How much backspace on factory G-body 15" aluminum wheels?

[454GrandPrix]

As some of you may have seen in my build thread, I recently completed the Blazer front brake upgrade. I had already been running 15x7 N90 alloy wheels from a 1980 Z28, and I'm very fond of them. But now these front wheels firmly contact the Blazer brake calipers, so I can't run them without spacers (which I don't want to do long term for a variety of reasons I will not explain here). Long story short, I need some different wheels.

My 235/60-15s tires are still like new, so I intend to keep using them and just swap them on to other 15" wheels. We all know the N90 wheel was also used on late Monte Carlo SS models. Snooping around online, I am led to believe that the G-body version of this wheel has a little less backspace than the F-body version, by perhaps half an inch. This might be all the difference I need.

Does anyone have a set of these just sitting around so you can go measure them for me? I believe my F-Body wheels have 4.0" from the seating surface to the outer (rear) edge of the rim. Can anyone verify the Monte SS N90 measures only 3.5" (or less)? For that matter, what about any of the other G-Body 15" alloy wheels? Can anyone measure one of those and let me know what they find?

With any luck, one of these wheel styles will be an affordable solution for me.

 

[UNGN]

T-type Wheels (and '85 GN wheels) have 3.75" BS and will fit even 12" B-body brakes without rubbing.

I had brake rub on the back face of my GTA's with LS1 brakes, but once the pads wore a little I was able to remove the thin spaces.

 

[79 USA 1]

Dempsey,
I have a set of the N90's from my 88 Super Sport in storage, I'll get a back space measurement this weekend. I also have a set of 8 hole Corvette YJ8/N90 aluminum wheels 15 x 8 which are a 4.00 back space.

Not my wheels just a borrowed picture!

Bob S.

 

[454GrandPrix]

T-type Wheels (and '85 GN wheels) have 3.75" BS and will fit even 12" B-body brakes without rubbing.

That sounds promising. I do like the look of the T-Type wheels, though I don't imagine it will be easy to find a set for cheap.

I also have a set of 8 hole Corvette YJ8/N90 aluminum wheels 15 x 8 which are a 4.00 back space.

Thanks, Bob, I'll watch for you to post your findings. As for these Vette wheels, the 4" backspacing is the same as my Z28 wheels. I'll definitely need less (unless the spokes are much more shallow than on my Z28 wheels).

 

[79 USA 1]

Dempsey,
Sorry on the delay, damn wheels were way at the back of the shelf. Anyway looks like the back space on the Monte Carlo N90's is 3.750, also I'm not sure if this will help but the measurement from the wheel edge to the back of the windows on these wheels is 4.375. Keep in mind the Monte Carlo N90 use a bulge seat lug nut (Far left) while the Z28 wheel should use the short shank lug nut on the far right.

The standard taper seat lug in the center will tear up the lug holes in a very short time.

Hope this helps!
Bob S.

 

[454GrandPrix]

Anyway looks like the back space on the Monte Carlo N90's is 3.750.

I went out and removed one wheel from my car so I could re-measure the backspace very precisely. From seating surface to the outside edge (like you measured), I have 4.25" total backspace. This gives me hope for Monte SS N90s, and also for the T-Type Vector-style wheels. I wonder if the hot air T-Type wheels (the ones used only in '84 and '85, with a million spokes) would measure the same?

I have no idea how much space there is to the back of the Z28 wheel spokes. I should have measured that, too.

Keep in mind the Monte Carlo N90 use a bulge seat lug nut (Far left) while the Z28 wheel should use the short shank lug nut on the far right.

Thanks for the reminder. Yes, I am using mag wheel style lug nuts with washers right now. I'll need to buy even more lug nuts once I switch wheels.

 

[rafael martinez jr]

hi i have a friend that has a set of rear wheels they are 15-8 with a 4-1/2 backspace wondering if i can fit them on my 80 malibu thx

 

[UNGN]

hi i have a friend that has a set of rear wheels they are 15-8 with a 4-1/2 backspace wondering if i can fit them on my 80 malibu thx

Depends on the tire.

A 235/60 should work.

A 255/60 will be close to the frame without spacers and may only rub in hard corners.

A 275/50 or 60 will rub the frame without spacers.

 

[Michael Bennett]

Hey 454 Grand Prix how did you wind up doing with your wheels and tires? I assume you went with the hot air wheels in your signature. What size are you running in the back? I've got monte ss alum wheels for my Malibu and want to run 255/60 or 275/60 preferably if I can get away with it but don't want a bunch of rubbing. Thinking about possibly using wagon springs for a little lift to prevent rubbing.