Radial tires size

[SteveR]

It is getting close to replacing my tires on my 37 Plymouth. Currently, I am running 205/80/r16 Driving wise they are fine but maneuvering for parking, is a struggle. I do little highway driving and usually keep my speed around 50-55mph. I was wondering how much damage am I doing to the steering box at crawl speed (parking) and what would be a good alternative.

I will be replacing the front tires first due to the cost. Going bias ply at £200+ each is out of my budget. I was thinking a 185/80/ r16 tire. It is a bit thinner than the 205s.

[Dan Hiebert]

I don't think there is much to worry about as far as wear and tear.  Skinnier tires will probably improve low speed and parking handling because they have a smaller contact patch with the pavement.  I've read that bias-ply tires actually put more stress and strain on the steering and suspension components than radials, if so, then the components that were originally engineered for bias-ply would probably breathe a sigh of relief with radials.  Story time - when I was working for the Border Patrol in west Texas, (early 1990's), we got a bunch of shiny new Ford Broncos for patrol vehicles that were delivered with radial tires.  Border Patrol operations go through tires rather quickly.  Someone got the bright idea that we could save money by buying a truck load of bias-ply tires to replace the radials when it came time.  Bias-plies at the time being notably less expensive than radials.  That idea drastically shortened the service life of those Broncos.  Where usually a cruiser could go a normal 4 or 5 years of service with no major issues, just about every one of those Broncos had to have the steering rebuilt at least once, suspension components replaced, and they all developed body cracks.  Only lasted 2 or 3 years.  Moral of the story being that those Broncos were engineered for radials, running bias-ply tires destroyed them.

[Sniper]

Gee I'm thinking about putting p245 in the front to match the Rears

[Ivan_B]

3 hours ago, SteveR said:

I will be replacing the front tires first due to the cost. Going bias ply at £200+ each is out of my budget. I was thinking a 185/80/ r16 tire. It is a bit thinner than the 205s.

I think that, unless you are buying them fancy radial replacements for classic cars, it is simply what ever you can find to fit your rims with the closest possible height, at this point  

 

1 hour ago, Dan Hiebert said:

Only lasted 2 or 3 years.  Moral of the story being that those Broncos were engineered for radials, running bias-ply tires destroyed them.

So, did you have a chance to compare a representative sample of Broncos running with radials + radials replacement versus the radials + ply replacements? The story is a bit condensed, so I am trying to clarify the experimental controls employed here 😁

[SteveR]

1 hour ago, Ivan_B said:

I think that, unless you are buying them fancy radial replacements for classic cars, it is simply what ever you can find to fit your rims with the closest possible height, at this point

Nope, I'm not going down the fancy/original route. My biggest concern is parking, say in a tight spot which here in England is what you get in parking lots. Grabbing the steering wheel and muscling it is quite a workout.

[Adam H P15 D30]

Make sure your steering box is full of oil, I found mine empty a few years ago and filling it made the steering noticeably easier at slow speeds.  If it leaks out slowly, mix a slurry of gear oil and bearing grease to the consistency of pancake batter and fill it up.

[Ivan_B]

1 hour ago, Adam H P15 D30 said:

Make sure your steering box is full of oil, I found mine empty a few years ago and filling it made the steering noticeably easier at slow speeds.

Good point, same here. Also, greasing the suspension is very useful  

Steve's car looks to be in great shape, though, so I think he is all set there.

[Los_Control]

I'm also thinking along the lines of check your front end for issues.

 

We have different vehicles, I have a 1949 1/2 ton truck with a straight axle ... did 37 Plymouth have a straight axle? ... not sure when the cars changed.

 

With my tires in the air, I can steer them from side to side with almost zero resistance. Grab the tire at 3:00 0'clock and 9:00 0'clock and steer back and forth.

It is totally smooth with no play. ... On the ground the truck steers so easily while moving it around .... is just a non issue.

I have 235 75r 15 with a aggressive tire tread.

 

I just feel if your front end was in good condition, you would not be asking this question.

Worn king pins could be a issue giving tire lean and fight your efforts.

 

@Sniper might need to stock up on wheaties if going with 245 

[Sniper]

1 hour ago, Los_Control said:

@Sniper might need to stock up on wheaties if going with 245 

 

Ha, my son needs to build up his guns, mine can do the job lol.

[kencombs]

5 hours ago, Adam H P15 D30 said:

Make sure your steering box is full of oil, I found mine empty a few years ago and filling it made the steering noticeably easier at slow speeds.  If it leaks out slowly, mix a slurry of gear oil and bearing grease to the consistency of pancake batter and fill it up.

