I need some consensus on back spacing - Team Camaro Tech
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post #1 of 14 (permalink) Old Oct 8th, 07, 07:12 PM Thread Starter
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Kevin
 
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I need some consensus on back spacing

While rethinking the whole wheel situation, since the Boyd Coddington's I received were defective (and sent back), I've come to the conclusion I want to stay with Rallys. But...mine are 15x7's all around and I'm going to buy 15x8's for all four corners.

So, I'm trying to figure out back spacing for 15x8's. I can get them with 4", 4.5" & 5" in the 15x8s. I know that with the 17"x8 wheels the BS for front was 4.75, ideally.....and 5.5" for the rear using 17x9.5. But these will be 15x8 and the dynamics change.

I've looked at the entire sticky thread w/pics several times. It appears the few members who run 15x8's use 4.5 bs in a few cases, but some look like the tires stick out too far from the car. I guess I'm looking for 4.5" or 5"...or would 4.75 be ideal? I have a 69' w/disc fronts and drum rears...and want to run 235/255 combo. What back spacing would you suggest for front & back for 15x8's all around?

Learning & Relearning about the cars I grew up with.
69' - Built 350, 750 Holley, Elgin E920P Cam, 283 PP Heads, Long Comp Headers, MSD, TKO-600, 12 Bolt Posi 3.73, Hotchkis Rear, Eibach Front w/Hotchkis Sway, SPC UCAs, 3rd Gen PS, AR TTII's. Still working on it.
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post #2 of 14 (permalink) Old Oct 8th, 07, 07:25 PM
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Re: I need some consensus on back spacing

From Chevyhiperformance.com

Front: 15 inch wheel, 3.75 backspace, 7.0in width, 225/55 tire
Rear : 15 inch wheel, 4.87 backspace, 8.5in width, 28X10.5 tire

I had on my camaro when I bought it 15" x 7" 3.5" Backspace Weld Draglites, they fit perfect all around, if they were 1" wider I would have wanted an additional 1/2" of backspace, thus keeping them centered. I was running a 295/50 mickey thompson indy profile H50-15 and it actually fit with the fender well lip rolled although it rubbed at some angles. I switched the tires out to Dunlop SP Sport A2 225/60R15 Front - Dunlop GT Qualifier T 255/60R15 Rear and they had no tire rub issues what so ever.
I would recommend a 4.5" backspace

1969 Camaro - GM 2003 Electron Blue
Beck Racing 383 cu in 465HP Engine - Sean Murphy Inductions Stage 2 Quadrajet
TCI Streetfighter 350 - 3.73:1 Posi 10 Bolt Rear - 12.6 sec qtr mile

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post #3 of 14 (permalink) Old Oct 8th, 07, 07:26 PM
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Re: I need some consensus on back spacing

Well...

First, you looked at the sticky, but did you catch this thread?

https://www.camaros.net/forums/showthread.php?t=116838

I have some pics of mine from a trial fit with 15 x 8 and 4 inch BS and the 255 you're looking at. I can either put pics of the front in that same thread, post them here, or send 'em to you direct.

15 x 7 up front is nice with 4.25 inch. My car is low, probably as low or lower than you've considered. With a 15 x 7 with 4 inch BS and a 215 65 15, the tires were really close to those inner fender bolts. Let me see what pics of the front I can find.

Eric
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!
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post #4 of 14 (permalink) Old Oct 8th, 07, 07:29 PM
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Re: I need some consensus on back spacing

Did you figure out if you are going to lower it after the new tires are on it?


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post #5 of 14 (permalink) Old Oct 8th, 07, 07:36 PM
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Re: I need some consensus on back spacing

Here's one shot of the 15 x 7 4 inch BS rallys. I had not corrected a slight positive camber issue when the photo was taken, but I wouldn't feel comfortable with less than 4, or with a 15 x 8 (another inch of rim width toward the fender lip? Not me )



More in this thread...

https://www.camaros.net/forums/showthread.php?t=107056

My Nitrous wheels up front are 15 x 7 with 4.75 BS, and with 215 60 15 no rubs anywhere.

Eric
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!
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post #6 of 14 (permalink) Old Oct 8th, 07, 08:11 PM Thread Starter
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Re: I need some consensus on back spacing

As always, you guys are awesome. Eric, yeah, I actually did see that thread the other day, but damned if I remembered it today. The only problem with that thread is that only 3 (I think) 69' owners posted. One of them didn't mention BS, and the other two mentioned 51x7 up front and 15x8 rear...or something like that. This one came the closest: https://www.camaros.net/forums/showpo...7&postcount=10

Having Fun, I'm intending on going the Hotchkis way (1907F/2407C), and will probably do this in the next 60 days.

