Rear Versus Front Tire Widths

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AJ/FormS said:
Ok so just to get the terminology squared away;
Everybody I know, when talking about tires, never mentions the tread size. But, the profile width is an ethereal number, that is only accurate when the tire is installed on the checking wheel, on which it was installed, at the tire factory.

Now, when the tire company designs a 215 tire, it will only be a 215 on a checking wheel that is equal to 70% of the branded 215 size. Since a 215, converts to 215/25.4= 8.46 inches, and 70% of that is 5.925, which rounds to a 6" wheel.
Therefore, when you mount a 215, on a 6" wheel, it should have a profile width of 215 +/- 5mm.
Now then,
If you mount a 215 on a 7"wheel, the profile will be about half the wheel-difference larger . so then, your 215 become 215 plus half of one inch(an inch being 25.4mm), equals 227.5mm, +/- 5mm

I just thought that you should know this ... in case you didn't.
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Yup!
That's why I said my head was swimming with numbers and calculations right now.

And now the more I calculate and look, the more I think I need to go back to 14s.
 
On my 67 coupe, I'm running 15x8 Cragars (4.25 inch backspacing) on the rear with Nitto 275/60/15 radials; 15x7 Cragars on the front with 225/60/15 Falkens.

Chassis is stock height front and rear. The larger diameter rear tires raise the back end by about an inch.

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soonercruiser said:
So, as I am narrowing down new wheels and tires for my 67 Barracuda, the thought occurs to me....
Although I am used to seeing all 4 tires the same width on passenger cars, that does not seem to be what I see on Classic cars.
In order to get my wheels and tires back into the wheel wells, I intend to go with narrower tires.
Currently, I have 255s on the rear; and 205s on the front.

So, the question it begs is.....
Can I go with 225s all the way around?
Why fatter tires on the rear?
Why so narrow on my fronts - 205?
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You didn't mention what bodystyle your Barracuda is. Fastbacks and convertibles have more weight on the rear axle than the coupes. As someone else has pointed out, bigger tires on the rear are what you want if you're going racing, or if you want "the look". Putting bigger tires on the rear pretty much makes your car a fair weather driver. Any sort of liquid or moisture on the road means the rear end of your car is going to lose traction. Are you a big fan over oversteer or "loose" as the NASCAR folks call it?

Yes, bigger tires on the rear mean you've got a slightly bigger contact patch between you and the road, but looking at pounds per square inch, you've got LESS. Same weight, bigger contact patch, less force per square inch of the contact patch. This will REALLY bite you in the *** if the road is wet, or even if you drive through somebody's oil leak. Going in a straight line, you might get away with it, but if you're even THINKING about hustling the car through a corner, anything other than a bone dry road will just about guarantee you'll be able to see all around where the car is taking you, because as it's spinning, you're not going to catch it, and you'll just be along for the ride until it stops spinning. Either because you've spun out in the middle of the road, or because you've pile it up on some solid object (or another car).

All of this applies to virtually any Abody. The '29' bodies are the worst in this scenario. That fastback body is just a giant mass of air contained within a sheetmetal envelope.
 
I run 245/60R14 all the way around. Like the rotate advantage and 1sz spare. Right front occ rubs on right turn with full load but minimal.

IMG_9919.jpeg
 
kmccabe56 said:
You didn't mention what bodystyle your Barracuda is. Fastbacks and convertibles have more weight on the rear axle than the coupes. As someone else has pointed out, bigger tires on the rear are what you want if you're going racing, or if you want "the look". Putting bigger tires on the rear pretty much makes your car a fair weather driver. Any sort of liquid or moisture on the road means the rear end of your car is going to lose traction. Are you a big fan over oversteer or "loose" as the NASCAR folks call it?

Yes, bigger tires on the rear mean you've got a slightly bigger contact patch between you and the road, but looking at pounds per square inch, you've got LESS. Same weight, bigger contact patch, less force per square inch of the contact patch. This will REALLY bite you in the *** if the road is wet, or even if you drive through somebody's oil leak. Going in a straight line, you might get away with it, but if you're even THINKING about hustling the car through a corner, anything other than a bone dry road will just about guarantee you'll be able to see all around where the car is taking you, because as it's spinning, you're not going to catch it, and you'll just be along for the ride until it stops spinning. Either because you've spun out in the middle of the road, or because you've pile it up on some solid object (or another car).

All of this applies to virtually any Abody. The '29' bodies are the worst in this scenario. That fastback body is just a giant mass of air contained within a sheetmetal envelope.
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Thanks for the post.
But, I have already thought thru all that.
I've got a Notchback, and am changing things to be more road friendly; including tires not rubbing the fenders.
Tires already here from Tire Rack. Wheels on the way from Jegs.
Gonna give Gabriel Hijackers a try for custom height.

Some of the details are just personal preference; like I have always loved the look of raised letter tires.
If it doesn't look right, or when they become a PITA, I'll just turn them inside out like the previous owner.
Yes, smaller tires.
 
soonercruiser said:
Thanks for the post.
But, I have already thought thru all that.
I've got a Notchback, and am changing things to be more road friendly; including tires not rubbing the fenders.
Tires already here from Tire Rack. Wheels on the way from Jegs.
Gonna give Gabriel Hijackers a try for custom height.

Some of the details are just personal preference; like I have always loved the look of raised letter tires.
If it doesn't look right, or when they become a PITA, I'll just turn them inside out like the previous owner.
Yes, smaller tires.
Click to expand...
just be warned...the shock mounts were not designed to carry vehicle weight, only transient damping loads. when we bought my duster when I was 16 in 1991, the car had air shocks on it and both shock mounts were ripped out of the floorpan. it only had 50000 miles on it.

your mileage may vary, buyer beware, etc...
 
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