17x8 wheel backspacing is there a definitive answer? - Team Camaro Tech
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post #1 of 14 (permalink) Old Mar 13th, 14, 06:43 AM Thread Starter
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17x8 wheel backspacing is there a definitive answer?

I've spent a couple of hours reading posts here and on other forums and still haven't found a consistent answer.

Some people say a 17x8" wheel with 4.5 back spacing will likely rub if used on the front and that a 4.75 is required. Some say the 4.5 back spacing works fine??

Some say a 235-45-17 is the biggest front tire that won't rub with stock suspension, others say a 245 works??

I'm ready to order wheels, I found a good deal on a set of 17x8s with 4.5 backspacing but I'm hesitant to buy them after searching the forums…..so, before I make a mistake, can I get some input from people that have used 17x8s with 4.5 back spacing on a 67-68 with stock front suspension (factory disc brakes)?? What tires did you use and did you have any clearance issues??

Thanks
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post #2 of 14 (permalink) Old Mar 13th, 14, 07:47 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

4.75" BS is ideal on an 8" rim. 4.5" will sit 1/4 closer to the fender/wheel well. 235's have a better chance of fitting than 245's.

The further you get away from ideal backspacing, the more likely you're going to have rubbing.

I have 5" BS on my 18x8's with a 245/40/18 and they rub on the subframe at full lock.


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post #3 of 14 (permalink) Old Mar 13th, 14, 08:06 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

every car is different. There are ideal measurements as Brent has posted above, but there's no telling how your car sits after 45+ years. There's quite a bit of adjustment in the subframe and if its shifted over .25" can make a big difference.

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post #4 of 14 (permalink) Old Mar 13th, 14, 08:16 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

The reason there is no single definitive or constant answer is because the best fitting wheels for a 1st gen Camaro are not the best fitting wheels for other cars and that typically means ordering custom wheels or settling for close because the wheels that are being produced and stocked by tire shops have to fit more than one make and model. Custom sized wheels start at about $400 each and go up from there. Mass produced wheels start around $100 each...

The magic number for the 1st gen is a +6 offset. What ever size wheel/tire combo you run, if the wheels have a +6 offset they will just about be perfectly centered between the inner and outer fender and you can run the widest tire possible this way. Of course this is not full proof on 45 year old cars where who knows what could have happened to the car over it's lifetime but it's the best place to start.

Years and years ago folks like Mark Stielow and Kyle Tucker declared the widest tires you could run on a '69 Camaro without major modifications were 245/45/17 in front on 8" wide wheels with a 4.75" back spacing (which is a +6 offset), and a 275/40/17 in the back on a 9.5" wide wheel with a 5.5" backspacing (again +6 offset). If you race back in time to the '69 Z/28 it came with 15x7" wheels with 4.25" backspacing and that too is a +6 offset.

If you push beyond the dimensions of the 245/45/17 and a 275/40/17 tire you'll require mini tubs in the rear and inner fender mods in the front.

There are other factors that come to play here, your suspension needs to be in as new condition, your body bushings have to be in as new condition and the cars alignment has to be just right to run these sizes! Then comes the dimensions and design of the '67/'68 vs the '69. My understanding is the '69 has a deeper wheel well (distance from inner fender to outer) than the '67/'68. The '69 doesn't have round wheel openings though so on the '69 the tires can't stick out any. Often the fender lip needs to be rolled or trimmed to fit these tires and turning radius has to be limited to keep the tires from scuffing the inner fender in the front in full lock turns.

The list goes on, you can find dozens of aftermarket disc brake kits and that can change the location of the hub some and that also messes with wheel fit. Don't forget the overall structure of the car, my convertible's 255/45/17's would scuff the inner fender well in the rear going diagonally through steep driveways to avoid spoiler scraping until I put a frame brace between the rear frame rails. I actually think I might be able to run 275/40's now...

Sorry this is so long but there is a lot to all this, not every Camaro owner uses his 1st gen in the same way. I know guys that have never had anyone in the back seat, never loaded their trunk down with stuff and never driven their car more than on and off the trailer or to the local drive-in for a burger. They may be running bigger tires/wheels than I have mentioned with reports of no rubbing. Just way too many variables for the answers to be cut and dry...

Look at this chart, pick a wheel width and backspacing that matches the +6 offset and if you'll be on the road to fitting your tires and wheels...



Here's the difference in offset and backspacing,




...Dennis

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post #5 of 14 (permalink) Old Mar 13th, 14, 08:24 AM Thread Starter
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Re: 17x8 wheel backspacing is there a definitive answer?

Thanks for the replies, I know what backspacing is, and how it relates to the position of the tire/wheel. I am also aware that each car can be a bit different. That's why I specifically asked for input from those who have actually used 17x8" wheels with 4.5" backspacing on a 67-68 with stock suspension…….I understand that, just because something worked on car "A" does not mean it will work on car "B"…….however, if several people respond and say it worked on their car, then odds are good it will work on mine……same is true if it didn't work.
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post #6 of 14 (permalink) Old Mar 13th, 14, 08:27 AM Thread Starter
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Re: 17x8 wheel backspacing is there a definitive answer?

