Centerbore and offset questions

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    Author Topic: Centerbore and offset questions  (Read 2270 times)

    Offline shadango

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    Centerbore and offset questions
    « on: July 20, 2013 - 09:01:48 AM »
    So looking at rims and I have narrowed my choice to the Torque thurst II and Classic 200S wheels from American Racing.

    I have 15x7 (F) and 15x8 (rear wheels now, both with 0 offset.  have not measured the center bore.

    Wondering if anyone knows off hand the size of the center bore needed for stock 8 3/4 axles and disk brake front hubs (using disks from a  1980 New Yorker)?  Would save me the effort in trying to measure...LOL  And how critical is the center bore as far as being spot on?    The wheel I have are bigger, I think...so I torque the wheels while on stands so the lugs center them properly.

    Also wondering about offset...  one of the wheels comes with zero offset front and rear...the other , the front is available only with "3mm offset".

    The application guides on the AR site SUCK....no info at all.

    Also, do you guys prefer two piece or one piece wheels?  I was thinking one piece are stronger......

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    Offline ToxicWolf

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    Re: Centerbore and offset questions
    « Reply #1 on: July 20, 2013 - 11:36:11 AM »
    For me, two piece wheels vs one piece wheels really comes down to how they are made. I really hate the two piece wheels that leak: you get a dirt ring around the line where they are joined. And, back in the late 70s I had a two piece come apart on me in a curve. But, in today’s world, I don’t expect separation to be a problem. Most of the two piece wheels I see are welded. I’ve never had an AR wheel, so I can’t give you any first hand on it, but I’m sure there are a lot of people around here that have them.
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    Offline dodj

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    Re: Centerbore and offset questions
    « Reply #2 on: July 21, 2013 - 12:58:34 AM »
    It's easier (IMO) to go with backspace measurements, but if you are going with offset, make sure you know if it is negative or positive.  :2cents:
    But, I guess,  3mm won't matter much with 7 or 8 inch wheels
    My torque thrusts have a centre bore of 72.6mm and fit the 8 3/4 rear.  :2cents: 
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    Scott
    1973 Challenger  440 4 spd 
    2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
    Good friends don't let friends do stupid things. ........alone.

    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #3 on: July 21, 2013 - 08:43:03 AM »
    Thanks guys.   I goofed...its actually  -6mm.   So the backspacing changes to 3.76" versus 4" (right?).  That means the rim part of the wheel moves out (deeper dish)......by 1/4" ??

    Seems to be my only choice in torqu thrust style for a 15x7.

    « Last Edit: July 21, 2013 - 09:21:46 AM by shadango »
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    Offline dodj

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    Re: Centerbore and offset questions
    « Reply #4 on: July 21, 2013 - 09:16:07 AM »
    Quote from: shadango on July 21, 2013 - 08:43:03 AM
    Thanks guys.   I goofed...its actually  -6mm.   So the backspacing changes to 3.76" versus 4" (right?).  That means the rim part of the wheel moves out (less deep)......

    Seems to be my only choice in that style for a 15x7

    Yes. Less back space, so a little more 'deep'. More 'street side' rim showing.
    http://recstuff.com/theanatomyofatrailerwheel.aspx
    Ya, i know it is off a trailer site, but the terms/measurements are the same.  :grinyes:
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    Scott
    1973 Challenger  440 4 spd 
    2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
    Good friends don't let friends do stupid things. ........alone.

    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #5 on: July 21, 2013 - 09:22:49 AM »
    Assuming the 15x7 0 offset wheel I have now has a 4" backspace and the 15x7  -6mm offset wheel has a 3.76" offset,  that would mean the tire itself would move out toward the fender lip about 1/4"?

    That doesnt seem like a big deal to me.

    I placed a flat edge (a level) spanning the tire sidewalls and the thickness measured one inch....there is at least another inch between the level's surface and the wheel well lip while the wheels are pointed straight....so compression/cycling of the wheel and tire should be fine.

    I guess I should also go lock to lock to check.

