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#1041849 - 07/27/16 02:29 AM Re: STICKY: Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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Beamer Offline
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Wyoming, MN
Thought I would put this out there in case someone wanted to know

Vision 143 Wheels - 18x9.5 w/ 5.25BS / 0mm Offset

These pics are with no spacers, stock frame rails - about 1/4" of clearance to the rail (not the "LH" plastic thingy)




#1050161 - 04/20/17 02:20 AM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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jclubb46 Offline
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Coal City IL
great thread very helpful

#1057278 - 05/12/18 04:53 PM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: BadSS]  
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BadSS Offline
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BadSS  Offline
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Pearl, MS, 39208
Adding the image back:

I had posted the chart below in another thread but thought it might be useful here. The measurements were taken utilizing stock upper and lower controls arms with drop spindles. The spindles won't affect the sub-frame and fender clearances, but by raising the mounting point of the wheel two inches in order to give the body a 2" drop, 17" or smaller wheels with 4.5" backspacing (or more) can or will give clearance problems at the tie rod. I know it was extremely close on my SS (less than 1/8") when using a 17x8 SLP ZR-1 wheel with a 4.5" backspacing. However, 1/2" more radius provided by an 18" wheel (compared to the 17" wheel I used for measurements) should give ample clearance at the tie rod for more than 4.5" backspacing but I have no idea how much more.

[Linked Image]

Basically it looks like clearance is tight, but good enough to run 245/45-17s and 245/40-18s on an 8" wheels with 4.5" backspacing. I know some have run a 255/45-17 and 255/40-18 tire on 8" wheels with 4.5" BS, but based on my measurements anything wider than a 9.8" section width is pushing things. Don"t just go by the tire size since section widths vary between manufacturers and even lines of their tires. Some have reported rubbing with 245/40-18s with a 4.5" backspacing and others have not. There may be suspension differences at play, but I'd lean towards the differences in section widths and sidewall stiffness between brands of tires as the issue.

It seems from the consensus of those that participated in the original thread containing the chart, 8" wheels with the more commonly available 4.5" backspacing give the appearance the tire is sitting in a little more than optimal, especially when running wider tires and wheels out back. It makes sense if you think about it. If you're taking the tire as close to the edge of the fender lip as you can in the rear, if you don't do the same for the front, the fronts could look a little sunken. If you're running the same size wheel/tire front and rear (or slightly larger for the rear) this probably won't be an issue. Also, if you're dropping the front more than a couple inches, you may need the tire to set in closer to the sub-frame than the fender anyway.

Looks aside, it appears an 8" wheel with a 4.25" backspacing will come close to centering the wheel in regard to sub-frame (under full lock) and fender lip clearance. As will an 8.5" wheel with a 4.5" BS, a 9" with a 4.75" BS and a 9.5" with a 5" BS. Technically, a 0.25" offset (bringing the center forward) is a negative 6.35mm (-6.35mm). The trend is to advertise offset and many advertise a -6mm and -7mm offset which is technically 0.236" and 0.276" respectively. I doubt that the few hundredths of an inch one way or the other will present an issue.


Original owner of 1985 SS black hardtop w/gray interior. Frame-on restoration in progress. 406 sleeper w/ heavily ported FIRST TPI. 1.875" headers and dual 3.5" Borla exhaust. TH400, Ford 9", anti-roll bar, and notched frame. Dropped 2", 18" wheels, and F/R disk brakes. 10-point cage w/swing-out bars, custom gauges, and audiophile stereo system.
#1059100 - 09/17/18 02:19 AM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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seasicksix Offline
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Cadillac, MI
i just joined the forum since i just bought a 85 ss and i was looking to run a bigger rim and a wider tire since i plan on running a ls engine in the future the rim i was looking at was 17x8 with 4.5 bs the tires the recommended was a 235/50 i dont know how this would fit rubbing was in the front and rear if anyone could help me with this id be thankful

#1059103 - 09/17/18 01:55 PM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: seasicksix]  
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Travis Jones Offline
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Travis Jones  Offline
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Ferndale, MI
Originally Posted by seasicksix
i just joined the forum since i just bought a 85 ss and i was looking to run a bigger rim and a wider tire since i plan on running a ls engine in the future the rim i was looking at was 17x8 with 4.5 bs the tires the recommended was a 235/50 i dont know how this would fit rubbing was in the front and rear if anyone could help me with this id be thankful


I ran a 245/45/17 on a 17x8 with 4.5in BS with no rubbing at stock ride height.

When I lowered it, I ran into some slight rubbing in the wheel wells and at the 12 o clock position of the wheel well.


86 SS 6.2l LS3, Ilmor intake, Summit Stage 4 Cam, Stainless long tube headers, Stainless 3in exhaust, Tremec T-56 Magnum 6 speed, Eaton Truetrac 8.8 LSD, UMI Cornermax Front Suspension, 3-link Rear suspension w/ UMI Control Arms, UMI Front & Rear Braces, Brembo Brakes
#1059105 - 09/17/18 05:53 PM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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seasicksix Offline
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Cadillac, MI
how much did you lower it

#1059107 - 09/17/18 08:27 PM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: seasicksix]  
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Travis Jones Offline
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Ferndale, MI
Originally Posted by seasicksix
how much did you lower it

it has 2 inch drop spindles, .5 inch taller lower ball joints which drop it another half inch, and coilovers. so a bit.


