P15 tire options

[John Fleming]

What size radial works best. My 1948 Plymouth P15 has original type 15X4.5'' wheels. Original tire size 670X15 bias ply. Tire size comparison charts are useful but real world experience is best. I would like to switch to radial tires. If you are using radial tires on a P15 with good results please tell tire size . 

[allbizz49]

215/75/15

[greg g]

I am running 205 75 15 fronts and 225 75 15 rears, but on aftermarket 5.5 inch wide wheels.  My shop guy said he wouldn't go larger than 215 75 on the stock 4.5 wide .

[Doug&Deb]

Bear in mind your speedometer will be off. The tires are smaller in diameter than the bias tires. If money is no problem Coker has bias look radials that are the correct size. I’m running 225/75-15 on 15x7 police wheels on my 52 Coronet. That’s another option to consider.

[Sniper]

13 minutes ago, Doug&Deb said:

I’m running 225/75-15 on 15x7 police wheels on my 52 Coronet

 

When I fitted cop car rims on my 51 Cambridge it hit the upper control arm upper pivot bolt.  Granted, I have P255/60-15's on them, wonder how you cleared?  Not sure 15mm more clearance would have made it clear

Edited July 28, 2021 by Sniper

[Doug&Deb]

I’ve not had any issues in 8 years knock wood. I average 3500 miles per year. The wheels were on the car when I got it. I’ve never had the originals. Now I’m curious. I’ll have to check out the clearance.

[Sniper]

The interference happened at full lock, straight ahead it clears just fine. 

 

 

 

 

[John Fleming]

My sincere thank you for the several people who answered my question. My tentative plan is to use 205/75R15 radial on the original wheels. I know the diameter is smaller by approximately one and one half inches.  I am told 295/75R15 radial tires vary only fraction of an inch in diameter from one brand to another. Please keep your old cars safe and  check your tires.

[Booger]

One last thought. the design of a modern radial tire is different than the old school stock rims that stock bias tires fitted. If a 70 yr old rim holds air on a tubeless tire, then great.

 

[Sniper]

Right rear tire on my 51 came apart on me the other day.  Tread looked good and deep.  No checking in the rubber.  But nonetheless I need new rear tires.  One pair of Riken Raptor sized at 255/50ZR-17 for the rear.  Going to run a set of late model Charger steelies in the back.  Haven't completely sorted out what I will run in the front, yet.  They are a bit shorter than stock, but I'd rather have the speedo read fast than slow.  Pics once I get them mounted up.

[Happy 46R]

I have a stock 46 Dodge D25C Club Coupe that has had some wheel modifications done somewhere in the past. There are a set of 15" wheels front and rear with nearly new Cocker Classic tires. I am about 12 miles per hour off at highway speed due to the lost circumference and wanted to move back to original 16" wheels. I also noted that the spacing dimples on the back of the 15" wheels allow the wheel to sit flush to the face of the brake drum but the center wheel hub looks proud of the axle hub. This spacing issue is not evident on the 16" rims I sourced. For cost cutting reasons I was thinking of leaving the 15" color matched rims on the front and putting new 600 x 16 on the rear. This should clear up the speedo problem but am wondering if it will create a different problem with different sizes front to back? Any information would be appreciated. 

[DonaldSmith]

Smaller wheels on the front? 

We were visiting my mother's family, when my Uncle Arthur explained to my dad that if you had a wagon with large wheels on the back and small wheels on the front, the wagon would slope forward, and would roll forever.   Perpetual motion   My dad, the professional engineer, tried unsuccessfully and heatedly to explain why that was impossible. 

I think Uncle Arthur was just getting my dad's goat.  Uncle Arthur operated a machine shop where all the machines ran off overhead leather belts powered by an old car engine.   Uncle Arthur was no dummy.

[Eneto-55]

41 minutes ago, DonaldSmith said:

Smaller wheels on the front? 

We were visiting my mother's family, when my Uncle Arthur explained to my dad that if you had a wagon with large wheels on the back and small wheels on the front, the wagon would slope forward, and would roll forever.   Perpetual motion   My dad, the professional engineer, tried unsuccessfully and heatedly to explain why that was impossible. 

I think Uncle Arthur was just getting my dad's goat.  Uncle Arthur operated a machine shop where all the machines ran off overhead leather belts powered by an old car engine.   Uncle Arthur was no dummy.

When I was a kid I bought a 26" bicycle frame from my brother, but only had a rear wheel for 26", so I put the 20" wheel off of my 20" bike on the front.  I then installed a steering wheel out of a 61 Oldsmobile.  Anyway, I often rode several miles over to a friend's house, and the route I took had me passing by the house where another kid on my school bus route lived.  He asked me once why I had a small wheel on the front.  That's what I told him - that with a small wheel on the front I was always going downhill.  (This was in Oklahoma, so there weren't any grades steep enough to "overcome" my downhill ride.)  I think he was fooled for just a bit, before he thought it through.  But it also reminds me of someone (a farmer, actually) who told us that you don't get the full value of your oatmeal if you put the milk in after the oatmeal, that you have to put the milk in your bowl first, then add the cereal.  He certainly seemed serious, so I just said "That's interesting."