Backspacing when adding Wilwood front disc brakes - Team Camaro Tech
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post #1 of 22 (permalink) Old Dec 1st, 18, 02:23 PM Thread Starter
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bob
 
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Backspacing when adding Wilwood front disc brakes

I'm going to be adding Wilwodd front disc brakes in few weeks and was wondering if I'm correct in the backspacing for new rims and tires I want to install on my '67.

I am thinking of replacing my 27 year old Cragar Street Star 14" rims/tires with American Racing VN504's in 15x7 in the fronts with 235/60r15 rubber. The brakes will push the rims out .19", so I should be looking at a 4.5" backspacing, correct? Currently the car has stock springs in the front and I am not dropping the front end down.

The rear will be (unless someone sees and issue): 15x8 with 4.5" backspacing with 255/60r15 rubber. Car has a multi-leaf rear spring (not sure who made them, as I had it installed 25 years ago due to not finding anyone who sold replacement springs only back in 1993).
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post #2 of 22 (permalink) Old Feb 8th, 19, 02:38 PM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

Any suggestions?

I found the rims I like, but they are 15x7 rims with 4" backspacing and 15x8 with 4.25".
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post #3 of 22 (permalink) Old Feb 8th, 19, 03:42 PM
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Re: Backspacing when adding Wilwood front disc brakes

Pretty sure that is not enough backspacing.

Don

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post #4 of 22 (permalink) Old Feb 8th, 19, 04:16 PM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

Kinda what I thought from my reading on this site....
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post #5 of 22 (permalink) Old Feb 8th, 19, 04:30 PM
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Re: Backspacing when adding Wilwood front disc brakes

[quote=bob15;1783118699]Kinda what I thought from my reading on this site....[/quote

Add your brake offset to these backspacing numbers:

17x7 = 4.25"bs
17x8 = 4.75"bs
17x8.5 = 5" bs
17x9 = 5.25"bs
17x9.5 = 5.5" bs

Don

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1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
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post #6 of 22 (permalink) Old Feb 8th, 19, 05:14 PM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

[quote=dhutton;1783118701]
Quote:
Originally Posted by bob15 View Post
Kinda what I thought from my reading on this site....[/quote

Add your brake offset to these backspacing numbers:

17x7 = 4.25"bs
17x8 = 4.75"bs
17x8.5 = 5" bs
17x9 = 5.25"bs
17x9.5 = 5.5" bs

Don

OK


I am curious why wouldn't I subtract from those numbers because the brakes are pushing the rims out a 1/4"?
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post #7 of 22 (permalink) Old Feb 8th, 19, 05:17 PM
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Re: Backspacing when adding Wilwood front disc brakes

[quote=bob15;1783118709]
Quote:
Originally Posted by dhutton View Post


OK


I am curious why wouldn't I subtract from those numbers because the brakes are pushing the rims out a 1/4"?
That’s right by increasing the backspacing the wheel stays where it would be without the brake offset.

Here’s an entertaining little tool for playing with backspacing, offsets, width etc.

https://rimsntires.com/specspro.jsp

Don

1969 Camaro LSA 6L90E AME subframe and IRS
1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
1959 El Camino project
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post #8 of 22 (permalink) Old Feb 8th, 19, 05:20 PM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

Thanks!!!! I like it as it give me visual idea of what I'm looking at.
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post #9 of 22 (permalink) Old Feb 11th, 19, 03:05 PM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

Still trying to find AR 200s rims for a 235/60r15 front......LOL

I think I found a set of 15x7 with 4.75" backspace & 19mm offset. Now if I subtract my front disc brakes, that would give me 4.5" backspace (I think). Now where does the 19mm offset play into this?

I also found 17x8's with 4.75" backspace with a +6mm offset that I thought about using on all four corners with 235/45R17 front and 255/50R17 rears....if I strike out on the 15" tires.

I seem to remember reading +6mm offset is good for 1st gen camaros, what about 19mm?
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post #10 of 22 (permalink) Old Feb 11th, 19, 03:41 PM
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Re: Backspacing when adding Wilwood front disc brakes

Offset is just a different way of specifying backspacing. Instead of measuring from the back face to the wheel mounting surface it specifies the wheel mounting surface offset from the center of the wheel. The tool I showed you lets you convert from backspacing to offset and vice versa.

Don

1969 Camaro LSA 6L90E AME subframe and IRS
1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
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post #11 of 22 (permalink) Old Feb 11th, 19, 03:56 PM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

OK. I thought backspacing and offset were similar but different.....

