quote Originally posted by Joe Torma: Fixed the image links. ...its' been a while I know.

Thnx Joe...Welcome back

Bob

Does anyone know if an 18x9.5 wheel with 45mm offset will fit on stock '87 rear? I know for a fact it will on an '88 but not sure how it varies. Do '87's have less or more clearance?

Removed my nonsense.

[This message has been edited by Imnuts (edited 04-19-2016).]

Removed more of my nonsense.

[This message has been edited by Imnuts (edited 04-19-2016).]

When you are talking about a few millimeters this way or that way......the build tolerance is bigger than that.....so who knows? It seems like your suspension would be a problem unless it is non-stock. Please post what you find out!

I dont know the mm, but my Ferrari kits rear wheels had a 4" offset to fit perfect in the body. I drove it 100,000 miles with no bearing or seal issues at all. The fronts had 2" offset. I had the 8x16" wheels custom made for it.

Are the offsets you have listed in the diagram positive or negative offset?

quote Originally posted by FieroWillie: Are the offsets you have listed in the diagram positive or negative offset?

Positive...

18x9.5 C5 Corvette wheels with 285/30-18 tires on a 1.125 thick adapter.

Here's the wheel adapter which I will use to install C5 Corvette 18x9.5 rears on The Mule. It was made from a random scrapped part that my dad pulled out of the bin at the place from which he is semi retired. That's why it has the one wonky hole and the extra 6 bolt circle.



With some nuts and washers dropped into the counterbores. I've had nuts and washers on the table for a couple of months. I snagged some Dorman 610-323's tonight and will be installing shortly.



High tech stud installation:



Adapter with studs:



Adapter with studs storing washers and nuts:



I used the wheel adapter this morning and pulled some numbers. The outer lip of the C5 wheel will stick out 1/2" further than the outer lip of the Grand Prix wheel.

Here's my measurement rig:



The sockets are 1.500 +/-.005 tall and the measurement at static ride height is 1 5/32, so the outer lip of the Grand Prix wheel is actually just under 3/8" inside the outer lip of the stock fender.
I repeated the measurement with the Grand Prix wheel with the suspension at full droop. That measurement is 1 3/4".
The corresponding measurement with the C5 rear wheel is just under 2 1/4"... so the Corvette wheel will stick out 1/2".

Adapter installed:



Would need slight modifications actually to work:



C5 wheel in place:



Clearance to the strut:



Not quite a banana for scale:



That is the narrowest gap between the wheel and the strut. I could gain 1/8" of clearance by snagging a new pair of Koni struts and modifying them to have the sleeve seat on the original spring perch weld rather than on the clamp.
I currently have 325# x 12" springs. If tire clearance to the spring perch is a thing, I could step down to 10" springs to resolve that.

Beefy rear view for a Fiero, but no wider than stock on a C5:



Next step: grab a cheap @$$ Sumitomo 285/30 from Tire Rack and look at tire clearances.

Current tires are 245/50-16's and calc to 25.64" tall.
The 285/30-18's calc to 24.72" tall... going to lose a bit more gear than just the 3.61 to 3.94 swap. The gear swap will be 9% and I'll gain about another 4% RPM from the tire swap. But I'll also gain 4% in acceleration
The new tires will be 0.92" shorter than the old.

At a ride height of 15 7/16.

Height difference (245 on right is also at ~halfway through its tread depth)


Width difference (both are Sumitomos)


However, it's really close, and probably would rub on a max effort corner. My finger won't fit. I'll see if I can get a better measurement, but I'd guess a 1/4-5/16" gap before initial contact. Initial contact would be harmless.
Also, as mentioned above, I can raise the spring perch over 1.5" by swapping to 10" springs. I'd probably up the rate to 400 in an effort to further copy-cat Steven, however.




Not too hideous, but needs moar low




No more stick-outy than the current 245's. If anything, it looks a smidge pokey-stretchy by comparison. I need to upgrade to a more expensive 285/30.



A smidge pokey-stretchy:



Needs moar low; ride height is 15 7/16 (center of axle to bottom edge of fender lip):

Does anyone know a hub swap we can do so that we have 5x114.3mm bolt pattern? It seems like I see a lot more of that hub pattern in the aftermarket

Took The Mule's suspension apart today. I surprised myself slightly by getting the spring out without unbolting anything but the top of the strut. I was *amazed* that after being installed close to 15 years, the spring perch still turned freely on the sleeve.

