radial tires replacing Bias plys

[HCD]

Im replacing bias plys on my 1948 New Yorker 8 Cylinder with radials. Ive googled and found that 225/75/R15s and 205/75/R15s may work. Anyone here replaced a similar Chrysler with these size Radials?

Kontio Tyres 155130KON WhitePaw Classic Narrow Radial Tire 205_75R15 [Whitewall] - JEGS.html

[Sbonesteel]

I replaced the 6.40-15 bias plys on my 47 P15C with radials.  You might find the 225s are a little wide--although I am not sure whether or not there is more underfender space with the New Yorker or if the backspacing on the rims is different.  I went with 205/75s on the front and 215/75s on the rear (although the rear rims were 16" to address a gearing issue I had).  Difference with the radials was like night and day.  SMB

[Dartgame]

225/70/15 is a nice size for my car.

[38plymouth]

3 hours ago, Sbonesteel said:

I replaced the 6.40-15 bias plys on my 47 P15C with radials.  You might find the 225s are a little wide--although I am not sure whether or not there is more underfender space with the New Yorker or if the backspacing on the rims is different.  I went with 205/75s on the front and 215/75s on the rear (although the rear rims were 16" to address a gearing issue I had).  Difference with the radials was like night and day.  SMB

What manufacturer and model are these tires? I can't quite make it out. The white wall on them looks to be bigger than the normal narrow white wall most tires come with. But it's also not quite as big as the extremely expensive cokers.

[Bob Riding]

Short answer: your correct modern radial replacement depends on which original tire size your specific 1948 Chrysler New Yorker had—but there are a few well-established conversions.

1) What the car originally used 

The New Yorker (straight-8 cars) typically ran very large bias-ply tires, commonly in this range:

• 8.20-15
• 8.90-15 (heavier models)

These are tall, narrow tires—very different from modern radials.

---

2) Direct modern radial equivalents 

Most commonly used conversions:

• P235/75R15 → closest overall diameter and stance
• P225/75R15 → slightly narrower, still very close
• P215/75R15 → acceptable but a bit undersized

Why these work:

• They approximate the original 29–30 inch overall diameter
• They fit most stock 15" rims
• They maintain speedometer accuracy reasonably well

---

3) If you want the correct look (not just function)

Modern radials don’t look like bias-ply tires. You have two paths:

A. Standard radials (cheap, easy)

• Better handling, braking, and lifespan
• But visually wrong (too wide, wrong sidewall shape)

B. “Bias-look radial” (correct solution for restorations)

• Sizes like 700R15, 750R15, or 820R15 equivalents
• Narrow tread, tall sidewall, correct profile
• Built with radial construction but vintage appearance

These are what serious restorations use.

---

4) What most people get wrong (important)

• They pick too small a tire (like 205/75R15) → car looks squat and wrong
• They go too wide → steering gets heavier, clearance issues
• They ignore diameter → throws off gearing and speedometer

---

5) Bottom-line recommendation 

If you want:

• Best overall driver setup:
  → P235/75R15
• Closer to original look without going expensive:
  → P225/75R15
• Correct vintage appearance + modern performance:
  → Bias-look radial in ~8.20–15 equivalent (e.g., 750R15/820R15)

---

If you want a precise answer (not generic), you need to confirm:

• Your exact wheel width (likely ~5.5")
• Whether you’re running skirts
• Clearance at full lock

Without that, any recommendation is just a “close enough” guess.

 

 

 

 

 

 

 

 

 

 

 

 

[Sbonesteel]

22 hours ago, 38plymouth said:

What manufacturer and model are these tires? I can't quite make it out. The white wall on them looks to be bigger than the normal narrow white wall most tires come with. But it's also not quite as big as the extremely expensive cokers.

As I indicated, I switched to 16" rims/tires in the rear to address a gearing ratio (my club coupe has the optional 'mountain area'/station wagon 4.11 gear ratio).  I also needed to maintain the diameter for the same reason, that is why I went with the 215r16 tires.  However, unless you go with the ultra-expensive Coker/Excelsior tires, you cannot get a whitewall in that size.  I went with standard 215r16 black walls with Atlas Portawalls.  These work just fine as long as you install them correctly (which is not easy/simple) and don't go wider than I did (radial sidewalls flex more than bias plys).  My car is a driver and for less than the cost of one Coker whitewall I was able to purchase two original 16" rims, two 16" black wall tires and a set of Portawalls.  Perfect for a driver.  SMB

