Rim sizes

[pflaming]

My b3B, '52 truck came with 16" rims probably the standard at the time, this was followed by 15", then 14", and my '87 T Bird has 13". Today rims are 17" and larger. What is the reasoning for the size changes.

I know that 15" give a better ride because the tire walls are higher, but why the other sizes?

[greg g]

Excuse for charging ridiculous amount for replacement tires. Low rolling resistance saves fuel. Designers gone crazy.

[Young Ed]

Excuse for charging ridiculous amount for replacement tires. Low rolling resistance saves fuel. Designers gone crazy.

Also bigger brakes behind that bigger wheel. 

[DrDoctor]

   Usually, smaller/lighter vehicles have smaller wheels/tires – costs less for mfgr, and less unsprung weight for the lighter vehicle to cope with. Generally, taller aspect tires (70/75/78) provide a better ride due to their taller sidewall. Shorter aspect tires (40/35/30/25/20) provide harsher ride, due to extremely short sidewall. I once saw a guy with a “rubber-band” tire on a huge wheel actually sitting on the side of the road with a broken wheel. He hit a pothole, and instead of the tire absorbing the shock (it couldn’t . . .), the wheel failed. Semi-related – putting super-large wheels and tires on a vehicle not designed for them increases the unsprung weight, =’s poor handling/ride. Also, it increases spinning mass, and with original brakes, stopping distance can be dramatically increased – not good.  Food for tho’t . . .  Thx.

[59bisquik]

I know its an old thread, but I am gonna vote that brake size has alot to do with wheel size. You couldnt squeeze a set of 15" wheels over my old Tundra's front brakes and you sure wouldnt over my new Dodge 3500 front brakes.

It is frustrating though that a 35x12.50x15 is cheaper than the 35x12.50x17. When the 17" tire has less rubber present...

But of course there is also the bigger is better aftermarket such as 20-26" for the wow factor.

[JBNeal]

Bigger wheels have been driven by marketing...I have seen several local examples of land yachts from the 70s where the kids stripped off the chrome rub strips on the side and stuck some 20s in there, and they fit remarkably well and make them buggies look sharp...I cannot comment on ride or handling on them mods tho.  As full size trucks have grown, so have their wheel wells and the wheels & tires have to be big so it all looks proportional...which is driven by marketing

[Plymouthy Adams]

running 12.1 rotors forces me to run minimum wheel size of 16" on my 48 Plymouth

[DrDoctor]

   JBNeal is quite correct in his observations concerning the larger sizes of wheels/tires on contemporary vehicles. And, I also agree with his premise that it’s about marketing. Along with that size increase is the corresponding increase in the diameter of the brake rotor, with a commensurate increase in the size of the brake caliper and its respective brake pads. This is necessary to deal with the increase of the rotating mass of the wheel/tire combination. And, on contemporary vehicles, this works out just fine. Put that same wheel/tire combination on a vehicle from the 60’s/70’s/80’s, and the result won’t be so good. Also, I’m hard pressed to think of any contemporary vehicle that comes equipped from the factory with rubber-band sidewall tires. We had Corvettes, and they had 35 and 40 series sidewall profiles, which worked fine, as the tires were huge!!!   The unsprung weight issue is easily dealt with by altering the spring rates. Thx.

[Plymouthy Adams]

while some select wheels by size style and metal composition..today's factory cars are sporting much larger brakes than their predecessors.  this size in rotor diameter coupled with the larger 4 and even 6 piston calipers forces the wheel cavity to be larger...larger cavity means larger rim larger rim coupled with the overall height limits of the body, the tire will reflect the more narrow sidewall and the increase in some harshness to the ride quality but needed to keep the sidewall flex out of the equation for handling purposes.. 

at 12.2 diameter I am forced to 16's, today the diameter of this same series brakes are sporting 12.6 rotors....thus the increase to a minimum size of 17 inch wheel...and the brake rotor to wheel size is linear..up one..up the other...the larger calipers and multipistons require a certain amount of mass for strength as it arcs over the rotor for the opposing pistons...retrofitting disc brakes to older cars of the 60's is easy to do and the retro fitter is FORCED by design to the larger diameter wheels...the car body design forces shorter sidewalls..as for retro...mopar brakes from say up to 1989 can be retrofitted to a as far back as 1962 by just bolt and go stock components..this forces the person who wants disc brakes of size to handle the stopping power for his beefed up drive train to change wheels.  This has led to the specialty companies to make special size rims that are cosmetically the same LOOK as stock to retain the look and accept the functionality of the large brakes.  As in all things when modifying, one accepts the fact that one mod may well force you to do two or three others to make it work and be safe.  It is when you do shortcuts that all this falls apart....safety should not be in the tradeoff...

[JaysonK]

On 7/19/2016 at 8:44 AM, pflaming said:

My b3B, '52 truck came with 16" rims probably the standard at the time, this was followed by 15", then 14", and my '87 T Bird has 13". Today rims are 17" and larger. What is the reasoning for the size changes.

I know that 15" give a better ride because the tire walls are higher, but why the other sizes?

I thought 15" rims were standard in '52? 

[Los_Control]

My 52 1/2 ton parts truck has 16" my 49 3/4 ton came with 15" with 5 on 5" bolt pattern. And a 1952 plymouth suburban parts car, has stock 16" wheels on it.

I bet you could order what you wanted, but think 16" was still pretty standard in 52.

[Eneto-55]

I've always heard that the P15's changed to 15's in late 1947 or 48.  I don't know about Suburbans.  Are they on a pickup frame?  If so, that would explain the 16's.  But people often changed wheel sizes back then (I guess they do now, too) - for example, about as soon as my Dad brought home a 62 Chrysler Newport (in 1966) he took the stock 14's off & put 15's on it off of our old DeSoto (53 model).  Later it was my first car, and they were still on it when I quit driving it around Christmas of 1977.

[kendall]

My 47 half ton came to me with 235r65-17 on 2006 Chrysler 300 wheels. I have some rubbing issues and it's a bear to maneuver at a crawl. I just ordered some 820r70-15 Diamondbacks on 15" Wheelsmith wires. Narrower and less contact patch will allow proper clearance and less turning resistance.