what is the correct backspacing for a 1968 with 15''x7" rally wheels ? - Team Camaro Tech
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post #1 of 10 (permalink) Old Feb 22nd, 11, 08:39 PM Thread Starter
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rohan
 
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what is the correct backspacing for a 1968 with 15''x7" rally wheels ?

hi guys,
hope you can help me.
i have a 1968 camaro with 15" x 7" rally wheels and firestone firehawke tyres p215/65r15. i have been told these wheels and tyres should be fine, but when i hit a dip in the road my front tyres rub / scrape against the wheel arch trim.
i am wondering if the back spacing is incorrect and would like to know what it should be ? also the trim rings sit about 20mm out from the the wheel centre. should the trim ring be hard up against the centre of the wheel ? any help would be appreciated.
thanks heaps,
cheers guys,
rohan
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post #2 of 10 (permalink) Old Feb 22nd, 11, 08:52 PM
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Bobby
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

What is the backspace on your rims?

I have 15x7 with 215/65 tires w/ 4.25" backspace on the front of a 67, haven't driven it too much with this set up because of the weather but so far no rubbing.

Can't comment on the trim rings, sorry.

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post #3 of 10 (permalink) Old Feb 22nd, 11, 09:07 PM Thread Starter
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rohan
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

thanks for that. i dont know what backspacing i have at the moment. i have just started looking into it. just thought i would throw it out there and see what comes back. i got 4.25" on crg also, so thats good confirmation.
cheers,
rohan

Last edited by malley67; Feb 22nd, 11 at 09:47 PM.
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post #4 of 10 (permalink) Old Feb 22nd, 11, 09:38 PM
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Steiner
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

4.25" will clear even with a 235 tire. If they are a GM rally rim, you can look for a code stamped by the valve stem and decipher it here:
http://forums.corvetteforum.com/1575168356-post7.html

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post #5 of 10 (permalink) Old Feb 23rd, 11, 01:42 AM
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Garth
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

Rohan, There's a gap, not sure how much exactly, between the trim ring and wheel center on a 4.25 bs, 15 x 7. I seen your car pictured at CRG.....http://camaros.org/images/pages/cars...alley-Full.jpg

They look like 4.25 bs rims. Sets pretty low... I kinda think it's suspension related ?

Front disc brakes ?...aftermarket or GM ??

  • '68 RS, AA, 749, L30, M(uncie)20 (originally a 3spd), 15yr backburner resto........

Last edited by Garfields Maro; Feb 23rd, 11 at 01:53 AM.
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post #6 of 10 (permalink) Old Feb 23rd, 11, 03:51 AM
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

Also, what are the alignment specs? If you don't have any negative camber you might get a rub when bottoming out.

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post #7 of 10 (permalink) Old Feb 23rd, 11, 03:44 PM Thread Starter
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rohan
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

hi rick,
i dont know what the alignment specs are ?
how do i find out this ?
thanks heaps,
rohan
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post #8 of 10 (permalink) Old Feb 23rd, 11, 03:51 PM Thread Starter
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rohan
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

hi garth,
yes, that is my car on crg at the moment.
if it is suspension why would the tyres hit the wheel arch mouldings ? shouldnt the tyres go up and down without hitting the wheel arch trim. thats why i am leaning towards backspacing and tyres and this stage. i have front disc brakes stock and new calipers from classic industries. also what does bs mean next to 4.25" ? thanks heaps for your help. i really appreciate it.
cheers,
rohan
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post #9 of 10 (permalink) Old Feb 23rd, 11, 04:22 PM
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Bobby
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

Hi Rohan,

bs is acronym for backspace.

Regarding alignment specs, a little extra negative camber will tilt the top of the wheel in a bit as the suspension travels upward possibly enough to avoid rubbing, if I understand it correctly

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post #10 of 10 (permalink) Old Feb 24th, 11, 01:26 AM
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Garth
 
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Re: what is the correct backspacing for a 1968 with 15''x7" rally whee

Thanks Bobby, for clearing that up...no bs intended.

Rohan, you're on the right track...for some reason, the tires are too far outboard. I'm just going by the fact that 215/65 15 on 15x7, 4.25 b/s is a popular choice and I've never heard of any clearance issues. You need to verify the b/s, either by measuring or looking for a code by the valve stem, as Steiner mentioned. Factory disc brakes do move the wheel out about 1/4" compared to drum. I dunno about aftermarket set-ups...could be more or less. I wonder about the actual dimensions of the Firestone compared to T/A's ? Could be wider or taller ? If not the tire/wheel set-up...not the disc brakes, it would have to be something associated with the suspension, I'd think. Could be something as simple as a slight camber adjustment ??

Just food for thought......

  • '68 RS, AA, 749, L30, M(uncie)20 (originally a 3spd), 15yr backburner resto........

Last edited by Garfields Maro; Feb 24th, 11 at 01:37 AM.
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