1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Another wheel backspacing question...

Old 12-18-12, 06:16 PM
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Another wheel backspacing question...

Hey guys, I am looking at getting a custom set of diamond racing wheels made for my car. I want to go 15x7 so I can use my existing tires, wheels to be as flush as possible with little to no rubbing. I know you can get pretty much any amount of backspacing, and I was wondering if anyone can shed some light on how many inches of backspacing I would need to get the desired result.

Thanks!
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Old 12-18-12, 06:43 PM
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I am running 15 x 7 with 205 50 15 and I have rolled my fender lips. I do not have any rubbing issues, except when turning against the stop, inside of the tire rubs the sway bar, not a problem. My wheels have a 20 mm offset, which if I measure correctly is a 4.25 backspacing. With the fenders rolled there maybe room to move the tire outboard a quarter to 1/2 inch but depending on hw low your suspension you may have rubbing.
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Old 12-18-12, 09:24 PM
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I was using some 15x8 0 offset diamond racing on my GS last year.I did roll the inner lip of the fenders and was using 195/50/15 tires and never had a problem with rubbing.
the wheel was prety much flush with the fenders.

Another wheel backspacing question...-img_0826.jpg
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Old 12-18-12, 10:17 PM
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well as of right now, im running stock suspension set up with 185/50 in the front and 205/50 in the back. i would like to avoid rolling the fenders but if i have to i will. honestly my biggest worry is that they clear the shock towers. also, did you guys have studs pressed into the hubs or did you run the standard acorns?
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Old 12-19-12, 01:29 AM
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I'm curious about this as well, I'm looking to get a set of Diamonds after my current tires cord. BrGreenSA, please keep us updated on what you get and how you like it.
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Old 12-19-12, 10:01 AM
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Another thing I didn't take into account, was the offset options I have. What should I be looking at in terms of that, or is it fundamentally the same thing as offset? Sorry, wheels aren't really my specialty.
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Old 12-19-12, 10:27 AM
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Backspacing and offset are two different ways to measure how far in or out the rim is in relation to the mounting surface. Backspacing is the distance from the mounting surface to the inside rim. Offset is the distance of the mounting surface from the center of the rim, positive is to the outside, negative is to the inside.
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Old 12-19-12, 10:39 AM
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Ah okay, in that case, for my situation, what kind of offset should i be looking for? From what I can see, Diamond only has 0 or negative offsets

Last edited by BrGreenSA; 12-19-12 at 10:59 AM.
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Old 12-19-12, 11:18 AM
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Originally Posted by BrGreenSA View Post
Ah okay, in that case, for my situation, what kind of offset should i be looking for? From what I can see, Diamond only has 0 or negative offsets
Zero off set diamonds should fit. That will get you a wheel with around 4" of backspacing. I own a set for rain tires on my race car and this is how they measure.

As far as lug nuts - most of their small car wheels use 60 degree lug nuts. If your wheels are built like this then you should be able to use the factory lug bolts. If they specify 45 degree lug nuts you will need to install studs and by 12mm 45 degree nuts. These are available in the Circle Track world. My personal preference would be to go with studs and lug nuts - I hate lug bolts.

When you have your wheels and tires balanced - find a servicer that can reference the lug holes and not the hub hole. Diamond wheels are not hub centric - they list this in their web site. This is not a bad thing it just means that you need to balance them by using the stud holes. High end Hunter wheel balancers are set up this way.
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Old 12-19-12, 11:32 AM
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Originally Posted by mustanghammer View Post
Zero off set diamonds should fit. That will get you a wheel with around 4" of backspacing. I own a set for rain tires on my race car and this is how they measure.

As far as lug nuts - most of their small car wheels use 60 degree lug nuts. If your wheels are built like this then you should be able to use the factory lug bolts. If they specify 45 degree lug nuts you will need to install studs and by 12mm 45 degree nuts. These are available in the Circle Track world. My personal preference would be to go with studs and lug nuts - I hate lug bolts.

