what is the point of having this chart if we still need to add 10mm to include rotor thickness? and where are we supposed to add 10 mm too? the offset? so if we go with a 7" wide rim with a 35mm offset, we are acutally supposed to reference a 7x45mm on this chart? Im sorry, it just doesnt make much sense to me.
Thanks,
Dan
The face that the wheel is bolted to IS the brake rotor. It is shaped like a top hat. The top of the hat sticks out and is the surface that the wheel butts up to. The brim, which is the braking portion of it, sits inboard of the wheel mounting surface as do the calipers. The rotor rim and the calipers sit inside the inner dish of the wheel. In stock form, you don't need to worry about the rotors or calipers or add anything to the chart. You may be thinking about brake upgrades. Those always include larger rotors which in turn, move the calipers outward. If you have 14 or 15 inch wheels, the larger calipers could come into contact on the back side of the wheel in the dished out area. I think 16 inch wheels will clear most if not all of the popular brake upgrades.
If the components of a particular brake upgrade caused the rotors to extend 10mm outward, you would ADD POSITIVE 10mm to the offset. This is only if you were replacing the stock wheels with any other wheel of the same WIDTH and you wanted the wheel to be in the original position with the same wheel track. Buying a wider wheel would change the number as would wanting the wheels to stick out farther or tuck in more.
Jonathan
[This message has been edited by Boostdreamer (edited 05-22-2012).]
You don't find a set... you look up other cars with the 5x100 bolt pattern and find one that has the correct offset, or close enough for your taste... You then by two for the front and two for the rear... welcome to owning a 1988 Pontiac Fiero. I know how you feel right now.
You don't find a set... you look up other cars with the 5x100 bolt pattern and find one that has the correct offset, or close enough for your taste... You then by two for the front and two for the rear... welcome to owning a 1988 Pontiac Fiero. I know how you feel right now.
yeah...i figured out how oboxious the 88's where when i rebuilt the front end...geeze...what a mess that was . lol
Well, for your front wheels, the stock rims are 15 X 6 ET37. If you like where they sit in relation to the outside fender lip, then your new proposed wheels will stick further out. The way you calculate how much further out is like this:
Your new front wheel is 7.5" wide which is 1.5" wider than stock. The offset on your new front wheels must be greater than the offset on the stock wheels by 1/2 of the additional width of the new wheel. Therefore 1/2 of 1.5" is 0.75" which is 19mm. So your 7.5" wide wheels would need to have an offset of [the OEM wheel (37mm)] plus [half the additional new width (19mm)] = 56mm. Since the new wheels only come with a maximum offset of 38 mm's, they will stick out of the wheel well 56 - 38 = 18 mm more than stock. That's 3/4".
The same can be done for your rear wheels except the stock rear wheels on an '88 were 15 X 7 ET 30.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Discovered something interesting - Yellowstone is running 17x8 wheels that have a 32mm offset on his 87 Fiero, and he has the Viper brake upgrade.
Looking at the chart, even without taking into account the extra thickness of the rotor, it looks like an 8 inch wide wheel with a 32mm offset should "stick out" from the fender. I sent him a PM about this, and he sent me back pics clearly showing that they do not (And he didn't mention any rubbing of the tire in the "downcurve" of the wheel well to the fender lip).
So... am I still not reading this chart correctly?
I do have coil-overs in the back, and I'm going to have the 11.25 LeBaron brake upgrade. I'd love to get a 7.5" or an 8" in the back, just trying to figure out the proper offsets to put the least extra strain on the bearings/hubs, and still clear things. I don't mind if the front are narrower (7" or 7.5" which could wind up matching the back).
Dennis, thank you for the link to the other online tool - but it never loaded completely for me. Just sat there saying "loading". I made sure my Javascript was up to date, going to it from Firefox.
I note with this chart that all of the offsets for the 88 GT's are ET40 both front and rear. They say that they offer staggered packages, but the only difference between fron tand back are the tire widths (i.e. 215 front / 235 rear). It's been a while since I've looked hard at the offsets for 88's, but wouldn't the ET40 offset both front and rear look a bit off? I'm torn between actually getting custom tires and wheels over my originals, but every so often I'm tempted.
