BACKSPACING AND OFFSET FOR THE WIDEST TIRE ON THE REAR.

Toddmc66

Import punisher.
Dec 26, 2012
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Orlando FL
I'm buying new wheels and tires. My frame (isn't notched). I'd like to put a 305 on the rear. I've seen other post saying they have 305's on the rear but never post what the backspace or offset is. Did some research and so far I've found for a 295 to 305 the backspace is 4.5" on a 10" wheel. Anyone have any experience with this or have 295 or 305's on their car ? if so what wheels and specs. Any help would be appreciated.
 

NOONG

Member
Apr 29, 2015
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EVERETT WA
I have a 295 with a 10” wheel with a 4.5” BS and that’s as wide as I could go without notching my frame. I did have to roll my fenders though. Pics with a stock type wheel and a drag wheels.



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crazyturbo

Member
Nov 23, 2014
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Never heard of a 305 fitting without a notch. I used to have a 295 and those still rubbed my frame but I did roll the fenders.
 

Turbo6inKY

Short Guy
Jun 18, 2001
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If you go through this worksheet, it'll get you all the measurements you need to know what will fit on one piece of paper.

https://4aah2h38qz0d1pp9jb46vzfw-wpengine.netdna-ssl.com/wp-content/uploads/2017/04/find_the_largest_tire_and_wheel_combo_for_my_vehicle.pdf

Going as big as you want, you likely will end up having to order a custom wheel with the right backspace to get the rubber under the car, and it's going to be tight.

If you don't have a lateral location device like a panhard or watts, you'll want one to keep the axle centered while it's operating.
 

NOONG

Member
Apr 29, 2015
106
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EVERETT WA
Fitting and fitting with airbags aired up are two different things. Over the years Ive seen countless people say there rim fits and doesnt rub and the dam air bags air pumped up to keep the body off tires
I forgot the day my airbags are aired up as well! Thanks for reminding me @turbonasty


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Beach

New Member
Sep 3, 2014
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I have 18x10 with a 5' backspace 285 nitto 555r. No notch, no roll and they don't rub
 

dynoman

Well-Known Member
Nov 30, 2009
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Ontario NY , near Rochester NY
My car has fenders rolled & frame notched . I tried 295/65/15 MT DR's on my car and they would rub slightly on a sweeping turn with bumps . The 295/65/15's are a 30" tall tire and the 295/55/15 is 28" . I'm guessing you are talking about the 55 because there is no room to fit a 65 without a notch and massaging the wheel tub with a sledge hammer . I am talking about fitting with NO air bags and the car sitting down over the tires like it's suppose to .
My wheels are 15x10 4" backspace , but my rear end is narrowed 1 1/2" each side so that would be like a 5 1/2" backspace as far as where the tire would sit in the wheel well on a stock width rear end .
These are pictures of the 295/65/15 mounted and one of a comparison of a 295/65/15 @ 30" tall & 275/60/15 @ 28" tall .
DSCN0600.JPG
DSCN0601.JPG
DSCN0603.JPG
 
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Toddmc66

Import punisher.
Dec 26, 2012
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Orlando FL
If you go through this worksheet, it'll get you all the measurements you need to know what will fit on one piece of paper.

https://4aah2h38qz0d1pp9jb46vzfw-wpengine.netdna-ssl.com/wp-content/uploads/2017/04/find_the_largest_tire_and_wheel_combo_for_my_vehicle.pdf

Going as big as you want, you likely will end up having to order a custom wheel with the right backspace to get the rubber under the car, and it's going to be tight.

If you don't have a lateral location device like a panhard or watts, you'll want one to keep the axle centered while it's operating.
Thanks for the measurement sheet.
 

scot w.

GNSperformance.com
Feb 19, 2005
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You know, There really isn't a "Magical" wheel size that fit's All... Although wheel sizes and BS stay the same "Tires" and their sizes Do Not! Each tire manufacture tire size actually vary to some degree, you can take 3 of the exact same tire size from three different tire manufactures and the width will be different on all three... For example: I ran a 285/35-18 Toyo proxis T1R and then went to the same size but a BFG KDW2.... the Toyo proxis was wider on the same exact wheel than the KDW2 was... So when I seen that the BFG tire was narrower I went ahead and bought the 295/35-18 and it fit great on a 10" wheel all I had to do was roll the lips....
DSC_0147.JPG
 

Toddmc66

Import punisher.
Dec 26, 2012
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Orlando FL
I purchased the factory replicas from Gbody Parts. I purchased the 10x15 with 4.5 back space. Has anyone put a 295/60/15 or any other 275 combination on this particular wheel? if so what brand?
 

SpeedRacerX

Well-Known Member
Jan 20, 2014
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Southern NJ
I purchased the factory replicas from Gbody Parts. I purchased the 10x15 with 4.5 back space. Has anyone put a 295/60/15 or any other 275 combination on this particular wheel? if so what brand?
Mickey Thompson ET Street SS 295/55-15, 28" tall, on that exact gbody rim. No frame issues. Newer springs and shocks fyi. Rubbed on fender lips on heavy bumps. Rolled the fender lips and problem gone. I have airbags but I no longer need them since I rolled the lips.



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Black Car

Member
May 25, 2001
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Late to the question.
I started running 305x50x15 BFG back in mid 90's . Continued till BFG quite making the 305x50x15 tire. Pulled them off in 2010 when they got low on the tread. Put on 275x60x15 BFG drag radials. I still have the Vectors and BFG 305 mounted in the garage.
I was using the american Vector rim 8.5" wide from the late 60's to the early 70's. Looks the same as 86/87 t-type rims or the 84 GN wheels except there was no black on them. Don't remember the back spacing. Think it was 3-3/4 or 4".
They were uni-lug wheels that would fit GM, Doges and Fords. Corvette used them in 70's.
Here are a few pictures of them on the car. Fenders were rolled tight and air bags at 5psi. Heavy bump would very slighty rub the drive side plastic piece on the frame.
Gary
 

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Toddmc66

Import punisher.
Dec 26, 2012
62
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Orlando FL
Update. Installed MT SS drag radials 295/55/15 on a 10" wheel 4".5 back spacing. Fenders are rolled, frame is not notched. Tires tuck right in no rubbing. Tire sits 5/8" away from the frame. Wheels are the replica wheels on the G Body Parts website. No airbags. Hope this helps when you purchase your tires and wheels.
 

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greeneyegi

Well-Known Member
Feb 21, 2010
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Update. Installed MT SS drag radials 295/55/15 on a 10" wheel 4".5 back spacing. Fenders are rolled, frame is not notched. Tires tuck right in no rubbing. Tire sits 5/8" away from the frame. Wheels are the replica wheels on the G Body Parts website. No airbags. Hope this helps when you purchase your tires and wheels.
If you put 4 people in car does it rub at all?
 

Toddmc66

Import punisher.
Dec 26, 2012
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Orlando FL
If you put 4 people in car does it rub at all?
Haven't tried that yet but,,,,had a couple big corn fed boys in the shop put some weight on the back bumper until it bottomed out and the tire still clears the rolled fenders. I'll let you know after I load it up with 4 people.
 
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