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  #1  
Old Dec 28th, 17, 12:51 PM
CarNova CarNova is offline
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Default Bad shocks or wrong tire size?

Lately my car has been making scraping noises on the rear passenger wheel whenever I go over a bump or a dip in the road. Also had three friends ride in my car the other day and had to rearrange seating arrangements due to the heaviest guy was sitting in the back seat over that tire and causing it to make huge scraping noises. Iím thinking I need new shocks.

A friend of mine said it might be due to tire size. I just checked my tire size and discovered my tires in the front are actually a whole inch taller than my tires in the back. That wouldnít cause scraping in the rear but makes me think I might need to change tires just the same. In the pic Iím including it shows my tire size comparison. Tire 1 is my rear tires and tire 2 is my front tire.

My rear tires are P235/60/R14 and my front tires are P225/70/R14

Iíve read that stock tires are P195/75/R14

My local tire shop says they could fit that size on my existing cragar rims. Would that be recommended?
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  #2  
Old Dec 28th, 17, 01:43 PM
Big Dave Big Dave is offline
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Default Re: Bad shocks or wrong tire size?

Big and littles has been the trend in the auto hobby for over a half century. It as been a fad since the invention of the L60 tire size (235R60-14 in Eurometric speak). The L60 was the biggest tire (at 9.50 inches wide with an 8 inch tread width) that existed when these cars were new and required an eight inch wide wheel (found on the Corvette if you wanted a Rally wheel, and in cast aluminum "mags"from the aftermarket) to mount it.

In the "good ole days" cars followed the stink bug stance of Funny Cars of the age; with the back end jacked up two inches above stock ride height and the nose dropped down two inches below stock ride height.

To keep the over sized rear tires from rubbing people used air shocks with 90 psi of air in them so that the car rode like a lumber wagon, combined with longer rear leaf spring shackles (baloney slicers). Add ladder bars or a slapper bar tightened to the max and the rear end was basically solid mounted with no suspension travel available. But people still rolled the rear inner fender lip in by sawing it into small pieces and hammering it flat against the inner fender to prevent the lip from carving off the raised white letters on the side wall of your brick hard bias ply tire.

With the original stock springs (you can not assume some previous owner has not changed them out in the past) the car will sit an inch and a half to two inches below factory ride height due to spring sag. This aggravates the tire rubbing problem.

If your car has been hit in the past the axle may not be centered under the body. Leaf springs not only hold the car up but locate the rear axle. If the front or rear mounting location has been pushed in the car will not track straight and the tire will be closer to one lip than the other side wheel well lip.

The Chevy II was designed to be an Economy Car; a second car for housewives to be mobile in suburbia (think of June Cleaver) and as such was under powered and light weight. It had small tires (the smallest size made to keep costs down) and it had a semi enclosed rear wheel well to impress women with it's style as back then only expensive luxury cars had fender skirts that hid most of the rear tire and wheel. Compare the rear wheel arch of a 1967-'68 Camaro to an early Chevy II or a 1968 Nova. My 1968 Camao swallowed a 14 inch wide by 15 inch wheel Firestone slick with nothing more than my buzzing the outer wheel well trim off with a saber saw.

Big Dave
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Old Dec 28th, 17, 02:03 PM
CarNova CarNova is offline
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Default

ďIn the "good ole days" cars followed the stink bug stance of Funny Cars of the age; with the back end jacked up two inches above stock ride height and the nose dropped down two inches below stock ride height.Ē


That would have been more what I was expecting for the rear tires to be taller than the front. I wasnít expecting the front ones to be an inch taller than the rear. Is that unusual? Now the rear tires are wider but shorter than the front.
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Old Dec 28th, 17, 02:59 PM
Big Dave Big Dave is offline
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Default Re: Bad shocks or wrong tire size?

"Tire's Ain't Perttee" to quote an old snake oil salesman from early seventies sales pitch from TV. They are what is printed on the side wall. If you are curious what those numbers translate into English units that 'Am-ari-kans' understand, you need only look at this chart.

https://www.tirerack.com/tires/tiret....jsp?techid=45

https://www.tirerack.com/tires/tiret...rsionchart.jsp

A narrow tire can be short or tall. VW bugs had a 145R-15 tire that was nearly thirty inches tall, to reduce rolling resistance and make for better mileage. They where closer to a motorcycle tire than a car tire. So the sectional width is not all defining. In the first link you will see three different tires with three different heights that have the same or very close sectional width ratio number (the ratio aspect is the 78, 70, 60, 50, 45, or 35 number on the tire that tells you width to height ratio).

You were asking about shocks before. Shocks will not keep a car body from hitting the tire. Worn out implies that there is little damping so the car is constantly oscilating (going to get you sea sick after a while). A new shock won't bounce up and down more than twice, but it won't hold the car up. That is the job of the springs.

I mentioned that your springs might not be original. This is because the base model car had mono-leaf springs that would wind up and cause wheel hop. They were frequently replaced by J.C. Whittney's three leaf replacement springs. The factory high performance cars had four (for a SBC) to five (for a BBC car) to six rear leaf springs (for TransAm racing) depending upon the application. So if you still have a Spicer ten bolt (as opposed to the AAW corporate ten bolt), but have mult-leaf springs they could have been replaced in the past.

Don't know what you have for suspension; but it makes a difference in how the car handles and performs from grocery getting cruiser to race car.

I wrote more on the subject in this Sticky under Suspension:

https://www.novas.net/forums/showthread.php?t=8625

Big Dave
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Old Jun 2nd, 19, 08:00 PM
Schurkey Schurkey is offline
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Default Re: Bad shocks or wrong tire size?

Quote:
Originally Posted by CarNova View Post
Lately my car has been making scraping noises on the rear passenger wheel whenever I go over a bump or a dip in the road. Also had three friends ride in my car the other day and had to rearrange seating arrangements due to the heaviest guy was sitting in the back seat over that tire and causing it to make huge scraping noises. Iím thinking I need new shocks.
You may or may not need new shocks. The shocks are not causing the scraping problem.


You almost certainly need new rear springs. The original springs are extremely prone to cracking where the axle mounts.


When I changed the rear springs on my '77 Concours, I found that both rear springs were broken, and the replacements didn't fit properly until I fabricated a spacer.


Good luck.
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  #6  
Old Jun 8th, 19, 03:17 AM
Aukai Aukai is online now
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Default Re: Bad shocks or wrong tire size?

If you add an anti roll bar, not to be confused with an anti sway bar, the ARB will only let the rear end go straight up, and down 0 body roll. Body roll is where I feel most of the scraping comes from. Just my opinion....
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