[Sbonesteel]

1 minute ago, Sbonesteel said:

As I indicated, I switched to 16" rims/tires in the rear to address a gearing ratio (my club coupe has the optional 'mountain area'/station wagon 4.11 gear ratio).  I also needed to maintain the diameter for the same reason, that is why I went with the 215r16 tires.  However, unless you go with the ultra-expensive Coker/Excelsior tires, you cannot get a whitewall in that size.  I went with standard 215r16 black walls with Atlas Portawalls.  These work just fine as long as you install them correctly (which is not easy/simple) and don't go wider than I did (radial sidewalls flex more than bias plys).  My car is a driver and for less than the cost of one Coker whitewall I was able to purchase two original 16" rims, two 16" black wall tires and a set of Portawalls.  Perfect for a driver.  SMB

Sorry, tire size is 215/75r16.

[D35 Torpedo]

Tire sizing is easy, there are a million threads about that. The tricky part is putting valve stems in the old rims. They were meant to run tubes and have an odd shaped large valve stem hole. You can get solid metal valve stems that nut and bolt in. I had to add washers and make seals to span the large hole and hold air.

Edited April 29 by D35 Torpedo

[Sbonesteel]

Seems to be the luck of the draw on the valve stem holes--I have seen them both ways, some with simply larger round holes and some with the oval holes that require the special stems (although they are easily available).  Another quick solution to potential air leaks is at the center section rivets to the rims.  Many manufacturers (Coker, e.g.) say their tires require tubes because the stock rims 'leak' at the rivets.  I have found that two coats of rubberized spray truck bed liner on the center strip of the rim inside where the rivets penetrate cures this problem--I have never had a leak on any of the rims I have treated in this manner prior to mounting the tires.

[Plymouthy Adams]

many on concerns of rivet leaks will clean the center section and apply a couple coats of POR15....about the only use of this product I will agree with.  

 

On radials, only two of the 4 I ordered arrived today, the other two just arrived in north Georgia....should be here tomorrow, tire delivery is always a touchy subject in these parts.  

Edited April 29 by Plymouthy Adams

[Booger]

when I upgraded to radials I changed rims. New radials on 75 year old rims made no sense to me. Steel 15s same price as Cragar knock-offs. 

[Plymouthy Adams]

I used stock mopar rims from the late 80's when going steel...full caps over poverties and no cause for alarm on stock caps.  When I sold that car I gave the man the option of originals and poverties or modern and full cap....he went with the modern.  

[D35 Torpedo]

My original rims were in great shape, so why change them. The stock hubcaps fit perfectly and they look sweet in gloss black. 

[Plymouthy Adams]

My rims were in great shape and I sold them along the way to offset cost of other items I wanted.....all comes out in the wash.  

[Sbonesteel]

2 hours ago, D35 Torpedo said:

My original rims were in great shape, so why change them. The stock hubcaps fit perfectly and they look sweet in gloss black. 

Agreed, I did the same (see photo above) except I used semi-gloss black.  Love the stock hubcaps and the trim rings tie it all together with the caps and the stainless trim on the fenders, etc.  SMB

[38plymouth]

16 hours ago, Sbonesteel said:

As I indicated, I switched to 16" rims/tires in the rear to address a gearing ratio (my club coupe has the optional 'mountain area'/station wagon 4.11 gear ratio).  I also needed to maintain the diameter for the same reason, that is why I went with the 215r16 tires.  However, unless you go with the ultra-expensive Coker/Excelsior tires, you cannot get a whitewall in that size.  I went with standard 215r16 black walls with Atlas Portawalls.  These work just fine as long as you install them correctly (which is not easy/simple) and don't go wider than I did (radial sidewalls flex more than bias plys).  My car is a driver and for less than the cost of one Coker whitewall I was able to purchase two original 16" rims, two 16" black wall tires and a set of Portawalls.  Perfect for a driver.  SMB

Thank you I have 16 in wheels on my 38 and it seems like the tire options are pretty limited. I love the look of the wide white walls on my bias plate tires but they are getting older and they don't drive the best. And I just feel like I don't want to throw away the kind of money cooker wants for a set of tires. It's insane what they charge. I'll look into the portawalls. Can you explain more about what you're saying about installation of them? I've never even seen them in person.

[38plymouth]

Sorry I just looked up the Porta walls, what is the width of the ones you got? It looks like they make several different ones.

