This shot of the front tire of today’s featured 1960 Cadillac very graphically shows why automotive bias-ply tires have become essentially obsolete except for some vintage reproductions. Look at where the rubber meets the road: the very substantial weight (over 5,000 lbs) of the car and the rigid bias-ply sidewalls have deflected the tread inwards from both sides, causing massive tread squirm and a substantially reduced contact patch. Something always has to give when a relatively soft tire (24 PSI) has to support a significant amount of weight, and in this case it’s the tread itself.
No wonder cars with bias-ply tires squealed and felt so mushy in corners, didn’t ride and track well and wore out so quickly. The tread was constantly being massively deformed. Here’s a graphic that shows that from the road’s point of view:
The bias tire tread is constantly being compressed from the sides, due to the rigid sidewalls, resulting in a distorted tread pattern and a significantly reduced contact patch, which is a critical factor in traction when cornering as well as accelerating and braking. The constant tread squirm wears the tread much more rapidly, and the resulting heat build up is a further negative factor.
In the radial ply tire the sidewalls deflect and the tread, reinforced by its stiff steel belt, stays largely unchanged, with the contact patch being larger, the tire running cooler, and the tread pattern able to do its job in wet or snowy conditions.
Here’s some Coker bias-ply look radials on a 1947 Cadillac; the normal radial tire sidewall bulge is very visible. This is the huge advantage of radials, as the more flexible—but still very strong—sidewall takes on the necessary deflection that is essential in any pneumatic tire.
The sidewall bulge is not so obvious from this angle, but clearly the tread is not being deflected and compressed as in the bias ply tire on the 1960 Cadillac. I can understand the desire for authenticity in a fine old car, but if it’s going to be driven to any reasonable extent, it’s hard to see why a radial wouldn’t be the obvious choice, especially given the quite authentic look of these tires.
It’s noteworthy that whereas radial tires were originally developed in the 1940s by Michelin for cars, their applications have widened drastically over the decades, a process that is still happening. A few years ago Michelin unveiled their XDR 59/80R63 radials for giant mining trucks, the largest to date (and costing some $150k each), but even larger ones are in the works. These, as well as an increasing number of industrial radial tires use steel in their carcass plies instead of nylon or polyester. Radial tires are increasingly found on agricultural and industrial equipment of all types and sizes as well as aircraft. Even bicycle tires are now available with radial ply construction.
Radial tires have come along way since 1948, when the Citroen 2CV was the first car with them as standard equipment — another aspect of why it was the most radical and original mass-produced new car ever.
Related CC Reading
Curbside Classic: 1969 Citroen 2CV – The Most Original Car Ever by PN
I ran bias ply RETREADS on my ’69 VW beetle. I never had the tread separate on one, but it’s scary to think about all the ways our cars were less safe back in the day.
Way, way back when I was in college in 1977, my dad allowed me to buy a worn out 1970 VW Beetle previously owned by one of his co-workers. Among the VW’s issues was that it came with a set of almost bald bias-ply tires. My dad told me not to worry because one of his buddies owned a tire store, and he’d be able to fix me up with new tires at a good price.
So off to the tire place I went. It was kind of a dump — located in an old industrial building with huge stacks of tires piled everywhere. The owner said that he thought he had a bunch of VW-sized tires up in the far reaches of the attic that he’d be happy to get rid of for $20 each. Although I was a poor college student, I advised him to go for it. 15 minutes later, he came down from the attic and said that the tires weren’t what he remembered — they were Vredestein radials, not the cheap bias-ply tires that he thought were there. But a deal’s a deal, so my lowly Beetle was shod with brand new radial tires. The difference in handling between radials and bias-ply tires was shocking, even on my crappy Beetle.
In the late ’60s Dad worked at a Sears Auto Service Center (remember those wonderful places?) and was an earlier adopter of radial tires on our ’64 Buick LeSabre wagon. As a very young child I recall being alerted more than once by other drivers that we were getting a flat.
