LM guys with the 7" and 8" wide wheel setup, got a question.

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SyntheticBlnkerFluid
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LM guys with the 7" and 8" wide wheel setup, got a question.

Post by SyntheticBlnkerFluid »

So I'm looking at buying a new set of 15" wheels for my '68 and want to do the 7" wide in the front and 8" wide in the back, the problem is, that I need to know what offset to go with because there are a few choices and I don't want to make the wrong one. Yes I have read Bryan Blackwell's page, but I want some real input from people who have purchased wheels. I know there's some guys on here who have done their research. :-)

The 7" wide wheels I'm looking at come in a +6mm offset (hub is .25" outboard from wheel centerline, 4.25" backspace) and Zero offset (4" backspace).

The 8" wheels I'm looking at come only in a -13mm offset (hub is .5" inboard from wheel centerline, 4" backspace)

My thought is that the 7" with the Zero Offset should be fine and the 8" should work fine as well, without causing an issue with the fender.

Any thoughts?


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Rob
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Re: LM guys with the 7

Post by bbodie52 »

If you haven't seen this already, it is informative and well-worth reading...

Sizing Corvair Wheels and Tires
:link: http://autoxer.skiblack.com/tires.html

More info...

SELECTING CUSTOM WHEELS AND TIRES FOR YOUR CORVAIR
:link: viewtopic.php?f=225&t=6066
Brad Bodie
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notched
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Re: LM guys with the 7

Post by notched »

You want as much back spacing as you can get on the front. 4" on a 7" wide rim is not enough on the front of a Corvair. The situation gets worse if you have disc brakes as it pushes the wheels out even more. The back rims don't need as much back spacing.
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SyntheticBlnkerFluid
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Re: LM guys with the 7" and 8" wide wheel setup, got a question.

Post by SyntheticBlnkerFluid »

bbodie52 wrote:If you haven't seen this already, it is informative and well-worth reading...

Sizing Corvair Wheels and Tires
:link: http://autoxer.skiblack.com/tires.html

More info...

SELECTING CUSTOM WHEELS AND TIRES FOR YOUR CORVAIR
:link: viewtopic.php?f=225&t=6066
Thanks for the info Brad, but that's why when I bring up stuff like this, I always say that I've already read Bryan Blackwells page (which was the first link you posted) to prevent someone from posting that page, because everyone seems to want to throw that at anyone who asks a wheel and tire question.

Your article is well written and has a lot of info, but I want to get some input from anyone who have installed them and if they have had any issues, that was my purpose of this post.


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Rob
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Re: LM guys with the 7" and 8" wide wheel setup, got a question.

Post by SyntheticBlnkerFluid »

notched wrote:You want as much back spacing as you can get on the front. 4" on a 7" wide rim is not enough on the front of a Corvair. The situation gets worse if you have disc brakes as it pushes the wheels out even more. The back rims don't need as much back spacing.
I'm curious to how 4" isn't enough. The factory 5.5" wheels only have 2-1/4" back space and a 7" rim with a Zero Offset is going to be almost 2" closer to the suspension. The +6mm rim is going to put it at 2" exactly.


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Re: LM guys with the 7

Post by Hank_jackson »

good morning all

I have a 69 with front disks and 15 x7" wheels with 4.25" backspace
had 205 60 15's at first and had a tad of rubbing up front b4 going to disks and 195 60 15's all around
no more rubbing or interference issues at all.

Hank
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Re: LM guys with the 7

Post by 66vairguy »

SyntheticBlnkerFluid wrote:
notched wrote:You want as much back spacing as you can get on the front. 4" on a 7" wide rim is not enough on the front of a Corvair. The situation gets worse if you have disc brakes as it pushes the wheels out even more. The back rims don't need as much back spacing.
I'm curious to how 4" isn't enough. The factory 5.5" wheels only have 2-1/4" back space and a 7" rim with a Zero Offset is going to be almost 2" closer to the suspension. The +6mm rim is going to put it at 2" exactly.


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No the factory backspace is 4.25"!! Not sure were you got 2.25" from. Maybe your confusing offsets (+ or -) that tend to be confusing, that's why backspace is typically used now. Note a 7" wide rim is bead to bead NOT rim to rim edges. Typically a 7" wide wheel is about 8" wide rim to rim edge and back space is from the flange mounting surface to the back side RIM edge.

Finally I have 14" X 7" wheels with a 4.5" backspace. Front tires are 205/70X14 and rears are 245/60X14 and they JUST clear at a stock ride height. If your car is lowered the front fender edges will probably have to be rolled or you'll have to avoid driveway ramps on turns.
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Re: LM guys with the 7" and 8" wide wheel setup, got a question.

