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1971 Cutlass base coupe. I still have the original 14" steel wheels (with covers), and have always run standard 225/70R14.
Several years ago I upgraded to a set of 14" SSIIIs, original as far as I know, and put the same tires on. I don't believe they are any different in width .. or are they? That's on me to check.
Here's the dumb question: If I get new rubber, can I put 60s (225/60R14) on those rims (rear only)? Seems like it's close enough, but what do I know.
PS Assuming I don't need to change the backspace at all, mostly concerned about the wheel-tire mating. Thanks in advance.
I know the tire is available, it's just a bit small for the rear. I would stick with the 225 70 14 because it fills the wheel well better. Unfortunately over the years, 14" tires don't have many choices anymore.
Simply because they are shorter. For example a 6 foot tall man with the same muscle mass as a 5'6' man. Mr 5'6' will look bigger ...
But in the case of tires you may not like the way the car sits/looks. It's a serious drop in height. Im sure thats Eric's concern. The rear of your ride will drop 3/4s of an inch and that much more wheel well will be showing. Plus speedometer will be off...
I agree that 225-60s are way too short, especially for the rear. My car had 245-60-14s all around for decades until I switched to 15” SSIII wheels and 245-60-15s.
And it looked phenomenal. 245 60 14s look awesome on 1968-1972 Cutlass. Here below from Streetside, 245 60 14s all around. If you open their pics they are so well taken and clear you can read all tires specs. (pics 24 and 33 are front and rear tire pics) Below is pic 25.
Just a sidebar: if you buy BFGs be prepared to mount them blackwall out because the white letters turn brown. As an alternative you might want to look into Cooper Cobras.
Thanks Phil.
Is that passing the eyeball test? Why do 60s look wider??
Math is your friend.
The section width is the three digit number. 225 = 225mm wide. A 225/70 and a 225/60 are BOTH 225 mm wide, period.
The two digit number is the ratio of sidewall height to section width. A 70 series tire has a sidewall height that is 70% of the width. A 60 series is 60% of the width. That is independent of anything else.
A 225/70 tire has a sidewall height of 225 x 0.70 = 157.5mm = 6.2". Add the sidewall height above and below the 14" wheel and you get 6.2 + 14 + 6.2 = 26.4" overall diameter
A 225/60 tire has a sidewall height of 225 x 0.60 = 135 mm = 5.3". Add the sidewall height above and below the 14" wheel and you get 5.3 + 14 + 5.3 = 24.6" overall diameter
The original tires on this car were F78x14, which were 26.5" in diameter. The 225/70-14s are almost exactly the same size and fill the wheel wells nicely. The 245/60-14s leave too much daylight around the tire in my opinion. If you are keeping the 14" wheels, the 225/70s are your best option, unless you want to pay big bucks for repro bias ply tires that are wider.
Great info Joe, thanks. Makes a lot of sense now.
My perception of 60s vs 70s was completely wrong.
Some of the confusion may come from the "plus one" marketing that was done with low profile tires first came out. The concept was that you could use a lower profile (ie, 60 series) tire but maintain the same outside diameter as the original narrow tire by going "plus one" on the wheel diameter. The difference here is that the larger wheel diameter makes the overall diameter the same, despite the lower sidewall height.
I used this concept for picking tires for my 1967 Delta 88. The OEM tires were 8.55 x 14", which were 28.52" in diameter and 8.20" wide. I used 235/70-15s on the front and 275/60-15s on the back. In both cases the new tires were just a hair under 28" outside diameter. The 235/70s and 275/60s have virtutally the same sidewall height, since 60% of 275 is nearly the same as 70% of 235.
if you buy BFGs be prepared to mount them blackwall out because the white letters turn brown.
And how, hard to believe the pic I posted of that beautiful Cutlass S are RWL. You need to expand photo just to see its not blackwall.
Originally Posted by SteveB
No, my car is not a "S".
👍 so just a plain ole Cutlass Coupe as my first car was. Magnificent vehicles, the reason I am an Olds guy, and on this very site. Opened your photo album, she is beautiful.
Originally Posted by SteveB
My perception of 60s vs 70s was completely wrong.
In addition to what Joe P said.
Your perception is shared by many a car guy. Including myself. It wasn't till tire height became incredibly important to me 15 years ago (for 1/4 mile purposes) that I fully locked on.
Many of us instinctually think 70s tall and thin, 60s wide, 50s super wide... without considering the main ingredient being the actual width. Growing up you would see wide tires and hear 50s or 60s without locking on to the other measurement.
👍 so just a plain ole Cutlass Coupe as my first car was.
In 1971 and 72, the 2dr models that used to be called "F85" were re-branded as "Cutlass" (without the "S"). The Fisher Body Code was still 3287, however.
Many of us instinctually think 70s tall and thin, 60s wide, 50s super wide... without considering the main ingredient being the actual width. Growing up you would see wide tires and hear 50s or 60s without locking on to the other measurement.
This was compounded by the fact that tire sizes like F70 x 14 or G60 x 15 didn't include the actual section width, so it was much more difficult to know what the dimensions were.
In 1971 and 72, the 2dr models that used to be called "F85" were re-branded as "Cutlass" (without the "S"). The Fisher Body Code was still 3287, however.
Ahh OK Joe so not like my 67 Cutlass as there was an F85 as well in 1967. Would always joke with my friend's back then that the original owner wanted zero options except V8 oomph, that's why he went with Cutlass and its 330. Rather than an F-85 and its base inline 6. Joe when I tell you my ride was basic, forget about it. 3 on the tree, bench, manual steering, manual drum brakes, AM only radio with single in dash speaker. And I loved her ! Turquoise with black interior. Wonderful car, I bet she is still getting the job done out there...
Originally Posted by joe_padavano
This was compounded by the fact that tire sizes like F70 x 14 or G60 x 15 didn't include the actual section width, so it was much more difficult to know what the dimensions were.
