New wheel backspacing - Team Camaro Tech
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post #1 of 11 (permalink) Old Apr 18th, 11, 07:32 PM Thread Starter
Alex
 
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New wheel backspacing

Greetings everybody. This is actually my official first post as I am a new member as of today. I've got a 69 camaro that I've fully restored over the last 8 years with a 526 hp/518 ft lbs torque 400 sbc. I'm about to get this baby on the road for my marriage as I just completed my second year tour to Iraq. Anyway, I just want to ensure I get the final touches correct to finish it out well. I understand how to measure backspacing on the wheel, though I'm not confident on how to measure bs for what is needed on a newly installed axle, WITHOUT the wheel. The camaro has disc brakes all around and am in need of some assistance of how to ensure the proper bs is ordered to whomever I purchase them from. In the front, I'm looking to run 17X7 wheels with 235/45/17 tires. In the rear I'm looking at a 17X8 wheel with 255/45/17 tires.
My questions are:
1. How do I properly gather the correct backspace to order that particular wheel? The axle is installed though vehicle is still on stands.

2. What is the power rating on a cast wheel, (american racing torq thrust II) as compared to a 2 piece alloy wheel?

I have a 2" front coil drop. I see others that have the drop, uses a lot of the 235's for the front. If there's any suggestions, warnings or additional info to research that is recommended, it would be really appreciated!
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post #2 of 11 (permalink) Old Apr 18th, 11, 07:56 PM
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Re: New wheel backspacing

Welcome to Tram Camaro and thank you for your service.
Summit has a wheel fitment tool tnat can help you nail it.
http://www.summitracing.com/parts/PHP-01201/

68 302 M20 - 85 IROC Z
The older I get the faster I was.
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post #3 of 11 (permalink) Old Apr 18th, 11, 10:45 PM
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Re: New wheel backspacing

[QUOTE=Army_ordnance83;1566527]In the front, I'm looking to run 17X7 wheels with 235/45/17 tires. In the rear I'm looking at a 17X8 wheel with 255/45/17 tires.
QUOTE]

Alex,

On the rear an 8" wide wheel should have 4.5" backspace if the wheelwell is stock.
On the front I'm not as sure but I think it's 3.75" on a 7" rim.

I'm sure someone else will weigh in. Welcome and we'd love to see some pics !!
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post #4 of 11 (permalink) Old Apr 19th, 11, 02:43 AM
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Re: New wheel backspacing

Any mods to the wheelwells ?

What size wheels would you like to run (15,16,17,18 ?)

Lots of combos here and one or more should work

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #5 of 11 (permalink) Old Apr 19th, 11, 10:24 AM Thread Starter
Alex
 
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Re: New wheel backspacing

Appreciate all the good info and links! I was sure to save those to my favorites. Doug-I'm looking at a 17" wheel for fronts and rears. I see many guys are running a 235/45/17 tire front and 255/45/17 for the rears while they have a 2" coil drop up front like me. I was mainly concerned about the correct backspace. There has been no modifications to the wheel well or frame rail. I think that Ms. Nashville Beth got me straightened out. I would think that most competent wheel dealers would be an expert on this though I was looking for some suggestions and insight on the matter before I talked to them. Thanks again!
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post #6 of 11 (permalink) Old Apr 19th, 11, 10:51 AM
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Re: New wheel backspacing

It sounds like you're home to stay, thanks for your service and congrats on the upcoming marriage.

Look at this link, lots of combo's; https://www.camaros.net/forums/showthread.php?t=153274

I'm running the exact same size tires but on wider wheels and I have 2" drop springs in front. Here's my car info clipped from that thread... Note my wheels and tires are about as centered in the wells as you can get them.

Quote:
Originally Posted by DjD View Post
Budnik Anvil 5's

  • Hotchkis drop springs front (2") and rear (1.5") Koni shocks
  • Front: 17x8 (4.75" backspacing) Nitto 555's 235/45-17
  • Back: 17x9.5 (5.5" backspacing) Nitto 555's 255/45-17
  • 4 wheel manual disc's (C5 front & C4 rear)



"White Wonder"

Car can handle a full trunk and 4 adults with only very slight scrubbing on the inner rear fender wells when going through a steep driveway at an angle to avoid scraping.
A 4.25 bs up front on a 7" and 4.75 ba on the 8" out back would place your tires where mine are even though mounted on narrower wheels.

Use the charts and dwgs on this link to compare the wheel size you are interested in to mine. If I did the math wrong you'll catch it... https://www.rsracing.com/tech-wheel.html

...Dennis

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post #7 of 11 (permalink) Old Apr 19th, 11, 11:25 AM Thread Starter
Alex
 
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Re: New wheel backspacing

Thank you DjD. I did go through the pics of all the combos and yours did stand out on on well they are tucked inside the wheel wells. I think that 17" looks very good on that chassis and will be ordering mine within the next day or 2!
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post #8 of 11 (permalink) Old Apr 19th, 11, 11:37 AM Thread Starter
Alex
 
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Re: New wheel backspacing

DjD-Did you run those wheels with a 0" offset?
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post #9 of 11 (permalink) Old Apr 19th, 11, 12:10 PM
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Re: New wheel backspacing

Quote:
Originally Posted by Army_ordnance83 View Post
DjD-Did you run those wheels with a 0" offset?
Offset and backspace are essentially the same thing.

In simplest terms, if the backspace is equal to half the wheel width then you have a 0 offset.

If the backspace is less than half the wheel width of the wheel, then you have a negative offset.

If the backspace is more than half the width of the wheel, then you have a positive offset.
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post #10 of 11 (permalink) Old Apr 19th, 11, 12:46 PM
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Re: New wheel backspacing

Quote:
Originally Posted by Army_ordnance83 View Post
DjD-Did you run those wheels with a 0" offset?
Offset measures from the dead center of the wheel to the wheels mounting surface (pad). Any width wheel with "0" (zero) offset is going to have the pad smack on the centerline dividing the wheel width in half. Look at this dwg to see that and also notice where the width of the wheel is measured from. It's on the inside of the lip or rim of the wheel. Then note where the back spacing is measured from, the outside of the wheels rim or lip.



Now use this chart to see what backspacing equals what offset. Note my 9.5" wide wheel with 5.5" bs has a positive 6mm offset.


For your 8" wide tire to have a positive 6mm offset (not on the chart but 0 and 12 are so split the difference) you need a 4.75" bs.

Offset and backspacing are as said just about the same thing in that if you understand them both they can help you fit a wheel on a car and get best fit.

...Dennis

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post #11 of 11 (permalink) Old Apr 19th, 11, 08:19 PM Thread Starter
Alex
 
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Re: New wheel backspacing

Appreciate the info gentlemen. That chart is helpful. There is a huge amount of information on this site and obvious experience as well. As I've been a heavy wheel diesel mechanic for the last 8 years, I hope that I can contribute to this site while I build on my knowledge!
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