86 SS 6.2l LS3, Ilmor intake, Summit Stage 4 Cam, Stainless long tube headers, Stainless 3in exhaust, Tremec T-56 Magnum 6 speed, Eaton Truetrac 8.8 LSD, UMI Cornermax Front Suspension, 3-link Rear suspension w/ UMI Control Arms, UMI Front & Rear Braces, Brembo Brakes
#1059121 - 09/19/18 08:28 AM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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seasicksix Offline
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Cadillac, MI
well looking around at tires the 235/50 are supposed to be 9.3 inches wide but there all 9.7 i would think that would be to wide for the front i would think the rear would be fine what would be a good size tire for the front end i plan to drop the car a inch or 2 in the future i was thinking about running a 225/50 which is 9.2 inches wide im not sure what to do for front tires

#1059146 - 09/21/18 01:57 AM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: seasicksix]  
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BadSS Offline
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BadSS  Offline
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Pearl, MS, 39208
Originally Posted by seasicksix
well looking around at tires the 235/50 are supposed to be 9.3 inches wide but there all 9.7 i would think that would be to wide for the front i would think the rear would be fine what would be a good size tire for the front end i plan to drop the car a inch or 2 in the future i was thinking about running a 225/50 which is 9.2 inches wide im not sure what to do for front tires


As Pez indicated the 245/45/17 is a proven fitment for the front. If you want a square fit - same on all four wheels, the 245/45/17 is a good choice. Some run a 255/45/17 on all four corners without issue. I have 2" drop spindles and 1" drop springs on the front and a 245/45/17 with a 4.5" backspacing and with the wheels I have, the tie rod hits the inner rim but will clear with a 1/4" spacer. I'm going to sell them and get a 8" with a 4.25" backspacing (like the 17x8" N90s).

If you're looking for a smaller tire on front and larger on the rear, the 225/50/17 on a 7" front and a 255/45/17 on an 8" rear would work and I'd think look pretty good. You could put a 225/50/17 on an 8" rim, but if I were going 8" on all four corners, I'd do the same size on all four tires, like a 245/45/17 to be able to rotate them.

I think with the right offset you may be able to get a 26.3" tire on the front with a dropped suspension, but I've asked the forum before if anyone has run that tire on the front with a dropped suspension but didn't get a response.


Original owner of 1985 SS black hardtop w/gray interior. Frame-on restoration in progress. 406 sleeper w/ heavily ported FIRST TPI. 1.875" headers and dual 3.5" Borla exhaust. TH400, Ford 9", anti-roll bar, and notched frame. Dropped 2", 18" wheels, and F/R disk brakes. 10-point cage w/swing-out bars, custom gauges, and audiophile stereo system.
#1059166 - 09/21/18 06:01 PM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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seasicksix Offline
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Cadillac, MI
i was going to put baer breaks all the way around and run their spindles which add .4 to the width so i shouldnt have any clearance issues

#1060179 - 12/11/18 04:51 PM Re: General Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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Nate1976 Offline
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Twin Lake MI
I am ready to purchase rims for my new car. I want 17 x 8 inch rims. I read through this thread and a few others but am a little confused on the recommendation for back spacing. Here is an actual link to the rims I am purchasing. If I go with 245/45/17 will that work for all 4 tires? And is the correct back spacing 4.75 (120.65)? They have these spacings available (Available PCDS: 5- 114.3, 120.65, 127). In this thread for 17 x 8 it is recommended 17 x 8": 3.75 - 4.0" B.S.? Your response is appreciated. Thanks

http://voxxwheel.com/virtual-wheel-...el=Old%20School%20Chrome&color=Black

#1068311 - 10/19/20 01:22 AM Re: STICKY: Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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lambeau40 Offline
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Benton, WI
Here is the rear clearance of a 255/45-R17. This car has a Quick Performance Ford 9" with Wilwood 4 piston disc brakes. The wheels are the reproduction 17 inch N90 from Mike's Montes.
[img]https://drive.google.com/file/d/1R50QCCm7KuyLEOuuAnnTYRhwWxh3Fftl/view?usp=sharing[/img]

#1068331 - 10/21/20 03:18 AM Re: STICKY: Wheel/Tire Fitment and Suspension Guide. [Re: SuprSlow]  
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
The tire contact point that touches first is usually the rearward side of the frame on my car. Also you need to check both sides for clearance. With a GM rear it's usually closer on the right side. I know you went 9". When clearance on fat tires is good on the inside the outer sidewall gets closer to the lips on the quarters.
I've run BFG 255/50x16, Hoosier A6 275/45x16 and Hoosier GTP 11.50x27 tires on my car. The trick is to run the minimum clearance on the inside so the tire stays inside the opening, and never touches/rubs the frame. When the tire contacts the frame is when turning corners, straight ahead doesn't mean squat.

The section width of a tire mounted on a specific rim width can vary, more on a 9" less on an 8 1/2". The tire size you mentioned, 255/45x17 has a section width on an 8 1/2 rim of 10.0 give or take. The Comp 2 255/50x16 I run is 10.4 on an 8". The 275/45x16 A6 has section width of 10 7/8" on an 8, and the fat QTP 11.50x27x15 are a whooping 11 3/8". The QTP slicks will touch the frame if I corner the car, but who corners a tire with 12 psi and no real sidewall. They are inside the body line but i don't consider it pretty, just a drag race car look.

With what you are building i would think fatter in the rear is in order, like a 275/40. But the N90 wheels are only 8" and the 275 wouldn't be a good fit on that wheel width.
Bob

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