Post by SyntheticBlnkerFluid »

66vairguy wrote:
SyntheticBlnkerFluid wrote:
notched wrote:You want as much back spacing as you can get on the front. 4" on a 7" wide rim is not enough on the front of a Corvair. The situation gets worse if you have disc brakes as it pushes the wheels out even more. The back rims don't need as much back spacing.
I'm curious to how 4" isn't enough. The factory 5.5" wheels only have 2-1/4" back space and a 7" rim with a Zero Offset is going to be almost 2" closer to the suspension. The +6mm rim is going to put it at 2" exactly.


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No the factory backspace is 4.25"!! Not sure were you got 2.25" from. Maybe your confusing offsets (+ or -) that tend to be confusing, that's why backspace is typically used now. Note a 7" wide rim is bead to bead NOT rim to rim edges. Typically a 7" wide wheel is about 8" wide rim to rim edge and back space is from the flange mounting surface to the back side RIM edge.
Yes, you are correct, it is 4.24". I went and measured the rim myself. I know where everything is measured from, I've just never measured the wheel personally, I was going by math.

Bryan Blackwells page said the Offset is 1" inboard and that is incorrect. It is 1" outboard, therefore I was confused. I keep forgetting he refers to the placement of the rim inboard and outboard, not the hub; the hub placement from the wheel centerline within the rim is what today's wheel Offset standard is. That's what I try not to refer to his page when it comes to wheel Offset.


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Re: LM guys with the 7

Post by maineyenko »

I have 15 x 7 and 15x8 wheels on my 67. front backspace is 4.5", measured with wheel off car. rear backspace is 5", measured same as front. front tires are 205/55/15, rear tires are 225/50/15. OD is the same front and rear, so spare tire works for both. I have cut coil springs 1.5 coils and reformed cut spring ends like stock. Rides well. No rubs.

Ken
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Re: LM guys with the 7

Post by notched »

Most modern front wheel drive and even many rear drive vehicles have most of the rim width on the inside and on the inside of the front bearing centerline.
While you might be able to run less back spacing with a wider rim which puts more of the rim width towards the outside, you can experience tramlining or darting from this. I experienced it on my car. I started with 7" wide rims with 4" back spacing with the stock brakes. It was just ok, not great. Once I added my disc brakes which made it terrible as the rotor hat was 1/4" thick which pushed the rims out that much further. In reality it was like having 3.75" back spacing. I ended up having American Racing make a pair of custom offset rims with 4.8" back spacing which was the most they would make with that rim design. This was perfection. With the rotor thickness it put me just a tick over 4.5" back spacing. No more darting or tramlining or whatever anyone wants to call it. So although rims with 4" or less back spacing might be a great deal and fit and look cool (some guys like rims sticking out of the wheel wells) it does not make for a pleasurable driving experince.
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Re: LM guys with the 7

Post by 66vairguy »

notched wrote:Most modern front wheel drive and even many rear drive vehicles have most of the rim width on the inside and on the inside of the front bearing centerline.
While you might be able to run less back spacing with a wider rim which puts more of the rim width towards the outside, you can experience tramlining or darting from this. I experienced it on my car. I started with 7" wide rims with 4" back spacing with the stock brakes. It was just ok, not great. Once I added my disc brakes which made it terrible as the rotor hat was 1/4" thick which pushed the rims out that much further. In reality it was like having 3.75" back spacing. I ended up having American Racing make a pair of custom offset rims with 4.8" back spacing which was the most they would make with that rim design. This was perfection. With the rotor thickness it put me just a tick over 4.5" back spacing. No more darting or tramlining or whatever anyone wants to call it. So although rims with 4" or less back spacing might be a great deal and fit and look cool (some guys like rims sticking out of the wheel wells) it does not make for a pleasurable driving experince.
Agreed. I had a number of opportunities to purchase 7" rims with a 4" backspace and waited until I found the 4.5" backspace rims and the car steers and handles fine (stock drum brakes). Ideally a 7" rim should have a 5" backspace, but that's just too tight to ensure clearance during suspension travel of inner suspension pieces front or rear on a Corvair - IMO.

There is a thing called "scrub radius" and the father off from factory the more handling issues you get into. Note the diameter of the wheel/tire also affects scrub radius.
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Re: LM guys with the 7" and 8" wide wheel setup, got a question.

Post by ptr »

This is an excellent thread full of great information. As I plan my LM build I've bookmarked this one to come back to when I get to the point of buying wheels and tires. Thanks to everyone who has shared their experience and knowledge.

On a forum for a different marque that I follow there is a section where they "sticky" threads such as this that cover a frequently asked topic so that it's easy to find and further information is appended rather than being spread across many threads. Has anyone considered doing something similar here?


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