Had two cars where I replaced the original tires with radial tires and the difference was crazy. No telling how many lives have been saved by these tires.
The good: A bias ply tire in 1965 could be had for $15.00. About $150 in today’s money.
The bad: You were lucky to get maybe 20,000 miles from said tire.
That $15 in 1965 seems quite expensive for a 14″ to 15″ tire, no? Not that those sizes are that common today but a radial in that size would be quite a bit less today.
I found a few newspaper ads including this one from 1959. Seems like they started at about $10-15 depending on quality. But I can’t make out the sizes. In any case, like so many things, modern tires are cheaper in adjusted terms, thanks to production being mostly automated and from imports. And of course they last at least twice as long or more.
I just recently threw a new pair of 195 60 15s on my Focus for a whopping $52 each!
That’s cheap as my 2004 are $155 a piece.
Very lucky to get 20,000 miles out of a set of bias ply tires. Most were shot at 15,000 miles. A new set of tires was a yearly event. In contrast, I replaced the Michelin radials on my Acura MDX at 74,000 miles, and there was tread left. Maybe a slow leak or two during their life due to a puncture that was easily repaired.
Blowouts were common in the bias ply era, especially in the pre tubeless days. Just hope it didn’t happen at 70 mph on a curve. The cause of untold fatal accidents.
Very good article on the difference between bias-ply and radial tires. It was 11-1/2 years ago that I purchased on the Internet my 1966 T-Bird convertible & had it shipped to where I was living at the time, Ottawa, Ontario. Lots of photos of the restoration process but upon receiving the auto, shortcuts had been taken on some mechanical stuff, now corrected. The previous owner was making an effort to make the car at least look factory original including a new set of bias-ply tires. I have the original window sticker & build sheet indicating my T-Bird came from the factory with the optional red-band whitewall bias-ply tires only offered on 1965-66 T-Birds. At the time you got either black walls, whitewalls, or whitewalls with an additional red band. So I received the car with almost new bias-ply reproduction red band whitewalls. Yes, I am old and drove a 1966 T-Bird when they were new so I knew how this car should handle. But upon receiving my Bird, yes I found some directional stability issues especially with the light touch, one finger, power steering. Not a big deal back in 1966 because many cars had sensitive power steering and bias-ply tires. I found only one manufacturer (not Coker) that could reproduce my factory looking red band whitewall tire in a radial. Ordered five tires (including spare), @ about $500 ea., shipped to Canada. This might sound extravagant but my T-Bird is a driver, not looking for judging points. Switching out the bias-ply tires with radials definitely made a difference on how the car handles. Looks factory stock and worth every dollar. My advice, if you have an old car from the 1960s or earlier with bias-ply tires go with radials, many can be found for far less money then I paid for my custom made red band whitewalls.
Very nice read!
I have heard conflicting claims about which car first had radial tires – according to Michelin itself, the Lancia Aurelia was the first to come out of the production line with radials ( https://news.michelin.co.uk/articles/the-triumph-of-the-radial-tyre )
Perhaps in the 2CV they were dealer fitted, or anyways optional?
I also find interesting that in Europe, radials were common already in the 1970s; in the US, adoption seems to have been much slower; perusing old brochures, the Nova had bias ply until at least 1978, AMC still had them in 1980 on the Spirit and Concord
The Honda Civic had bias-plies until about 1984 IIRC, on the base model.
I saw that same picture of the 1960 Fleetwood, and knew that the tire was underinflated. I still prefer bias on some of my older cars, they came that way. Some radials on the original rims can cause rim failure, the rims not designed for that tough of a tire. With bias, it’s true the contact with road is small, but with manual steering, the bias will steer easier than a radial. Also, the rubber compound of radials has a far shorter life span time wise. At around 7-9 years, radials can and will disintegrate, tread separation, or blow outs. There’s another myth of the directional stability of radials over bias. True, radials will tend to roll easier in the direction of travel. But complaints of “being all over the road” “poor steering” with bias, is always the suspension and steering of that vehicle is worn out. Bad king pins, tie rod, steering gears.
