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first64riv

Question on wheel fitment 15x8 4" Backspacing

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Hey all,

 

I've searched but nothing definitive.  Will a 15x8 with 4.00" backspacing fit the rear wheel wells of a first gen?  I would do 195 size tires.  My hunch tells me this will fit.

 

Chris

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Short answer is yes, they will. Longer answer is you may have to rework the existing exhaust to get them to fit. Plenty of clearance for the wheel and tire, but sometimes the exhaust pipes want to take up this same space. Depending on where the muffler man put the pipes. "Look at all this room" doesn't work when you fill it with tire.

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Why are you wanting to run 195 sized tire on a 8" rim?  I have a set of 20" x 8.5" rims and a 255 tire on it pretty much stretches it to its limit.

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Most tire people will agree that the tire and rim should be "paired" when it comes to width.

The 15 X 8 size mentioned first......the 8 inch measurement is inside the rim bead.   8 = 203 mm

If a 195 tire (7.68 inch) is installed on an 8 in rim the rim will extend past the tire rubber (look like a low-rider)

If you are not aware,  the 195 tire size/measurement is the width of the tire at the widest cross section. (not the tread width)

 

Ed says he has 255 (10 inch) on 8.5 (216 mm) which gives him rubber past the rim .....that rubber protects the rim should you curb a tire.

Also keep in mind that the 8 in measurement is the inside of the rim where the tire bead seats....there is about 1/2 inch on each rim flange,  so if you measure the rim on the outside an 8 in will be about 9 inches.

So in Ed's tire/rim combination he has about 1/4 inch of tire rubber extending past the rim on the front and back of the tire

This does not answer your clearance questions,  but is intended as input on choosing the tire for the rim.

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Isn't it more that the wheel will not fit over the drum.  Not even speaking of tire size.  Maybe I should state it this way.  You should check to see if the wheel fit over the drum.  I know for fact that my 15 x 7 's will not fit (4 5/16 BS) on my 64 Riviera.  A wheel with 3 7/16 BS may fit, because that the stock rally wheel dimensions.  I need to add a .875 spacer to make my wheel work. This is what I have seen.

 

Art

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4 hours ago, Barney Eaton said:

Most tire people will agree that the tire and rim should be "paired" when it comes to width.

The 15 X 8 size mentioned first......the 8 inch measurement is inside the rim bead.   8 = 203 mm

If a 195 tire (7.68 inch) is installed on an 8 in rim the rim will extend past the tire rubber (look like a low-rider)

If you are not aware,  the 195 tire size/measurement is the width of the tire at the widest cross section. (not the tread width)

 

Ed says he has 255 (10 inch) on 8.5 (216 mm) which gives him rubber past the rim .....that rubber protects the rim should you curb a tire.

Also keep in mind that the 8 in measurement is the inside of the rim where the tire bead seats....there is about 1/2 inch on each rim flange,  so if you measure the rim on the outside an 8 in will be about 9 inches.

So in Ed's tire/rim combination he has about 1/4 inch of tire rubber extending past the rim on the front and back of the tire

This does not answer your clearance questions,  but is intended as input on choosing the tire for the rim.

template  wheel.jpg

Thank you for the input.  I am aware of tire sizing.  I threw out 195 because I am currently running 15x7 with a negative offset and I rubbed the fender well in the rear with a 195.  I had to switch to a 185 tire.  So with a x8 I could probably get away with at least a 195.

 

My car is not a low rider.  It's just lowered with Supremes.  Funny you say that though because the wheels I found are Dayton wires.  I'm only interested because they're on sale for a steal of a price.

 

Thanks for the reply!

Chris

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Big wire wheel fan,  so hope you can make them work.    It might be worth having a tire mounted on one of the wire wheels and test it all around the car.   Check clearances and that will help you decide

what size tire you can use with the offset of the wires

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Not sure why your 7" wheel rubs. Inside or outside face? Just as a comparison, I am running 255x55x17s on 8.5 wide wheels on my bagged 63 with no rub unless I set it really low. You may be rubbing exhaust on the inside of the tire. And when I set it down, it is the outside face that makes contact with the inner tub first.

