#1  
Old 05-14-2024, 07:57 PM
grivera's Avatar
grivera grivera is online now
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Default Rear Tire Size and Wheel BS

My newly acquired 66 Lemans has a 12 bolt rear, supposedly from a 66 Chevelle. Does anyone know the maximum BS one can use with this rear and tire size if using a 15 wheel?

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Will Rivera

'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
66 Lemans, 455, KRE D-Ports, TH350, 12 bolt 3.90 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears (Traded)
'69 LeMans Vert, 350, #47 heads: Non-running project
  #2  
Old 05-15-2024, 04:47 AM
3X24SPD 3X24SPD is offline
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Better check your casting code/dates on the housing to be sure first.
The 65-67 Chevelle 12-bolts were the 1" narrower ones (54.25") vs the 68+ (55.25").

12-Bolt Housing: Casting #
1965 Chevelle 3859140N
1966 Chevelle 3875745N
1967 Chevelle 3894939NF
1967 Chevelle-Late 3917124NF
1968-Early 69 Chevelle 3917124NF
1969 Chevelle 3959038NF
1970-72 Chevelle 3969278NF

For reference, I run a 15X10 with 5.5"BS & 28X12 M/T on the back of my 66.

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1966 GTO (Red) WARPATH
455CI TriPower 4-Speed

1965 GTO (Black) TRIPOWR
464CI TriPower 4-Speed

1965 GTO (Blue) 3X24SPD
464CI TriPower 4-Speed
  #3  
Old 05-15-2024, 05:38 AM
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grivera grivera is online now
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Thanks- good point and will do.

do your back tires fit under fender lip?

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Will Rivera

'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
66 Lemans, 455, KRE D-Ports, TH350, 12 bolt 3.90 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears (Traded)
'69 LeMans Vert, 350, #47 heads: Non-running project
  #4  
Old 05-15-2024, 06:24 AM
3X24SPD 3X24SPD is offline
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Yes, but be advised that in my case, I also have wagon rear springs, and a later 55.5" width 8.2 10 bolt rear axle in this car.
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__________________
1966 GTO (Red) WARPATH
455CI TriPower 4-Speed

1965 GTO (Black) TRIPOWR
464CI TriPower 4-Speed

1965 GTO (Blue) 3X24SPD
464CI TriPower 4-Speed
  #5  
Old 05-15-2024, 12:05 PM
grivera's Avatar
grivera grivera is online now
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Thanks - mine has Catalina springs all around and Id like to lower it between what it is now and factory height. I believe the Weld wheels in rear are 15x8 with 4.5 BS.
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__________________
Will Rivera

'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
66 Lemans, 455, KRE D-Ports, TH350, 12 bolt 3.90 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears (Traded)
'69 LeMans Vert, 350, #47 heads: Non-running project
  #6  
Old 05-15-2024, 07:07 PM
grivera's Avatar
grivera grivera is online now
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The rear has the 66 Chevelle code:

3875745N with date code H215

But it has 4 wheel disc brakes so I assume it picks up about 1/2 from the rotors.
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__________________
Will Rivera

'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
66 Lemans, 455, KRE D-Ports, TH350, 12 bolt 3.90 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears (Traded)
'69 LeMans Vert, 350, #47 heads: Non-running project
  #7  
Old 05-15-2024, 09:51 PM
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grivera grivera is online now
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I measured the rear wheels -15x9 with 5.5 backspace, currently 275/60 MT Drag radials with the little screws into the perimeter of the wheel lip. The fronts are 15x7 wheels with 3.5 BS. I plan to install 15x8 wheels in rear with 255/60 tires and 215/70s in the front. I hope with the smaller rear wheel and tire combo I can put in springs with lower rate to get rid of that gasser look.

__________________
Will Rivera

'69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears
66 Lemans, 455, KRE D-Ports, TH350, 12 bolt 3.90 gears
'64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears (Traded)
'69 LeMans Vert, 350, #47 heads: Non-running project

Last edited by grivera; 05-15-2024 at 10:10 PM.
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