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Username Post: recommended tire pressure        (Topic#366375)
Original57 
Poster
Posts: 54

Loc: Houston, TX
Reg: 04-07-09
09-10-21 08:27 PM - Post#2826870    

On my 57 sedan, I have been running Coker re-manu BF Goodrich bias tires,7.50-14 at 30psi (prob. too high based on the tread wear) for years. The 57 green passenger car shop manual calls for 22 psi cold and 25 psi warm on those old bias 4 ply tires.

I just replaced them with 4 modern 205/75 R14 radials that have a max. inflation rating of 51 psi.
(a) is there an educated guess or scientific formula to decide what inflation on the modern radials? OR (b) request opinions or input.




 


Shepherd 
Frequent Contributor
Posts: 2331

Loc: Lake George, NY
Reg: 11-11-15
09-11-21 05:31 AM - Post#2826876    
    In response to Original57

51 is the maximum loaded pressure. 32-35 would suitable.



 
55MAS 
Senior Member
Posts: 1595

Loc: North Coast, USA
Reg: 12-19-01
09-11-21 05:38 AM - Post#2826877    
    In response to Original57

Everyone has a recommendation.

Right or wrong for my old cars running modern tires I run pressures that feel good and promote even tire wear. Generally this is lower than the tire label. It the tire pressure is too high you will feel it at the steering wheel. If you hit a pot hole or other you will know when the pressure is too high. If the pressure is too high the thread will wear in the middle and less at the edges. If the pressure is too low the thread will wear at the edges and less in the middle. You may start with a pressure recommended by others and watch my comments above and adjust to suit. Good luck.



 
55 Shaker 
Member
Posts: 1641

Age: 71
Loc: north central IL.
Reg: 03-13-06
09-11-21 07:00 AM - Post#2826880    
    In response to Original57

I run all my radials at 35 PSI.

The older I get, the more dangerous, I am !!!!


 
Original57 
Poster
Posts: 54

Loc: Houston, TX
Reg: 04-07-09
09-12-21 06:00 PM - Post#2826962    
    In response to 55 Shaker

Thanks, all...



 
Mercedes 
Contributor
Posts: 359

Reg: 07-09-18
09-13-21 03:12 PM - Post#2827033    
    In response to Original57

Radial tires have a built in flat plane that they ride on, thus, the radial belt. If you look at a tire inflated to 25 lbs vs 45 lbs, you will see that the tread is flat against the road. The higher pressure makes the tire stiffer and less sidewall movement.

I agree that 35 is a good number.



 
addspeed 
Newbie
Posts: 16

Reg: 08-11-21
09-13-21 04:26 PM - Post#2827037    
    In response to Original57

I usually rely on the sticker located at the driver's door for an accurate PSI. You can see it on the car manual as well.



 
Mercedes 
Contributor
Posts: 359

Reg: 07-09-18
09-14-21 09:16 AM - Post#2827070    
    In response to addspeed

The sticker will show the recommended tire pressure, however, the sticker assumes that you have the tires at the time of the manufacture.

Radials were not available then.



 
55MAS 
Senior Member
Posts: 1595

Loc: North Coast, USA
Reg: 12-19-01
09-14-21 09:48 AM - Post#2827073    
    In response to Mercedes

  • Mercedes Said:
The sticker will show the recommended tire pressure, however, the sticker assumes that you have the tires at the time of the manufacture.

Radials were not available then.



Nor was the door sticker.



 
pauldian 
Contributor
Posts: 415
pauldian
Loc: seligman,arizona
Reg: 05-14-09
09-15-21 06:22 AM - Post#2827126    
    In response to Original57

If were me I'd call Coker tire and ask them what tire pressure they commend for your tire.
No one knows better than the tire manufacture what is the correct pressure.

Remember,I'm not always right. But I'M never WRONG !


 
Rick_L 
Member #409
Posts: 27914
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
09-15-21 04:46 PM - Post#2827160    
    In response to pauldian

Most passenger car radials these days are supposed to run about 35 psi. A passenger car radial that's supposed to run at 50 psi would be pretty unusual. It wouldn't be uncommon though for a truck tire that had a higher load rating.