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1 hour ago, Barney Eaton said:

Big wire wheel fan,  so hope you can make them work.    It might be worth having a tire mounted on one of the wire wheels and test it all around the car.   Check clearances and that will help you decide

what size tire you can use with the offset of the wires

I'm a bit of a wheel whore.  I have a set of 5 1964 Wildcat wheels, a set of 5 Appliance Wire wheels, and the Supremes currently on my car.  This is a pair of Dayton's that I want to pick up but I'm starting to realize the other accessories will make these wheels add up.  They are brand new though....the struggle is real man!!!

 

Thank you for your thoughtful replies.

 

8 minutes ago, steelman said:

Not sure why your 7" wheel rubs. Inside or outside face? Just as a comparison, I am running 255x55x17s on 8.5 wide wheels on my bagged 63 with no rub unless I set it really low. You may be rubbing exhaust on the inside of the tire. And when I set it down, it is the outside face that makes contact with the inner tub first.

I have the Truespoke Supremes in a 15x7 Reverse Backspace 1.75" or 57mm offset.  That's the rub (so to speak).  I had to bang the inner fender to stop the rubbing and get slimmer tires.

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So what backspacing are you guys using on your 17 x 8.5 or 20 x 8.5?

 

Art

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9 hours ago, awk409ak said:

So what backspacing are you guys using on your 17 x 8.5 or 20 x 8.5?

 

Art

3 5/8 is the backspacing on my 17s.

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Somewhere I read that before front wheel drive cars,  most wheels had the hub mounting surface centered in the wheel.

This equalized the wheel loading and made things simple.    When front wheel drive vehicles came out,  they wanted to make the drive shafts as long as possible

so the outside bearing and hub was further out than rear wheel drive cars and the wheels had a big offset toward the outside (positive offset) the first Toronado is a good example.

Now we have all these different wheel sizes, offsets, and widths that make selecting a wheel confusing but you do have many options to get the clearance you need.

when selecting wheels......the first criteria is the bolt pattern that MUST match your vehicle, they you have wheel diameter (sometimes larger wheels are needed to clear the larger brakes you installed)

wheel width, and offset..........then the easy part.....what design do you want.

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Posted (edited)

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.

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Edited by rapom
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Are running replacement drum then?  Because I think factory drums are larger in diameter (the fins make the outside diameter of the drum larger).

 

Art

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Posted (edited)

I am running what appears to be the factory drums.  Aluminum up front and cast iron in the rear.  The drum fins look to be very close to the rim but still clear.  I can take pictures if you want to see.  I painted the front drums black where they would be seen through the wheels.

Edited by rapom
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I'm not doubting you.  I have the 15 x 7 rally's and they will not fit over my rear drums without using a .875 spacer, because the drum have fins on them.

 

Art

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Posted (edited)

I know the 15x7 Chevy rallys have more backspacing than the 15x8 corvette  rallys.  Which doesn’t make sense but it is the case.  Might be the same case with the Buick.  Several friends of mine couldn’t fit the 15x7 rallys on their gm g bodies, because they would hit the rear frame rail with the tires installed.  15x8 rallys would solve the problem.

 

It would appear from the pictures that any more than 4” of backspacing would hit the drum fins.

Edited by rapom
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Thanks.  That must be it then a 4" BS seem to work.  My 15 x 7 rallys are 4.312" BS.   So they are too deep and hit the drum before the wheel mounting surface.   I thought I was going to have to match what the 15 x 6 rally's BS is, which is 3.4375 by adding a spacer.  I was thinking of the 15 x 6 with 225/70R15 on the front, rears would be 15 x 7 with 255/70R15.  I'll have to try this wheel setup again.

Thanks again for the help.

 

Art

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Posted (edited)

That should look good.  You will have to use longer wheel studs if you use a spacer but you probably already know that.

Edited by rapom
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4 hours ago, rapom said:

I am running what appears to be the factory drums.  Aluminum up front and cast iron in the rear.  The drum fins look to be very close to the rim but still clear.  I can take pictures if you want to see.  I painted the front drums black where they would be seen through the wheels.

Painting cast aluminum will seal the pores in the metal. When the pores seal, because of painting or polishing, they loose their ability to cool.  😕

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