    The spacing for the brakes etc wont change at all the way I am understanding it....offset will affect only the distance between the tire and wheel well.............right?
    « Last Edit: July 21, 2013 - 09:38:08 AM by shadango »
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    Offline dodj

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    Re: Centerbore and offset questions
    « Reply #6 on: July 21, 2013 - 09:35:02 AM »
    Quote from: shadango on July 21, 2013 - 09:22:49 AM
    That would mean the tire itself would move out toward the fender lip about 1/4" right?
    yup.
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    Scott
    1973 Challenger  440 4 spd 
    2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
    Good friends don't let friends do stupid things. ........alone.

    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #7 on: July 21, 2013 - 09:39:07 AM »
    Wow...you are quick..>LOL   I just updated my last post.....

    Seems like the extra 1/4" "deep dishness" would really be no big deal......
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    Offline dodj

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    Re: Centerbore and offset questions
    « Reply #8 on: July 21, 2013 - 12:07:17 PM »
    Not really related to your original question, but if you are going with new wheels, you might want to consider 17". Your performance tire choices go up dramatically.
    Or do I remember you recently buying new rubber? :clueless:
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    Scott
    1973 Challenger  440 4 spd 
    2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
    Good friends don't let friends do stupid things. ........alone.

    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #9 on: July 21, 2013 - 12:19:16 PM »
     I bought new tires a couple years back.....still good tread.....

    Plus, honestly, I like the look of the 15" wheels.  Old school look....lol
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    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #10 on: July 21, 2013 - 12:53:57 PM »
    I checked the measurements lock to lock.....

    On the right side, I think it would be just fine.

    On the left, the clearance between the tire and the front lower edge of the fender is close.  When I first got the new tires I had to gently tweak the inside lip of that lower section just a tad...and no problems since.

    But its tough to figure out of that 1/4" of less backspace  would really make a difference there or not.....

    Dammit why cant they just make the wheel in a zero backspace!!!!!!!!!!!!!!!!!!!!!
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    Offline dodj

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    Re: Centerbore and offset questions
    « Reply #11 on: July 21, 2013 - 09:17:41 PM »
    Put 6mm worth of washers over three wheel studs then mount your tire again (using those three studs). Go lock to lock and see how it looks?
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    Scott
    1973 Challenger  440 4 spd 
    2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
    Good friends don't let friends do stupid things. ........alone.

    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #12 on: July 22, 2013 - 11:07:03 AM »
    Quote from: dodj on July 21, 2013 - 09:17:41 PM
    Put 6mm worth of washers over three wheel studs then mount your tire again (using those three studs). Go lock to lock and see how it looks?


    Thanks for the idea!

    Did that this morning....had washers that fit and were 6.5 mm stacked.........

    There is only point in the lock-to-lock that I am worried about, and that is the lower front fender lip on the left side…….

    I added some 6.5mm shims behind my current wheels on that side  and have what amounts to be about 3.7 mm space gap at its closest point after some additional careful hammering so given the shims being slightly bigger etc, about  4.2mm clearance.  That is with a 235x60x15 tire that is about 50%....that side of the tire is slightly worn more due to alignment......but no idea if a new tire would hit or not.

    Cyling the suspension DOWN is no problem as I am already past the centerline of the wheel.  Cydling UP, not sure but that would only be an issue in a hard right turn.

    I suppose I could go to a slightly smaller (less wide or slightly shorter) front tire or lower the front end a tad? Or just never turn hard right - of course that would make getting into my driveway hard....  LOL.... :bigsmile:

    Its a close call.     :clueless: :dunno:  The right side of the car has no issues at all....double or maybe triple the space.

    What would you guys do?  We all know that once we mount a wheel/tire, its OURS.  And even if that were not the case, shipping wheels can get pricey.

    I guess its a gamble.  Or go with another rim altogether with zero offset...but I am after the PVD as well as the style.

    I found that Cragar makes a 15x7 0 offset in the SS styler with the correct bolt hole pattern......(not unilug)....but i am unsure of the steel-welded-to-aluminum approach they take plus its standard chrome versus the PVD.

    « Last Edit: July 22, 2013 - 11:52:16 AM by shadango »
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    Offline shadango

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    Re: Centerbore and offset questions
    « Reply #13 on: July 31, 2013 - 06:44:25 AM »
    Well, just ordered the wheels.  Gonna try it and see what happens.  LOL  Got tired of obsessing over it.
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    Offline ToxicWolf

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    Re: Centerbore and offset questions
    « Reply #14 on: July 31, 2013 - 04:39:52 PM »
    Which ones did you order?
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