running 5" backspacing on the front ? - Team Camaro Tech
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post #1 of 12 (permalink) Old Jul 5th, 10, 06:29 AM Thread Starter
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Terry
 
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running 5" backspacing on the front ?

Hi guys would their be any problems running a 5" backspacing on the front , came across some ADR sterling wheels 18x8.5 with 38 offset , doing the math it should be 4.9 backspacing . currently stock springs and drum brakes , but have 2" drop springs coming shortly along with a disc brake conversion , just wondering if their will be fitment issues or other reasons ,looks like the rims where on a bmw and then a 98 camaro . tire size is 255 35 18 , Thanks for any help . Terry
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post #2 of 12 (permalink) Old Jul 5th, 10, 07:45 AM
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Re: running 5" backspacing on the front ?

This gets a bit complicated but if you understand the width of the rim is measured from the inside of the rim lip (where the tire bead mounts) and the backspacing is to the outside of the rim lip it will make more sense.

An 8"wide wheel with 0 offset has a 4.5" backspacing (reference www.rsracing.com/tech-wheel.html) and your 8.5" wheel with 0 offset will have 4.75" backspacing. Add the 38mm offset (1.5") and an 8" wheel has 6" backspacing and the 8.5" wheel has 6.25" backspacing.

An 8" wheel with 4.75" BS is about the most you can put on the front of a '69 and you'll want a tire that is about 25-26" tall with no more than a 9.6" section width. The 255/35 is 25" tall but has a 10.2" section width...

...Dennis

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post #3 of 12 (permalink) Old Jul 5th, 10, 09:36 AM Thread Starter
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Re: running 5" backspacing on the front ?

OK but is this wrong .Offset to Backspace conversion:
Take offset, divide by 25.4, then add the overall rim width divided by 2

or are my math skills shot . so 38 offset divided by 25.4 = 1.49 + 8.5 = 9.99 divide by 2 = 4.9 ?
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post #4 of 12 (permalink) Old Jul 5th, 10, 09:51 AM
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Re: running 5" backspacing on the front ?

Your math skills are fine... Offset is from the pad surface to the wheel center line. Back spacing is from the pad to outer lip of the wheels rim. Wheel width is measured from inside of the rim lips (where the tire bead sits). Look at this drawing (from the link I provided in the 1st reply) and the dimensions...



A wheel width of 8" will measure 9" over all because each lip is 1/2".

...Dennis

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post #5 of 12 (permalink) Old Jul 5th, 10, 10:02 AM
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Re: running 5" backspacing on the front ?

Some great info there Dennis...as always.

Short answer is yes,it'll probably work and I know guys who run that combo,keep in mind lock-to-lock it'll probably certainly rub badly there on the inside.

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post #6 of 12 (permalink) Old Jul 5th, 10, 10:19 AM
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Re: running 5" backspacing on the front ?

Quote:
Originally Posted by musclecarjohn View Post
Some great info there Dennis...as always.

Short answer is yes,it'll probably work and I know guys who run that combo,keep in mind lock-to-lock it'll probably certainly rub badly there on the inside.
Thanks John,

Who do you know running 6.25" back spacing on the front of a '69 or other 1st gen? Terry are we talking a '69 here?

...Dennis

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post #7 of 12 (permalink) Old Jul 5th, 10, 10:50 AM
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Re: running 5" backspacing on the front ?

Quote:
Originally Posted by DjD View Post

Who do you know running 6.25" back spacing on the front of a '69 or other 1st gen? Terry are we talking a '69 here?
No one I know of,I was referring to 5" of b/s...

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post #8 of 12 (permalink) Old Jul 5th, 10, 11:17 AM Thread Starter
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Re: running 5" backspacing on the front ?

Ok I get it , so not possible with out using a spacer , which is more than I want to deal with , Thanks Dennis , this was just another of my craigslist dreams shot down , They sure looked sweet though.
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post #9 of 12 (permalink) Old Jul 6th, 10, 08:10 PM
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Re: running 5" backspacing on the front ?

I'm running a 15x8 wheel with 5" of backspace on the front and it works on my 68. I didn't see the year car your asking about in the post.

When I backup and turn the wheel all the way, I do get a rub somewhere, but I really need to have the wheel turned all the way for it to happen.

I am running tubular upper arms. The wheel lip just barely clears the upper ball joint, but that's not a big deal because those two things move in relation to each other. I'm not sure if the stock uppers would have some metal that would interfere though.

Wouldn't an 18" wheel give you a bit more space to work with since the wheel opening would probably give you more clearance over the ball joint?

Dan

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post #10 of 12 (permalink) Old Jul 11th, 10, 10:44 PM
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Re: running 5" backspacing on the front ?

Im running 5" bs on my 18's and they fit perfect.

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post #11 of 12 (permalink) Old Jul 21st, 10, 10:23 PM
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Re: running 5" backspacing on the front ?

[IMG][/IMG]
17/8 5in backspace no rub lock to lock


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post #12 of 12 (permalink) Old Jul 22nd, 10, 08:40 AM
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Re: running 5" backspacing on the front ?

Guys the wheels he was talking about don't have 5" back spacing like the title says, they are 6.25" back spacing...

...Dennis

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