DJD

Looks like you posted while I was typing out a response to earlier posts………thanks for the info you posted, it is very helpful.


When it gets back on the road, my car will have new poly subframe bushings and a completely rebuilt front suspension with stock type replacement parts (MOOG), including new front springs. I also have access to a four wheel alignment machine and someone who knows how to use it well…….so, a custom alignment is in the works too and it's not a big deal to try more than one set up if necessary.
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post #7 of 14 (permalink) Old Mar 13th, 14, 08:39 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

Quote:
Originally Posted by DjD View Post
The reason there is no single definitive or constant answer is because the best fitting wheels for a 1st gen Camaro are not the best fitting wheels for other cars and that typically means ordering custom wheels or settling for close because the wheels that are being produced and stocked by tire shops have to fit more than one make and model. Custom sized wheels start at about $400 each and go up from there. Mass produced wheels start around $100 each...

The magic number for the 1st gen is a +6 offset. What ever size wheel/tire combo you run, if the wheels have a +6 offset they will just about be perfectly centered between the inner and outer fender and you can run the widest tire possible this way. Of course this is not full proof on 45 year old cars where who knows what could have happened to the car over it's lifetime but it's the best place to start.

Years and years ago folks like Mark Stielow and Kyle Tucker declared the widest tires you could run on a '69 Camaro without major modifications were 245/45/17 in front on 8" wide wheels with a 4.75" back spacing (which is a +6 offset), and a 275/40/17 in the back on a 9.5" wide wheel with a 5.5" backspacing (again +6 offset). If you race back in time to the '69 Z/28 it came with 15x7" wheels with 4.25" backspacing and that too is a +6 offset.

If you push beyond the dimensions of the 245/45/17 and a 275/40/17 tire you'll require mini tubs in the rear and inner fender mods in the front.

There are other factors that come to play here, your suspension needs to be in as new condition, your body bushings have to be in as new condition and the cars alignment has to be just right to run these sizes! Then comes the dimensions and design of the '67/'68 vs the '69. My understanding is the '69 has a deeper wheel well (distance from inner fender to outer) than the '67/'68. The '69 doesn't have round wheel openings though so on the '69 the tires can't stick out any. Often the fender lip needs to be rolled or trimmed to fit these tires and turning radius has to be limited to keep the tires from scuffing the inner fender in the front in full lock turns.

The list goes on, you can find dozens of aftermarket disc brake kits and that can change the location of the hub some and that also messes with wheel fit. Don't forget the overall structure of the car, my convertible's 255/45/17's would scuff the inner fender well in the rear going diagonally through steep driveways to avoid spoiler scraping until I put a frame brace between the rear frame rails. I actually think I might be able to run 275/40's now...

Sorry this is so long but there is a lot to all this, not every Camaro owner uses his 1st gen in the same way. I know guys that have never had anyone in the back seat, never loaded their trunk down with stuff and never driven their car more than on and off the trailer or to the local drive-in for a burger. They may be running bigger tires/wheels than I have mentioned with reports of no rubbing. Just way too many variables for the answers to be cut and dry...

Look at this chart, pick a wheel width and backspacing that matches the +6 offset and if you'll be on the road to fitting your tires and wheels...



Here's the difference in offset and backspacing,



What an excellent explanation.
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post #8 of 14 (permalink) Old Mar 13th, 14, 08:44 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

Quote:
Originally Posted by GonHuntin View Post
Thanks for the replies, I know what backspacing is, and how it relates to the position of the tire/wheel. I am also aware that each car can be a bit different. That's why I specifically asked for input from those who have actually used 17x8" wheels with 4.5" backspacing on a 67-68 with stock suspension…….I understand that, just because something worked on car "A" does not mean it will work on car "B"…….however, if several people respond and say it worked on their car, then odds are good it will work on mine……same is true if it didn't work.
Yeah, sorry. I was just trying to provide an example where I thought I could get away with stuffing the biggest tire possible on a wheel that didn't have the ideal offset. I was advised by the company that I bought the wheel/tire combo from that they had done hundreds of setups exactly like mine with no problems. Luckily I have steering stops built into my LCA's so I can keep them from scrubbing.

One thing to consider is that you can always add a high quality spacer if you have too much BS, but not much you can do other than roll the fender (or go with a smaller tire) if you have too little.


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post #9 of 14 (permalink) Old Mar 13th, 14, 09:22 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

Quote:
Originally Posted by DjD View Post
The reason there is no single definitive or constant answer is because the best fitting wheels for a 1st gen Camaro are not the best fitting wheels for other cars and that typically means ordering custom wheels or settling for close because the wheels that are being produced and stocked by tire shops have to fit more than one make and model. Custom sized wheels start at about $400 each and go up from there. Mass produced wheels start around $100 each...