The 6 5/8" metal to metal travel limit checks out.
Full droop ride height: 19 5/8"
Metal to metal contact ride height: 12 1/4"
Bump stop *contact* ride height: 13 11/16"

"Metal-to-metal" means that the top of the strut body just touches the bottom "bell washer" that installs under the strut top bushing. The bell washer is there the retain the end of the strut approximately where it needs to be if the bushing comes apart. A really hard hit would both deflect and maybe tear the bushing as well as possibly flattening the bell washer, so this isn't he "structural contact" ride height that would do serious damage to the tub or the strut... that's maybe 1/4 - 3/8" more jounce travel that what I measured.

The difference between the bump stop and metal-to-metal ride heights is 1 7/16". The bump stop measures a smidge over 1 3/4". This discrepancy is there because the top of the bump stop fits into the bell of the bell washer, so the bell washer cuts down on the difference between metal-to-metal and touching the bump stop.

Full droop travel:



Metal-to-metal contact:



Gap to the outer fender lip:



Gap to the rear trim strip:



Gap to the front trim strip:



From the four photos above, rubbing on the front trim strip is probably the first contact point, but it can be mitigated by moving the wheel back in the wheel house a bit. An adjustable trailing arm could do this on an '88 and a custom fully adjustable control arm could do it on an early car.

2 7/8" from the tread surface to the rear fascia:



Can't really get a comparable measurement, but ~2" for the corresponding measurement to the quarter panel:



Inner lip clearance to everything in front of the axle--nothing is even close to the top of the tire:



Inner lip clearance to everything behind the axle--I can still get my finger between the top of the tire and the wheel well liner:



The toe link is danger close to the frame rail:



I bumped my spring rate up 200 ppi, shortened the springs by 2", lowered the car slightly to a 15 3/8" ride height... and the spring perch barely moved :roll:



The spring is seated directly against the strut top plate, so it won't be going up any more. If I build a fancier top mount with an axial load spherical bearing and a needle bearing set to let the spring squirm, the perch could come down another 1/2" easily. Shoot, I may have to go to 8" springs.

Also, flipping the strut top plates, or making new ones that put a spherical bearing strut top mount ABOVE the top of the strut tower could lower the metal-to-metal contact ride height by *maybe* as much as 2", but that really just means that the current metal-to-metal height becomes the new bump stop height. Still not bad, though. I haven't run the numbers yet to see if I can get 8" springs that will have enough travel from ~15" static ride height to hit the bump stops a meaningful distance before they coil bind.

If I could get the current metal-to-metal height to be the new bump stop height (unlikely that everything can package in the space available), then a 14 3/4" ride height, which is about what Steven's running, would still have 2.5" of compression travel before even touching the bump stop. With 550# springs, that's 1375 extra pounds on the outside tire in a corner... that's a LOT of cornering g's!

Currently, at 15 3/8", I'm only 1 11/16" off the bump stops.

Hello, I've been searching on the web for a nice set of wheels to upgrade to and I believe I've finally found the perfect set. I just need to know if a wheel measuring 17x8 with an offset of 35mm would look good on an 86? I looked at the chart on the first page, but I honestly can't understand it at all. Any help would be greatly appreciated. Thanks!

Each horizontal bar shows a wheel width and offset, so you want to look at the bar that says 8 / 35mm. It shows that there is plenty of space on the left (the red line would be where it hits suspension components), but it will probably hit the wheel well (2 little black lines) on the right. As you can see by the other bars, an offset of 40mm would be a safer choice.

[This message has been edited by Gall757 (edited 08-08-2017).]

Ah, okay, I see what you mean now, thank you for your response. My car isn't lowered at all, and I'm planning on using lower profile tires in order to keep the overall diameter of the wheel+tire the same. I don't think it'll actually hit the wheel well, but extend past it a little instead.

Can you add 18 inch wheels with a 45 offset?

Per my post above, I have C5 Corvette rears on with a 1" spacer. These wheels are 18x9.5 with 61mm offset. Wheel specs here: http://image.mamotorworksme...eference_Guide-a.pdf

With the spacer, this calculates to an 18x9.5 with 36 mm offset. Can you add that to the diagram?

NVM, I'm blind. There's already a 9.5-35 block.

[This message has been edited by Will (edited 08-15-2019).]

Please add 9.5 +50 and 8.5 +50

Also, someone verify that the red line is the spring, and this is accurate for 1985 model year

Is there a current version available?