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Wheels Back spacing and width

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Old Jun 24, 2012 | 08:38 PM
  #1  
yota4runnernut's Avatar
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From: Norwood, Colorado
Car: 1992 RS
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Wheels Back spacing and width

Ok, please dont tell me to search, I have looked at this site for about 12 hours over the last 2 days!

I am looking at a set of center lines that are front 15x7 with 4" of back spacing and the rear are 15x10 with 6" of back spacing ,will the front work and will the back tuck in the rear fender well?
Any photos W/ tire sizes would be awesome.
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Old Jun 24, 2012 | 09:06 PM
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width

The 6" of back space would put the rim almost inside the outside uper lip.
almost tucking it under.(almost)

you would have to remove your bumpstops
and get a set of offset LCA's (founders) $120 with off set bushings(order them that way and save $25)

now if you are going to use the smallish 275/60/15.(27/28"tall 9"wide) then it should just tuck under. or sit just about right.
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Old Jun 24, 2012 | 10:14 PM
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From: Norwood, Colorado
Car: 1992 RS
Engine: 305
Transmission: 700r4
Axle/Gears: stock
Re: Wheels Back spacing and width

i thought you could do 6" back spacing with out removing bump stops?
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Old Jun 25, 2012 | 12:47 AM
  #4  
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width

any tire with a slight bulg at the sidewall, cant go any deeper then a 5" back space.on the back rim.

the tires are going to rub the LCA also with a 6" back space

not just a bolt on thing, over 4 1/5 " back space on a 15" rim

ya got to check rear brakes/LCA/bumpstops
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Old Jun 25, 2012 | 01:25 AM
  #5  
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From: Central Texas
Car: GTA
Engine: 350 TPI
Transmission: 700R4
Axle/Gears: Aussie 9-bolt/3.27 posi
Re: Wheels Back spacing and width

Your front wheel choice will be perfectly fine.

Based on everything I encountered when I did my rear 17"x11" wide/7"bs wheels, I am going to "slightly disagree" with arcticwhitez.

I say slightly disagree because I do not believe that you will have to touch the LCAs & I believe that the 6" will get you very close to the bumpstop & whether or not you have to remove them will be more of a tire sidewall bulge issue than a rim issue. But with only a 15" hoop that also puts the wheel closer to the bumpstop so that may be an issue affecting the clearance. Might be that is clears with the car on the car but jacked up or as the suspension becomes unloaded that it may in fact hit. If that is the case then you might have to resort to Limiting Straps like the 4x4 guys use.

A 10" wheel with 6"bs gives a front face of 4" out. I have 5" out & tuck perfectly fine. Outwards will be fine with your choice. It is the inwards that will be borderline.
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Old Jun 25, 2012 | 06:19 PM
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Engine: 408 stroker sbc
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Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: Wheels Back spacing and width

both will work. the rear will require some light metal work. Should not be anything crazy though. However, the rear tire size will add some variables, a larger sidewall will create some clearance issues and will require more work.

you can easily use more that 5" of bs on the rear. The factory 16x8 has 5.125, with room to spare.

a 15x10 with 5.5" of bs is a old common size for the rear people use for drag cars, it puts the wheel a little too far out IMO, and wont work with a lowered car.
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Old Jun 25, 2012 | 08:30 PM
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width

like i posted...

it's not a bolt on item. (6" back space)

i just did 3 diff wheel makes(billit street lites/centr lines/welds/ and 4 diff back space mock ups 5.5/6.0/6.5/7.0

and only 1 camaro.
this shot shows a15x10. 6.5 back space wheel with a 13.4 sec width tire on it
just tucks under. (before rear end) is centerd this side comes out another 3/8 inch
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this shot shows how a 15" rim sits so close to the bumpstop at ride Ht. it would rub.
Note! you cant see bump stop..cusss it's inside of the rim lip. on the back side
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this shot shows how close to the LCA a 6.5 back space rime is. add anothe 1/2 and i could get a finger in there.. just dont run a tire with a bulgn side wall?
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but then i got the mother load of side wall...
Name:  sportsmen039.jpg
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Last edited by articwhiteZ; Jun 25, 2012 at 08:57 PM.
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Old Jun 25, 2012 | 09:58 PM
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From: Norwood, Colorado
Car: 1992 RS
Engine: 305
Transmission: 700r4
Axle/Gears: stock
Re: Wheels Back spacing and width

articwhitez,
Thanks for the photos, those tires look sic under your car!
What size were the draglites you had on before?
I dont think there is anyway to get away from the mother load of side wall on a 15" rim if you wanna fill your fender wells!

