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Contributing Member
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6,137 Posts
Discussion Starter #1
Rick,

Thanks for providing your services to the group. As you know, wheels are a hot topic here. I was hoping to get your opinion on my idea.

I know that the maximum width to put on the front of a '67 or '68 is 8 inches with 4.50 inch backspacing and a 245 series tire. I was planning to go with a 7 inch width and a 235 series tire. Would it make sense for me to go with a 4.25 inch backspacing to better center the wheel in the wheelwell?

I will also mention that my front end is lowered. But, I can't tell how much yet since the motor is not in at the time. I won't be purchasing anything until ALL the weight is back on the front of the car. I just want your opinion as to whether you think I'm on the right track or not.

Thanks,

Mark
 

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Premium Member
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156 Posts
Hello Mark,

First off, I apologize for the late reply, I was out of town. It is my pleasure to provide services to this group. I am scrambling to get my site 100% complete, so I may have been premature with any advertising.

Now down to business.

You didn't mention the diameter of the wheels that you have in mind for your car. That is a factor in the profile of tire that you choose. If you are thinking 17x7 then the tire could be 245/45 17 which will work nicely with the lowered front end that you mentioned.

Also the proper sizing up of a wheel and tire combo means that each time you add 1 inch to the wheel diameter, add 20mm to the tire width and subtract 10% from the aspect ratio.

Breakdown: 245 is your width in mm, 45 is the height of the sidewall (45% of the width, this is known as the ASPECT RATIO)

Say your original tire/wheel combo was
15" 205/65 R15, then you wanted to go to
16" 225/55 R16, then later you wanted to go to
17" 245/45 R17

See how the tire width increases by 20mm and the aspect ratio drops by 10% each time you go up one inch in diameter?

By following this formula you will not only improve the look and performance of your cat. This will keep your odometer and speedometer changes to an extreme minimum.

As for the 4 1/4 backspacing to center the wheel in the wheel well as you mentioned. You must keep in mind that when you go with less backspacing that moves the wheel out toward the edge of the wheel well which may contact the tire on hard cornering, but the wheel will look somewhat deeper, of course we are only talking a 1/4 inch difference so that point is probably mute.

Keep in mind, as well, that all wheels do not come with the same backspace. So, if you choose a wheel that does not come with the backspace that you desire. You may have to use a spacer.

So you see that there are many, many variables that you must consider in your decision on the type of wheels.

I hope this helped you and others. Any more questions, please ask.

Regards
RickJ
 

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Contributing Member
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6,137 Posts
Discussion Starter #3
Thanks Rick for all the info. And thanks for the PM as well. I was planning on going with the 17" diameter and I know my brand can be made with a 4.25 backspace. But, I never thought about the appearance of the rim looking deeper with the shallower backspace. Good Point! While I do have a moderate knowledge of wheel sizes and spacings, I'm a little nervouse at this point about making this purchase because I need to get it right the first time. It's too expensive and not returnable. That's why I'm trying to educate myself even more while I still have time before I need to go out and drop the $$$$. Thanks again for the info.

Mark

P.S. Glad to have you back!
 

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Premium Member
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156 Posts
I understand the stress. If you want to be more confident go take the measurements on your car yourself. Its very easy and will make you feel much better.

You will have to post more pics when you are done. I know you have been redoing your car. You gave me ideas for mine. LOL
 

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Contributing Member
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6,137 Posts
Discussion Starter #5
I will be taking the measurements once the motor is in and the hood is on. I will also be using my last set of wheels as a baseline. The reason I'm kind of in a dilemma is because I want to match the tires on the rear and the front sizes are pretty limited. They do come in a 235/45/17 which I think will go well with the 285/40/17 on the rear. I know the rear size is out of spec for what is recommended. But, I've already done the major mods to get them to fit. I'm just glad they only need to roll instead of turning right and left.

I'm gunning to get the whole thing finished by early June. It's definately going to be close and I'll post more pics then. Thanks again, Rick.

Mark
 
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