So by having a 4.75" backspacing on the rim, less the ~.25" the brakes move the rim out, this would give me a ~4.5" backspace on the car; whereas if I still had the drums on it, I would have the 4.75" backspace? Maybe....LOL

Rim specs:

WHEEL DIAMETER: 15 in.
COLOR: Gray
FINISH: Machined
BOLT PATTERN: 5x120.7 mm
OFFSET: 19 mm
WHEEL SIZE: 15x7
MATERIAL: Aluminum
MARKETING COLOR: Machined Black
OEM #: VN402576147
BACKSPACING: 4.75 in.

Calculator:

Wheel size: 15x7 ET 19
BackSpace: 120 mm (4.7'')
Rim Lip: 40 mm (1.6'') wider
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post #12 of 22 (permalink) Old Feb 13th, 19, 12:42 AM
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Re: Backspacing when adding Wilwood front disc brakes

Will the wilwood caliphers fit with 15” rims
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post #13 of 22 (permalink) Old Feb 13th, 19, 03:42 AM
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Re: Backspacing when adding Wilwood front disc brakes

For a 15x7 wheel 4 1/2” bs.

You could go 4 3/4” bs and if too close to subframe you can move it out with 1/8” - 1/4” spacers.

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post #14 of 22 (permalink) Old Feb 13th, 19, 05:55 AM Thread Starter
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Re: Backspacing when adding Wilwood front disc brakes

The Wilwoods would fit the 15" rims. They move the width out .19" (part # 140-13202)

My choice of 200s rims & back spacing's:

(for 15", I' wanting to use Mickey Thompson Street Radials RWL in 235/60R15 & 255/60R15)

Part # Size Offset Backspacing


AMRAC-VN402576137 15x7 -6 3.76
AMRAC-VN402576140 15x7 0 4.00

AMRAC-VN402586137 15x8 -19 3.75
AMRAC-VN402586140 15x8 -13 3.99
AMRAC-VN402586142 15x8 -6 4.26
AMRAC-VN402586145 15x8 0 4.50
AMRAC-VN402586147 15x8 6 4.74
AMRAC-VN402586150 15x8 13 5.01


My 17" choices are (would be probably go with Nitto 235/45R17 0r 245/45R17 in the front and 255/50R17 rears):

AMRAC-VN402776135 17x7 -13 3.49
AMRAC-VN402776140 17x7 0 4.00

AMRAC-VN402786140 17x8 -13 3.99
AMRAC-VN402786145 17x8 0 4.50
AMRAC-VN402786147 17x8 6 4.74
AMRAC-VN402786150 17x8 13 5.01
AMRAC-VN402786152 17x8 19 5.25

AMRAC-VN4027956155 17x9.5 6 5.49
AMRAC-VN4027956160 17x9.5 19 6.00
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post #15 of 22 (permalink) Old Feb 13th, 19, 07:15 AM
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Re: Backspacing when adding Wilwood front disc brakes

Quote:
Originally Posted by bob15 View Post
The Wilwoods would fit the 15" rims. They move the width out .19" (part # 140-13202)

My choice of 200s rims & back spacing's:

(for 15", I' wanting to use Mickey Thompson Street Radials RWL in 235/60R15 & 255/60R15)

Part # Size Offset Backspacing


AMRAC-VN402576137 15x7 -6 3.76
AMRAC-VN402576140 15x7 0 4.00

AMRAC-VN402586137 15x8 -19 3.75
AMRAC-VN402586140 15x8 -13 3.99
AMRAC-VN402586142 15x8 -6 4.26
AMRAC-VN402586145 15x8 0 4.50
AMRAC-VN402586147 15x8 6 4.74
AMRAC-VN402586150 15x8 13 5.01


My 17" choices are (would be probably go with Nitto 235/45R17 0r 245/45R17 in the front and 255/50R17 rears):

AMRAC-VN402776135 17x7 -13 3.49
AMRAC-VN402776140 17x7 0 4.00

AMRAC-VN402786140 17x8 -13 3.99
AMRAC-VN402786145 17x8 0 4.50
AMRAC-VN402786147 17x8 6 4.74
AMRAC-VN402786150 17x8 13 5.01
AMRAC-VN402786152 17x8 19 5.25

AMRAC-VN4027956155 17x9.5 6 5.49
AMRAC-VN4027956160 17x9.5 19 6.00
I gave you the exact backspacing requirements above. Are you hoping for some kind of miracle intervention to allow you to use wheels with considerably less backspacing?

Don

1969 Camaro LSA 6L90E AME subframe and IRS
1969 Camaro vert LS3 4L65E Ridetech level 2 - sold
1959 El Camino project
1969 Mustang Sportsroof project
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