When you have your wheels and tires balanced - find a servicer that can reference the lug holes and not the hub hole. Diamond wheels are not hub centric - they list this in their web site. This is not a bad thing it just means that you need to balance them by using the stud holes. High end Hunter wheel balancers are set up this way.
Thank you for the info! Now i know what to look for. Just need to get past xmas and to my next paycheck
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Old 12-19-12, 06:09 PM
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WA Wheel offset and Backspacing

I came across this wheel and tire site that lets you do a virtual set-up when you punch in the specs, its www.rimsntires.com/specs
I've been looking around, and put in an email to Dayton Wire wheels, and they can do any offset, backspacing combo, with a 4 lug knockoff adapter, I think my little Bronze Beauty will look cool with the matching wires.
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Old 12-19-12, 07:19 PM
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Use the following site to get a general idea if wheel/tire combo will fit, plug in original size and the size u are thinking of getting: www.willtheyfit.com

Here's a good site that explains all about wheels: http://www.mrw-wheels.com/wheel%20te...t%20chart.html

Keep in mind that a 7" wheel is actually 8" from outer to outer lip if ur are going to be measuring and calculating ur backspacing urself. If ur really wanting the wheels to sit flush, most likely u will need to roll ur fenders, unless u do like the "stance" group and get skinny tires.
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Old 12-19-12, 09:51 PM
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You should message or look up dmclean's car..I think he kind of sets the standard for how a fb should look with diamond racing wheels.

Good luck!
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Old 12-20-12, 11:35 PM
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Originally Posted by RxTex View Post
You should message or look up dmclean's car..I think he kind of sets the standard for how a fb should look with diamond racing wheels.

Good luck!
+1... his stance is proper!
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Old 12-21-12, 07:22 AM
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i looked ^ this guy up, here's his thread: https://www.rx7club.com/1st-generati...kspace-908826/

he's running 15x8 w/ 4.5" backspacing. if u read through that thread, u will see that he had to roll his fenders and run 185's. if u want 15x7's, ur outter lip will sit in an inch towards the inside compared to his (which will help clear the fender...depending on ur tire width). but he's also way low.
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Old 12-21-12, 10:00 AM
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@craaaazy i will be running 185's out front, and 205's out back at stock height. i could possibly run 15x6 because i want ti avoid rolling the fenders if possible
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Old 12-21-12, 11:26 AM
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I have 205's all around just running the stock LE wheels...
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Old 12-21-12, 02:13 PM
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i think i'm just going to go with the 15x7 0 offset, if i have to do a mild fender roll, i will. i just want to be able to put this car back to stock in the future just in case....
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Old 12-31-12, 10:39 AM
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Originally Posted by BrGreenSA View Post
i think i'm just going to go with the 15x7 0 offset, if i have to do a mild fender roll, i will. i just want to be able to put this car back to stock in the future just in case....
A 7" wheel with zero offset will stick like an inch out of the fender. You do not want zero offset with a 7" wheel. A zero offset with an 8" wheel is about correct. With a 7" wheel you want between 12 and 20 offset or 4.5-5" of backspacing.
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Old 12-31-12, 10:49 AM
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Ideal for a 1st gen is 15x7 with 4.5 backspace or 4.75 max.

with panasports
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this is with my 15x8 epsilons backspace is 4.75
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Old 04-10-13, 12:45 AM
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So if I go out and buy a set of 4 Diamond Pro Streets in 15x7(+12 offset) and have a 81 Rx7 at the stock ride height, I should see no issues with rubbing or hitting the shock tower? I just want to make sure and order the right rims that will work the first time since i'm new to the Rx world and am a poor student.. lol
Can anyone shed any light on this?
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Old 04-10-13, 11:25 PM
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I actually just checked out the diamond racing website and I see that they only offer the SC and Pro Street in 15x7 in a 0 though -64 offset with no positive offset options. Would a 0 offset be okay to run and fit well with the car I mentioned above?
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Old 04-13-13, 09:43 AM
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Originally Posted by 82FanTC View Post
A 7" wheel with zero offset will stick like an inch out of the fender. You do not want zero offset with a 7" wheel. A zero offset with an 8" wheel is about correct. With a 7" wheel you want between 12 and 20 offset or 4.5-5" of backspacing.
Um... I'm no rocket surgeon, but im pretty sure a 7" wheel with 0 offset would be 1/2" skinnier than an 8" wheel with 0 offset... how would it stick out an inch further? There's an inch and a half of unspoken for wheel there...
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