EDIT: Ah, no big deal on this. Once I looked deeper and found their "Direct Fit" packages I see that they have better offsets listed, with what appears to be 17" and 18" combinations. If I'm reading this correctly... <shrugs>
Does anybody have any pictures of 88 GT's with the 18" ET40 offset wheels mounted?
Robert
[This message has been edited by Axdrenalin (edited 09-20-2012).]
15x6 37mm Diamond Spoke 1988 GT/Formula Front Only 15x7 30mm Diamond Spoke 14x6 35mm High Tech Aluminum
And keep in mind that the 88 hubs are about 1 inch further outboard than the previous years. I would not go wider than 7 inches for a wheel on the front of an 88...
Blooz demonstrates it best...
quote
Originally posted by Bloozberry:
Well, for your front wheels, the stock rims are 15 X 6 ET37. If you like where they sit in relation to the outside fender lip, then your new proposed wheels will stick further out. The way you calculate how much further out is like this:
Your new front wheel is 7.5" wide which is 1.5" wider than stock. The offset on your new front wheels must be greater than the offset on the stock wheels by 1/2 of the additional width of the new wheel. Therefore 1/2 of 1.5" is 0.75" which is 19mm. So your 7.5" wide wheels would need to have an offset of [the OEM wheel (37mm)] plus [half the additional new width (19mm)] = 56mm. Since the new wheels only come with a maximum offset of 38 mm's, they will stick out of the wheel well 56 - 38 = 18 mm more than stock. That's 3/4".
The same can be done for your rear wheels except the stock rear wheels on an '88 were 15 X 7 ET 30.
[This message has been edited by carbon (edited 05-15-2013).]
i'd like to know how wide i can go on the rear ('88 GT) with coilovers?
thanks
I believe Joe did it originally in Excel. So, unless someone has the native files, it would have to be recreated from scratch.
Honestly, while looking at Troyboy's Enterra build thread, the wheels Archie is using called into question the accuracy of this list in my opinion. I was using it as gospel, but based upon Archie, I don't think the wheels I was planning on using would fit, even with coilovers. It would definitely need re-evaluation.
I have an 88 Formula I'm putting an LS-1 in and want to get more grip, I want as wide as I can fit within reason in the back and maybe an inch or two smaller in the front. I am thinking about doing these sizes
I like the black rim on red car look and am thinking about the Motegi MR116 which comes in a 5x100 pattern and 35mm offset
also considering Drag DR31 in the same size (slightly different offset)
my stock 215/60/R15 on 15x7" wheels already stick out of the rear fenders a little I don't mind that too much, but is there any advice anyone can give me here? anyone put 9" wheels on the back? I've seen fender flares and widebody kits that I'm pretty sure people have put 10 or 11" wheels on, but anyone have a picture of a 9" wheel on a stock body? I actually love how cheap it is to buy tires for 15" wheels, but I don't think they will grip enough with the torque i'll have after the swap, and I was thinking about getting into doing track days and HDPE events and figure I could use a nice brake upgrade but would be limited on rotor size with the stock wheels.
thanks for all the contributions here, really a great thread!
I just picked up a couple of 88 GT's over the past few weeks and eventually I would like to add the corvette brake packages to each along with 1.5 inch drop spindles and new wheels. As the brake package will have to wait until the current pads wear out I have decided to install the 1.5 inch drop spindles and wheels now.
Is anyone familiar with what the corvette brake package adds to the offset? Also I am thinking of 17x7.5 and 18x9 or 19x9 on the rears. What would be the best offsets to order with all of these changes in mind to keep the front wheels within the fenders and the rear wheels close or just beyond the fenders? Thanks
What is your guys opinion on 18x8.5 ET35 for front and back? Looks like it will poke out just a little bit. Any pictures? Also what tire size would be good with that? 215 45 front and 245 45 rear? I have coilovers in the rear and will be doing Rodney Dickman 1" Lowering Ball joints and cut springs up front.
I just picked up a couple of 88 GT's over the past few weeks and eventually I would like to add the corvette brake packages to each along with 1.5 inch drop spindles and new wheels. As the brake package will have to wait until the current pads wear out I have decided to install the 1.5 inch drop spindles and wheels now.