 
Mercedes 
Contributor
Posts: 359

Reg: 07-09-18
09-16-21 08:26 AM - Post#2827191    
    In response to Rick_L

On my Mercedes vehicles, the tire card calls for increased tire pressures if sustained speeds above 100 MPH are expected.

Not sure that it goes above 50 PSI, but you add more pressure.



 
japete92 
"7th Year" Silver Supporting Member
Posts: 1787
japete92
Loc: No. Virginia
Reg: 01-18-13
09-16-21 09:12 AM - Post#2827194    
    In response to Mercedes

  • Mercedes Said:
On my Mercedes vehicles, the tire card calls for increased tire pressures if sustained speeds above 100 MPH are expected.

Not sure that it goes above 50 PSI, but you add more pressure.




Here's some more irrelevant minutiae:

Bugatti Chiron w/top speed of 273mph has recommended tire pressure of 41 psi.

That (and anything Mercedes) is useless info for a '57 Chevy with P205/75R x 14 tires (the topic of the original question).

Original57; cold pressure of approx 35 PSI should keep the radials' sidewalls from flexing too much for your suspension (designed for bias ply tires). That's what I run on my '63 Impala's radials.

Hope that is helpful.

Pete



 
pauldian 
Contributor
Posts: 415
pauldian
Loc: seligman,arizona
Reg: 05-14-09
09-16-21 11:46 AM - Post#2827200    
    In response to japete92

https://tirepressure.com/p205-70r14-tire-press ure

Remember,I'm not always right. But I'M never WRONG !


 
japete92 
"7th Year" Silver Supporting Member
Posts: 1787
japete92
Loc: No. Virginia
Reg: 01-18-13
09-16-21 01:40 PM - Post#2827206    
    In response to pauldian

  • pauldian Said:



Not sure why you are toe tapping at me. I do not see anything on the site that contradicts my recommendation of approx 35 psi. Also, I don't see any reason to expect the folks who assembled that data to know anything about tires they don not sell (bias ply for a '57 Chevy).

I stand by my recommendation (for this poster's question) of approx 35 cold psi. But there is no one 'correct number' for tires pressures for modern tires installed on old classic vehicles not designed for them; too many variables.

The '57 Chevy was designed for the stiffer sidewalls of the bias ply tires of the day. Adding more PSI (over the 22 cold psi for the '57 bias ply tires) helps reduce the flex of the radial and better replicate the bias tire.

Use whatever you like.

Pete





 
TAT_2 
Site Ambassador - Member #26 - "20th Year" Silver Supporting Member
Posts: 37401
TAT_2
Age: 68
Loc: "UNDER THE BOARDWALK"
Reg: 10-29-00
09-16-21 04:07 PM - Post#2827216    
    In response to japete92

18 WHEELS & A DOZEN DONUTS.
105 LBS IN EACH.

09 PONTIAC- VIBE
08 PONTIAC- G6
93 VETTE - 40TH ANNIV- RUBY RED- LT1/6-SPD/RAG TOP

PREVIOUS VETTE'S 58,68,70,76,78,85,90


QUOTE FROM HELEN
"WHY YOU LOOKING AT THAT? YA KNOW YA WANT ANOTHER VETTE"












 
japete92 
"7th Year" Silver Supporting Member
Posts: 1787
japete92
Loc: No. Virginia
Reg: 01-18-13
09-17-21 05:09 AM - Post#2827249    
    In response to TAT_2

Don't forget the coffee, and 'oldies' on the radio

Pete



 
pauldian 
Contributor
Posts: 415
pauldian
Loc: seligman,arizona
Reg: 05-14-09
09-17-21 06:30 AM - Post#2827254    
    In response to japete92





Remember,I'm not always right. But I'M never WRONG !


 
65 Impala BV 
Newbie
Posts: 8

Age: 55
Loc: Willow Springs, IL
Reg: 10-12-20
09-22-21 04:55 AM - Post#2827674    
    In response to Original57

The switch to radials was a definite good call. You'll enjoy all the benefits of a modern tire including improved ride quality, longevity and traction. My rule of thumb for heavier cars such as yours is a 0.8 multiplier to the max pressure rating of the radial tires and do this when they're hot. That way that's the highest pressure they will see. You'll get great, even wear, traction with no doming or cupping. So 0.8 x 51psi = 40.8 psi. You could round down to 40 and be fine. Good luck and enjoy your ride.