As already stated, I have 15x7's all around. But since I'm not going to 17" wheels, I want less tire hangover front and rear, you know? This is what I'm currently running on 15x7's: Front-215/65/15 & Rear-255/60/15. This is what I'd like to run: Front- 235/60/15 & Rear- 255/60/15. (I realize I might have to go 225/60/15 for front, but hope not to have to)

It appears to me from what I've read and what you guys are saying (trying to pick out what I can ), that 4.5" might be ideal for the front, but 5" might be better than 4.5" bs for the rear? I can order these repros in either 4, 4.5 or 5" bs. I just want to get it right.

Learning & Relearning about the cars I grew up with.
69' - Built 350, 750 Holley, Elgin E920P Cam, 283 PP Heads, Long Comp Headers, MSD, TKO-600, 12 Bolt Posi 3.73, Hotchkis Rear, Eibach Front w/Hotchkis Sway, SPC UCAs, 3rd Gen PS, AR TTII's. Still working on it.
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post #7 of 14 (permalink) Old Oct 8th, 07, 08:33 PM
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Re: I need some consensus on back spacing

No, no, no, tire hangover is what you'll have by the time we work through this

I went back through some of your other threads looking for the pics of the car as it sits now, but the ones I saw were missing the photos. Anyway, have we ever figured out what the BS is on the rallys you have?

Just as a heads up if you didn't know, the "repro" rallys made by Wheel Vintiques and others are lug centric vs. the originals being hub centric. Lug centric puts all the load on the lug studs, and has been suspected as the source of some vibration issues. You can buy little rings to make them hub centric again, but I don't know how well they work. I ran into this when I was looking at rallys, and I am very anal about things like that, so I can tell you I wouldn't run anything but GM rallys or the Kelsey Hayes repros that Year One sells. Problem is then you are limited to factory BS.

5 inch BS on an 8 inch rim might allow you to use a Camaro trim ring vs. the rolled Vette rings, so that would be a plus. There's so much car to car variability, I'm not sure anyone will state that with 100% certainty that a 27 inch tall tire on a 15 x 8 inch rim with 5 inch BS will absolutely fit and not rub. 4.5 worked well on my car, but more would have meant I needed to move the dual exhaust hangers to try and adjust the tailpipes out of the way. The 4 inch of my Foose's isn't quite enough, but it was all they had in a 15 x 8.

Tell us what you mean by "tire hangover". Are they too far out, or do you think they are too bulgy on the rim?

Eric
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!
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post #8 of 14 (permalink) Old Oct 8th, 07, 08:51 PM Thread Starter
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Kevin
 
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Re: I need some consensus on back spacing

Quote:
Originally Posted by Eric Kammerer View Post
I went back through some of your other threads looking for the pics of the car as it sits now, but the ones I saw were missing the photos. Anyway, have we ever figured out what the BS is on the rallys you have?
No, I do not currently know what the BS is. I can measure it tomorrow. I can tell you that it looks like I have space in the back to add a wider wheel and tire. The front is a little dicier by eyeball.

Quote:
Originally Posted by eric Kammerer
Just as a heads up if you didn't know, the "repro" rallys made by Wheel Vintiques and others are lug centric vs. the originals being hub centric. Lug centric puts all the load on the lug studs, and has been suspected as the source of some vibration issues. You can buy little rings to make them hub centric again, but I don't know how well they work. I ran into this when I was looking at rallys, and I am very anal about things like that, so I can tell you I wouldn't run anything but GM rallys or the Kelsey Hayes repros that Year One sells. Problem is then you are limited to factory BS.

5 inch BS on an 8 inch rim might allow you to use a Camaro trim ring vs. the rolled Vette rings, so that would be a plus. There's so much car to car variability, I'm not sure anyone will state that with 100% certainty that a 27 inch tall tire on a 15 x 8 inch rim with 5 inch BS will absolutely fit and not rub. 4.5 worked well on my car, but more would have meant I needed to move the dual exhaust hangers to try and adjust the tailpipes out of the way. The 4 inch of my Foose's isn't quite enough, but it was all they had in a 15 x 8.

Tell us what you mean by "tire hangover". Are they too far out, or do you think they are too bulgy on the rim?
Sent you a message to answer one part. Great ^, now you've thrown more into the mix . And by hangover, yes, I mean bulge. I'll go find a side pic of the car and edit it in.

EDIT: Here's a deceiving pic of the stance: https://www.camaros.net/forums/showpo...21&postcount=5

Learning & Relearning about the cars I grew up with.
69' - Built 350, 750 Holley, Elgin E920P Cam, 283 PP Heads, Long Comp Headers, MSD, TKO-600, 12 Bolt Posi 3.73, Hotchkis Rear, Eibach Front w/Hotchkis Sway, SPC UCAs, 3rd Gen PS, AR TTII's. Still working on it.
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post #9 of 14 (permalink) Old Oct 8th, 07, 10:49 PM
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Re: I need some consensus on back spacing

Quote:
Originally Posted by dbx1969 View Post
So, I'm trying to figure out back spacing for 15x8's. I can get them with 4", 4.5" & 5" in the 15x8s. I know that with the 17"x8 wheels the BS for front was 4.75, ideally.....and 5.5" for the rear using 17x9.5. But these will be 15x8 and the dynamics change.