I just dont think I am ready to take the "cut the fender well" plunge yet!
Thanks for the work and willingness to post your findings!
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Old Jun 26, 2012 | 01:17 AM
  #9  
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width

my weld wheels (drag lights)
15x8 4.5" back space 15x29x12.5 ET Street (wheel tire combo,is bolt on)
no mods needed (and is tucked inside of lip.)
note: tire would rub if turning left or right. with speed. see pics you can see rub marks, nothing Bad. but that tires side wall was..well a slick ya know

they do look good, thank you, back having the Car in a few Years, after this upgrade!
Name:  sportsmen193.jpg
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Size:  196.4 KB

Last edited by articwhiteZ; Jul 6, 2012 at 03:42 AM.
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Old Feb 29, 2020 | 04:29 PM
  #10  
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Re: Wheels Back spacing and width

Originally Posted by articwhiteZ
my weld wheels (drag lights)
15x8 4.5" back space 15x29x12.5 ET Street (wheel tire combo,is bolt on)
no mods needed (and is tucked inside of lip.)
note: tire would rub if turning left or right. with speed. see pics you can see rub marks, nothing Bad. but that tires side wall was..well a slick ya know

they do look good, thank you, back having the Car in a few Years, after this upgrade!
Attachment 366656
Thx for keeping the advice available to all of us! I need to pick your brain for something I'm sure you have the formula for. I just finished my 91 Z28 project and took the advice of a buddy of mine a purchased the Iroc 1

7" repo wheels with 275/40/17 all around. I'm bummed out to see that my rear tires stick out like 1/2"or better and I can't run the car it rubs right on top of the tire... Now I'm stock with yet another set of wheels. It looks goofy in the back like that. What are my wheel options to tuck that size tire in with out rubbing? What back space and offset do I need in the back? The front seems ok with the 0 offset. The repo Iroc only comes with 0 off set I'm told. Much appreciated any Ideas or known wheels that you know would look good and fit
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Old Feb 29, 2020 | 04:32 PM
  #11  
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Re: Wheels Back spacing and width

Thx for the advice available to all of us! I need to pick your brain for something I'm sure you have the formula for. I just finished my 91 Z28 project and took the advice of a buddy of mine a purchased the Iroc 17" repo wheels with 275/40/17 all around. I'm bummed out to see that my rear tires stick out like 1/2"or better and I can't run the car it rubs right on top of the tire... Now I'm stock with yet another set of wheels. It looks goofy in the back like that. What are my wheel options to tuck that size tire in with out rubbing? What back space and offset do I need in the back? The front seems ok with the 0 offset. The repo Iroc only comes with 0 off set I'm told. Much appreciated any Ideas or known wheels that you know would look good and fit

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Old Feb 29, 2020 | 05:10 PM
  #12  
articwhiteZ's Avatar
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width


this is a 6.5 back space on a 10.25 wide wheel (15" rim) . with a stock with rear end..a 17" wide rim would give you a bit more rear caliper room
.
but with this type of back space you will need to remove your bump stops..and do inner wheel well modes.
always have rims for tires..not tires for rims..(the race tire set)

the street tire set..

Last edited by articwhiteZ; Feb 29, 2020 at 05:23 PM.
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Old Feb 29, 2020 | 05:32 PM
  #13  
articwhiteZ's Avatar
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width

some basic pics
https://i573.photobucket.com/albums/...heels009-1.jpg
this shot shows 4.5 back space wheel 8.5" wide rim (10 years of sitting)
https://i573.photobucket.com/albums/...k21/z28490.jpg
10 years...
https://i573.photobucket.com/albums/...k21/Z28002.jpg

Last edited by articwhiteZ; Feb 29, 2020 at 05:52 PM.
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Old Feb 29, 2020 | 06:11 PM
  #14  
articwhiteZ's Avatar
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From: Spokane WA
Car: 92 Lingenfelter Z28 articwhite
Engine: Aluminum 615BBC
Transmission: Th400wbrake/curri entps9" locker
Axle/Gears: 4.11/4.30/4.56
Re: Wheels Back spacing and width

most of the info ya might need..
https://www.thirdgen.org/forums/whee...-6-5-back.html
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