You don’t actually know that this tire is under inflated. And what you’re saying about rubber compounds aging differently is clearly a reflection of your bias. I’ve had radials that were well over 20 years old and still worked just fine. Rubber deterioration affects all tires, but is significantly impacted by UV exposure and high ozone exposure. The improved handling of radials is just not debatable. You’re free to have a pro-bias tire bias, but please don’t spread misinformation.
Hey Paul I know radials are popular. However, the very second I saw the fleetwood tire in another article, (not this article), I remarked wow that tire is low. Maybe I’m wrong, but I doubt it. There are big displays at the local Discount Tire, and they clearly say that radials expire after 7 years. Most tire shops refuse to service a radial if it’s out of date. Remember when radials were new, and GM cars came out with “Radial Tuned Suspension” ? It’s true that radials sometimes work better with modern radial specific designed suspensions. It’s true that sometimes, not always, that the correct sized bias tire will perform better on an older car designed for bias tires. Nothing I said was misinformation. Quite a few years ago there was a controversy in many car magazines about radial tires splitting the rims on some older cars. This is still a safety concern and shouldn’t be brushed under the rug.
Rubber deterioration affects bias and radial ply tires equally. The reason tire shops won’t service older tires is strictly a legal liability issue demanded by their insurance companies. The reality is that this issue is heavily dependent on the tire’s exposure to UVs and ozone and height temperatures, just like so many other things are, like paint on a house (or car). I would have no qualms driving on tires older than seven years if I had reason to believe or know that they did not have high exposure to those factors.
Not to be argumentative, but the Discount Tire display mentioned that radials are manufactured with a different rubber compound, and the purpose of that is for better handling and performance. I’ve had piles of tires sitting outside in the weather, I’m talking 10 years, and there have been radials there with a million cracks, and yet in the same pile a bias ply, and no cracks at all. I’ve had radials that were new, with no use, yet stored in trunks as spares, or in my Dodge van, mounted inside in the back, and some of those just explode from the age. Just my experience.
I don’t know about individual signs in shops, but here’s Discount Tire’s policy on tire age at their official website. Bottom line: they won’t service tires more than ten years old (not six like you claim). There’s nothing about different rubber compounds. The reality is that there is a huge range of rubber compounds used in tires. Winter tires have a very different compound, as do high speed and performance tires. Each manufacturer creates their own for various tire lines in their brand. The issue is what they say here: it’s impossible to judge when a tire is truly aged out without knowing the conditions it was exposed to.
https://www.michelinman.com/auto/auto-tips-and-advice/tire-buying-guide/when-do-i-need-new-tires
It starts with “There is no way to tell exactly how long a tire lasts”
Michelin themselves go on to say they recommend replacement after ten years “as a precaution” and recommends “inspection” after five Nothing whatsoever about “expiration” but plenty about various factors involved in affecting the lifespan of tires.
Both Michelin and Discount Tire are in the business of selling tires. Michelin as a manufacturer likely knows far more about tires than a retailer of them.
In my experience, carmakers’ recommended tire pressures in the 1960s WERE underinflation. Instead of 24 psi as General Motors recommended, my Dad always ran at 30. He never had problems with premature wear at the center of the tread, either.
I would submit that this was for the purpose of ride comfort. So if that Cadillac is at 24 psi, it is FUNCTIONALLY underinflated, even if not by specification.
The Roadmaster I just bought had Uniroyal Tiger Paws. If I had to guess, I’d say they had less than 1,000 miles on them as indicated by the nubbies on the edges and the nearly 11/32 tire depth.
But there was a problem. The date code was 2012. And even though the car and tires were stored indoors, I replaced them immediately before making the 900 mile roadtrip back home.