Or, go to a John Deere dealler and gut a tube of'corn head grease'.   Thick and won't leak out but thins under pressure, lubing the sliding contact areas.

[andyd]

Apart from ensuring that the steering box has some sort of lubricant in it, ideally a proper steering box oil tho' guys on here swear by that "Corn head grease" I'd be checking what air pressure is in the tyres......I'd be running them at around 35psi.......or at least check with a reputable tyre supply place re what pressure the tyres can handle.....andyd 

[SteveR]

12 hours ago, Los_Control said:

With my tires in the air, I can steer them from side to side with almost zero resistance. Grab the tire at 3:00 0'clock and 9:00 0'clock and steer back and forth.

It is totally smooth with no play.

Tires in the air and all is very easy and smooth. I do have a little play (3:00-9:00) that seems to come from the steering box. Grabbing the tires and turning them is easy and smooth. I do not see any play in any of the linkages except the pitman at the gearbox One thing I have noticed lately is when driving and using a full turn on the wheel I will hear a clunk. Could this be worn kingpins?

Edited Friday at 08:27 AM by SteveR

[SteveR]

7 hours ago, andyd said:

I'd be running them at around 35psi

Yep, That is where I like running my tire pressures.

[andyd]

I'm no expert but I'd be surprised if the "clunk" on full lock is the kingpins, I'd think more likely its the steering box bearings and/or worm & sector......also as your 1937 plymouth steering box is mounted with a different arangement to the independant front ends from 1939 I'd also check the actual steering box mounting bolts and as it uses a drag link that moves forward  & back also check it for any excessive wear or movement...........again I'm no expert so these are purely some ideas I've had sitting here in Oz 12,000 miles away.....lol.........andyd  

[Dan Hiebert]

22 hours ago, Ivan_B said:

So, did you have a chance to compare a representative sample of Broncos running with radials + radials replacement versus the radials + ply replacements? The story is a bit condensed, so I am trying to clarify the experimental controls employed here 😁

I think you're being at least quasi facetious, but yes.  Although it was an after-the-fact and unintentional comparison.  And since you mention it - here goes; Each USBP Sector (20 of them) doesn't buy its own vehicles, HQ in DC does, but it does buy its own expendable parts - tires, oil, maintenance items when out of warranty, etc.  El Paso was the only Sector that bought bias-ply tires for its Bronco fleet.  Every other Sectors' Broncos lasted as long as they were supposed to.  El Paso Sector had to ask for supplemental funding for maintenance and had to ask for vehicle replacements out of the fleet cycle.  (The latter wasn't approved, no money, so we had to drive junk for a couple years.)   HQ and the Union duly noted the difference, neither were happy about it, and let that be known, which is how the rank-and-file found out about it.  I wouldn't go as far as to call it a scandal, but it was used by other Federal fleet services as an example of what not to do.  FWIW - the Border Patrol's fleet program vastly improved once it went under DHS's Customs and Border Protection.    

Edited Friday at 12:03 PM by Dan Hiebert
typo

[Roofus]

Quote

Could this be worn kingpins?

No it's the steering box that begins to loosen

[Los_Control]

6 hours ago, SteveR said:

when driving and using a full turn on the wheel I will hear a clunk. Could this be worn kingpins?

With my remark on king pins, I was trying to make a generalization sweep, of any worn parts in the system might make it harder to turn with weight on the tires.

 

With what you say, a little play and the rotation of 1 full turn, I would think the steering box may be worn and the gears are meshing or binding at a certain spot.

I do not know what the proper procedure would be to test and verify ... hope others can clarify.

Can you adjust the gears on yours? ... that might do it.

 

The worn steering box would make it difficult to steer. Most boxes have a lock nut  on a slotted screw. To adjust you need to mark the location of the screw.

While holding the screw, loosen the lock nut ant turn the screw clockwise 1/4 turn and tighten lock nut.

 

I just feel it is important to mark existing location and then no more then 1/4 turn.

Too tight and the gears will bind, also the play is from the gears wearing thin ... the more times they need adjusted, the thinner the gears are getting and can eventually break.

So adjust once or twice, then time for repair/replace.

 

[Sniper]

On 3/7/2025 at 9:33 AM, Roofus said:

No it's the steering box that begins to loosen

 

You have a point.  I was checked the torque on the steering box mounting bolts on my 51 and they were loose