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first64riv

Question on wheel fitment 15x8 4" Backspacing

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On 7/11/2019 at 7:28 AM, rapom said:

Your combo will fit.  My wheels are made by U.S. Wheel and are 15" x 8"'s with 4" backspacing (Bonus with this wheel is that the stock hub caps fit)  and I have 295/55/15's in the rear and 255/60/15's in the front with no problems.  The wheels even have divots to clear the front drum rivets.  Had to do some slight clearancing for the front hub.  All clearances are close in the back with the 2.25" exhaust pipes with some apparent rubbing at times that I never hear but can see when I take off the tires and see the shiny spot on the exhaust pipe.  Even though there is over 1/2" clearance between the tire and the exhaust at rest.  Must come from tight turns on inclines or declines.  I have over 12,000 miles in 3 years on these wheels and tires.

That's some serious rubber. I was interested in some 15x8.5 torque thrust on CL, and used your car as inspiration. I chickened out, and went with some old 15x6 mags instead.

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Jsgun,

Thanks, nice link.  I've alway went to the BF Goodrich site for tire sizes, better this is easier.  I'm still suck on if there are any issues with using the Car Inc replacement rear drums on my 64 Riviera.  If I use them I will not need to use spacers to fit the 15 x 7 Buick Rallys on the rear.  The wheels will clear the outside diameter of the drums.

 

Thanks,

Art

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Cast ir9n is cast iron.  As long as they fit every other place, bolt pattern, bolt hole diameter, center hole diameter, width, etc. you shouldn't have any problems.  

 

How do you know for sure your wheels will fit? Just because they don't show any fins in the illustration?

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Hi Rivnut,

Your right, I don't know for sure.  I had called Cars Inc and had them measure the large diameter, which measured 14.375, I measured the ID of my wheel which is at least 14.625.  Per the numbers it may work.  I know that is still close, but before I ordered these drums I wanted to check to see if any members had any other issues with these drums.  I know they are cast iron, but the factories were cast iron in the rears too, right?  So should not be too much brake performance change.   Just trying to figure out a way to mount these 15 x 7s Buick Rallys without a thick spacer and longer studs.  According to Rapom, his wheels were 4.00 BS wheels and they fit (not Buick Rallys).  My 15 x 7s are 4.312 BS, 15 x 6s are 3.4375 BS.  Again this is ONLY in the rear.  So if I can get the wheel over these drums without interference then I'm only looking at a spacer for tire clearance if needed.

 

Let say I get these drum, I need to have them balanced, right?  Would that be a auto machine shop that does this?

 

If I'm missing something in all this, please let me know.  All comments welcome.

Thanks,

Art

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Posted (edited)

I would be leaving the OE drums and using longer studs and a spacer.  The new drums probably come from overseas and who knows what quality they are.  

 

The balancing question is something you seek an answer from CARS.

Edited by RivNut (see edit history)

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So to install longer studs, I would no doubt need to pull the rear axles, correct?

 

Art

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Posted (edited)

That depends on the length of the stud and how much space there is between the back of the axle flange and the backing plate.  Could be you could hammer the old ones out but the new ones would be too long to get back in.  That would be a bummer deal.  Perhaps someone else knows for sure. Are the 7" wheels the only ones you have or are you just in love with them 😍😍😍

Edited by RivNut (see edit history)

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No no.  I have the four so called Buick Wildcat rallys on the car now 15 x 6s.   Looking to change all tires to redline and acquired two Buick station wagon rallys 15 x 7s for the rear.   Would like to go with a wider tire on the rears.  That's if I can make this work.  Don't want to pull the axles.  Like what you said " if not broken, don't fix it"😁😁

 

Art 

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You can probably run the wider rear tire on the 6" rim and the ride and handling will be the same.

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I just went back and started reading from post #1.  When I got to the pictures you posted, I took a look at the fins and how they interfered with the wheels.  If you would, pull a wheel and post a picture of a complete drum.  I've never seen a Buick rear drum whose fins stuck out beyond the drum itself.  I'm curious to see if someone has not installed a set of 12 x 2 inch drums off of something other than a Buick.  Those just do not look correct to me from what i can see. No matter what the offset, I would think you could get the 7" wheels to fit 9n Buick drums.  I may be all wet, but someting doesn't look right.