I was in a tire store long ago, behind a woman in line who told the salesman “I don’t want none of them RAY-dial (like radio dial) tires!” I laugh about this every time I pass a tire store.
Radials hands down the winner .
I took the time to figure out the correct radial size tire for my 1949 Chevy shop truck, it rode like a Cadillac and handled well too .
My old Mercedes W123’s are heavy like tanks, in 5 ~ 7 years the sidewalls begin to crack and leak air, I drive these old Mercedes as fast ans they’ll go nd lots of canyon carving, I’ve not been able to wear out a set yet .
-Nate
I went the opposite direction back in the late 70’s. I inherited the family 1970 Olds 88 that the old man had put a set of Michelin radials on. Unfortunately they were shot and a few weeks after I started driving (I was 16 years old) I went to the tire shop. With very little income from a part time job, cost was paramount I bought a set of cheap bias ply tires. The difference was dramatic and it felt like I was driving a Flintstone car with rocks for tires. The only good thing was that my driving was limited to city excursions. I got rid of the car and the tires within a year.
I also went the same way, also cost driven. My first car was an Austin 1800 (aka landcrab). It was a 65 that I got in 68. It came with Dunlop SP41 radials, but after a couple of months one of the front tires was wearing unevenly and was down to the cords in one spot. I thought it was an alignment problem, but it seems it was a fault in the tire. It actually had a warranty based on the amount of tread wear. The problem was that the replacement was based on on the list price of the tire, which I remember being about double the retail price. In the end I could get 4 decent Canadian Tire bias tires for the price of replacing the Dunlop. They were certainly acceptable and outlasted the car.
My dad had Dunlops on his TR3a from the dealer in 1959, he called them Dunslips, as did all his sports car friends. Dad quickly swappwed to Michelin X radials and suddenly he was placin 2nd or 3rd in the 2 liter and under class at SCCA gymkhanas every time…
I can’t say that the Schwalbe (ice spiker) brand impresses me in terms of the durability of their casings. My studded winter tires for my bike are equipped with them; they’re wonderful on ice, but the sidewall pleats are fragile. If they applied the radial principle to all their tires, it might be better.
I remember “The Great Radial Debate” all too well. It was commonly held that radials somehow had much harsher ride than bias ply equipped cars. There was also considerable misinformation about radial tires, too. One was they didn’t last as long as bias plies. My dad actually believed this and his first car with radial tires was his 1979 Chevrolet Impala. He then realised the error of his ways.
My only experience with bias-ply vs. radials was back in ’91 or so.with my ’79 Bronco.
The previous owner had put it’s original rims and tires on it for the sale so he could keep his upgrades.
They were quite old but had been stored inside for years and ar least appeared to be in good shape.
I didn’t have any great expectations for ride or handling, having driven so.many trucks and jeeps from the era.
But after a few months I was able to purchase a set of new tires, along with some five-slot mag wheels, which I think we’re a little lighter.
I figured it would drive better, but I was happily surprised to find that it felt SO much better. The ride and turning were vastly improved.
Still the nicest truck from that time I ever drove, and one of the few vehicles I wish I.could have back. (I had no idea they would go up in value like they have either)
Happy Thanksgiving.
I’ve driven a fair number of bias-ply shod 4 wheeled vehicles but probably not for almost 50 years. Replacing the worn bias plies on my first car with Continental radials (TS771’s, 165R-15 … how can I remember that after half a century?) was transformational. As was my first radial motorcycle tire, a Pirelli MP7 on the rear of my Honda CB900F which cured its propensity for high speed wobbles.
I haven’t tried the new Schwalbe mountain bike radials but have heard mostly good things about them. I’m not a huge Schwalbe fan so I might wait until Maxxis introduces a radial.
Author should have designed the article so that bias and radial didn’t swap left and right sides between the two illustrations.
I’m old enough to remember when tire salesmen were telling people with older cars that they shouldn’t run radial tires because their cars weren’t ‘built’ for them. (Goodyear store)
Great article, thank you.