Thanks,

1965 Sierra Tan Impala SS 2D Coupe, LS3, BTR Stage 3 Cam, T56, 4.11s, 8.2" 10 Bolt

Brian


 
83_Burbin 
Member
Posts: 198

Age: 67
Loc: Neenah, Wisconsin
Reg: 04-28-03
09-22-21 07:37 AM - Post#2827681    
    In response to pauldian

  • pauldian Said:
If were me I'd call Coker tire and ask them what tire pressure they commend for your tire.
No one knows better than the tire manufacture what is the correct pressure.


"Calling Coker Tire" might get you an answer. Considering todays automated voice mail technology though, I would kind of doubt it. We purchased a set of Coopers for our current vehicle a few months back (Not a Chev, we won't go there ...) anyway, back to the subject at hand, ... I had the same issue ... The tires are rated at 51 PSI. The door jamb sticker says 35 PSI. The tire shops paperwork said they were inflated to 35 PSI. So, I contacted Cooper by email (a "Contact us" link). Their reply was to go by the vehicles recommended pressure. Given that, I would definitely go by the majority of the memberships recommendation as they have probably gone through the transition themselves. Run them at 35 PSI for a while and keep an eye on the tread wear.

Old Chevies Never Die, They Just Rust Away .... used to believe this to be true but ... my S-10 died while rusting away!

'01 Coleman Santa Fe Pop-up camper
'07 Ford Freestyle Limited


 
jadatis 
Newbie
Posts: 3

Reg: 02-10-15
09-22-21 09:06 AM - Post#2827689    
    In response to Original57

I am able to calculate it for you.
Got hold of the official european formula end 2007 and went running with it

Need your GAWR's , GVWR, but better real axle loads in your use. Succes with dermining that, the most tricky part in it all.
Then also max speed youbwont go over for even a minute.

And tire-specifications, maxload and loadrange to determine the reference-pressure.

Radial tires need higher pressure then diagonal.
But if oversised tires, probably in the 20tees range.




Edited by jadatis on 09-22-21 09:07 AM. Reason for edit: No reason given.

 
jadatis 
Newbie
Posts: 3

Reg: 02-10-15
09-22-21 01:52 PM - Post#2827711    
    In response to pauldian

  • pauldian Said:

Followed the link and checked the calculation.
They calculate for P-tires standard load with the old formula that results in lower pressure for the load, or higher loadcapacity for the pressure.
In 2006 TRA stepped over to the calculation of ETRTO, wich leads to better result.
The 26 psi in their list gives 1235 lbs loadcapacity. Calculated with the European formula( and after 2006 also American for P-tires), gives for 26 psi 1130 lbs loadcapacity.



 
bill911denton 
Newbie
Posts: 1

Age: 74
Loc: OK
Reg: 05-09-21
09-27-21 01:19 PM - Post#2828127    
    In response to 55 Shaker

Front and Rear ?
Summer and Winter ?



 
Original57 
Poster
Posts: 54

Loc: Houston, TX
Reg: 04-07-09
09-27-21 06:33 PM - Post#2828145    
    In response to 83_Burbin

I tried the question to "Contact" with Coker, but no reply for their tire of their same size P205/75 R14. I will just run 35 psi as so many have suggested.



 
OverKnight 
Member
Posts: 59

Loc: Central New Jersey
Reg: 10-29-04
10-12-21 03:26 PM - Post#2829035    
    In response to Original57

I think it was commonly accepted that the manufacturer's tire pressure recommendations were always geared towards comfort, rather than handling, gas mileage and tread wear. I used to run my bias-ply tires at 32 psi, and I run my radials at 36 psi.

"I shall pass through this world but once. Any good I can do, or any kindness that I can show any human being, let me do it now and not defer it, for I shall not pass this way again."
- Stephen Grellet


 


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