The magic number for the 1st gen is a +6 offset. What ever size wheel/tire combo you run, if the wheels have a +6 offset they will just about be perfectly centered between the inner and outer fender and you can run the widest tire possible this way. Of course this is not full proof on 45 year old cars where who knows what could have happened to the car over it's lifetime but it's the best place to start.

Years and years ago folks like Mark Stielow and Kyle Tucker declared the widest tires you could run on a '69 Camaro without major modifications were 245/45/17 in front on 8" wide wheels with a 4.75" back spacing (which is a +6 offset), and a 275/40/17 in the back on a 9.5" wide wheel with a 5.5" backspacing (again +6 offset). If you race back in time to the '69 Z/28 it came with 15x7" wheels with 4.25" backspacing and that too is a +6 offset.

If you push beyond the dimensions of the 245/45/17 and a 275/40/17 tire you'll require mini tubs in the rear and inner fender mods in the front.

There are other factors that come to play here, your suspension needs to be in as new condition, your body bushings have to be in as new condition and the cars alignment has to be just right to run these sizes! Then comes the dimensions and design of the '67/'68 vs the '69. My understanding is the '69 has a deeper wheel well (distance from inner fender to outer) than the '67/'68. The '69 doesn't have round wheel openings though so on the '69 the tires can't stick out any. Often the fender lip needs to be rolled or trimmed to fit these tires and turning radius has to be limited to keep the tires from scuffing the inner fender in the front in full lock turns.

The list goes on, you can find dozens of aftermarket disc brake kits and that can change the location of the hub some and that also messes with wheel fit. Don't forget the overall structure of the car, my convertible's 255/45/17's would scuff the inner fender well in the rear going diagonally through steep driveways to avoid spoiler scraping until I put a frame brace between the rear frame rails. I actually think I might be able to run 275/40's now...

Sorry this is so long but there is a lot to all this, not every Camaro owner uses his 1st gen in the same way. I know guys that have never had anyone in the back seat, never loaded their trunk down with stuff and never driven their car more than on and off the trailer or to the local drive-in for a burger. They may be running bigger tires/wheels than I have mentioned with reports of no rubbing. Just way too many variables for the answers to be cut and dry...

Look at this chart, pick a wheel width and backspacing that matches the +6 offset and if you'll be on the road to fitting your tires and wheels...



Here's the difference in offset and backspacing,



Can you add this post to the start of the stickies for the three years? It would have REALLY came in handy when I was figuring out my wheels.

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post #10 of 14 (permalink) Old Mar 13th, 14, 09:40 AM Thread Starter
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Re: 17x8 wheel backspacing is there a definitive answer?

I agree……this post would have saved me a bunch of searching!
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post #11 of 14 (permalink) Old Mar 14th, 14, 04:38 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

I took my car to a local tire store and tried the wheel/tire combo on for size, like trying on a pair of jeans. I told the guy what I was doing and he had no problem. I paid him for his time. Then decided to keep the Vette rally wheels after all!!!!
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post #12 of 14 (permalink) Old Mar 14th, 14, 06:57 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

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Originally Posted by The Camaro Guy View Post
I took my car to a local tire store and tried the wheel/tire combo on for size, like trying on a pair of jeans. I told the guy what I was doing and he had no problem. I paid him for his time. Then decided to keep the Vette rally wheels after all!!!!
That's pretty cool of them. The tire stores around here said that once I mounted the tires, I owned them.


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post #13 of 14 (permalink) Old Mar 14th, 14, 10:27 PM
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Re: 17x8 wheel backspacing is there a definitive answer?

As confirmed by the chart, for my 69 Vert, for the FRONT I should get 17 x 8 wheels with 4.75" BS and mount tires of 235/45/17 and on the REAR 17 x 9.5 wheels with 5.5" BS and mount tires of 255/40/17. I have DISC brakes on the front with coil overs so I can adjust my ride height accordingly and DISC brakes on the rear as well with stock springs and rear-end. Will I be good to go?

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post #14 of 14 (permalink) Old Mar 15th, 14, 06:39 AM
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Re: 17x8 wheel backspacing is there a definitive answer?

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Originally Posted by camaromaniac View Post
As confirmed by the chart, for my 69 Vert, for the FRONT I should get 17 x 8 wheels with 4.75" BS and mount tires of 235/45/17 and on the REAR 17 x 9.5 wheels with 5.5" BS and mount tires of 255/40/17. I have DISC brakes on the front with coil overs so I can adjust my ride height accordingly and DISC brakes on the rear as well with stock springs and rear-end. Will I be good to go?
That should be a safe combo. Back spacing and tire size look good.

If DjD hadn't just said he had scuffing with the 255/45/17's in his vert, I might suggest those. I like just a little more sidewall on the rear tire than on the front.

With a 235/45/17 and 255/40/17 they'll be almost identical, but the fronts will be just a little more than 1/8" taller than the rear. It's nitpicking and probably not discernable with the naked eye.


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