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Those pictures were of the front wheels and drums of Rapom's car.  I'll get some pictures of the rear wheel and drums of mine this morning.  Here the picture of mine as it is with the 15 x 6s.20190708_193447_resized.thumb.jpg.efdddb994bbf2a379a01748c38acc508.jpg 

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Three pictures of left rear Buick Rallys on the drums.  Plenty of clearance as long as the BS (3.4375) does not increase.  You can see the fins will make contact with the ID of the wheel.  Third picture is my drum.

Art

20190716_092729.thumb.jpg.d2da72fb6dd669d43fe75d1b61564858.jpg20190716_092904.thumb.jpg.be351957ff2a77302c54aefce0907156.jpg20190716_093314.thumb.jpg.7366b722cae8ec3e4ed4b72db00dd2f2.jpg

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Here's the latest info.  I made up four equally thick spacers with a 1/2-20 nut and washer measuring .556 from the drum surface.  The wheel barely clears the drum on the inside.  Leaves me about 6-7 thread on the studs.  Not too comfortable with any of this.  US Wheel Adapter will make me adapter, but .875 would be the minimum, these would bolt on.  This would solve the the inside drum clearance, but does eat up outside tire clearance.  Need to check more into this.

 

Art

 

 

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Posted (edited)

My rear drums also are cast iron and look like the ones just posted. Stockton wheels may be able to change the backspacing of your Buick wheels (depending on how they are made) as another option, but it would be pricer than wheel spacers.

Edited by rapom
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Posted (edited)

Well actually 15 x 7 wheel, with 4.312 BS and the .875 spacer works out pretty good as far as wheel and tire fitting.  It puts the wheel and tire pretty much right in the middle of the fender.  I could go with the 255/60r15 with no problem, 275/60r15 would fit, but they advise a 7.5 wheel.  The spacer/adapter are custom made with stud inserted in spacer.  The spacer has lug nuts to fasten to drum.  Something to think about.  You would never see them behind the Buick Rally wheels.  I could alway go back to the 15 x 6 wheels and tires just remove the spacer/adapter.

Thoughts????

 

 

 

Art

Edited by awk409ak (see edit history)

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If using a spacer, the best type is the one you described.  

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Art, if you go with spacers, need to check your math. How long are the original wheel studs? 7/8" spacer off that will be how much the original stud projects past the mounting surface of the wheel. Does the wheel have a recess on the back side to accept the extra stud length? How deep is the countersink in the spacer? How tall is the lug nut? When installed, does the lug nut project past the face of the spacer and if so, is there room in the back of the wheel mounting surface for them? Most of these spacers are deeper, 1.5, 2, 2.5 or 3" and don't present these issues. If you are having these custom made, you can't take them back.

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These adapters are used to install custom wheels as well as by off roaders to install bigger tire/wheel combinations.  The only problem you might run into is that they don't come in narrow sizes.  The narrowest I've seen is about 1/2". May be too much for what you're trying to do.

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Great comments and questions!

The minimum thickness spacer/adapter per the manufacture is .875".  That is because the lug nut that holds it to the drum must not project above the spacer.  The .875 thick spacer/adapter is what I'm planning on using, 5-5 to 5-5 adapters.  They assured me that the nut will not project beyond the thickness.  As for the exist stud I"ve taken a picture of the back side of the wheel with a 1/2-20 bolt in the space between the stud holes on the 5" bolt pattern.  I have about .650" of bolt length in that space.  I did not check the wheel stud length when I had the wheel off, my bad, but will check, plus should check all dimensions on the right side too.  I could if I need to, taper the ends of the existing stud a little.  So what I have is 6.00" from wheel mounting surface (drum)
to exhaust pipe.  After I add the spacer it's 6.875 to exhaust pipe.  I have 13" from exhaust to lip on outer fender.  Wheel has a 4.312 BS.  If I was to use the larger tire which is 275/60r15, I would have 1.06" clearance on the inside and .094 clearance on the outside.  255/60r15 is not a problem.

 

Please check me out.

 

Art

 

20190717_170030resized.thumb.jpg.bb0e6c22a4176c73a78069247ff5a4ec.jpg

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