[Tom Skinner]

Gents,

Tractor Supply has the larger Valve Stems that fit our old Mopar's perfectly, they are Tractor Valve Stems, wider and new. Fit like a glove.

Tom

[Sbonesteel]

7 hours ago, 38plymouth said:

Thank you I have 16 in wheels on my 38 and it seems like the tire options are pretty limited. I love the look of the wide white walls on my bias plate tires but they are getting older and they don't drive the best. And I just feel like I don't want to throw away the kind of money cooker wants for a set of tires. It's insane what they charge. I'll look into the portawalls. Can you explain more about what you're saying about installation of them? I've never even seen them in person.

There is a pretty complete set of instructions that come with them but there are a couple of items you absolutely need to do.

First, make sure the bead area on the tire and the rim are completely clean of any lubricants, grease, tire mounting liquid, etc.  They recommend cleaning the area with brake cleaner fluid and that seemed to work well.  Second--and I found this to be the most important after attempting a couple times without--rough up the bead area of the rim with coarse sandpaper, I used 60 grit.  Easiest to do before the tire is mounted but if the tire is on, break the bead, push the tire down and run the paper around underneath the rim.  I then wiped off all of the sanding residue with a lint free, dry rag.  

Installation beyond these is a matter of patience and attention to detail.  Slip the Portawall around the edge of the rim and center it as closely as you can.  Then SLOWLY inflate the tire, making sure that the Portawall is shoved EVENLY into the bead area, up to a iine on the Portawall that forms the edge of the visible whitewall.  Work slowly and make sure it lays flat on the sidewall and is fully inserted.  Some folks say to pound it in with a white rubber mallet but I found that if you work slowly as you inflate in stages you can push it in with the heel of your hand.  If you get blisters in the sidewall, deflate and start over.  Again, a little tricky but they work fine--I have over 200 miles on mine and they haven't budged or wrinkled a bit.  Note that they also suggest that you keep your tires inflated at the high end of their normal range to ensure the Portawalls stay in place.

Mine are, I believe, 1 3/4" whitewalls.

Final point:  some radial tires have a 'ridge' in the sidewall, close to the bead.  Avoid those as the Portawall will not lie flat.

Good luck.  SMB

P.S.  I am assuming you are doing these yourself--I would not trust the operation to a tire shop, even the very experienced shop I use.  I installed mine using a Harbor Freight tire 'machine', hand operated for breaking beads and giving you a mounting surface for working on the tires.  Cheap, simple and works great if you bolt it to the floor or to a pallet.  SMB

[Sbonesteel]

One thing that has not been addressed in this discussion (except briefly in passing in Bob Riding's post) is RIM width.  This probably isn't an issue with the OP's '48 Chrysler but may be an issue for the 16" rims on 38plymouth's eponymous vehicle, which probably has 4" wide rims.  I haven't seen a 225 tire spec that includes such a narrow rim, so that may limit choices to the 195 or 205 range, depending on the tire manufacturer.  Again, probably not an issue for the '48, which probably has 5.5" or at least 5" rim widths.  SMB

[Sniper]

I am running 17x7" steelies from an 08 Challenger, bought them new from Rock Auto.  On my 51 Cambridge so YMMV.

 

 

[Plymouthy Adams]

I prefer the modern alloys..and upgraded suspension and rear ratio....beside better handling, excellent brakes, the beefy tires are an excellent by-product of that process.

[HCD]

On 4/30/2026 at 8:22 AM, Tom Skinner said:

Gents,

Tractor Supply has the larger Valve Stems that fit our old Mopar's perfectly, they are Tractor Valve Stems, wider and new. Fit like a glove.

Tom

Tractor supply has several valve stems do you remember which ones or part number that work?

[Plymouthy Adams]

check your local tractor supply they may or may not stock them your store.....but at least with the information freely given, one would think it would be beneficial for you to check.   While the ones at TSC I do not think are true ovals......congratulations, you are on the list just the same.  

Edited May 1 by Plymouthy Adams

[HCD]

4 hours ago, Plymouthy Adams said:

check your local tractor supply they may or may not stock them your store.....but at least with the information freely given, one would think it would be beneficial for you to check.   While the ones at TSC I do not think are true ovals......congratulations, you are on the list just the same.  

i was asking if the other guy posting recommending that you buy valve stems from Tractor Supply,  if he knows, or remembers the parts he purchased from them