Is anyone familiar with what the corvette brake package adds to the offset? Also I am thinking of 17x7.5 and 18x9 or 19x9 on the rears. What would be the best offsets to order with all of these changes in mind to keep the front wheels within the fenders and the rear wheels close or just beyond the fenders? Thanks
Robb
Just looking at the diagram, a 9" wide wheel will need at least 30mm offset to clear the strut. It looks like it will be about 1/2" to 3/4" past the fender lip.
Please take with a grain of salt and measure first.
When you say at least 30 do you mean less than 30 or more than 30 ÉÉ
30 or less, i.e.: 30mm, 25mm, 20mm, etc. As the number decreases, the hub flange gets closer to the center of the wheel. This causes the wheel to move outwards, toward the fender lip.
Bob
[This message has been edited by RCR (edited 09-03-2013).]
I just picked up a couple of 88 GT's over the past few weeks and eventually I would like to add the corvette brake packages to each along with 1.5 inch drop spindles and new wheels. As the brake package will have to wait until the current pads wear out I have decided to install the 1.5 inch drop spindles and wheels now.
Is anyone familiar with what the corvette brake package adds to the offset? Also I am thinking of 17x7.5 and 18x9 or 19x9 on the rears. What would be the best offsets to order with all of these changes in mind to keep the front wheels within the fenders and the rear wheels close or just beyond the fenders? Thanks
Robb
The 12" C4 kit has a rotor hat thickness of 0.312" My 13" rotor kit for the 88's has a rotor hat thickness of 0.294"
On the 88's, you can run 17x7 48mm in front and 18x9 45mm in the rear (must do rear coil over conversion).
quote
Originally posted by RCR: Just looking at the diagram, a 9" wide wheel will need at least 30mm offset to clear the strut. It looks like it will be about 1/2" to 3/4" past the fender lip.
Please take with a grain of salt and measure first. Bob
What this chart is really missing is the impact wheel diameter has on available clearance. For example on the 88 rear, 17" wheels will hit the strut/upright flange first (well before hitting the strut body or trailing link), so by going to 18" diameter, you gain over 1" of available room on the inside vs. the 17. So if you want to run the widest wheels on an 88, you want to run an 18" wheel in the rear.
The strut flange is slightly lower on the 84-87 cars (upright design, struts are the same), so I think the 17" wheel might clear it just fine.
[This message has been edited by fieroguru (edited 09-03-2013).]
sometimes I just feel dumb. I have used this calculator and I am looking at these wheels with all of the size options listed.
I have an 87GT and am looking at the 18x 7.5 front with 42mm offset, which looks to be about 7mm greater in backspacing for the front. I am looking at the 18x 8.5 with 35mm backspacing. Leaving with an offset total of 6.1". which is about .30" greater...I think..but I may have my stock numbers wrong.
With a stock set up, Unless I am missing something these should fit? Or would I require a spacer to make the rears fit?
Assuming that I add the Corvette brakes what do you guys think would be the most appropriate offset for about 17x7 fronts and 18x10 rears?
Robb
17x7 48mm would fit the front great. 18x9 45mm will fit the rear.
18x10 will not fit under the rear body work without pulling the struts inboard and getting shorter axles & lateral links. I mocked up putting some 10 1/2" wheels under the stock 88 body, but had to pull the rear suspension in 1 5/8" to get them under the body. In this thread you can see what I did and the areas that were interference issues. https://www.fiero.nl/forum/Forum2/HTML/120740.html
Before you buy your brake kit for the 88, you might want to consider the 13" one that I offer for the 88. It is economical, fits great, looks great, and no fitment issues with stock suspension/ball joints: https://www.fiero.nl/forum/Forum4/HTML/060122.html
What about purchasing parts readily for your brake system as in will that be a problem in later years? What offsets do you like this scenario:
Front 17X7 IN ?? mm offset 17x7.5 in ?? mm offset
Rear 18x9 in ?? mm offset 18x9.5 ?? mm offset 18x10 ?? mm offset
I don't care if they stick out on the back but not the front FIEROGURU is there a number that I could call you to discuss as I am needing to order the wheels and tires soon thanks
Robb
[This message has been edited by Robb Craige (edited 09-05-2013).]
yeah...i figured out how oboxious the 88's where when i rebuilt the front end...geeze...what a mess that was . lol
