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Check my backspace math. Can you help me choose a wheel?

C

Coupe

Member
I want to get some 17" wheels on my 65 but I keep seeing 17X7 with a 4.5BS and I think that a 4.75 would do a better job of not rubbing the wheel well lip. I dont want to roll the rear lips, the front I could but since its a manual steering car I cant see the point of going wider than 7". Am I thinking wrong here?

Most of the $1300 wheel & Tire combos I see on Ebay run less back space than I really want. Does anybody know of a 17" Torque thrust D or TQ2 look thats on the cheaper side that will offer me 4.75 BS on a 7" wide rim?


Goodguys is this weekend and so is a big local swap meet, so I may even look at used wheels if I see any opportunity but I dont want to buy something and find out later they rub.

Here is my car, I am open to ideas on what would look best. These 14" tires are really spooky on the interstate.



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I think that a 17x7 wheel with 4.75 backspacing will do an excellent job of producing hard contact on your upper arms.
 
So what then? I have read in a few posts that the 4.5 BS will hit the rear quarter lip with a few tire sizes.

I guess that 4.75" BS only on the 8" wide rim? I think I am getting confused because I thought 4.75 on a narrower rim would give me lip clearance and still not impact the arm, since the 8" rim does not hit it.
 
17x7 4.5 BS will fit fine on all 4 corners and should have plenty of clearance.... as long as you don't go crazy and try to stuff tires that are too wide for a 7" wheel.

Many people run 17x8 4.75 BS on all 4. In comparison, your 17x7 / 4.5BS will have an extra 1/4 clearance on the inside and 3/4 extra clearance to the fender lip..

4.75"BS is 4.75 BS, regardless of the wheel width. A 17x13 (or 17x8) wheel with 4.75 BS will still have the same inner clearance that a 7" wide wheel has - the extra width is all on the wheel lip side. Now, the OFFSET does change with wheel width, Backspace does not.
 
Thanks!

I think I am going to try to find some 17x7 @4.25 (or 4.5?) backspace for the front with 215/45R17 tires. I just cant figure out if these should use 4.25 or 4.5BS. I have an arning drop and a 1" drop spring.

And 17x8 @ 4.75BS on the rear with 225/45R17 with 4.5 mid eye leafs.

I think the tires are conservative enough to fit and still fill out the wheel wells and look good. I would not mind going wider in the rear, do you think I could bump that up on width?
 
Yes, I'd shoot for a 17x7 4.5"BS on front. IF you felt they were TOO tucked, you can always add a 1/4" spacer to end up with 4.25" BS - but you can't do the reverse!!! 4.25"BS on a 17x7 centers the wheel exactly the same as a 4.75"BS 17x8 - just gives a little more clearance both inside & outside.

17x8 4.75"BS on rear is a tried & true size - IIRC, you might need some MINOR clearance work on the INSIDE of the wheelwell, but the lips should be fine, especially given your conservative 225 tire width.

For reference, here are 17x8 4.75"BS (equivalent-long story) at all 4 corners with 225/45/17 front and 235/45/17 rear:

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Your car looks awesome wit those wheels.
To keep this vintage look , what about 15 or 16 inch rims ??
You still have that vintage look and more solid sidewall tires ????
Just my thoughts. :confu :confu
 
Thanks so much Bob! That helps. I dont want really wide because gas is expensive and I plan on driving this car a bunch. I kinda abuse it as is, I am pondering a bit more width in the rear, but I hate to hammer on my new wheel houses.

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B67FSTB I am thinking TQ "D" or II's to keep that old school look, but I drive this car hard and am trying to get away from that squishy feel of a huge side wall. I would not mind 16" wheels at all, but I want to be able to get a replacement tire easy and fast and I dont know how prolific the 16" tires are at local shops or even out and about if I decide to do a tour. Do you think 16" tires and wheels would use the same backspace math? I think the rims can hit the UCA easier but I really dont know much about wheel math? (But I do know more now!)
 
As you can see I have TTII 17X8 back and front.
If I had to choose again , I would have taken CMAYNA's setup on Shag.
As for 16 inch wheels , yes there is a chance that they will rub the UCA.
There are plenty of articles which discus this matter.Take and search MustangMonthly to find an article in the tech section.
This can help also IMO
http://www.rimsntires.com/specs.jsp
 
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