What back spacing would you suggest for front & back for 15x8's all around?
I just went through something similar. I had old school 15x8" rally chromes on my '67. I think - 4.5" BS front with 235/60R15 front and 15x10" rally chromes on the rear with 255/60R15. The front cleared with stock springs and the rear stuck out so far the air shock needed 100psi minimum.

I took the wheel off of my 56' Belair, and put them on the Camaro - 15x8" Cragar S/S rims front & rear 4" BS (same tires as above). The rears worked fine and w/o 100 psi - good clearance. The front did not work at all. I went to a 225/60R15 on a 7" Cragar with 4 1/8" BS and they do not rub at all.

For me this is temporary. I am going with 17's as soon as I use up some of the rubber I have laying around in my garage (too many classics).

Here is a pic.
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post #10 of 14 (permalink) Old Oct 9th, 07, 10:01 AM Thread Starter
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Re: I need some consensus on back spacing

Quote:
Originally Posted by Eric Kammerer View Post
Anyway, have we ever figured out what the BS is on the rallys you have?


5 inch BS on an 8 inch rim might allow you to use a Camaro trim ring vs. the rolled Vette rings, so that would be a plus.
I just checked the BS on my rear 15x7 (I assume the fronts are the same), and they're 4.25.

Why would the BS have anything to do with which trim ring I can use?

Learning & Relearning about the cars I grew up with.
69' - Built 350, 750 Holley, Elgin E920P Cam, 283 PP Heads, Long Comp Headers, MSD, TKO-600, 12 Bolt Posi 3.73, Hotchkis Rear, Eibach Front w/Hotchkis Sway, SPC UCAs, 3rd Gen PS, AR TTII's. Still working on it.
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post #11 of 14 (permalink) Old Oct 9th, 07, 10:15 AM
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Re: I need some consensus on back spacing

Quote:
Originally Posted by dbx1969 View Post
Why would the BS have anything to do with which trim ring I can use?
Maybe he means the body (wheelwell) trim ring --> ?

My example may not apply to your application, mine is a '67 (sorry).

Strick
'67 'Vert (408" SBC), V-Rod, Street Glide, and too many other motorcycles to list.
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post #12 of 14 (permalink) Old Oct 9th, 07, 10:55 AM Thread Starter
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Re: I need some consensus on back spacing

Quote:
Originally Posted by Strick View Post
Maybe he means the body (wheelwell) trim ring --> ?

My example may not apply to your application, mine is a '67 (sorry).
After I thought about it, I remember Eric hates the 1" space the 8" wheel leaves with the 3" trim rings. With the BS at 5", it would lessen the gap that shows. Pretty sure that's what he meant.

If my understanding of back spacing is correct..... going from a 4.25" on a 7" wheel to a 4.5" BS on a 8" wheel, means I'm moving the wheel inward 3/4", and outward toward the well 1/4". This should work fine on the rear, and I'll assume the front, too, with the only variable being possible frame rub.

Learning & Relearning about the cars I grew up with.
69' - Built 350, 750 Holley, Elgin E920P Cam, 283 PP Heads, Long Comp Headers, MSD, TKO-600, 12 Bolt Posi 3.73, Hotchkis Rear, Eibach Front w/Hotchkis Sway, SPC UCAs, 3rd Gen PS, AR TTII's. Still working on it.
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post #13 of 14 (permalink) Old Oct 9th, 07, 11:11 AM
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Re: I need some consensus on back spacing

Is your suspension stock?

Strick
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post #14 of 14 (permalink) Old Oct 9th, 07, 11:31 AM Thread Starter
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Re: I need some consensus on back spacing

Quote:
Originally Posted by Strick View Post
Is your suspension stock?
Not exactly. It originally had mono rear, and now has a 12 bolt w/multi. The front might be stock.

After just looking closer on the fronts, I believe an 8" wheel might be too big in size 15. The tie rods are too close to move the wheel inward very much, and going the other way isn't really an option if I lower it. It looks like I either have to settle for 7" up front & 8" in the rear....or go back to rethinking 17" wheels to get that front, minimal bulge, wide footprint I'd like. But I could also run a 225 or 235 up front. Decisions, decisions........

EDIT: Back to square one. Just got off the phone with my wheel guy. He knew I might be interested in TTII's polished, so he got AR to agree to send me these for the same price...and throw in a set of lug nuts . Looks like I'm moving into the 21st century, after all.

Learning & Relearning about the cars I grew up with.
69' - Built 350, 750 Holley, Elgin E920P Cam, 283 PP Heads, Long Comp Headers, MSD, TKO-600, 12 Bolt Posi 3.73, Hotchkis Rear, Eibach Front w/Hotchkis Sway, SPC UCAs, 3rd Gen PS, AR TTII's. Still working on it.

Last edited by dbx1969; Oct 9th, 07 at 12:00 PM.
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