Not mentioned in the article is the “bias belted” tire , which was a transitional design. As I recall, the bias ply tire received a belt under the tread , an effort to reduce the squirm and deforming described in this article. I saw these tires a lot in the early 1970s, as a kid.
I’m assuming they were an improvement, but not nearly as good as radials
Like others here, I vividly remember the experience of replacing bias ply tires with radials on the same car. For me it was a 71 Plymouth Scamp. I still remember the first couple of blocks out of the tire store where I had bought a set of 4 used radials. It had always been a fairly hard-riding car, but those radials made it feel like it had clouds for wheels. On the flip side, I could tell that the added stickiness of the radials taxed the suspension, because the car would lean more in turns than before, probably because the grippier tires allowed faster turns.
The only downside – ever since I got those first radials, I have always had trouble telling from a glance when a tire is just moderately low on air. 🙂
The only comment that I would add that NASCAR used bias-ply tires until the late 1980’s. And of course, they were driven at extremely high speeds with high loads on banked ovals. Here is what was said. The point being that well designed bias-ply tires with the right suspension set up could perform.
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In the late 1980s, NASCAR’s twofold quest for speed and success took a sharp turn as tire supplier Goodyear introduced the radial tire to the sanctioning body’s premier series.
Bias-ply tires had been the standard for stock car competition from the very beginning. But radial tire technology had vastly improved, and major open-wheel series had already made the swap to radials. Off the track, radials had also begun replacing bias-ply as the tires of choice for passenger vehicles.
But the bias-ply tires still used in NASCAR provided teams with another tool in the toolbox, a way to “tune” the car’s setup through the use of air pressures and tire stagger (the variation in the circumference of the car’s tires), something radial tire technology couldn’t duplicate at the time.
Goodyear officials were working toward implementing radials in NASCAR when the company got an unexpected push from Hoosier Tire Company in 1988.
The competition between the two was fierce, and not without consequences. “Softer” tires produced by both brands generated higher speeds, but durability faltered. The “fall-off” in the product led to numerous tire failures and hard crashes.
The following year, Goodyear officials rolled out radial race tires in an effort to provide both speed and durability. It was an ongoing project — problems before the season-opening Daytona 500 forced the company to withdraw its product for that event.
It wasn’t until the spring race of 1989 at North Wilkesboro that Goodyear debuted the radial tire that officials felt was far more durable and could provide the necessary consistency and speed.
“We were going to step through it,” said Greg Stucker, head of race tire sales for Goodyear. “We were going to introduce them at the short tracks and then slowly step into the other race tracks.”
Rusty Wallace, driving for team owner Raymond Beadle, won the pole after the Blue Max team made the switch to Hoosiers.
“We knew the Hoosiers were quick,” Stucker said. “We also knew that the radials were extremely good over the long run. We went the first 100-some odd laps under green, which you don’t do at North Wilkesboro very often. And Rusty got lapped, I think, about Lap 70.”
Dale Earnhardt won the race, thanks in part to the Richard Childress team’s use of the Goodyear radials.
I recall some cars needed suspension settings changed to adapt to radial’s different behavior under load hence “radial tuned suspension”. As a child I remember ads for Sears Steel Belted Radials, and my parent’s choice of imported cars meant every vehicle I’ve driven had radial tires, although my motorcycles and bicycles are still on bias ply rubber.
I’m 16 and I just put 7.50 X 14 Biasply tires on my 1957 ChevroletBel-Air and my 1958 Buick Special and they run just fine. The power steering on both of them is immaculent, I could use a tooth pick to turn the car and everything is original and numbers matching. even the engine which for the 57 chevrolet is a 283 with a Rochester 4 bbl and for the Buick was a 364 nailhead engine with a 4bbl carb as well, they are just fine and I anticipate to run the cars with their new tires for 25,000 miles. not only for the benefit of the car, but as for my bank account, LOL.